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Merge pull request #4248 from hanno-arm/tls13_populate_transform

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Fix and test compliance of TLS 1.3 record protection
This commit is contained in:
Dave Rodgman 2021-08-11 16:41:51 +01:00 • committed by GitHub
commit 2aec149e13
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GPG key ID: 4AEE18F83AFDEB23
8 changed files with 399 additions and 50 deletions
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3
library/ssl_misc.h
View file

@ -740,7 +740,8 @@ struct mbedtls_ssl_transform
#if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION)
/* We need the Hello random bytes in order to re-derive keys from the
* Master Secret and other session info, see ssl_populate_transform() */
* Master Secret and other session info,
* see ssl_tls12_populate_transform() */
unsigned char randbytes[64]; /*!< ServerHello.random+ClientHello.random */
#endif /* MBEDTLS_SSL_CONTEXT_SERIALIZATION */
};

53
library/ssl_msg.c
View file

@ -384,7 +384,8 @@ static int ssl_parse_inner_plaintext( unsigned char const *content,
static void ssl_extract_add_data_from_record( unsigned char* add_data,
size_t *add_data_len,
mbedtls_record *rec,
unsigned minor_ver )
unsigned minor_ver,
size_t taglen )
{
/* Quoting RFC 5246 (TLS 1.2):
*
@ -403,15 +404,37 @@ static void ssl_extract_add_data_from_record( unsigned char* add_data,
*
* For TLS 1.3, the record sequence number is dropped from the AAD
* and encoded within the nonce of the AEAD operation instead.
* Moreover, the additional data involves the length of the TLS
* ciphertext, not the TLS plaintext as in earlier versions.
* Quoting RFC 8446 (TLS 1.3):
*
* additional_data = TLSCiphertext.opaque_type ||
* TLSCiphertext.legacy_record_version ||
* TLSCiphertext.length
*
* We pass the tag length to this function in order to compute the
* ciphertext length from the inner plaintext length rec->data_len via
*
* TLSCiphertext.length = TLSInnerPlaintext.length + taglen.
*
*/
unsigned char *cur = add_data;
size_t ad_len_field = rec->data_len;
#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
if( minor_ver != MBEDTLS_SSL_MINOR_VERSION_4 )
if( minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 )
{
/* In TLS 1.3, the AAD contains the length of the TLSCiphertext,
* which differs from the length of the TLSInnerPlaintext
* by the length of the authentication tag. */
ad_len_field += taglen;
}
else
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
{
((void) minor_ver);
((void) taglen);
memcpy( cur, rec->ctr, sizeof( rec->ctr ) );
cur += sizeof( rec->ctr );
}
@ -431,15 +454,15 @@ static void ssl_extract_add_data_from_record( unsigned char* add_data,
*cur = rec->cid_len;
cur++;
cur[0] = ( rec->data_len >> 8 ) & 0xFF;
cur[1] = ( rec->data_len >> 0 ) & 0xFF;
cur[0] = ( ad_len_field >> 8 ) & 0xFF;
cur[1] = ( ad_len_field >> 0 ) & 0xFF;
cur += 2;
}
else
#endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
{
cur[0] = ( rec->data_len >> 8 ) & 0xFF;
cur[1] = ( rec->data_len >> 0 ) & 0xFF;
cur[0] = ( ad_len_field >> 8 ) & 0xFF;
cur[1] = ( ad_len_field >> 0 ) & 0xFF;
cur += 2;
}
@ -646,7 +669,8 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
unsigned char mac[MBEDTLS_SSL_MAC_ADD];
ssl_extract_add_data_from_record( add_data, &add_data_len, rec,
transform->minor_ver );
transform->minor_ver,
transform->taglen );
mbedtls_md_hmac_update( &transform->md_ctx_enc, add_data,
add_data_len );
@ -743,7 +767,8 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
* This depends on the TLS version.
*/
ssl_extract_add_data_from_record( add_data, &add_data_len, rec,
transform->minor_ver );
transform->minor_ver,
transform->taglen );
MBEDTLS_SSL_DEBUG_BUF( 4, "IV used (internal)",
iv, transform->ivlen );
@ -897,7 +922,8 @@ int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,
}
ssl_extract_add_data_from_record( add_data, &add_data_len,
rec, transform->minor_ver );
rec, transform->minor_ver,
transform->taglen );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data,
@ -1304,7 +1330,8 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context const *ssl,
* This depends on the TLS version.
*/
ssl_extract_add_data_from_record( add_data, &add_data_len, rec,
transform->minor_ver );
transform->minor_ver,
transform->taglen );
MBEDTLS_SSL_DEBUG_BUF( 4, "additional data used for AEAD",
add_data, add_data_len );
@ -1414,7 +1441,8 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context const *ssl,
* Further, we still know that data_len > minlen */
rec->data_len -= transform->maclen;
ssl_extract_add_data_from_record( add_data, &add_data_len, rec,
transform->minor_ver );
transform->minor_ver,
transform->taglen );
/* Calculate expected MAC. */
MBEDTLS_SSL_DEBUG_BUF( 4, "MAC'd meta-data", add_data,
@ -1606,7 +1634,8 @@ int mbedtls_ssl_decrypt_buf( mbedtls_ssl_context const *ssl,
*/
rec->data_len -= transform->maclen;
ssl_extract_add_data_from_record( add_data, &add_data_len, rec,
transform->minor_ver );
transform->minor_ver,
transform->taglen );
#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
/*

70
library/ssl_tls.c
View file

@ -664,14 +664,14 @@ typedef int ssl_tls_prf_t(const unsigned char *, size_t, const char *,
* - MBEDTLS_SSL_EXPORT_KEYS: ssl->conf->{f,p}_export_keys
* - MBEDTLS_DEBUG_C: ssl->conf->{f,p}_dbg
*/
static int ssl_populate_transform( mbedtls_ssl_transform *transform,
static int ssl_tls12_populate_transform( mbedtls_ssl_transform *transform,
int ciphersuite,
const unsigned char master[48],
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC)
#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) && \
defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
int encrypt_then_mac,
#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_MAC */
#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC &&
MBEDTLS_SSL_SOME_SUITES_USE_MAC */
ssl_tls_prf_t tls_prf,
const unsigned char randbytes[64],
int minor_ver,
@ -713,6 +713,15 @@ static int ssl_populate_transform( mbedtls_ssl_transform *transform,
memcpy( transform->randbytes, randbytes, sizeof( transform->randbytes ) );
#endif
#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
if( minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 )
{
/* At the moment, we keep TLS <= 1.2 and TLS 1.3 transform
* generation separate. This should never happen. */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
/*
* Get various info structures
*/
@ -805,19 +814,10 @@ static int ssl_populate_transform( mbedtls_ssl_transform *transform,
* sequence number).
*/
transform->ivlen = 12;
#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
if( minor_ver == MBEDTLS_SSL_MINOR_VERSION_4 )
{
if( cipher_info->mode == MBEDTLS_MODE_CHACHAPOLY )
transform->fixed_ivlen = 12;
}
else
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
{
if( cipher_info->mode == MBEDTLS_MODE_CHACHAPOLY )
transform->fixed_ivlen = 12;
else
transform->fixed_ivlen = 4;
}
transform->fixed_ivlen = 4;
/* Minimum length of encrypted record */
explicit_ivlen = transform->ivlen - transform->fixed_ivlen;
@ -1327,22 +1327,22 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
}
/* Populate transform structure */
ret = ssl_populate_transform( ssl->transform_negotiate,
ssl->session_negotiate->ciphersuite,
ssl->session_negotiate->master,
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC)
#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
ssl->session_negotiate->encrypt_then_mac,
#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC */
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_MAC */
ssl->handshake->tls_prf,
ssl->handshake->randbytes,
ssl->minor_ver,
ssl->conf->endpoint,
ssl );
ret = ssl_tls12_populate_transform( ssl->transform_negotiate,
ssl->session_negotiate->ciphersuite,
ssl->session_negotiate->master,
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) && \
defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
ssl->session_negotiate->encrypt_then_mac,
#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC &&
MBEDTLS_SSL_SOME_SUITES_USE_MAC */
ssl->handshake->tls_prf,
ssl->handshake->randbytes,
ssl->minor_ver,
ssl->conf->endpoint,
ssl );
if( ret != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "ssl_populate_transform", ret );
MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls12_populate_transform", ret );
return( ret );
}
@ -5923,14 +5923,14 @@ static int ssl_context_load( mbedtls_ssl_context *ssl,
if( (size_t)( end - p ) < sizeof( ssl->transform->randbytes ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
ret = ssl_populate_transform( ssl->transform,
ret = ssl_tls12_populate_transform( ssl->transform,
ssl->session->ciphersuite,
ssl->session->master,
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC)
#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
#if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC) && \
defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
ssl->session->encrypt_then_mac,
#endif
#endif /* MBEDTLS_SSL_SOME_SUITES_USE_MAC */
#endif /* MBEDTLS_SSL_ENCRYPT_THEN_MAC &&
MBEDTLS_SSL_SOME_SUITES_USE_MAC */
ssl_tls12prf_from_cs( ssl->session->ciphersuite ),
p, /* currently pointing to randbytes */
MBEDTLS_SSL_MINOR_VERSION_3, /* (D)TLS 1.2 is forced */

121
library/ssl_tls13_keys.c
View file

@ -699,4 +699,125 @@ exit:
return( ret );
}
int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
int endpoint,
int ciphersuite,
mbedtls_ssl_key_set const *traffic_keys,
mbedtls_ssl_context *ssl /* DEBUG ONLY */ )
{
int ret;
mbedtls_cipher_info_t const *cipher_info;
const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
unsigned char const *key_enc;
unsigned char const *iv_enc;
unsigned char const *key_dec;
unsigned char const *iv_dec;
#if !defined(MBEDTLS_DEBUG_C)
ssl = NULL; /* make sure we don't use it except for those cases */
(void) ssl;
#endif
ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( ciphersuite );
if( ciphersuite_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "ciphersuite info for %d not found",
ciphersuite ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
cipher_info = mbedtls_cipher_info_from_type( ciphersuite_info->cipher );
if( cipher_info == NULL )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "cipher info for %u not found",
ciphersuite_info->cipher ) );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
/*
* Setup cipher contexts in target transform
*/
if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_enc,
cipher_info ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
return( ret );
}
if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_dec,
cipher_info ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
return( ret );
}
#if defined(MBEDTLS_SSL_SRV_C)
if( endpoint == MBEDTLS_SSL_IS_SERVER )
{
key_enc = traffic_keys->server_write_key;
key_dec = traffic_keys->client_write_key;
iv_enc = traffic_keys->server_write_iv;
iv_dec = traffic_keys->client_write_iv;
}
else
#endif /* MBEDTLS_SSL_SRV_C */
#if defined(MBEDTLS_SSL_CLI_C)
if( endpoint == MBEDTLS_SSL_IS_CLIENT )
{
key_enc = traffic_keys->client_write_key;
key_dec = traffic_keys->server_write_key;
iv_enc = traffic_keys->client_write_iv;
iv_dec = traffic_keys->server_write_iv;
}
else
#endif /* MBEDTLS_SSL_CLI_C */
{
/* should not happen */
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
memcpy( transform->iv_enc, iv_enc, traffic_keys->iv_len );
memcpy( transform->iv_dec, iv_dec, traffic_keys->iv_len );
if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_enc,
key_enc, cipher_info->key_bitlen,
MBEDTLS_ENCRYPT ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
return( ret );
}
if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_dec,
key_dec, cipher_info->key_bitlen,
MBEDTLS_DECRYPT ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
return( ret );
}
/*
* Setup other fields in SSL transform
*/
if( ( ciphersuite_info->flags & MBEDTLS_CIPHERSUITE_SHORT_TAG ) != 0 )
transform->taglen = 8;
else
transform->taglen = 16;
transform->ivlen = traffic_keys->iv_len;
transform->maclen = 0;
transform->fixed_ivlen = transform->ivlen;
transform->minor_ver = MBEDTLS_SSL_MINOR_VERSION_4;
/* We add the true record content type (1 Byte) to the plaintext and
* then pad to the configured granularity. The mimimum length of the
* type-extended and padded plaintext is therefore the padding
* granularity. */
transform->minlen =
transform->taglen + MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY;
return( 0 );
}
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */

33
library/ssl_tls13_keys.h
View file

@ -498,4 +498,37 @@ int mbedtls_ssl_tls1_3_create_psk_binder( mbedtls_ssl_context *ssl,
unsigned char const *transcript,
unsigned char *result );
/**
* \bref Setup an SSL transform structure representing the
* record protection mechanism used by TLS 1.3
*
* \param transform The SSL transform structure to be created. This must have
* been initialized through mbedtls_ssl_transform_init() and
* not used in any other way prior to calling this function.
* In particular, this function does not clean up the
* transform structure prior to installing the new keys.
* \param endpoint Indicates whether the transform is for the client
* (value #MBEDTLS_SSL_IS_CLIENT) or the server
* (value #MBEDTLS_SSL_IS_SERVER).
* \param ciphersuite The numerical identifier for the ciphersuite to use.
* This must be one of the identifiers listed in
* ssl_ciphersuites.h.
* \param traffic_keys The key material to use. No reference is stored in
* the SSL transform being generated, and the caller
* should destroy the key material afterwards.
* \param ssl (Debug-only) The SSL context to use for debug output
* in case of failure. This parameter is only needed if
* #MBEDTLS_DEBUG_C is set, and is ignored otherwise.
*
* \return \c 0 on success. In this case, \p transform is ready to
* be used with mbedtls_ssl_transform_decrypt() and
* mbedtls_ssl_transform_encrypt().
* \return A negative error code on failure.
*/
int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
int endpoint,
int ciphersuite,
mbedtls_ssl_key_set const *traffic_keys,
mbedtls_ssl_context *ssl );
#endif /* MBEDTLS_SSL_TLS1_3_KEYS_H */