mirror of
https://github.com/yuzu-emu/mbedtls.git
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Use AES-GCM-256 for session ticket protection
This commit is contained in:
Manuel Pégourié-Gonnard
parent
8eff512274
commit
1041a39338
@ -25,7 +25,7 @@
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#define MBEDTLS_SSL_TICKET_H
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#include "ssl.h"
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#include "aes.h"
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#include "cipher.h"
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#if defined(MBEDTLS_THREADING_C)
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#include "threading.h"
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@ -40,10 +40,8 @@ extern "C" {
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*/
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typedef struct
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{
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unsigned char key_name[16]; /*!< name to quickly reject bad tickets */
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mbedtls_aes_context enc; /*!< encryption context */
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mbedtls_aes_context dec; /*!< decryption context */
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unsigned char mac_key[16]; /*!< authentication key */
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unsigned char key_name[4]; /*!< name to quickly reject bad tickets */
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mbedtls_cipher_context_t cipher;/*!< cipher context */
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uint32_t ticket_lifetime; /*!< lifetime of tickets in seconds */
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@ -64,33 +64,39 @@ int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
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uint32_t lifetime )
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{
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int ret;
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unsigned char buf[16];
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unsigned char buf[32];
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ctx->f_rng = f_rng;
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ctx->p_rng = p_rng;
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ctx->ticket_lifetime = lifetime;
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mbedtls_aes_init( &ctx->enc );
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mbedtls_aes_init( &ctx->dec );
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if( ( ret = f_rng( p_rng, ctx->key_name, 16 ) != 0 ) ||
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( ret = f_rng( p_rng, ctx->mac_key, 16 ) != 0 ) ||
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( ret = f_rng( p_rng, buf, 16 ) != 0 ) )
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if( ( ret = mbedtls_cipher_setup( &ctx->cipher,
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mbedtls_cipher_info_from_type(
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MBEDTLS_CIPHER_AES_256_GCM ) ) ) != 0 )
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{
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return( ret );
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goto cleanup;
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}
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if( ( ret = mbedtls_aes_setkey_enc( &ctx->enc, buf, 128 ) ) != 0 ||
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( ret = mbedtls_aes_setkey_dec( &ctx->dec, buf, 128 ) ) != 0 )
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if( ( ret = f_rng( p_rng, buf, sizeof( buf ) ) != 0 ) )
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{
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mbedtls_ssl_ticket_free( ctx );
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return( ret );
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goto cleanup;
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}
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/* With GCM and CCM, same context can encrypt & decrypt */
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if( ( ret = mbedtls_cipher_setkey( &ctx->cipher, buf, 256,
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MBEDTLS_ENCRYPT ) ) != 0 )
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{
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goto cleanup;
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}
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cleanup:
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mbedtls_zeroize( buf, sizeof( buf ) );
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return( 0 );
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if( ret != 0 )
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mbedtls_ssl_ticket_free( ctx );
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return( ret );
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}
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/*
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@ -203,16 +209,17 @@ static int ssl_load_session( mbedtls_ssl_session *session,
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}
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/*
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* Create session ticket, secured as recommended in RFC 5077 section 4:
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* Create session ticket, with the following structure:
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*
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* struct {
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* opaque key_name[16];
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* opaque iv[16];
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* opaque key_name[4];
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* opaque iv[12];
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* opaque encrypted_state<0..2^16-1>;
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* opaque mac[32];
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* opaque tag[16];
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* } ticket;
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*
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* (the internal state structure differs, however).
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* The key_name, iv, and length of encrypted_state are the additional
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* authenticated data.
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*/
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int mbedtls_ssl_ticket_write( void *p_ticket,
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const mbedtls_ssl_session *session,
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@ -223,20 +230,21 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
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{
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int ret;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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unsigned char *p = start;
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unsigned char *state;
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unsigned char iv[16];
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size_t clear_len, enc_len, pad_len, i;
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unsigned char *key_name = start;
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unsigned char *iv = start + 4;
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unsigned char *state_len_bytes = iv + 12;
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unsigned char *state = state_len_bytes + 2;
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unsigned char *tag;
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size_t clear_len, ciph_len;
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*tlen = 0;
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if( ctx == NULL )
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if( ctx == NULL || ctx->f_rng == NULL )
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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/* We need at least 16 bytes for key_name, 16 for IV, 2 for len
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* 16 for padding, 32 for MAC, in addition to session itself,
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* that will be checked when writing it. */
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if( end - start < 16 + 16 + 2 + 16 + 32 )
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/* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
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* in addition to session itself, that will be checked when writing it. */
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if( end - start < 4 + 12 + 2 + 16 )
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return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
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#if defined(MBEDTLS_THREADING_C)
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@ -246,52 +254,36 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
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*ticket_lifetime = ctx->ticket_lifetime;
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/* Write key name */
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memcpy( p, ctx->key_name, 16 );
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p += 16;
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memcpy( key_name, ctx->key_name, 4 );
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/* Generate and write IV (with a copy for aes_crypt) */
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if( ( ret = ctx->f_rng( ctx->p_rng, p, 16 ) ) != 0 )
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if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
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goto cleanup;
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memcpy( iv, p, 16 );
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p += 16;
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/* Dump session state */
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state = p + 2;
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if( ( ret = ssl_save_session( session,
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state, end - state, &clear_len ) ) != 0 )
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state, end - state, &clear_len ) ) != 0 ||
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(unsigned long) clear_len > 65535 )
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{
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goto cleanup;
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}
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state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
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state_len_bytes[1] = ( clear_len ) & 0xff;
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/* Apply PKCS padding */
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pad_len = 16 - clear_len % 16;
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enc_len = clear_len + pad_len;
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for( i = clear_len; i < enc_len; i++ )
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state[i] = (unsigned char) pad_len;
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/* Encrypt */
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if( ( ret = mbedtls_aes_crypt_cbc( &ctx->enc, MBEDTLS_AES_ENCRYPT,
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enc_len, iv, state, state ) ) != 0 )
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/* Encrypt and authenticate */
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tag = state + clear_len;
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if( ( ret = mbedtls_cipher_auth_encrypt( &ctx->cipher,
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iv, 12, key_name, 4 + 12 + 2,
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state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
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{
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goto cleanup;
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}
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/* Write length */
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*p++ = (unsigned char)( ( enc_len >> 8 ) & 0xFF );
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*p++ = (unsigned char)( ( enc_len ) & 0xFF );
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p = state + enc_len;
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/* Compute and write MAC( key_name + iv + enc_state_len + enc_state ) */
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if( ( ret = mbedtls_md_hmac( mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ),
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ctx->mac_key, 16,
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start, p - start, p ) ) != 0 )
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if( ciph_len != clear_len )
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{
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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}
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p += 32;
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*tlen = p - start;
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*tlen = 4 + 12 + 2 + 16 + ciph_len;
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cleanup:
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#if defined(MBEDTLS_THREADING_C)
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@ -313,16 +305,17 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
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int ret;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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unsigned char *key_name = buf;
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unsigned char *iv = buf + 16;
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unsigned char *enc_len_p = iv + 16;
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unsigned char *iv = buf + 4;
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unsigned char *enc_len_p = iv + 12;
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unsigned char *ticket = enc_len_p + 2;
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unsigned char *mac;
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unsigned char computed_mac[32];
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size_t enc_len, clear_len, i;
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unsigned char pad_len, diff;
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unsigned char *tag;
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size_t enc_len, clear_len;
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if( len < 34 || ctx == NULL )
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if( ctx == NULL || ctx->f_rng == NULL ||
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len < 4 + 12 + 2 + 16 )
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{
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return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
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}
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#if defined(MBEDTLS_THREADING_C)
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if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
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@ -330,57 +323,34 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
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#endif
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enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
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mac = ticket + enc_len;
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tag = ticket + enc_len;
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if( len != enc_len + 66 )
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if( len != 4 + 12 + 2 + enc_len + 16 )
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{
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ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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goto cleanup;
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}
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/* Check name, in constant time though it's not a big secret */
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diff = 0;
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for( i = 0; i < 16; i++ )
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diff |= key_name[i] ^ ctx->key_name[i];
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/* don't return yet, check the MAC anyway */
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/* Check mac, with constant-time buffer comparison */
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if( ( ret = mbedtls_md_hmac( mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ),
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ctx->mac_key, 16,
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buf, len - 32, computed_mac ) ) != 0 )
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{
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goto cleanup;
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}
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for( i = 0; i < 32; i++ )
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diff |= mac[i] ^ computed_mac[i];
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/* Now return if ticket is not authentic, since we want to avoid
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* decrypting arbitrary attacker-chosen data */
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if( diff != 0 )
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/* Check name (public data) */
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if( memcmp( key_name, ctx->key_name, 4 ) != 0 )
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{
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ret = MBEDTLS_ERR_SSL_INVALID_MAC;
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goto cleanup;
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}
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/* Decrypt */
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if( ( ret = mbedtls_aes_crypt_cbc( &ctx->dec, MBEDTLS_AES_DECRYPT,
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enc_len, iv, ticket, ticket ) ) != 0 )
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/* Decrypt and authenticate */
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if( ( ret = mbedtls_cipher_auth_decrypt( &ctx->cipher, iv, 12,
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key_name, 4 + 12 + 2, ticket, enc_len,
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ticket, &clear_len, tag, 16 ) ) != 0 )
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{
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/* TODO: convert AUTH_FAILED to INVALID_MAC */
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goto cleanup;
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}
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/* Check PKCS padding */
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pad_len = ticket[enc_len - 1];
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ret = 0;
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for( i = 2; i < pad_len; i++ )
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if( ticket[enc_len - i] != pad_len )
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ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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if( ret != 0 )
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if( clear_len != enc_len )
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{
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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clear_len = enc_len - pad_len;
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}
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/* Actually load session */
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if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
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@ -414,8 +384,7 @@ cleanup:
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*/
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void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
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{
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mbedtls_aes_free( &ctx->enc );
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mbedtls_aes_free( &ctx->dec );
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mbedtls_cipher_free( &ctx->cipher );
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_free( &ctx->mutex );
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