x509v3.c

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/*
 * X.509v3 certificate parsing and processing (RFC 3280 profile)
 * Copyright (c) 2006-2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "crypto/crypto.h"
#include "asn1.h"
#include "x509v3.h"


static void x509_free_name(struct x509_name *name)
{
        os_free(name->cn);
        os_free(name->c);
        os_free(name->l);
        os_free(name->st);
        os_free(name->o);
        os_free(name->ou);
        os_free(name->email);
        name->cn = name->c = name->l = name->st = name->o = name->ou = NULL;
        name->email = NULL;

        os_free(name->alt_email);
        os_free(name->dns);
        os_free(name->uri);
        os_free(name->ip);
        name->alt_email = name->dns = name->uri = NULL;
        name->ip = NULL;
        name->ip_len = 0;
        os_memset(&name->rid, 0, sizeof(name->rid));
}


void x509_certificate_free(struct x509_certificate *cert)
{
        if (cert == NULL)
                return;
        if (cert->next) {
                wpa_printf(MSG_DEBUG, "X509: x509_certificate_free: cer=%p "
                           "was still on a list (next=%p)\n",
                           cert, cert->next);
        }
        x509_free_name(&cert->issuer);
        x509_free_name(&cert->subject);
        os_free(cert->public_key);
        os_free(cert->sign_value);
        os_free(cert);
}


void x509_certificate_chain_free(struct x509_certificate *cert)
{
        struct x509_certificate *next;

        while (cert) {
                next = cert->next;
                cert->next = NULL;
                x509_certificate_free(cert);
                cert = next;
        }
}


static int x509_whitespace(char c)
{
        return c == ' ' || c == '\t';
}


static void x509_str_strip_whitespace(char *a)
{
        char *ipos, *opos;
        int remove_whitespace = 1;

        ipos = opos = a;

        while (*ipos) {
                if (remove_whitespace && x509_whitespace(*ipos))
                        ipos++;
                else {
                        remove_whitespace = x509_whitespace(*ipos);
                        *opos++ = *ipos++;
                }
        }

        *opos-- = '\0';
        if (opos > a && x509_whitespace(*opos))
                *opos = '\0';
}


static int x509_str_compare(const char *a, const char *b)
{
        char *aa, *bb;
        int ret;

        if (!a && b)
                return -1;
        if (a && !b)
                return 1;
        if (!a && !b)
                return 0;

        aa = os_strdup(a);
        bb = os_strdup(b);

        if (aa == NULL || bb == NULL) {
                os_free(aa);
                os_free(bb);
                return os_strcasecmp(a, b);
        }

        x509_str_strip_whitespace(aa);
        x509_str_strip_whitespace(bb);

        ret = os_strcasecmp(aa, bb);

        os_free(aa);
        os_free(bb);

        return ret;
}


int x509_name_compare(struct x509_name *a, struct x509_name *b)
{
        int res;

        if (!a && b)
                return -1;
        if (a && !b)
                return 1;
        if (!a && !b)
                return 0;

        res = x509_str_compare(a->cn, b->cn);
        if (res)
                return res;
        res = x509_str_compare(a->c, b->c);
        if (res)
                return res;
        res = x509_str_compare(a->l, b->l);
        if (res)
                return res;
        res = x509_str_compare(a->st, b->st);
        if (res)
                return res;
        res = x509_str_compare(a->o, b->o);
        if (res)
                return res;
        res = x509_str_compare(a->ou, b->ou);
        if (res)
                return res;
        res = x509_str_compare(a->email, b->email);
        if (res)
                return res;

        return 0;
}


static int x509_parse_algorithm_identifier(
        const u8 *buf, size_t len,
        struct x509_algorithm_identifier *id, const u8 **next)
{
        struct asn1_hdr hdr;
        const u8 *pos, *end;

        /*
         * AlgorithmIdentifier ::= SEQUENCE {
         *     algorithm            OBJECT IDENTIFIER,
         *     parameters           ANY DEFINED BY algorithm OPTIONAL
         * }
         */

        if (asn1_get_next(buf, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(AlgorithmIdentifier) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;
        end = pos + hdr.length;

        if (end > buf + len)
                return -1;

        *next = end;

        if (asn1_get_oid(pos, end - pos, &id->oid, &pos))
                return -1;

        /* TODO: optional parameters */

        return 0;
}


static int x509_parse_public_key(const u8 *buf, size_t len,
                                 struct x509_certificate *cert,
                                 const u8 **next)
{
        struct asn1_hdr hdr;
        const u8 *pos, *end;

        /*
         * SubjectPublicKeyInfo ::= SEQUENCE {
         *     algorithm            AlgorithmIdentifier,
         *     subjectPublicKey     BIT STRING
         * }
         */

        pos = buf;
        end = buf + len;

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(SubjectPublicKeyInfo) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;

        if (pos + hdr.length > end)
                return -1;
        end = pos + hdr.length;
        *next = end;

        if (x509_parse_algorithm_identifier(pos, end - pos,
                                            &cert->public_key_alg, &pos))
                return -1;

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_BITSTRING) {
                wpa_printf(MSG_DEBUG, "X509: Expected BITSTRING "
                           "(subjectPublicKey) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        if (hdr.length < 1)
                return -1;
        pos = hdr.payload;
        if (*pos) {
                wpa_printf(MSG_DEBUG, "X509: BITSTRING - %d unused bits",
                           *pos);
                /*
                 * TODO: should this be rejected? X.509 certificates are
                 * unlikely to use such a construction. Now we would end up
                 * including the extra bits in the buffer which may also be
                 * ok.
                 */
        }
        os_free(cert->public_key);
        cert->public_key = os_malloc(hdr.length - 1);
        if (cert->public_key == NULL) {
                wpa_printf(MSG_DEBUG, "X509: Failed to allocate memory for "
                           "public key");
                return -1;
        }
        os_memcpy(cert->public_key, pos + 1, hdr.length - 1);
        cert->public_key_len = hdr.length - 1;
        wpa_hexdump(MSG_MSGDUMP, "X509: subjectPublicKey",
                    cert->public_key, cert->public_key_len);

        return 0;
}


static int x509_parse_name(const u8 *buf, size_t len, struct x509_name *name,
                           const u8 **next)
{
        struct asn1_hdr hdr;
        const u8 *pos, *end, *set_pos, *set_end, *seq_pos, *seq_end;
        struct asn1_oid oid;
        char **fieldp;

        /*
         * Name ::= CHOICE { RDNSequence }
         * RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
         * RelativeDistinguishedName ::= SET OF AttributeTypeAndValue
         * AttributeTypeAndValue ::= SEQUENCE {
         *     type     AttributeType,
         *     value    AttributeValue
         * }
         * AttributeType ::= OBJECT IDENTIFIER
         * AttributeValue ::= ANY DEFINED BY AttributeType
         */

        if (asn1_get_next(buf, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(Name / RDNSequencer) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;

        if (pos + hdr.length > buf + len)
                return -1;

        end = *next = pos + hdr.length;

        while (pos < end) {
                if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_UNIVERSAL ||
                    hdr.tag != ASN1_TAG_SET) {
                        wpa_printf(MSG_DEBUG, "X509: Expected SET "
                                   "(RelativeDistinguishedName) - found class "
                                   "%d tag 0x%x", hdr.class, hdr.tag);
                        x509_free_name(name);
                        return -1;
                }

                set_pos = hdr.payload;
                pos = set_end = hdr.payload + hdr.length;

                if (asn1_get_next(set_pos, set_end - set_pos, &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_UNIVERSAL ||
                    hdr.tag != ASN1_TAG_SEQUENCE) {
                        wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                                   "(AttributeTypeAndValue) - found class %d "
                                   "tag 0x%x", hdr.class, hdr.tag);
                        x509_free_name(name);
                        return -1;
                }

                seq_pos = hdr.payload;
                seq_end = hdr.payload + hdr.length;

                if (asn1_get_oid(seq_pos, seq_end - seq_pos, &oid, &seq_pos)) {
                        x509_free_name(name);
                        return -1;
                }

                if (asn1_get_next(seq_pos, seq_end - seq_pos, &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_UNIVERSAL) {
                        wpa_printf(MSG_DEBUG, "X509: Failed to parse "
                                   "AttributeValue");
                        x509_free_name(name);
                        return -1;
                }

                /* RFC 3280:
                 * MUST: country, organization, organizational-unit,
                 * distinguished name qualifier, state or province name,
                 * common name, serial number.
                 * SHOULD: locality, title, surname, given name, initials,
                 * pseudonym, generation qualifier.
                 * MUST: domainComponent (RFC 2247).
                 */
                fieldp = NULL;
                if (oid.len == 4 &&
                    oid.oid[0] == 2 && oid.oid[1] == 5 && oid.oid[2] == 4) {
                        /* id-at ::= 2.5.4 */
                        switch (oid.oid[3]) {
                        case 3:
                                /* commonName */
                                fieldp = &name->cn;
                                break;
                        case 6:
                                /*  countryName */
                                fieldp = &name->c;
                                break;
                        case 7:
                                /* localityName */
                                fieldp = &name->l;
                                break;
                        case 8:
                                /* stateOrProvinceName */
                                fieldp = &name->st;
                                break;
                        case 10:
                                /* organizationName */
                                fieldp = &name->o;
                                break;
                        case 11:
                                /* organizationalUnitName */
                                fieldp = &name->ou;
                                break;
                        }
                } else if (oid.len == 7 &&
                           oid.oid[0] == 1 && oid.oid[1] == 2 &&
                           oid.oid[2] == 840 && oid.oid[3] == 113549 &&
                           oid.oid[4] == 1 && oid.oid[5] == 9 &&
                           oid.oid[6] == 1) {
                        /* 1.2.840.113549.1.9.1 - e-mailAddress */
                        fieldp = &name->email;
                }

                if (fieldp == NULL) {
                        wpa_hexdump(MSG_DEBUG, "X509: Unrecognized OID",
                                    (u8 *) oid.oid,
                                    oid.len * sizeof(oid.oid[0]));
                        wpa_hexdump_ascii(MSG_MSGDUMP, "X509: Attribute Data",
                                          hdr.payload, hdr.length);
                        continue;
                }

                os_free(*fieldp);
                *fieldp = os_malloc(hdr.length + 1);
                if (*fieldp == NULL) {
                        x509_free_name(name);
                        return -1;
                }
                os_memcpy(*fieldp, hdr.payload, hdr.length);
                (*fieldp)[hdr.length] = '\0';
                if (os_strlen(*fieldp) != hdr.length) {
                        wpa_printf(MSG_INFO, "X509: Reject certificate with "
                                   "embedded NUL byte in a string (%s[NUL])",
                                   *fieldp);
                        x509_free_name(name);
                        return -1;
                }
        }

        return 0;
}


void x509_name_string(struct x509_name *name, char *buf, size_t len)
{
        char *pos, *end;
        int ret;

        if (len == 0)
                return;

        pos = buf;
        end = buf + len;

        if (name->c) {
                ret = os_snprintf(pos, end - pos, "C=%s, ", name->c);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }
        if (name->st) {
                ret = os_snprintf(pos, end - pos, "ST=%s, ", name->st);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }
        if (name->l) {
                ret = os_snprintf(pos, end - pos, "L=%s, ", name->l);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }
        if (name->o) {
                ret = os_snprintf(pos, end - pos, "O=%s, ", name->o);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }
        if (name->ou) {
                ret = os_snprintf(pos, end - pos, "OU=%s, ", name->ou);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }
        if (name->cn) {
                ret = os_snprintf(pos, end - pos, "CN=%s, ", name->cn);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }

        if (pos > buf + 1 && pos[-1] == ' ' && pos[-2] == ',') {
                *pos-- = '\0';
                *pos-- = '\0';
        }

        if (name->email) {
                ret = os_snprintf(pos, end - pos, "/emailAddress=%s",
                                  name->email);
                if (ret < 0 || ret >= end - pos)
                        goto done;
                pos += ret;
        }

done:
        end[-1] = '\0';
}


static int x509_parse_time(const u8 *buf, size_t len, u8 asn1_tag,
                           os_time_t *val)
{
        const char *pos;
        int year, month, day, hour, min, sec;

        /*
         * Time ::= CHOICE {
         *     utcTime        UTCTime,
         *     generalTime    GeneralizedTime
         * }
         *
         * UTCTime: YYMMDDHHMMSSZ
         * GeneralizedTime: YYYYMMDDHHMMSSZ
         */

        pos = (const char *) buf;

        switch (asn1_tag) {
        case ASN1_TAG_UTCTIME:
                if (len != 13 || buf[12] != 'Z') {
                        wpa_hexdump_ascii(MSG_DEBUG, "X509: Unrecognized "
                                          "UTCTime format", buf, len);
                        return -1;
                }
                if (sscanf(pos, "%02d", &year) != 1) {
                        wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse "
                                          "UTCTime year", buf, len);
                        return -1;
                }
                if (year < 50)
                        year += 2000;
                else
                        year += 1900;
                pos += 2;
                break;
        case ASN1_TAG_GENERALIZEDTIME:
                if (len != 15 || buf[14] != 'Z') {
                        wpa_hexdump_ascii(MSG_DEBUG, "X509: Unrecognized "
                                          "GeneralizedTime format", buf, len);
                        return -1;
                }
                if (sscanf(pos, "%04d", &year) != 1) {
                        wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse "
                                          "GeneralizedTime year", buf, len);
                        return -1;
                }
                pos += 4;
                break;
        default:
                wpa_printf(MSG_DEBUG, "X509: Expected UTCTime or "
                           "GeneralizedTime - found tag 0x%x", asn1_tag);
                return -1;
        }

        if (sscanf(pos, "%02d", &month) != 1) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse Time "
                                  "(month)", buf, len);
                return -1;
        }
        pos += 2;

        if (sscanf(pos, "%02d", &day) != 1) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse Time "
                                  "(day)", buf, len);
                return -1;
        }
        pos += 2;

        if (sscanf(pos, "%02d", &hour) != 1) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse Time "
                                  "(hour)", buf, len);
                return -1;
        }
        pos += 2;

        if (sscanf(pos, "%02d", &min) != 1) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse Time "
                                  "(min)", buf, len);
                return -1;
        }
        pos += 2;

        if (sscanf(pos, "%02d", &sec) != 1) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse Time "
                                  "(sec)", buf, len);
                return -1;
        }

        if (os_mktime(year, month, day, hour, min, sec, val) < 0) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to convert Time",
                                  buf, len);
                if (year < 1970) {
                        /*
                         * At least some test certificates have been configured
                         * to use dates prior to 1970. Set the date to
                         * beginning of 1970 to handle these case.
                         */
                        wpa_printf(MSG_DEBUG, "X509: Year=%d before epoch - "
                                   "assume epoch as the time", year);
                        *val = 0;
                        return 0;
                }
                return -1;
        }

        return 0;
}


static int x509_parse_validity(const u8 *buf, size_t len,
                               struct x509_certificate *cert, const u8 **next)
{
        struct asn1_hdr hdr;
        const u8 *pos;
        size_t plen;

        /*
         * Validity ::= SEQUENCE {
         *     notBefore      Time,
         *     notAfter       Time
         * }
         *
         * RFC 3280, 4.1.2.5:
         * CAs conforming to this profile MUST always encode certificate
         * validity dates through the year 2049 as UTCTime; certificate
         * validity dates in 2050 or later MUST be encoded as GeneralizedTime.
         */

        if (asn1_get_next(buf, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(Validity) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;
        plen = hdr.length;

        if (pos + plen > buf + len)
                return -1;

        *next = pos + plen;

        if (asn1_get_next(pos, plen, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            x509_parse_time(hdr.payload, hdr.length, hdr.tag,
                            &cert->not_before) < 0) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse notBefore "
                                  "Time", hdr.payload, hdr.length);
                return -1;
        }

        pos = hdr.payload + hdr.length;
        plen = *next - pos;

        if (asn1_get_next(pos, plen, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            x509_parse_time(hdr.payload, hdr.length, hdr.tag,
                            &cert->not_after) < 0) {
                wpa_hexdump_ascii(MSG_DEBUG, "X509: Failed to parse notAfter "
                                  "Time", hdr.payload, hdr.length);
                return -1;
        }

        wpa_printf(MSG_MSGDUMP, "X509: Validity: notBefore: %lu notAfter: %lu",
                   (unsigned long) cert->not_before,
                   (unsigned long) cert->not_after);

        return 0;
}


static int x509_id_ce_oid(struct asn1_oid *oid)
{
        /* id-ce arc from X.509 for standard X.509v3 extensions */
        return oid->len >= 4 &&
                oid->oid[0] == 2 /* joint-iso-ccitt */ &&
                oid->oid[1] == 5 /* ds */ &&
                oid->oid[2] == 29 /* id-ce */;
}


static int x509_parse_ext_key_usage(struct x509_certificate *cert,
                                    const u8 *pos, size_t len)
{
        struct asn1_hdr hdr;

        /*
         * KeyUsage ::= BIT STRING {
         *     digitalSignature        (0),
         *     nonRepudiation          (1),
         *     keyEncipherment         (2),
         *     dataEncipherment        (3),
         *     keyAgreement            (4),
         *     keyCertSign             (5),
         *     cRLSign                 (6),
         *     encipherOnly            (7),
         *     decipherOnly            (8) }
         */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_BITSTRING ||
            hdr.length < 1) {
                wpa_printf(MSG_DEBUG, "X509: Expected BIT STRING in "
                           "KeyUsage; found %d tag 0x%x len %d",
                           hdr.class, hdr.tag, hdr.length);
                return -1;
        }

        cert->extensions_present |= X509_EXT_KEY_USAGE;
        cert->key_usage = asn1_bit_string_to_long(hdr.payload, hdr.length);

        wpa_printf(MSG_DEBUG, "X509: KeyUsage 0x%lx", cert->key_usage);

        return 0;
}


static int x509_parse_ext_basic_constraints(struct x509_certificate *cert,
                                            const u8 *pos, size_t len)
{
        struct asn1_hdr hdr;
        unsigned long value;
        size_t left;

        /*
         * BasicConstraints ::= SEQUENCE {
         * cA                      BOOLEAN DEFAULT FALSE,
         * pathLenConstraint       INTEGER (0..MAX) OPTIONAL }
         */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE in "
                           "BasicConstraints; found %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        cert->extensions_present |= X509_EXT_BASIC_CONSTRAINTS;

        if (hdr.length == 0)
                return 0;

        if (asn1_get_next(hdr.payload, hdr.length, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL) {
                wpa_printf(MSG_DEBUG, "X509: Failed to parse "
                           "BasicConstraints");
                return -1;
        }

        if (hdr.tag == ASN1_TAG_BOOLEAN) {
                if (hdr.length != 1) {
                        wpa_printf(MSG_DEBUG, "X509: Unexpected "
                                   "Boolean length (%u) in BasicConstraints",
                                   hdr.length);
                        return -1;
                }
                cert->ca = hdr.payload[0];

                if (hdr.payload + hdr.length == pos + len) {
                        wpa_printf(MSG_DEBUG, "X509: BasicConstraints - cA=%d",
                                   cert->ca);
                        return 0;
                }

                if (asn1_get_next(hdr.payload + hdr.length, len - hdr.length,
                                  &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_UNIVERSAL) {
                        wpa_printf(MSG_DEBUG, "X509: Failed to parse "
                                   "BasicConstraints");
                        return -1;
                }
        }

        if (hdr.tag != ASN1_TAG_INTEGER) {
                wpa_printf(MSG_DEBUG, "X509: Expected INTEGER in "
                           "BasicConstraints; found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        pos = hdr.payload;
        left = hdr.length;
        value = 0;
        while (left) {
                value <<= 8;
                value |= *pos++;
                left--;
        }

        cert->path_len_constraint = value;
        cert->extensions_present |= X509_EXT_PATH_LEN_CONSTRAINT;

        wpa_printf(MSG_DEBUG, "X509: BasicConstraints - cA=%d "
                   "pathLenConstraint=%lu",
                   cert->ca, cert->path_len_constraint);

        return 0;
}


static int x509_parse_alt_name_rfc8222(struct x509_name *name,
                                       const u8 *pos, size_t len)
{
        /* rfc822Name IA5String */
        wpa_hexdump_ascii(MSG_MSGDUMP, "X509: altName - rfc822Name", pos, len);
        os_free(name->alt_email);
        name->alt_email = os_zalloc(len + 1);
        if (name->alt_email == NULL)
                return -1;
        os_memcpy(name->alt_email, pos, len);
        if (os_strlen(name->alt_email) != len) {
                wpa_printf(MSG_INFO, "X509: Reject certificate with "
                           "embedded NUL byte in rfc822Name (%s[NUL])",
                           name->alt_email);
                os_free(name->alt_email);
                name->alt_email = NULL;
                return -1;
        }
        return 0;
}


static int x509_parse_alt_name_dns(struct x509_name *name,
                                   const u8 *pos, size_t len)
{
        /* dNSName IA5String */
        wpa_hexdump_ascii(MSG_MSGDUMP, "X509: altName - dNSName", pos, len);
        os_free(name->dns);
        name->dns = os_zalloc(len + 1);
        if (name->dns == NULL)
                return -1;
        os_memcpy(name->dns, pos, len);
        if (os_strlen(name->dns) != len) {
                wpa_printf(MSG_INFO, "X509: Reject certificate with "
                           "embedded NUL byte in dNSName (%s[NUL])",
                           name->dns);
                os_free(name->dns);
                name->dns = NULL;
                return -1;
        }
        return 0;
}


static int x509_parse_alt_name_uri(struct x509_name *name,
                                   const u8 *pos, size_t len)
{
        /* uniformResourceIdentifier IA5String */
        wpa_hexdump_ascii(MSG_MSGDUMP,
                          "X509: altName - uniformResourceIdentifier",
                          pos, len);
        os_free(name->uri);
        name->uri = os_zalloc(len + 1);
        if (name->uri == NULL)
                return -1;
        os_memcpy(name->uri, pos, len);
        if (os_strlen(name->uri) != len) {
                wpa_printf(MSG_INFO, "X509: Reject certificate with "
                           "embedded NUL byte in uniformResourceIdentifier "
                           "(%s[NUL])", name->uri);
                os_free(name->uri);
                name->uri = NULL;
                return -1;
        }
        return 0;
}


static int x509_parse_alt_name_ip(struct x509_name *name,
                                       const u8 *pos, size_t len)
{
        /* iPAddress OCTET STRING */
        wpa_hexdump(MSG_MSGDUMP, "X509: altName - iPAddress", pos, len);
        os_free(name->ip);
        name->ip = os_malloc(len);
        if (name->ip == NULL)
                return -1;
        os_memcpy(name->ip, pos, len);
        name->ip_len = len;
        return 0;
}


static int x509_parse_alt_name_rid(struct x509_name *name,
                                   const u8 *pos, size_t len)
{
        char buf[80];

        /* registeredID OBJECT IDENTIFIER */
        if (asn1_parse_oid(pos, len, &name->rid) < 0)
                return -1;

        asn1_oid_to_str(&name->rid, buf, sizeof(buf));
        wpa_printf(MSG_MSGDUMP, "X509: altName - registeredID: %s", buf);

        return 0;
}


static int x509_parse_ext_alt_name(struct x509_name *name,
                                   const u8 *pos, size_t len)
{
        struct asn1_hdr hdr;
        const u8 *p, *end;

        /*
         * GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
         *
         * GeneralName ::= CHOICE {
         *     otherName                       [0]     OtherName,
         *     rfc822Name                      [1]     IA5String,
         *     dNSName                         [2]     IA5String,
         *     x400Address                     [3]     ORAddress,
         *     directoryName                   [4]     Name,
         *     ediPartyName                    [5]     EDIPartyName,
         *     uniformResourceIdentifier       [6]     IA5String,
         *     iPAddress                       [7]     OCTET STRING,
         *     registeredID                    [8]     OBJECT IDENTIFIER }
         *
         * OtherName ::= SEQUENCE {
         *     type-id    OBJECT IDENTIFIER,
         *     value      [0] EXPLICIT ANY DEFINED BY type-id }
         *
         * EDIPartyName ::= SEQUENCE {
         *     nameAssigner            [0]     DirectoryString OPTIONAL,
         *     partyName               [1]     DirectoryString }
         */

        for (p = pos, end = pos + len; p < end; p = hdr.payload + hdr.length) {
                int res;

                if (asn1_get_next(p, end - p, &hdr) < 0) {
                        wpa_printf(MSG_DEBUG, "X509: Failed to parse "
                                   "SubjectAltName item");
                        return -1;
                }

                if (hdr.class != ASN1_CLASS_CONTEXT_SPECIFIC)
                        continue;

                switch (hdr.tag) {
                case 1:
                        res = x509_parse_alt_name_rfc8222(name, hdr.payload,
                                                          hdr.length);
                        break;
                case 2:
                        res = x509_parse_alt_name_dns(name, hdr.payload,
                                                      hdr.length);
                        break;
                case 6:
                        res = x509_parse_alt_name_uri(name, hdr.payload,
                                                      hdr.length);
                        break;
                case 7:
                        res = x509_parse_alt_name_ip(name, hdr.payload,
                                                     hdr.length);
                        break;
                case 8:
                        res = x509_parse_alt_name_rid(name, hdr.payload,
                                                      hdr.length);
                        break;
                case 0: /* TODO: otherName */
                case 3: /* TODO: x500Address */
                case 4: /* TODO: directoryName */
                case 5: /* TODO: ediPartyName */
                default:
                        res = 0;
                        break;
                }
                if (res < 0)
                        return res;
        }

        return 0;
}


static int x509_parse_ext_subject_alt_name(struct x509_certificate *cert,
                                           const u8 *pos, size_t len)
{
        struct asn1_hdr hdr;

        /* SubjectAltName ::= GeneralNames */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE in "
                           "SubjectAltName; found %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        wpa_printf(MSG_DEBUG, "X509: SubjectAltName");
        cert->extensions_present |= X509_EXT_SUBJECT_ALT_NAME;

        if (hdr.length == 0)
                return 0;

        return x509_parse_ext_alt_name(&cert->subject, hdr.payload,
                                       hdr.length);
}


static int x509_parse_ext_issuer_alt_name(struct x509_certificate *cert,
                                          const u8 *pos, size_t len)
{
        struct asn1_hdr hdr;

        /* IssuerAltName ::= GeneralNames */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE in "
                           "IssuerAltName; found %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        wpa_printf(MSG_DEBUG, "X509: IssuerAltName");
        cert->extensions_present |= X509_EXT_ISSUER_ALT_NAME;

        if (hdr.length == 0)
                return 0;

        return x509_parse_ext_alt_name(&cert->issuer, hdr.payload,
                                       hdr.length);
}


static int x509_parse_extension_data(struct x509_certificate *cert,
                                     struct asn1_oid *oid,
                                     const u8 *pos, size_t len)
{
        if (!x509_id_ce_oid(oid))
                return 1;

        /* TODO: add other extensions required by RFC 3280, Ch 4.2:
         * certificate policies (section 4.2.1.5)
         * name constraints (section 4.2.1.11)
         * policy constraints (section 4.2.1.12)
         * extended key usage (section 4.2.1.13)
         * inhibit any-policy (section 4.2.1.15)
         */
        switch (oid->oid[3]) {
        case 15: /* id-ce-keyUsage */
                return x509_parse_ext_key_usage(cert, pos, len);
        case 17: /* id-ce-subjectAltName */
                return x509_parse_ext_subject_alt_name(cert, pos, len);
        case 18: /* id-ce-issuerAltName */
                return x509_parse_ext_issuer_alt_name(cert, pos, len);
        case 19: /* id-ce-basicConstraints */
                return x509_parse_ext_basic_constraints(cert, pos, len);
        default:
                return 1;
        }
}


static int x509_parse_extension(struct x509_certificate *cert,
                                const u8 *pos, size_t len, const u8 **next)
{
        const u8 *end;
        struct asn1_hdr hdr;
        struct asn1_oid oid;
        int critical_ext = 0, res;
        char buf[80];

        /*
         * Extension  ::=  SEQUENCE  {
         *     extnID      OBJECT IDENTIFIER,
         *     critical    BOOLEAN DEFAULT FALSE,
         *     extnValue   OCTET STRING
         * }
         */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Unexpected ASN.1 header in "
                           "Extensions: class %d tag 0x%x; expected SEQUENCE",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;
        *next = end = pos + hdr.length;

        if (asn1_get_oid(pos, end - pos, &oid, &pos) < 0) {
                wpa_printf(MSG_DEBUG, "X509: Unexpected ASN.1 data for "
                           "Extension (expected OID)");
                return -1;
        }

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            (hdr.tag != ASN1_TAG_BOOLEAN &&
             hdr.tag != ASN1_TAG_OCTETSTRING)) {
                wpa_printf(MSG_DEBUG, "X509: Unexpected ASN.1 header in "
                           "Extensions: class %d tag 0x%x; expected BOOLEAN "
                           "or OCTET STRING", hdr.class, hdr.tag);
                return -1;
        }

        if (hdr.tag == ASN1_TAG_BOOLEAN) {
                if (hdr.length != 1) {
                        wpa_printf(MSG_DEBUG, "X509: Unexpected "
                                   "Boolean length (%u)", hdr.length);
                        return -1;
                }
                critical_ext = hdr.payload[0];
                pos = hdr.payload;
                if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
                    (hdr.class != ASN1_CLASS_UNIVERSAL &&
                     hdr.class != ASN1_CLASS_PRIVATE) ||
                    hdr.tag != ASN1_TAG_OCTETSTRING) {
                        wpa_printf(MSG_DEBUG, "X509: Unexpected ASN.1 header "
                                   "in Extensions: class %d tag 0x%x; "
                                   "expected OCTET STRING",
                                   hdr.class, hdr.tag);
                        return -1;
                }
        }

        asn1_oid_to_str(&oid, buf, sizeof(buf));
        wpa_printf(MSG_DEBUG, "X509: Extension: extnID=%s critical=%d",
                   buf, critical_ext);
        wpa_hexdump(MSG_MSGDUMP, "X509: extnValue", hdr.payload, hdr.length);

        res = x509_parse_extension_data(cert, &oid, hdr.payload, hdr.length);
        if (res < 0)
                return res;
        if (res == 1 && critical_ext) {
                wpa_printf(MSG_INFO, "X509: Unknown critical extension %s",
                           buf);
                return -1;
        }

        return 0;
}


static int x509_parse_extensions(struct x509_certificate *cert,
                                 const u8 *pos, size_t len)
{
        const u8 *end;
        struct asn1_hdr hdr;

        /* Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension */

        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Unexpected ASN.1 data "
                           "for Extensions: class %d tag 0x%x; "
                           "expected SEQUENCE", hdr.class, hdr.tag);
                return -1;
        }

        pos = hdr.payload;
        end = pos + hdr.length;

        while (pos < end) {
                if (x509_parse_extension(cert, pos, end - pos, &pos)
                    < 0)
                        return -1;
        }

        return 0;
}


static int x509_parse_tbs_certificate(const u8 *buf, size_t len,
                                      struct x509_certificate *cert,
                                      const u8 **next)
{
        struct asn1_hdr hdr;
        const u8 *pos, *end;
        size_t left;
        char sbuf[128];
        unsigned long value;

        /* tbsCertificate TBSCertificate ::= SEQUENCE */
        if (asn1_get_next(buf, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: tbsCertificate did not start "
                           "with a valid SEQUENCE - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }
        pos = hdr.payload;
        end = *next = pos + hdr.length;

        /*
         * version [0]  EXPLICIT Version DEFAULT v1
         * Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
         */
        if (asn1_get_next(pos, end - pos, &hdr) < 0)
                return -1;
        pos = hdr.payload;

        if (hdr.class == ASN1_CLASS_CONTEXT_SPECIFIC) {
                if (asn1_get_next(pos, end - pos, &hdr) < 0)
                        return -1;

                if (hdr.class != ASN1_CLASS_UNIVERSAL ||
                    hdr.tag != ASN1_TAG_INTEGER) {
                        wpa_printf(MSG_DEBUG, "X509: No INTEGER tag found for "
                                   "version field - found class %d tag 0x%x",
                                   hdr.class, hdr.tag);
                        return -1;
                }
                if (hdr.length != 1) {
                        wpa_printf(MSG_DEBUG, "X509: Unexpected version field "
                                   "length %u (expected 1)", hdr.length);
                        return -1;
                }
                pos = hdr.payload;
                left = hdr.length;
                value = 0;
                while (left) {
                        value <<= 8;
                        value |= *pos++;
                        left--;
                }

                cert->version = value;
                if (cert->version != X509_CERT_V1 &&
                    cert->version != X509_CERT_V2 &&
                    cert->version != X509_CERT_V3) {
                        wpa_printf(MSG_DEBUG, "X509: Unsupported version %d",
                                   cert->version + 1);
                        return -1;
                }

                if (asn1_get_next(pos, end - pos, &hdr) < 0)
                        return -1;
        } else
                cert->version = X509_CERT_V1;
        wpa_printf(MSG_MSGDUMP, "X509: Version X.509v%d", cert->version + 1);

        /* serialNumber CertificateSerialNumber ::= INTEGER */
        if (hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_INTEGER) {
                wpa_printf(MSG_DEBUG, "X509: No INTEGER tag found for "
                           "serialNumber; class=%d tag=0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        pos = hdr.payload;
        left = hdr.length;
        while (left) {
                cert->serial_number <<= 8;
                cert->serial_number |= *pos++;
                left--;
        }
        wpa_printf(MSG_MSGDUMP, "X509: serialNumber %lu", cert->serial_number);

        /* signature AlgorithmIdentifier */
        if (x509_parse_algorithm_identifier(pos, end - pos, &cert->signature,
                                            &pos))
                return -1;

        /* issuer Name */
        if (x509_parse_name(pos, end - pos, &cert->issuer, &pos))
                return -1;
        x509_name_string(&cert->issuer, sbuf, sizeof(sbuf));
        wpa_printf(MSG_MSGDUMP, "X509: issuer %s", sbuf);

        /* validity Validity */
        if (x509_parse_validity(pos, end - pos, cert, &pos))
                return -1;

        /* subject Name */
        if (x509_parse_name(pos, end - pos, &cert->subject, &pos))
                return -1;
        x509_name_string(&cert->subject, sbuf, sizeof(sbuf));
        wpa_printf(MSG_MSGDUMP, "X509: subject %s", sbuf);

        /* subjectPublicKeyInfo SubjectPublicKeyInfo */
        if (x509_parse_public_key(pos, end - pos, cert, &pos))
                return -1;

        if (pos == end)
                return 0;

        if (cert->version == X509_CERT_V1)
                return 0;

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_CONTEXT_SPECIFIC) {
                wpa_printf(MSG_DEBUG, "X509: Expected Context-Specific"
                           " tag to parse optional tbsCertificate "
                           "field(s); parsed class %d tag 0x%x",
                           hdr.class, hdr.tag);
                return -1;
        }

        if (hdr.tag == 1) {
                /* issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL */
                wpa_printf(MSG_DEBUG, "X509: issuerUniqueID");
                /* TODO: parse UniqueIdentifier ::= BIT STRING */

                if (hdr.payload + hdr.length == end)
                        return 0;

                if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_CONTEXT_SPECIFIC) {
                        wpa_printf(MSG_DEBUG, "X509: Expected Context-Specific"
                                   " tag to parse optional tbsCertificate "
                                   "field(s); parsed class %d tag 0x%x",
                                   hdr.class, hdr.tag);
                        return -1;
                }
        }

        if (hdr.tag == 2) {
                /* subjectUniqueID [2]  IMPLICIT UniqueIdentifier OPTIONAL */
                wpa_printf(MSG_DEBUG, "X509: subjectUniqueID");
                /* TODO: parse UniqueIdentifier ::= BIT STRING */

                if (hdr.payload + hdr.length == end)
                        return 0;

                if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
                    hdr.class != ASN1_CLASS_CONTEXT_SPECIFIC) {
                        wpa_printf(MSG_DEBUG, "X509: Expected Context-Specific"
                                   " tag to parse optional tbsCertificate "
                                   "field(s); parsed class %d tag 0x%x",
                                   hdr.class, hdr.tag);
                        return -1;
                }
        }

        if (hdr.tag != 3) {
                wpa_printf(MSG_DEBUG, "X509: Ignored unexpected "
                           "Context-Specific tag %d in optional "
                           "tbsCertificate fields", hdr.tag);
                return 0;
        }

        /* extensions      [3]  EXPLICIT Extensions OPTIONAL */

        if (cert->version != X509_CERT_V3) {
                wpa_printf(MSG_DEBUG, "X509: X.509%d certificate and "
                           "Extensions data which are only allowed for "
                           "version 3", cert->version + 1);
                return -1;
        }

        if (x509_parse_extensions(cert, hdr.payload, hdr.length) < 0)
                return -1;

        pos = hdr.payload + hdr.length;
        if (pos < end) {
                wpa_hexdump(MSG_DEBUG,
                            "X509: Ignored extra tbsCertificate data",
                            pos, end - pos);
        }

        return 0;
}


static int x509_rsadsi_oid(struct asn1_oid *oid)
{
        return oid->len >= 4 &&
                oid->oid[0] == 1 /* iso */ &&
                oid->oid[1] == 2 /* member-body */ &&
                oid->oid[2] == 840 /* us */ &&
                oid->oid[3] == 113549 /* rsadsi */;
}


static int x509_pkcs_oid(struct asn1_oid *oid)
{
        return oid->len >= 5 &&
                x509_rsadsi_oid(oid) &&
                oid->oid[4] == 1 /* pkcs */;
}


static int x509_digest_oid(struct asn1_oid *oid)
{
        return oid->len >= 5 &&
                x509_rsadsi_oid(oid) &&
                oid->oid[4] == 2 /* digestAlgorithm */;
}


static int x509_sha1_oid(struct asn1_oid *oid)
{
        return oid->len == 6 &&
                oid->oid[0] == 1 /* iso */ &&
                oid->oid[1] == 3 /* identified-organization */ &&
                oid->oid[2] == 14 /* oiw */ &&
                oid->oid[3] == 3 /* secsig */ &&
                oid->oid[4] == 2 /* algorithms */ &&
                oid->oid[5] == 26 /* id-sha1 */;
}


static int x509_sha256_oid(struct asn1_oid *oid)
{
        return oid->len == 9 &&
                oid->oid[0] == 2 /* joint-iso-itu-t */ &&
                oid->oid[1] == 16 /* country */ &&
                oid->oid[2] == 840 /* us */ &&
                oid->oid[3] == 1 /* organization */ &&
                oid->oid[4] == 101 /* gov */ &&
                oid->oid[5] == 3 /* csor */ &&
                oid->oid[6] == 4 /* nistAlgorithm */ &&
                oid->oid[7] == 2 /* hashAlgs */ &&
                oid->oid[8] == 1 /* sha256 */;
}


struct x509_certificate * x509_certificate_parse(const u8 *buf, size_t len)
{
        struct asn1_hdr hdr;
        const u8 *pos, *end, *hash_start;
        struct x509_certificate *cert;

        cert = os_zalloc(sizeof(*cert) + len);
        if (cert == NULL)
                return NULL;
        os_memcpy(cert + 1, buf, len);
        cert->cert_start = (u8 *) (cert + 1);
        cert->cert_len = len;

        pos = buf;
        end = buf + len;

        /* RFC 3280 - X.509 v3 certificate / ASN.1 DER */

        /* Certificate ::= SEQUENCE */
        if (asn1_get_next(pos, len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Certificate did not start with "
                           "a valid SEQUENCE - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                x509_certificate_free(cert);
                return NULL;
        }
        pos = hdr.payload;

        if (pos + hdr.length > end) {
                x509_certificate_free(cert);
                return NULL;
        }

        if (pos + hdr.length < end) {
                wpa_hexdump(MSG_MSGDUMP, "X509: Ignoring extra data after DER "
                            "encoded certificate",
                            pos + hdr.length, end - pos + hdr.length);
                end = pos + hdr.length;
        }

        hash_start = pos;
        cert->tbs_cert_start = cert->cert_start + (hash_start - buf);
        if (x509_parse_tbs_certificate(pos, end - pos, cert, &pos)) {
                x509_certificate_free(cert);
                return NULL;
        }
        cert->tbs_cert_len = pos - hash_start;

        /* signatureAlgorithm AlgorithmIdentifier */
        if (x509_parse_algorithm_identifier(pos, end - pos,
                                            &cert->signature_alg, &pos)) {
                x509_certificate_free(cert);
                return NULL;
        }

        /* signatureValue BIT STRING */
        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_BITSTRING) {
                wpa_printf(MSG_DEBUG, "X509: Expected BITSTRING "
                           "(signatureValue) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                x509_certificate_free(cert);
                return NULL;
        }
        if (hdr.length < 1) {
                x509_certificate_free(cert);
                return NULL;
        }
        pos = hdr.payload;
        if (*pos) {
                wpa_printf(MSG_DEBUG, "X509: BITSTRING - %d unused bits",
                           *pos);
                /* PKCS #1 v1.5 10.2.1:
                 * It is an error if the length in bits of the signature S is
                 * not a multiple of eight.
                 */
                x509_certificate_free(cert);
                return NULL;
        }
        os_free(cert->sign_value);
        cert->sign_value = os_malloc(hdr.length - 1);
        if (cert->sign_value == NULL) {
                wpa_printf(MSG_DEBUG, "X509: Failed to allocate memory for "
                           "signatureValue");
                x509_certificate_free(cert);
                return NULL;
        }
        os_memcpy(cert->sign_value, pos + 1, hdr.length - 1);
        cert->sign_value_len = hdr.length - 1;
        wpa_hexdump(MSG_MSGDUMP, "X509: signature",
                    cert->sign_value, cert->sign_value_len);

        return cert;
}


int x509_certificate_check_signature(struct x509_certificate *issuer,
                                     struct x509_certificate *cert)
{
        struct crypto_public_key *pk;
        u8 *data;
        const u8 *pos, *end, *next, *da_end;
        size_t data_len;
        struct asn1_hdr hdr;
        struct asn1_oid oid;
        u8 hash[32];
        size_t hash_len;

        if (!x509_pkcs_oid(&cert->signature.oid) ||
            cert->signature.oid.len != 7 ||
            cert->signature.oid.oid[5] != 1 /* pkcs-1 */) {
                wpa_printf(MSG_DEBUG, "X509: Unrecognized signature "
                           "algorithm");
                return -1;
        }

        pk = crypto_public_key_import(issuer->public_key,
                                      issuer->public_key_len);
        if (pk == NULL)
                return -1;

        data_len = cert->sign_value_len;
        data = os_malloc(data_len);
        if (data == NULL) {
                crypto_public_key_free(pk);
                return -1;
        }

        if (crypto_public_key_decrypt_pkcs1(pk, cert->sign_value,
                                            cert->sign_value_len, data,
                                            &data_len) < 0) {
                wpa_printf(MSG_DEBUG, "X509: Failed to decrypt signature");
                crypto_public_key_free(pk);
                os_free(data);
                return -1;
        }
        crypto_public_key_free(pk);

        wpa_hexdump(MSG_MSGDUMP, "X509: Signature data D", data, data_len);

        /*
         * PKCS #1 v1.5, 10.1.2:
         *
         * DigestInfo ::= SEQUENCE {
         *     digestAlgorithm DigestAlgorithmIdentifier,
         *     digest Digest
         * }
         *
         * DigestAlgorithmIdentifier ::= AlgorithmIdentifier
         *
         * Digest ::= OCTET STRING
         *
         */
        if (asn1_get_next(data, data_len, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(DigestInfo) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                os_free(data);
                return -1;
        }

        pos = hdr.payload;
        end = pos + hdr.length;

        /*
         * X.509:
         * AlgorithmIdentifier ::= SEQUENCE {
         *     algorithm            OBJECT IDENTIFIER,
         *     parameters           ANY DEFINED BY algorithm OPTIONAL
         * }
         */

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_SEQUENCE) {
                wpa_printf(MSG_DEBUG, "X509: Expected SEQUENCE "
                           "(AlgorithmIdentifier) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                os_free(data);
                return -1;
        }
        da_end = hdr.payload + hdr.length;

        if (asn1_get_oid(hdr.payload, hdr.length, &oid, &next)) {
                wpa_printf(MSG_DEBUG, "X509: Failed to parse digestAlgorithm");
                os_free(data);
                return -1;
        }

        if (x509_sha1_oid(&oid)) {
                if (cert->signature.oid.oid[6] !=
                    5 /* sha-1WithRSAEncryption */) {
                        wpa_printf(MSG_DEBUG, "X509: digestAlgorithm SHA1 "
                                   "does not match with certificate "
                                   "signatureAlgorithm (%lu)",
                                   cert->signature.oid.oid[6]);
                        os_free(data);
                        return -1;
                }
                goto skip_digest_oid;
        }

        if (x509_sha256_oid(&oid)) {
                if (cert->signature.oid.oid[6] !=
                    11 /* sha2561WithRSAEncryption */) {
                        wpa_printf(MSG_DEBUG, "X509: digestAlgorithm SHA256 "
                                   "does not match with certificate "
                                   "signatureAlgorithm (%lu)",
                                   cert->signature.oid.oid[6]);
                        os_free(data);
                        return -1;
                }
                goto skip_digest_oid;
        }

        if (!x509_digest_oid(&oid)) {
                wpa_printf(MSG_DEBUG, "X509: Unrecognized digestAlgorithm");
                os_free(data);
                return -1;
        }
        switch (oid.oid[5]) {
        case 5: /* md5 */
                if (cert->signature.oid.oid[6] != 4 /* md5WithRSAEncryption */)
                {
                        wpa_printf(MSG_DEBUG, "X509: digestAlgorithm MD5 does "
                                   "not match with certificate "
                                   "signatureAlgorithm (%lu)",
                                   cert->signature.oid.oid[6]);
                        os_free(data);
                        return -1;
                }
                break;
        case 2: /* md2 */
        case 4: /* md4 */
        default:
                wpa_printf(MSG_DEBUG, "X509: Unsupported digestAlgorithm "
                           "(%lu)", oid.oid[5]);
                os_free(data);
                return -1;
        }

skip_digest_oid:
        /* Digest ::= OCTET STRING */
        pos = da_end;
        end = data + data_len;

        if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
            hdr.class != ASN1_CLASS_UNIVERSAL ||
            hdr.tag != ASN1_TAG_OCTETSTRING) {
                wpa_printf(MSG_DEBUG, "X509: Expected OCTETSTRING "
                           "(Digest) - found class %d tag 0x%x",
                           hdr.class, hdr.tag);
                os_free(data);
                return -1;
        }
        wpa_hexdump(MSG_MSGDUMP, "X509: Decrypted Digest",
                    hdr.payload, hdr.length);

        switch (cert->signature.oid.oid[6]) {
        case 4: /* md5WithRSAEncryption */
                md5_vector(1, &cert->tbs_cert_start, &cert->tbs_cert_len,
                           hash);
                hash_len = 16;
                wpa_hexdump(MSG_MSGDUMP, "X509: Certificate hash (MD5)",
                            hash, hash_len);
                break;
        case 5: /* sha-1WithRSAEncryption */
                sha1_vector(1, &cert->tbs_cert_start, &cert->tbs_cert_len,
                            hash);
                hash_len = 20;
                wpa_hexdump(MSG_MSGDUMP, "X509: Certificate hash (SHA1)",
                            hash, hash_len);
                break;
        case 11: /* sha256WithRSAEncryption */
                sha256_vector(1, &cert->tbs_cert_start, &cert->tbs_cert_len,
                              hash);
                hash_len = 32;
                wpa_hexdump(MSG_MSGDUMP, "X509: Certificate hash (SHA256)",
                            hash, hash_len);
                break;
        case 2: /* md2WithRSAEncryption */
        case 12: /* sha384WithRSAEncryption */
        case 13: /* sha512WithRSAEncryption */
        default:
                wpa_printf(MSG_INFO, "X509: Unsupported certificate signature "
                           "algorithm (%lu)", cert->signature.oid.oid[6]);
                os_free(data);
                return -1;
        }

        if (hdr.length != hash_len ||
            os_memcmp(hdr.payload, hash, hdr.length) != 0) {
                wpa_printf(MSG_INFO, "X509: Certificate Digest does not match "
                           "with calculated tbsCertificate hash");
                os_free(data);
                return -1;
        }

        os_free(data);

        wpa_printf(MSG_DEBUG, "X509: Certificate Digest matches with "
                   "calculated tbsCertificate hash");

        return 0;
}


static int x509_valid_issuer(const struct x509_certificate *cert)
{
        if ((cert->extensions_present & X509_EXT_BASIC_CONSTRAINTS) &&
            !cert->ca) {
                wpa_printf(MSG_DEBUG, "X509: Non-CA certificate used as an "
                           "issuer");
                return -1;
        }

        if (cert->version == X509_CERT_V3 &&
            !(cert->extensions_present & X509_EXT_BASIC_CONSTRAINTS)) {
                wpa_printf(MSG_DEBUG, "X509: v3 CA certificate did not "
                           "include BasicConstraints extension");
                return -1;
        }

        if ((cert->extensions_present & X509_EXT_KEY_USAGE) &&
            !(cert->key_usage & X509_KEY_USAGE_KEY_CERT_SIGN)) {
                wpa_printf(MSG_DEBUG, "X509: Issuer certificate did not have "
                           "keyCertSign bit in Key Usage");
                return -1;
        }

        return 0;
}


int x509_certificate_chain_validate(struct x509_certificate *trusted,
                                    struct x509_certificate *chain,
                                    int *reason)
{
        long unsigned idx;
        int chain_trusted = 0;
        struct x509_certificate *cert, *trust;
        char buf[128];
        struct os_time now;

        *reason = X509_VALIDATE_OK;

        wpa_printf(MSG_DEBUG, "X509: Validate certificate chain");
        os_get_time(&now);

        for (cert = chain, idx = 0; cert; cert = cert->next, idx++) {
                x509_name_string(&cert->subject, buf, sizeof(buf)); 
                wpa_printf(MSG_DEBUG, "X509: %lu: %s", idx, buf);

                if (chain_trusted)
                        continue;

                if ((unsigned long) now.sec <
                    (unsigned long) cert->not_before ||
                    (unsigned long) now.sec >
                    (unsigned long) cert->not_after) {
                        wpa_printf(MSG_INFO, "X509: Certificate not valid "
                                   "(now=%lu not_before=%lu not_after=%lu)",
                                   now.sec, cert->not_before, cert->not_after);
                        *reason = X509_VALIDATE_CERTIFICATE_EXPIRED;
                        return -1;
                }

                if (cert->next) {
                        if (x509_name_compare(&cert->issuer,
                                              &cert->next->subject) != 0) {
                                wpa_printf(MSG_DEBUG, "X509: Certificate "
                                           "chain issuer name mismatch");
                                x509_name_string(&cert->issuer, buf,
                                                 sizeof(buf)); 
                                wpa_printf(MSG_DEBUG, "X509: cert issuer: %s",
                                           buf);
                                x509_name_string(&cert->next->subject, buf,
                                                 sizeof(buf)); 
                                wpa_printf(MSG_DEBUG, "X509: next cert "
                                           "subject: %s", buf);
                                *reason = X509_VALIDATE_CERTIFICATE_UNKNOWN;
                                return -1;
                        }

                        if (x509_valid_issuer(cert->next) < 0) {
                                *reason = X509_VALIDATE_BAD_CERTIFICATE;
                                return -1;
                        }

                        if ((cert->next->extensions_present &
                             X509_EXT_PATH_LEN_CONSTRAINT) &&
                            idx > cert->next->path_len_constraint) {
                                wpa_printf(MSG_DEBUG, "X509: pathLenConstraint"
                                           " not met (idx=%lu issuer "
                                           "pathLenConstraint=%lu)", idx,
                                           cert->next->path_len_constraint);
                                *reason = X509_VALIDATE_BAD_CERTIFICATE;
                                return -1;
                        }

                        if (x509_certificate_check_signature(cert->next, cert)
                            < 0) {
                                wpa_printf(MSG_DEBUG, "X509: Invalid "
                                           "certificate signature within "
                                           "chain");
                                *reason = X509_VALIDATE_BAD_CERTIFICATE;
                                return -1;
                        }
                }

                for (trust = trusted; trust; trust = trust->next) {
                        if (x509_name_compare(&cert->issuer, &trust->subject)
                            == 0)
                                break;
                }

                if (trust) {
                        wpa_printf(MSG_DEBUG, "X509: Found issuer from the "
                                   "list of trusted certificates");
                        if (x509_valid_issuer(trust) < 0) {
                                *reason = X509_VALIDATE_BAD_CERTIFICATE;
                                return -1;
                        }

                        if (x509_certificate_check_signature(trust, cert) < 0)
                        {
                                wpa_printf(MSG_DEBUG, "X509: Invalid "
                                           "certificate signature");
                                *reason = X509_VALIDATE_BAD_CERTIFICATE;
                                return -1;
                        }

                        wpa_printf(MSG_DEBUG, "X509: Trusted certificate "
                                   "found to complete the chain");
                        chain_trusted = 1;
                }
        }

        if (!chain_trusted) {
                wpa_printf(MSG_DEBUG, "X509: Did not find any of the issuers "
                           "from the list of trusted certificates");
                if (trusted) {
                        *reason = X509_VALIDATE_UNKNOWN_CA;
                        return -1;
                }
                wpa_printf(MSG_DEBUG, "X509: Certificate chain validation "
                           "disabled - ignore unknown CA issue");
        }

        wpa_printf(MSG_DEBUG, "X509: Certificate chain valid");

        return 0;
}


struct x509_certificate *
x509_certificate_get_subject(struct x509_certificate *chain,
                             struct x509_name *name)
{
        struct x509_certificate *cert;

        for (cert = chain; cert; cert = cert->next) {
                if (x509_name_compare(&cert->subject, name) == 0)
                        return cert;
        }
        return NULL;
}


int x509_certificate_self_signed(struct x509_certificate *cert)
{
        return x509_name_compare(&cert->issuer, &cert->subject) == 0;
}