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- From a3303e196e5d304ec955c4d63afb923ade66c6e8 Mon Sep 17 00:00:00 2001
- From: Simon Kelley <simon@thekelleys.org.uk>
- Date: Thu, 7 Sep 2017 20:45:00 +0100
- Subject: [PATCH] Don't return arcount=1 if EDNS0 RR won't fit in the packet.
- Omitting the EDNS0 RR but setting arcount gives a malformed packet.
- Also, don't accept UDP packet size less than 512 in recieved EDNS0.
- ---
- src/edns0.c | 5 ++++-
- src/forward.c | 2 ++
- 2 files changed, 6 insertions(+), 1 deletion(-)
- diff --git a/src/edns0.c b/src/edns0.c
- index 3fde17f..f5b798c 100644
- --- a/src/edns0.c
- +++ b/src/edns0.c
- @@ -208,7 +208,10 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
- free(buff);
- p += rdlen;
- }
- - header->arcount = htons(ntohs(header->arcount) + 1);
- +
- + /* Only bump arcount if RR is going to fit */
- + if (((ssize_t)optlen) <= (limit - (p + 4)))
- + header->arcount = htons(ntohs(header->arcount) + 1);
- }
-
- if (((ssize_t)optlen) > (limit - (p + 4)))
- diff --git a/src/forward.c b/src/forward.c
- index e3fa94b..942b02d 100644
- --- a/src/forward.c
- +++ b/src/forward.c
- @@ -1412,6 +1412,8 @@ void receive_query(struct listener *listen, time_t now)
- defaults to 512 */
- if (udp_size > daemon->edns_pktsz)
- udp_size = daemon->edns_pktsz;
- + else if (udp_size < PACKETSZ)
- + udp_size = PACKETSZ; /* Sanity check - can't reduce below default. RFC 6891 6.2.3 */
- }
-
- #ifdef HAVE_AUTH
- --
- 1.7.10.4
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