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Free future buffers if next handshake messages can't be reassembled

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If the next expected handshake message can't be reassembled because
buffered future messages have already used up too much of the available
space for buffering, free those future message buffers in order to
make space for the reassembly, starting with the handshake message
that's farthest in the future.
This commit is contained in:
Hanno Becker 2018-08-21 16:07:55 +01:00
parent e605b19631
commit 55e9e2aa6b
1 changed files with 28 additions and 5 deletions
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33
library/ssl_tls.c
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@ -4522,6 +4522,8 @@ static int ssl_buffer_message( mbedtls_ssl_context *ssl )
if( reassembly_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
hs->buffering.total_bytes_buffered ) )
{
int offset;
if( recv_msg_seq_offset > 0 )
{
/* If we can't buffer a future message because
@ -4532,13 +4534,34 @@ static int ssl_buffer_message( mbedtls_ssl_context *ssl )
goto exit;
}
/* TODO: Remove future messages in the attempt to make
* space for the current one. */
MBEDTLS_SSL_DEBUG_MSG( 2, ( "Reassembly of next message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- fail\n",
/* We don't have enough space to buffer the next expected
* handshake message. Remove buffers used for future msgs
* to gain space, starting with the most distant one. */
for( offset = MBEDTLS_SSL_MAX_BUFFERED_HS - 1;
offset >= 0; offset-- )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "Free buffering slot %d to make space for reassembly of next handshake message",
offset ) );
ssl_buffering_free_slot( ssl, offset );
/* Check if we have enough space available now. */
if( reassembly_buf_sz <=
( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
hs->buffering.total_bytes_buffered ) )
{
break;
}
}
if( offset == -1 )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "Reassembly of next message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- fail\n",
(unsigned) msg_len, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
(unsigned) hs->buffering.total_bytes_buffered ) );
ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
goto exit;
ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
goto exit;
}
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",