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Fix memory leak from zero-length DTLS fragments.

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The |pqueue_insert| function can fail if one attempts to insert a
duplicate sequence number. When handling a fragment of an out of
sequence message, |dtls1_process_out_of_seq_message| would not call
|dtls1_reassemble_fragment| if the fragment's length was zero. It would
then allocate a fresh fragment and attempt to insert it, but ignore the
return value, leaking the fragment.

This allows an attacker to exhaust the memory of a DTLS peer.

Fixes CVE-2014-3507

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Emilia Käsper <emilia@openssl.org>
This commit is contained in:
Adam Langley 2014-06-06 14:30:33 -07:00 committed by Matt Caswell
parent 1250f12613
commit d0a4b7d1a2
1 changed files with 19 additions and 3 deletions
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22
ssl/d1_both.c
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@ -616,6 +616,9 @@ dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok)
msg_hdr->msg_len > dtls1_max_handshake_message_len(s))
goto err;
if (frag_len == 0)
return DTLS1_HM_FRAGMENT_RETRY;
/* Try to find item in queue */
memset(seq64be,0,sizeof(seq64be));
seq64be[6] = (unsigned char) (msg_hdr->seq>>8);
@ -693,7 +696,12 @@ dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok)
goto err;
}
pqueue_insert(s->d1->buffered_messages, item);
item = pqueue_insert(s->d1->buffered_messages, item);
/* pqueue_insert fails iff a duplicate item is inserted.
* However, |item| cannot be a duplicate. If it were,
* |pqueue_find|, above, would have returned it and control
* would never have reached this branch. */
OPENSSL_assert(item != NULL);
}
return DTLS1_HM_FRAGMENT_RETRY;
@ -751,7 +759,7 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
}
else
{
if (frag_len && frag_len < msg_hdr->msg_len)
if (frag_len < msg_hdr->msg_len)
return dtls1_reassemble_fragment(s, msg_hdr, ok);
if (frag_len > dtls1_max_handshake_message_len(s))
@ -780,7 +788,15 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
if ( item == NULL)
goto err;
pqueue_insert(s->d1->buffered_messages, item);
item = pqueue_insert(s->d1->buffered_messages, item);
/* pqueue_insert fails iff a duplicate item is inserted.
* However, |item| cannot be a duplicate. If it were,
* |pqueue_find|, above, would have returned it. Then, either
* |frag_len| != |msg_hdr->msg_len| in which case |item| is set
* to NULL and it will have been processed with
* |dtls1_reassemble_fragment|, above, or the record will have
* been discarded. */
OPENSSL_assert(item != NULL);
}
return DTLS1_HM_FRAGMENT_RETRY;