Diff: library/ssl_ticket.c

Revision:

0:cdf462088d13

diff -r 000000000000 -r cdf462088d13 library/ssl_ticket.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/library/ssl_ticket.c	Thu Jan 05 00:18:44 2017 +0000
@@ -0,0 +1,489 @@
+/*
+ *  TLS server tickets callbacks implementation
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_SSL_TICKET_C)
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdlib.h>
+#define mbedtls_calloc    calloc
+#define mbedtls_free      free
+#endif
+
+#include "mbedtls/ssl_ticket.h"
+
+#include <string.h>
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+/*
+ * Initialze context
+ */
+void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
+{
+    memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
+
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_init( &ctx->mutex );
+#endif
+}
+
+#define MAX_KEY_BYTES 32    /* 256 bits */
+
+/*
+ * Generate/update a key
+ */
+static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
+                               unsigned char index )
+{
+    int ret;
+    unsigned char buf[MAX_KEY_BYTES];
+    mbedtls_ssl_ticket_key *key = ctx->keys + index;
+
+#if defined(MBEDTLS_HAVE_TIME)
+    key->generation_time = (uint32_t) mbedtls_time( NULL );
+#endif
+
+    if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
+        return( ret );
+
+    if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
+        return( ret );
+
+    /* With GCM and CCM, same context can encrypt & decrypt */
+    ret = mbedtls_cipher_setkey( &key->ctx, buf,
+                                 mbedtls_cipher_get_key_bitlen( &key->ctx ),
+                                 MBEDTLS_ENCRYPT );
+
+    mbedtls_zeroize( buf, sizeof( buf ) );
+
+    return( ret );
+}
+
+/*
+ * Rotate/generate keys if necessary
+ */
+static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
+{
+#if !defined(MBEDTLS_HAVE_TIME)
+    ((void) ctx);
+#else
+    if( ctx->ticket_lifetime != 0 )
+    {
+        uint32_t current_time = (uint32_t) mbedtls_time( NULL );
+        uint32_t key_time = ctx->keys[ctx->active].generation_time;
+
+        if( current_time > key_time &&
+            current_time - key_time < ctx->ticket_lifetime )
+        {
+            return( 0 );
+        }
+
+        ctx->active = 1 - ctx->active;
+
+        return( ssl_ticket_gen_key( ctx, ctx->active ) );
+    }
+    else
+#endif /* MBEDTLS_HAVE_TIME */
+        return( 0 );
+}
+
+/*
+ * Setup context for actual use
+ */
+int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
+    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+    mbedtls_cipher_type_t cipher,
+    uint32_t lifetime )
+{
+    int ret;
+    const mbedtls_cipher_info_t *cipher_info;
+
+    ctx->f_rng = f_rng;
+    ctx->p_rng = p_rng;
+
+    ctx->ticket_lifetime = lifetime;
+
+    cipher_info = mbedtls_cipher_info_from_type( cipher);
+    if( cipher_info == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    if( cipher_info->mode != MBEDTLS_MODE_GCM &&
+        cipher_info->mode != MBEDTLS_MODE_CCM )
+    {
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+    }
+
+    if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 ||
+        ( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
+        ( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    return( 0 );
+}
+
+/*
+ * Serialize a session in the following format:
+ *  0   .   n-1     session structure, n = sizeof(mbedtls_ssl_session)
+ *  n   .   n+2     peer_cert length = m (0 if no certificate)
+ *  n+3 .   n+2+m   peer cert ASN.1
+ */
+static int ssl_save_session( const mbedtls_ssl_session *session,
+                             unsigned char *buf, size_t buf_len,
+                             size_t *olen )
+{
+    unsigned char *p = buf;
+    size_t left = buf_len;
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    size_t cert_len;
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+    if( left < sizeof( mbedtls_ssl_session ) )
+        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
+
+    memcpy( p, session, sizeof( mbedtls_ssl_session ) );
+    p += sizeof( mbedtls_ssl_session );
+    left -= sizeof( mbedtls_ssl_session );
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    if( session->peer_cert == NULL )
+        cert_len = 0;
+    else
+        cert_len = session->peer_cert->raw.len;
+
+    if( left < 3 + cert_len )
+        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
+
+    *p++ = (unsigned char)( cert_len >> 16 & 0xFF );
+    *p++ = (unsigned char)( cert_len >>  8 & 0xFF );
+    *p++ = (unsigned char)( cert_len       & 0xFF );
+
+    if( session->peer_cert != NULL )
+        memcpy( p, session->peer_cert->raw.p, cert_len );
+
+    p += cert_len;
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+    *olen = p - buf;
+
+    return( 0 );
+}
+
+/*
+ * Unserialise session, see ssl_save_session()
+ */
+static int ssl_load_session( mbedtls_ssl_session *session,
+                             const unsigned char *buf, size_t len )
+{
+    const unsigned char *p = buf;
+    const unsigned char * const end = buf + len;
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    size_t cert_len;
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+    if( p + sizeof( mbedtls_ssl_session ) > end )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    memcpy( session, p, sizeof( mbedtls_ssl_session ) );
+    p += sizeof( mbedtls_ssl_session );
+
+#if defined(MBEDTLS_X509_CRT_PARSE_C)
+    if( p + 3 > end )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
+    p += 3;
+
+    if( cert_len == 0 )
+    {
+        session->peer_cert = NULL;
+    }
+    else
+    {
+        int ret;
+
+        if( p + cert_len > end )
+            return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+        session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
+
+        if( session->peer_cert == NULL )
+            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+
+        mbedtls_x509_crt_init( session->peer_cert );
+
+        if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
+                                        p, cert_len ) ) != 0 )
+        {
+            mbedtls_x509_crt_free( session->peer_cert );
+            mbedtls_free( session->peer_cert );
+            session->peer_cert = NULL;
+            return( ret );
+        }
+
+        p += cert_len;
+    }
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
+
+    if( p != end )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    return( 0 );
+}
+
+/*
+ * Create session ticket, with the following structure:
+ *
+ *    struct {
+ *        opaque key_name[4];
+ *        opaque iv[12];
+ *        opaque encrypted_state<0..2^16-1>;
+ *        opaque tag[16];
+ *    } ticket;
+ *
+ * The key_name, iv, and length of encrypted_state are the additional
+ * authenticated data.
+ */
+int mbedtls_ssl_ticket_write( void *p_ticket,
+                              const mbedtls_ssl_session *session,
+                              unsigned char *start,
+                              const unsigned char *end,
+                              size_t *tlen,
+                              uint32_t *ticket_lifetime )
+{
+    int ret;
+    mbedtls_ssl_ticket_context *ctx = p_ticket;
+    mbedtls_ssl_ticket_key *key;
+    unsigned char *key_name = start;
+    unsigned char *iv = start + 4;
+    unsigned char *state_len_bytes = iv + 12;
+    unsigned char *state = state_len_bytes + 2;
+    unsigned char *tag;
+    size_t clear_len, ciph_len;
+
+    *tlen = 0;
+
+    if( ctx == NULL || ctx->f_rng == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
+     * in addition to session itself, that will be checked when writing it. */
+    if( end - start < 4 + 12 + 2 + 16 )
+        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
+        goto cleanup;
+
+    key = &ctx->keys[ctx->active];
+
+    *ticket_lifetime = ctx->ticket_lifetime;
+
+    memcpy( key_name, key->name, 4 );
+
+    if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
+        goto cleanup;
+
+    /* Dump session state */
+    if( ( ret = ssl_save_session( session,
+                                  state, end - state, &clear_len ) ) != 0 ||
+        (unsigned long) clear_len > 65535 )
+    {
+         goto cleanup;
+    }
+    state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
+    state_len_bytes[1] = ( clear_len      ) & 0xff;
+
+    /* Encrypt and authenticate */
+    tag = state + clear_len;
+    if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx,
+                    iv, 12, key_name, 4 + 12 + 2,
+                    state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
+    {
+        goto cleanup;
+    }
+    if( ciph_len != clear_len )
+    {
+        ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
+        goto cleanup;
+    }
+
+    *tlen = 4 + 12 + 2 + 16 + ciph_len;
+
+cleanup:
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Select key based on name
+ */
+static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
+        mbedtls_ssl_ticket_context *ctx,
+        const unsigned char name[4] )
+{
+    unsigned char i;
+
+    for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
+        if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
+            return( &ctx->keys[i] );
+
+    return( NULL );
+}
+
+/*
+ * Load session ticket (see mbedtls_ssl_ticket_write for structure)
+ */
+int mbedtls_ssl_ticket_parse( void *p_ticket,
+                              mbedtls_ssl_session *session,
+                              unsigned char *buf,
+                              size_t len )
+{
+    int ret;
+    mbedtls_ssl_ticket_context *ctx = p_ticket;
+    mbedtls_ssl_ticket_key *key;
+    unsigned char *key_name = buf;
+    unsigned char *iv = buf + 4;
+    unsigned char *enc_len_p = iv + 12;
+    unsigned char *ticket = enc_len_p + 2;
+    unsigned char *tag;
+    size_t enc_len, clear_len;
+
+    if( ctx == NULL || ctx->f_rng == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+    /* See mbedtls_ssl_ticket_write() */
+    if( len < 4 + 12 + 2 + 16 )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
+#if defined(MBEDTLS_THREADING_C)
+    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
+        return( ret );
+#endif
+
+    if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
+        goto cleanup;
+
+    enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
+    tag = ticket + enc_len;
+
+    if( len != 4 + 12 + 2 + enc_len + 16 )
+    {
+        ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
+        goto cleanup;
+    }
+
+    /* Select key */
+    if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
+    {
+        /* We can't know for sure but this is a likely option unless we're
+         * under attack - this is only informative anyway */
+        ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
+        goto cleanup;
+    }
+
+    /* Decrypt and authenticate */
+    if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx, iv, 12,
+                    key_name, 4 + 12 + 2, ticket, enc_len,
+                    ticket, &clear_len, tag, 16 ) ) != 0 )
+    {
+        if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
+            ret = MBEDTLS_ERR_SSL_INVALID_MAC;
+
+        goto cleanup;
+    }
+    if( clear_len != enc_len )
+    {
+        ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
+        goto cleanup;
+    }
+
+    /* Actually load session */
+    if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
+        goto cleanup;
+
+#if defined(MBEDTLS_HAVE_TIME)
+    {
+        /* Check for expiration */
+        mbedtls_time_t current_time = mbedtls_time( NULL );
+
+        if( current_time < session->start ||
+            (uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
+        {
+            ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
+            goto cleanup;
+        }
+    }
+#endif
+
+cleanup:
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
+        return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
+#endif
+
+    return( ret );
+}
+
+/*
+ * Free context
+ */
+void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
+{
+    mbedtls_cipher_free( &ctx->keys[0].ctx );
+    mbedtls_cipher_free( &ctx->keys[1].ctx );
+
+#if defined(MBEDTLS_THREADING_C)
+    mbedtls_mutex_free( &ctx->mutex );
+#endif
+
+    mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
+}
+
+#endif /* MBEDTLS_SSL_TICKET_C */