Merge pull request #9872 from rojer/tls_hs_defrag_in
Defragment incoming TLS handshake messages
diff --git a/ChangeLog.d/tls-hs-defrag-in.txt b/ChangeLog.d/tls-hs-defrag-in.txt
new file mode 100644
index 0000000..55103c9
--- /dev/null
+++ b/ChangeLog.d/tls-hs-defrag-in.txt
@@ -0,0 +1,5 @@
+Bugfix
+ * Support re-assembly of fragmented handshake messages in TLS, as mandated
+ by the spec. Lack of support was causing handshake failures with some
+ servers, especially with TLS 1.3 in practice (though both protocol
+ version could be affected in principle, and both are fixed now).
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index e0c0eae..0c0c8bb 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1795,6 +1795,8 @@
size_t MBEDTLS_PRIVATE(in_hslen); /*!< current handshake message length,
including the handshake header */
+ size_t MBEDTLS_PRIVATE(in_hsfraglen); /*!< accumulated length of hs fragments
+ (up to in_hslen) */
int MBEDTLS_PRIVATE(nb_zero); /*!< # of 0-length encrypted messages */
int MBEDTLS_PRIVATE(keep_current_message); /*!< drop or reuse current message
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 9f91861..2140ac4 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1756,10 +1756,11 @@
MBEDTLS_CHECK_RETURN_CRITICAL
int mbedtls_ssl_check_timer(mbedtls_ssl_context *ssl);
-void mbedtls_ssl_reset_in_out_pointers(mbedtls_ssl_context *ssl);
+void mbedtls_ssl_reset_in_pointers(mbedtls_ssl_context *ssl);
+void mbedtls_ssl_update_in_pointers(mbedtls_ssl_context *ssl);
+void mbedtls_ssl_reset_out_pointers(mbedtls_ssl_context *ssl);
void mbedtls_ssl_update_out_pointers(mbedtls_ssl_context *ssl,
mbedtls_ssl_transform *transform);
-void mbedtls_ssl_update_in_pointers(mbedtls_ssl_context *ssl);
MBEDTLS_CHECK_RETURN_CRITICAL
int mbedtls_ssl_session_reset_int(mbedtls_ssl_context *ssl, int partial);
diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index 97c4866..a87785c 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -2962,13 +2962,17 @@
int mbedtls_ssl_prepare_handshake_record(mbedtls_ssl_context *ssl)
{
- if (ssl->in_msglen < mbedtls_ssl_hs_hdr_len(ssl)) {
+ /* First handshake fragment must at least include the header. */
+ if (ssl->in_msglen < mbedtls_ssl_hs_hdr_len(ssl) && ssl->in_hslen == 0) {
MBEDTLS_SSL_DEBUG_MSG(1, ("handshake message too short: %" MBEDTLS_PRINTF_SIZET,
ssl->in_msglen));
return MBEDTLS_ERR_SSL_INVALID_RECORD;
}
- ssl->in_hslen = mbedtls_ssl_hs_hdr_len(ssl) + ssl_get_hs_total_len(ssl);
+ if (ssl->in_hslen == 0) {
+ ssl->in_hslen = mbedtls_ssl_hs_hdr_len(ssl) + ssl_get_hs_total_len(ssl);
+ ssl->in_hsfraglen = 0;
+ }
MBEDTLS_SSL_DEBUG_MSG(3, ("handshake message: msglen ="
" %" MBEDTLS_PRINTF_SIZET ", type = %u, hslen = %"
@@ -3034,10 +3038,60 @@
}
} else
#endif /* MBEDTLS_SSL_PROTO_DTLS */
- /* With TLS we don't handle fragmentation (for now) */
- if (ssl->in_msglen < ssl->in_hslen) {
- MBEDTLS_SSL_DEBUG_MSG(1, ("TLS handshake fragmentation not supported"));
- return MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
+ if (ssl->in_hsfraglen <= ssl->in_hslen) {
+ int ret;
+ const size_t hs_remain = ssl->in_hslen - ssl->in_hsfraglen;
+ MBEDTLS_SSL_DEBUG_MSG(3,
+ ("handshake fragment: %" MBEDTLS_PRINTF_SIZET " .. %"
+ MBEDTLS_PRINTF_SIZET " of %"
+ MBEDTLS_PRINTF_SIZET " msglen %" MBEDTLS_PRINTF_SIZET,
+ ssl->in_hsfraglen,
+ ssl->in_hsfraglen +
+ (hs_remain <= ssl->in_msglen ? hs_remain : ssl->in_msglen),
+ ssl->in_hslen, ssl->in_msglen));
+ if (ssl->in_msglen < hs_remain) {
+ ssl->in_hsfraglen += ssl->in_msglen;
+ ssl->in_hdr = ssl->in_msg + ssl->in_msglen;
+ ssl->in_msglen = 0;
+ mbedtls_ssl_update_in_pointers(ssl);
+ return MBEDTLS_ERR_SSL_CONTINUE_PROCESSING;
+ }
+ if (ssl->in_hsfraglen > 0) {
+ /*
+ * At in_first_hdr we have a sequence of records that cover the next handshake
+ * record, each with its own record header that we need to remove.
+ * Note that the reassembled record size may not equal the size of the message,
+ * there may be more messages after it, complete or partial.
+ */
+ unsigned char *in_first_hdr = ssl->in_buf + MBEDTLS_SSL_SEQUENCE_NUMBER_LEN;
+ unsigned char *p = in_first_hdr, *q = NULL;
+ size_t merged_rec_len = 0;
+ do {
+ mbedtls_record rec;
+ ret = ssl_parse_record_header(ssl, p, mbedtls_ssl_in_hdr_len(ssl), &rec);
+ if (ret != 0) {
+ return ret;
+ }
+ merged_rec_len += rec.data_len;
+ p = rec.buf + rec.buf_len;
+ if (q != NULL) {
+ memmove(q, rec.buf + rec.data_offset, rec.data_len);
+ q += rec.data_len;
+ } else {
+ q = p;
+ }
+ } while (merged_rec_len < ssl->in_hslen);
+ ssl->in_hdr = in_first_hdr;
+ mbedtls_ssl_update_in_pointers(ssl);
+ ssl->in_msglen = merged_rec_len;
+ /* Adjust message length. */
+ MBEDTLS_PUT_UINT16_BE(merged_rec_len, ssl->in_len, 0);
+ ssl->in_hsfraglen = 0;
+ MBEDTLS_SSL_DEBUG_BUF(4, "reassembled record",
+ ssl->in_hdr, mbedtls_ssl_in_hdr_len(ssl) + merged_rec_len);
+ }
+ } else {
+ return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
}
return 0;
@@ -4382,6 +4436,16 @@
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
+ if (ssl->in_hsfraglen != 0) {
+ /* Not all handshake fragments have arrived, do not consume. */
+ MBEDTLS_SSL_DEBUG_MSG(3,
+ ("waiting for more fragments (%" MBEDTLS_PRINTF_SIZET " of %"
+ MBEDTLS_PRINTF_SIZET ", %" MBEDTLS_PRINTF_SIZET " left)",
+ ssl->in_hsfraglen, ssl->in_hslen,
+ ssl->in_hslen - ssl->in_hsfraglen));
+ return 0;
+ }
+
/*
* Get next Handshake message in the current record
*/
@@ -4407,6 +4471,7 @@
ssl->in_msglen -= ssl->in_hslen;
memmove(ssl->in_msg, ssl->in_msg + ssl->in_hslen,
ssl->in_msglen);
+ MBEDTLS_PUT_UINT16_BE(ssl->in_msglen, ssl->in_len, 0);
MBEDTLS_SSL_DEBUG_BUF(4, "remaining content in record",
ssl->in_msg, ssl->in_msglen);
@@ -5081,7 +5146,7 @@
} else
#endif
{
- ssl->in_ctr = ssl->in_hdr - MBEDTLS_SSL_SEQUENCE_NUMBER_LEN;
+ ssl->in_ctr = ssl->in_buf;
ssl->in_len = ssl->in_hdr + 3;
#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
ssl->in_cid = ssl->in_len;
@@ -5097,24 +5162,35 @@
* Setup an SSL context
*/
-void mbedtls_ssl_reset_in_out_pointers(mbedtls_ssl_context *ssl)
+void mbedtls_ssl_reset_in_pointers(mbedtls_ssl_context *ssl)
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+ if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
+ ssl->in_hdr = ssl->in_buf;
+ } else
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+ {
+ ssl->in_hdr = ssl->in_buf + MBEDTLS_SSL_SEQUENCE_NUMBER_LEN;
+ }
+
+ /* Derive other internal pointers. */
+ mbedtls_ssl_update_in_pointers(ssl);
+}
+
+void mbedtls_ssl_reset_out_pointers(mbedtls_ssl_context *ssl)
{
/* Set the incoming and outgoing record pointers. */
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
ssl->out_hdr = ssl->out_buf;
- ssl->in_hdr = ssl->in_buf;
} else
#endif /* MBEDTLS_SSL_PROTO_DTLS */
{
ssl->out_ctr = ssl->out_buf;
- ssl->out_hdr = ssl->out_buf + 8;
- ssl->in_hdr = ssl->in_buf + 8;
+ ssl->out_hdr = ssl->out_buf + MBEDTLS_SSL_SEQUENCE_NUMBER_LEN;
}
-
/* Derive other internal pointers. */
mbedtls_ssl_update_out_pointers(ssl, NULL /* no transform enabled */);
- mbedtls_ssl_update_in_pointers(ssl);
}
/*
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 60f2e1c..7d20b3c 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -339,12 +339,13 @@
size_t out_buf_new_len)
{
int modified = 0;
- size_t written_in = 0, iv_offset_in = 0, len_offset_in = 0;
+ size_t written_in = 0, iv_offset_in = 0, len_offset_in = 0, hdr_in = 0;
size_t written_out = 0, iv_offset_out = 0, len_offset_out = 0;
if (ssl->in_buf != NULL) {
written_in = ssl->in_msg - ssl->in_buf;
iv_offset_in = ssl->in_iv - ssl->in_buf;
len_offset_in = ssl->in_len - ssl->in_buf;
+ hdr_in = ssl->in_hdr - ssl->in_buf;
if (downsizing ?
ssl->in_buf_len > in_buf_new_len && ssl->in_left < in_buf_new_len :
ssl->in_buf_len < in_buf_new_len) {
@@ -376,7 +377,10 @@
}
if (modified) {
/* Update pointers here to avoid doing it twice. */
- mbedtls_ssl_reset_in_out_pointers(ssl);
+ ssl->in_hdr = ssl->in_buf + hdr_in;
+ mbedtls_ssl_update_in_pointers(ssl);
+ mbedtls_ssl_reset_out_pointers(ssl);
+
/* Fields below might not be properly updated with record
* splitting or with CID, so they are manually updated here. */
ssl->out_msg = ssl->out_buf + written_out;
@@ -1277,7 +1281,8 @@
goto error;
}
- mbedtls_ssl_reset_in_out_pointers(ssl);
+ mbedtls_ssl_reset_in_pointers(ssl);
+ mbedtls_ssl_reset_out_pointers(ssl);
#if defined(MBEDTLS_SSL_DTLS_SRTP)
memset(&ssl->dtls_srtp_info, 0, sizeof(ssl->dtls_srtp_info));
@@ -1342,7 +1347,8 @@
/* Cancel any possibly running timer */
mbedtls_ssl_set_timer(ssl, 0);
- mbedtls_ssl_reset_in_out_pointers(ssl);
+ mbedtls_ssl_reset_in_pointers(ssl);
+ mbedtls_ssl_reset_out_pointers(ssl);
/* Reset incoming message parsing */
ssl->in_offt = NULL;
@@ -1350,6 +1356,7 @@
ssl->in_msgtype = 0;
ssl->in_msglen = 0;
ssl->in_hslen = 0;
+ ssl->in_hsfraglen = 0;
ssl->keep_current_message = 0;
ssl->transform_in = NULL;
diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
index fc9b860..a302af4 100644
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -1015,28 +1015,6 @@
MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message"));
return MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE;
}
- {
- size_t handshake_len = MBEDTLS_GET_UINT24_BE(buf, 1);
- MBEDTLS_SSL_DEBUG_MSG(3, ("client hello v3, handshake len.: %u",
- (unsigned) handshake_len));
-
- /* The record layer has a record size limit of 2^14 - 1 and
- * fragmentation is not supported, so buf[1] should be zero. */
- if (buf[1] != 0) {
- MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message: %u != 0",
- (unsigned) buf[1]));
- return MBEDTLS_ERR_SSL_DECODE_ERROR;
- }
-
- /* We don't support fragmentation of ClientHello (yet?) */
- if (msg_len != mbedtls_ssl_hs_hdr_len(ssl) + handshake_len) {
- MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message: %u != %u + %u",
- (unsigned) msg_len,
- (unsigned) mbedtls_ssl_hs_hdr_len(ssl),
- (unsigned) handshake_len));
- return MBEDTLS_ERR_SSL_DECODE_ERROR;
- }
- }
#if defined(MBEDTLS_SSL_PROTO_DTLS)
if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {