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Set pointer to start of plaintext at record decryption time

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The SSL context structure mbedtls_ssl_context contains several pointers
ssl->in_hdr, ssl->in_len, ssl->in_iv, ssl->in_msg pointing to various
parts of the record header in an incoming record, and they are setup
in the static function ssl_update_in_pointers() based on the _expected_
transform for the next incoming record.
In particular, the pointer ssl->in_msg is set to where the record plaintext
should reside after record decryption, and an assertion double-checks this
after each call to ssl_decrypt_buf().

This commit removes the dependency of ssl_update_in_pointers() on the
expected incoming transform by setting ssl->in_msg to ssl->in_iv --
the beginning of the record content (potentially including the IV) --
and adjusting ssl->in_msg after calling ssl_decrypt_buf() on a protected
record.

Care has to be taken to not load ssl->in_msg before calling
mbedtls_ssl_read_record(), then, which was previously the
case in ssl_parse_server_hello(); the commit fixes that.
This commit is contained in:
Hanno Becker 2019-05-08 09:38:41 +01:00
parent 82e2a3961c
commit 79594fd0d4
2 changed files with 19 additions and 22 deletions
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4
library/ssl_cli.c
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@ -1658,8 +1658,6 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse server hello" ) );
buf = ssl->in_msg;
if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
{
/* No alert on a read error. */
@ -1667,6 +1665,8 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
return( ret );
}
buf = ssl->in_msg;
if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE )
{
#if defined(MBEDTLS_SSL_RENEGOTIATION)