eap_server_tls_common.c

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/*
 * EAP-TLS/PEAP/TTLS/FAST server common functions
 * Copyright (c) 2004-2009, 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/sha1.h"
#include "crypto/tls.h"
#include "eap_i.h"
#include "eap_tls_common.h"


static void eap_server_tls_free_in_buf(struct eap_ssl_data *data);


int eap_server_tls_ssl_init(struct eap_sm *sm, struct eap_ssl_data *data,
                            int verify_peer)
{
        data->eap = sm;
        data->phase2 = sm->init_phase2;

        data->conn = tls_connection_init(sm->ssl_ctx);
        if (data->conn == NULL) {
                wpa_printf(MSG_INFO, "SSL: Failed to initialize new TLS "
                           "connection");
                return -1;
        }

        if (tls_connection_set_verify(sm->ssl_ctx, data->conn, verify_peer)) {
                wpa_printf(MSG_INFO, "SSL: Failed to configure verification "
                           "of TLS peer certificate");
                tls_connection_deinit(sm->ssl_ctx, data->conn);
                data->conn = NULL;
                return -1;
        }

        /* TODO: make this configurable */
        data->tls_out_limit = 1398;
        if (data->phase2) {
                /* Limit the fragment size in the inner TLS authentication
                 * since the outer authentication with EAP-PEAP does not yet
                 * support fragmentation */
                if (data->tls_out_limit > 100)
                        data->tls_out_limit -= 100;
        }
        return 0;
}


void eap_server_tls_ssl_deinit(struct eap_sm *sm, struct eap_ssl_data *data)
{
        tls_connection_deinit(sm->ssl_ctx, data->conn);
        eap_server_tls_free_in_buf(data);
        wpabuf_free(data->tls_out);
        data->tls_out = NULL;
}


u8 * eap_server_tls_derive_key(struct eap_sm *sm, struct eap_ssl_data *data,
                               char *label, size_t len)
{
        struct tls_keys keys;
        u8 *rnd = NULL, *out;

        out = os_malloc(len);
        if (out == NULL)
                return NULL;

        if (tls_connection_prf(sm->ssl_ctx, data->conn, label, 0, out, len) ==
            0)
                return out;

        if (tls_connection_get_keys(sm->ssl_ctx, data->conn, &keys))
                goto fail;

        if (keys.client_random == NULL || keys.server_random == NULL ||
            keys.master_key == NULL)
                goto fail;

        rnd = os_malloc(keys.client_random_len + keys.server_random_len);
        if (rnd == NULL)
                goto fail;
        os_memcpy(rnd, keys.client_random, keys.client_random_len);
        os_memcpy(rnd + keys.client_random_len, keys.server_random,
                  keys.server_random_len);

        if (tls_prf(keys.master_key, keys.master_key_len,
                    label, rnd, keys.client_random_len +
                    keys.server_random_len, out, len))
                goto fail;

        os_free(rnd);
        return out;

fail:
        os_free(out);
        os_free(rnd);
        return NULL;
}


struct wpabuf * eap_server_tls_build_msg(struct eap_ssl_data *data,
                                         int eap_type, int version, u8 id)
{
        struct wpabuf *req;
        u8 flags;
        size_t send_len, plen;

        wpa_printf(MSG_DEBUG, "SSL: Generating Request");
        if (data->tls_out == NULL) {
                wpa_printf(MSG_ERROR, "SSL: tls_out NULL in %s", __func__);
                return NULL;
        }

        flags = version;
        send_len = wpabuf_len(data->tls_out) - data->tls_out_pos;
        if (1 + send_len > data->tls_out_limit) {
                send_len = data->tls_out_limit - 1;
                flags |= EAP_TLS_FLAGS_MORE_FRAGMENTS;
                if (data->tls_out_pos == 0) {
                        flags |= EAP_TLS_FLAGS_LENGTH_INCLUDED;
                        send_len -= 4;
                }
        }

        plen = 1 + send_len;
        if (flags & EAP_TLS_FLAGS_LENGTH_INCLUDED)
                plen += 4;

        req = eap_msg_alloc(EAP_VENDOR_IETF, eap_type, plen,
                            EAP_CODE_REQUEST, id);
        if (req == NULL)
                return NULL;

        wpabuf_put_u8(req, flags); /* Flags */
        if (flags & EAP_TLS_FLAGS_LENGTH_INCLUDED)
                wpabuf_put_be32(req, wpabuf_len(data->tls_out));

        wpabuf_put_data(req, wpabuf_head_u8(data->tls_out) + data->tls_out_pos,
                        send_len);
        data->tls_out_pos += send_len;

        if (data->tls_out_pos == wpabuf_len(data->tls_out)) {
                wpa_printf(MSG_DEBUG, "SSL: Sending out %lu bytes "
                           "(message sent completely)",
                           (unsigned long) send_len);
                wpabuf_free(data->tls_out);
                data->tls_out = NULL;
                data->tls_out_pos = 0;
                data->state = MSG;
        } else {
                wpa_printf(MSG_DEBUG, "SSL: Sending out %lu bytes "
                           "(%lu more to send)", (unsigned long) send_len,
                           (unsigned long) wpabuf_len(data->tls_out) -
                           data->tls_out_pos);
                data->state = WAIT_FRAG_ACK;
        }

        return req;
}


struct wpabuf * eap_server_tls_build_ack(u8 id, int eap_type, int version)
{
        struct wpabuf *req;

        req = eap_msg_alloc(EAP_VENDOR_IETF, eap_type, 1, EAP_CODE_REQUEST,
                            id);
        if (req == NULL)
                return NULL;
        wpa_printf(MSG_DEBUG, "SSL: Building ACK");
        wpabuf_put_u8(req, version); /* Flags */
        return req;
}


static int eap_server_tls_process_cont(struct eap_ssl_data *data,
                                       const u8 *buf, size_t len)
{
        /* Process continuation of a pending message */
        if (len > wpabuf_tailroom(data->tls_in)) {
                wpa_printf(MSG_DEBUG, "SSL: Fragment overflow");
                return -1;
        }

        wpabuf_put_data(data->tls_in, buf, len);
        wpa_printf(MSG_DEBUG, "SSL: Received %lu bytes, waiting for %lu "
                   "bytes more", (unsigned long) len,
                   (unsigned long) wpabuf_tailroom(data->tls_in));

        return 0;
}


static int eap_server_tls_process_fragment(struct eap_ssl_data *data,
                                           u8 flags, u32 message_length,
                                           const u8 *buf, size_t len)
{
        /* Process a fragment that is not the last one of the message */
        if (data->tls_in == NULL && !(flags & EAP_TLS_FLAGS_LENGTH_INCLUDED)) {
                wpa_printf(MSG_DEBUG, "SSL: No Message Length field in a "
                           "fragmented packet");
                return -1;
        }

        if (data->tls_in == NULL) {
                /* First fragment of the message */

                /* Limit length to avoid rogue peers from causing large
                 * memory allocations. */
                if (message_length > 65536) {
                        wpa_printf(MSG_INFO, "SSL: Too long TLS fragment (size"
                                   " over 64 kB)");
                        return -1;
                }

                data->tls_in = wpabuf_alloc(message_length);
                if (data->tls_in == NULL) {
                        wpa_printf(MSG_DEBUG, "SSL: No memory for message");
                        return -1;
                }
                wpabuf_put_data(data->tls_in, buf, len);
                wpa_printf(MSG_DEBUG, "SSL: Received %lu bytes in first "
                           "fragment, waiting for %lu bytes more",
                           (unsigned long) len,
                           (unsigned long) wpabuf_tailroom(data->tls_in));
        }

        return 0;
}


int eap_server_tls_phase1(struct eap_sm *sm, struct eap_ssl_data *data)
{
        if (data->tls_out) {
                /* This should not happen.. */
                wpa_printf(MSG_INFO, "SSL: pending tls_out data when "
                           "processing new message");
                wpabuf_free(data->tls_out);
                WPA_ASSERT(data->tls_out == NULL);
        }

        data->tls_out = tls_connection_server_handshake(sm->ssl_ctx,
                                                        data->conn,
                                                        data->tls_in, NULL);
        if (data->tls_out == NULL) {
                wpa_printf(MSG_INFO, "SSL: TLS processing failed");
                return -1;
        }
        if (tls_connection_get_failed(sm->ssl_ctx, data->conn)) {
                /* TLS processing has failed - return error */
                wpa_printf(MSG_DEBUG, "SSL: Failed - tls_out available to "
                           "report error");
                return -1;
        }

        return 0;
}


static int eap_server_tls_reassemble(struct eap_ssl_data *data, u8 flags,
                                     const u8 **pos, size_t *left)
{
        unsigned int tls_msg_len = 0;
        const u8 *end = *pos + *left;

        if (flags & EAP_TLS_FLAGS_LENGTH_INCLUDED) {
                if (*left < 4) {
                        wpa_printf(MSG_INFO, "SSL: Short frame with TLS "
                                   "length");
                        return -1;
                }
                tls_msg_len = WPA_GET_BE32(*pos);
                wpa_printf(MSG_DEBUG, "SSL: TLS Message Length: %d",
                           tls_msg_len);
                *pos += 4;
                *left -= 4;
        }

        wpa_printf(MSG_DEBUG, "SSL: Received packet: Flags 0x%x "
                   "Message Length %u", flags, tls_msg_len);

        if (data->state == WAIT_FRAG_ACK) {
                if (*left != 0) {
                        wpa_printf(MSG_DEBUG, "SSL: Unexpected payload in "
                                   "WAIT_FRAG_ACK state");
                        return -1;
                }
                wpa_printf(MSG_DEBUG, "SSL: Fragment acknowledged");
                return 1;
        }

        if (data->tls_in &&
            eap_server_tls_process_cont(data, *pos, end - *pos) < 0)
                return -1;
                
        if (flags & EAP_TLS_FLAGS_MORE_FRAGMENTS) {
                if (eap_server_tls_process_fragment(data, flags, tls_msg_len,
                                                    *pos, end - *pos) < 0)
                        return -1;

                data->state = FRAG_ACK;
                return 1;
        }

        if (data->state == FRAG_ACK) {
                wpa_printf(MSG_DEBUG, "SSL: All fragments received");
                data->state = MSG;
        }

        if (data->tls_in == NULL) {
                /* Wrap unfragmented messages as wpabuf without extra copy */
                wpabuf_set(&data->tmpbuf, *pos, end - *pos);
                data->tls_in = &data->tmpbuf;
        }

        return 0;
}


static void eap_server_tls_free_in_buf(struct eap_ssl_data *data)
{
        if (data->tls_in != &data->tmpbuf)
                wpabuf_free(data->tls_in);
        data->tls_in = NULL;
}


struct wpabuf * eap_server_tls_encrypt(struct eap_sm *sm,
                                       struct eap_ssl_data *data,
                                       const struct wpabuf *plain)
{
        struct wpabuf *buf;

        buf = tls_connection_encrypt(sm->ssl_ctx, data->conn,
                                     plain);
        if (buf == NULL) {
                wpa_printf(MSG_INFO, "SSL: Failed to encrypt Phase 2 data");
                return NULL;
        }

        return buf;
}


int eap_server_tls_process(struct eap_sm *sm, struct eap_ssl_data *data,
                           struct wpabuf *respData, void *priv, int eap_type,
                           int (*proc_version)(struct eap_sm *sm, void *priv,
                                               int peer_version),
                           void (*proc_msg)(struct eap_sm *sm, void *priv,
                                            const struct wpabuf *respData))
{
        const u8 *pos;
        u8 flags;
        size_t left;
        int ret, res = 0;

        pos = eap_hdr_validate(EAP_VENDOR_IETF, eap_type, respData, &left);
        if (pos == NULL || left < 1)
                return 0; /* Should not happen - frame already validated */
        flags = *pos++;
        left--;
        wpa_printf(MSG_DEBUG, "SSL: Received packet(len=%lu) - Flags 0x%02x",
                   (unsigned long) wpabuf_len(respData), flags);

        if (proc_version &&
            proc_version(sm, priv, flags & EAP_TLS_VERSION_MASK) < 0)
                return -1;

        ret = eap_server_tls_reassemble(data, flags, &pos, &left);
        if (ret < 0) {
                res = -1;
                goto done;
        } else if (ret == 1)
                return 0;

        if (proc_msg)
                proc_msg(sm, priv, respData);

        if (tls_connection_get_write_alerts(sm->ssl_ctx, data->conn) > 1) {
                wpa_printf(MSG_INFO, "SSL: Locally detected fatal error in "
                           "TLS processing");
                res = -1;
        }

done:
        eap_server_tls_free_in_buf(data);

        return res;
}