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Merge pull request #3424 from ronald-cron-arm/ssl_write_client_hello-2.7

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[Backport 2.7] Bounds checks in ssl_write_client_hello
This commit is contained in:
Manuel Pégourié-Gonnard 2020-06-15 10:57:58 +02:00 committed by GitHub
commit 693768f8e9
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GPG Key ID: 4AEE18F83AFDEB23
9 changed files with 712 additions and 397 deletions
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9
ChangeLog.d/uniformize_bounds_checks.txt Normal file
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@ -0,0 +1,9 @@
Bugfix
* Add additional bounds checks in ssl_write_client_hello() preventing
output buffer overflow if the configuration declared a buffer that was
too small.
Changes
* Abort the ClientHello writing function as soon as some extension doesn't
fit into the record buffer. Previously, such extensions were silently
dropped. As a consequence, the TLS handshake now fails when the output
buffer is not large enough to hold the ClientHello.

1
include/mbedtls/error.h
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@ -94,6 +94,7 @@
* RSA 4 11
* ECP 4 9 (Started from top)
* MD 5 5
* SSL 5 1 (Started from 0x5E80)
* CIPHER 6 8
* SSL 6 17 (Started from top)
* SSL 7 31

4
include/mbedtls/ssl.h
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@ -110,6 +110,7 @@
#define MBEDTLS_ERR_SSL_UNEXPECTED_RECORD -0x6700 /**< Record header looks valid but is not expected. */
#define MBEDTLS_ERR_SSL_NON_FATAL -0x6680 /**< The alert message received indicates a non-fatal error. */
#define MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH -0x6600 /**< Couldn't set the hash for verifying CertificateVerify */
#define MBEDTLS_ERR_SSL_BAD_CONFIG -0x5E80 /**< Invalid value in SSL config */
/*
* Various constants
@ -124,6 +125,9 @@
#define MBEDTLS_SSL_TRANSPORT_DATAGRAM 1 /*!< DTLS */
#define MBEDTLS_SSL_MAX_HOST_NAME_LEN 255 /*!< Maximum host name defined in RFC 1035 */
#define MBEDTLS_SSL_MAX_ALPN_NAME_LEN 255 /*!< Maximum size in bytes of a protocol name in alpn ext., RFC 7301 */
#define MBEDTLS_SSL_MAX_ALPN_LIST_LEN 65535 /*!< Maximum size in bytes of list in alpn ext., RFC 7301 */
/* RFC 6066 section 4, see also mfl_code_to_length in ssl_tls.c
* NONE must be zero so that memset()ing structure to zero works */

41
include/mbedtls/ssl_internal.h
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@ -156,6 +156,12 @@
+ MBEDTLS_SSL_PADDING_ADD \
)
/* Maximum size in bytes of list in sig-hash algorithm ext., RFC 5246 */
#define MBEDTLS_SSL_MAX_SIG_HASH_ALG_LIST_LEN 65534
/* Maximum size in bytes of list in supported elliptic curve ext., RFC 4492 */
#define MBEDTLS_SSL_MAX_CURVE_LIST_LEN 65535
/*
* Check that we obey the standard's message size bounds
*/
@ -184,6 +190,41 @@
#define MBEDTLS_TLS_EXT_SUPPORTED_POINT_FORMATS_PRESENT (1 << 0)
#define MBEDTLS_TLS_EXT_ECJPAKE_KKPP_OK (1 << 1)
/**
* \brief This function checks if the remaining size in a buffer is
* greater or equal than a needed space.
*
* \param cur Pointer to the current position in the buffer.
* \param end Pointer to one past the end of the buffer.
* \param need Needed space in bytes.
*
* \return Zero if the needed space is available in the buffer, non-zero
* otherwise.
*/
static inline int mbedtls_ssl_chk_buf_ptr( const uint8_t *cur,
const uint8_t *end, size_t need )
{
return( ( cur > end ) || ( need > (size_t)( end - cur ) ) );
}
/**
* \brief This macro checks if the remaining size in a buffer is
* greater or equal than a needed space. If it is not the case,
* it returns an SSL_BUFFER_TOO_SMALL error.
*
* \param cur Pointer to the current position in the buffer.
* \param end Pointer to one past the end of the buffer.
* \param need Needed space in bytes.
*
*/
#define MBEDTLS_SSL_CHK_BUF_PTR( cur, end, need ) \
do { \
if( mbedtls_ssl_chk_buf_ptr( ( cur ), ( end ), ( need ) ) != 0 ) \
{ \
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); \
} \
} while( 0 )
#ifdef __cplusplus
extern "C" {
#endif

2
library/error.c
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@ -495,6 +495,8 @@ void mbedtls_strerror( int ret, char *buf, size_t buflen )
mbedtls_snprintf( buf, buflen, "SSL - The alert message received indicates a non-fatal error" );
if( use_ret == -(MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH) )
mbedtls_snprintf( buf, buflen, "SSL - Couldn't set the hash for verifying CertificateVerify" );
if( use_ret == -(MBEDTLS_ERR_SSL_BAD_CONFIG) )
mbedtls_snprintf( buf, buflen, "SSL - Invalid value in SSL config" );
#endif /* MBEDTLS_SSL_TLS_C */
#if defined(MBEDTLS_X509_USE_C) || defined(MBEDTLS_X509_CREATE_C)

844
library/ssl_cli.c
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File diff suppressed because it is too large Load Diff

6
library/ssl_cookie.c
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@ -137,8 +137,7 @@ static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,
{
unsigned char hmac_out[COOKIE_MD_OUTLEN];
if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_HMAC_LEN );
if( mbedtls_md_hmac_reset( hmac_ctx ) != 0 ||
mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||
@ -168,8 +167,7 @@ int mbedtls_ssl_cookie_write( void *p_ctx,
if( ctx == NULL || cli_id == NULL )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
if( (size_t)( end - *p ) < COOKIE_LEN )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
MBEDTLS_SSL_CHK_BUF_PTR( *p, end, COOKIE_LEN );
#if defined(MBEDTLS_HAVE_TIME)
t = (unsigned long) mbedtls_time( NULL );

58
library/ssl_ticket.c
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@ -35,6 +35,7 @@
#define mbedtls_free free
#endif
#include "mbedtls/ssl_internal.h"
#include "mbedtls/ssl_ticket.h"
#include <string.h>
@ -58,6 +59,19 @@ void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
#define MAX_KEY_BYTES 32 /* 256 bits */
#define TICKET_KEY_NAME_BYTES 4
#define TICKET_IV_BYTES 12
#define TICKET_CRYPT_LEN_BYTES 2
#define TICKET_AUTH_TAG_BYTES 16
#define TICKET_MIN_LEN ( TICKET_KEY_NAME_BYTES + \
TICKET_IV_BYTES + \
TICKET_CRYPT_LEN_BYTES + \
TICKET_AUTH_TAG_BYTES )
#define TICKET_ADD_DATA_LEN ( TICKET_KEY_NAME_BYTES + \
TICKET_IV_BYTES + \
TICKET_CRYPT_LEN_BYTES )
/*
* Generate/update a key
*/
@ -282,6 +296,7 @@ static int ssl_load_session( mbedtls_ssl_session *session,
* 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,
@ -293,9 +308,9 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
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 *iv = start + TICKET_KEY_NAME_BYTES;
unsigned char *state_len_bytes = iv + TICKET_IV_BYTES;
unsigned char *state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
unsigned char *tag;
size_t clear_len, ciph_len;
@ -306,8 +321,7 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
/* 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 );
MBEDTLS_SSL_CHK_BUF_PTR( start, end, TICKET_MIN_LEN );
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
@ -321,9 +335,9 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
*ticket_lifetime = ctx->ticket_lifetime;
memcpy( key_name, key->name, 4 );
memcpy( key_name, key->name, TICKET_KEY_NAME_BYTES );
if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
if( ( ret = ctx->f_rng( ctx->p_rng, iv, TICKET_IV_BYTES ) ) != 0 )
goto cleanup;
/* Dump session state */
@ -339,8 +353,11 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
/* 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 )
iv, TICKET_IV_BYTES,
/* Additional data: key name, IV and length */
key_name, TICKET_ADD_DATA_LEN,
state, clear_len, state, &ciph_len,
tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
{
goto cleanup;
}
@ -350,7 +367,7 @@ int mbedtls_ssl_ticket_write( void *p_ticket,
goto cleanup;
}
*tlen = 4 + 12 + 2 + 16 + ciph_len;
*tlen = TICKET_MIN_LEN + ciph_len;
cleanup:
#if defined(MBEDTLS_THREADING_C)
@ -389,17 +406,16 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
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 *iv = buf + TICKET_KEY_NAME_BYTES;
unsigned char *enc_len_p = iv + TICKET_IV_BYTES;
unsigned char *ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
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 )
if( len < TICKET_MIN_LEN )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
#if defined(MBEDTLS_THREADING_C)
@ -413,7 +429,7 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
tag = ticket + enc_len;
if( len != 4 + 12 + 2 + enc_len + 16 )
if( len != TICKET_MIN_LEN + enc_len )
{
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto cleanup;
@ -429,9 +445,13 @@ int mbedtls_ssl_ticket_parse( void *p_ticket,
}
/* 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_cipher_auth_decrypt( &key->ctx,
iv, TICKET_IV_BYTES,
/* Additional data: key name, IV and length */
key_name, TICKET_ADD_DATA_LEN,
ticket, enc_len,
ticket, &clear_len,
tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
{
if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
ret = MBEDTLS_ERR_SSL_INVALID_MAC;

4
library/ssl_tls.c
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@ -6526,7 +6526,9 @@ int mbedtls_ssl_conf_alpn_protocols( mbedtls_ssl_config *conf, const char **prot
cur_len = strlen( *p );
tot_len += cur_len;
if( cur_len == 0 || cur_len > 255 || tot_len > 65535 )
if( ( cur_len == 0 ) ||
( cur_len > MBEDTLS_SSL_MAX_ALPN_NAME_LEN ) ||
( tot_len > MBEDTLS_SSL_MAX_ALPN_LIST_LEN ) )
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}