75 lines
3.0 KiB
Diff
75 lines
3.0 KiB
Diff
@@ -, +, @@
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bgpd: CVE-2012-1820, DoS in bgp_capability_orf()
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An ORF (code 3) capability TLV is defined to contain exactly one
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AFI/SAFI block. Function bgp_capability_orf(), which parses ORF
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capability TLV, uses do-while cycle to call its helper function
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bgp_capability_orf_entry(), which actually processes the AFI/SAFI data
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block. The call is made at least once and repeated as long as the input
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buffer has enough data for the next call.
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The helper function, bgp_capability_orf_entry(), uses "Number of ORFs"
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field of the provided AFI/SAFI block to verify, if it fits the input
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buffer. However, the check is made based on the total length of the ORF
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TLV regardless of the data already consumed by the previous helper
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function call(s). This way, the check condition is only valid for the
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first AFI/SAFI block inside an ORF capability TLV.
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For the subsequent calls of the helper function, if any are made, the
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check condition may erroneously tell, that the current "Number of ORFs"
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field fits the buffer boundary, where in fact it does not. This makes it
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possible to trigger an assertion by feeding an OPEN message with a
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specially-crafted malformed ORF capability TLV.
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This commit fixes the vulnerability by making the implementation follow
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the spec.
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--- a/bgpd/bgp_open.c
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+++ a/bgpd/bgp_open.c
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@@ -231,7 +231,7 @@ bgp_capability_orf_entry (struct peer *peer, struct capability_header *hdr)
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}
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/* validate number field */
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- if (sizeof (struct capability_orf_entry) + (entry.num * 2) > hdr->length)
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+ if (sizeof (struct capability_orf_entry) + (entry.num * 2) != hdr->length)
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{
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zlog_info ("%s ORF Capability entry length error,"
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" Cap length %u, num %u",
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@@ -335,28 +335,6 @@ bgp_capability_orf_entry (struct peer *peer, struct capability_header *hdr)
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}
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static int
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-bgp_capability_orf (struct peer *peer, struct capability_header *hdr)
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-{
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- struct stream *s = BGP_INPUT (peer);
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- size_t end = stream_get_getp (s) + hdr->length;
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-
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- assert (stream_get_getp(s) + sizeof(struct capability_orf_entry) <= end);
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-
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- /* We must have at least one ORF entry, as the caller has already done
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- * minimum length validation for the capability code - for ORF there must
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- * at least one ORF entry (header and unknown number of pairs of bytes).
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- */
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- do
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- {
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- if (bgp_capability_orf_entry (peer, hdr) == -1)
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- return -1;
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- }
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- while (stream_get_getp(s) + sizeof(struct capability_orf_entry) < end);
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-
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- return 0;
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-}
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-
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-static int
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bgp_capability_restart (struct peer *peer, struct capability_header *caphdr)
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{
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struct stream *s = BGP_INPUT (peer);
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@@ -573,7 +551,7 @@ bgp_capability_parse (struct peer *peer, size_t length, int *mp_capability,
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break;
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case CAPABILITY_CODE_ORF:
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case CAPABILITY_CODE_ORF_OLD:
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- if (bgp_capability_orf (peer, &caphdr))
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+ if (bgp_capability_orf_entry (peer, &caphdr))
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return -1;
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break;
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case CAPABILITY_CODE_RESTART:
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