Fix DTLS handshake message size checks.
In |dtls1_reassemble_fragment|, the value of
|msg_hdr->frag_off+frag_len| was being checked against the maximum
handshake message size, but then |msg_len| bytes were allocated for the
fragment buffer. This means that so long as the fragment was within the
allowed size, the pending handshake message could consume 16MB + 2MB
(for the reassembly bitmap). Approx 10 outstanding handshake messages
are allowed, meaning that an attacker could consume ~180MB per DTLS
connection.
In the non-fragmented path (in |dtls1_process_out_of_seq_message|), no
check was applied.
Fixes CVE-2014-3506
Wholly based on patch by Adam Langley with one minor amendment.
Reviewed-by: Emilia Käsper <emilia@openssl.org>
(Imported from upstream's 0598468fc04fb0cf2438c4ee635b587aac1bcce6)
Change-Id: I4849498eabb45ec973fcb988d639b23145891e25
Reviewed-on: https://boringssl-review.googlesource.com/1434
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/d1_both.c b/ssl/d1_both.c
index b0e749c..5d95921 100644
--- a/ssl/d1_both.c
+++ b/ssl/d1_both.c
@@ -595,6 +595,16 @@
return 0;
}
+/* dtls1_max_handshake_message_len returns the maximum number of bytes
+ * permitted in a DTLS handshake message for |s|. The minimum is 16KB, but may
+ * be greater if the maximum certificate list size requires it. */
+static unsigned long dtls1_max_handshake_message_len(const SSL *s)
+ {
+ unsigned long max_len = DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH;
+ if (max_len < (unsigned long)s->max_cert_list)
+ return s->max_cert_list;
+ return max_len;
+ }
static int
dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok)
@@ -603,20 +613,10 @@
pitem *item = NULL;
int i = -1, is_complete;
unsigned char seq64be[8];
- unsigned long frag_len = msg_hdr->frag_len, max_len;
+ unsigned long frag_len = msg_hdr->frag_len;
- if ((msg_hdr->frag_off+frag_len) > msg_hdr->msg_len)
- goto err;
-
- /* Determine maximum allowed message size. Depends on (user set)
- * maximum certificate length, but 16k is minimum.
- */
- if (DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH < s->max_cert_list)
- max_len = s->max_cert_list;
- else
- max_len = DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH;
-
- if ((msg_hdr->frag_off+frag_len) > max_len)
+ if ((msg_hdr->frag_off+frag_len) > msg_hdr->msg_len ||
+ msg_hdr->msg_len > dtls1_max_handshake_message_len(s))
goto err;
/* Try to find item in queue */
@@ -756,6 +756,9 @@
if (frag_len && frag_len < msg_hdr->msg_len)
return dtls1_reassemble_fragment(s, msg_hdr, ok);
+ if (frag_len > dtls1_max_handshake_message_len(s))
+ goto err;
+
frag = dtls1_hm_fragment_new(frag_len, 0);
if ( frag == NULL)
goto err;
