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45 lines
1.4 KiB
45 lines
1.4 KiB
From 2c1aec1e979a209eb2f2b035314a8c973b4ac269 Mon Sep 17 00:00:00 2001 |
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From: Simon Kelley <simon@thekelleys.org.uk> |
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Date: Thu, 7 Sep 2017 20:45:00 +0100 |
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Subject: [PATCH 7/9] Don't return arcount=1 if EDNS0 RR won't fit in the |
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packet. |
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Omitting the EDNS0 RR but setting arcount gives a malformed packet. |
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Also, don't accept UDP packet size less than 512 in recieved EDNS0. |
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--- |
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src/edns0.c | 5 ++++- |
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src/forward.c | 2 ++ |
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2 files changed, 6 insertions(+), 1 deletion(-) |
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diff --git a/src/edns0.c b/src/edns0.c |
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index 5bdc133..a8d0167 100644 |
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--- a/src/edns0.c |
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+++ b/src/edns0.c |
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@@ -221,7 +221,10 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l |
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free(buff); |
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p += rdlen; |
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} |
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- header->arcount = htons(ntohs(header->arcount) + 1); |
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+ |
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+ /* Only bump arcount if RR is going to fit */ |
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+ if (((ssize_t)optlen) <= (limit - (p + 4))) |
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+ header->arcount = htons(ntohs(header->arcount) + 1); |
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} |
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if (((ssize_t)optlen) > (limit - (p + 4))) |
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diff --git a/src/forward.c b/src/forward.c |
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index 9b464d3..0f8f462 100644 |
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--- a/src/forward.c |
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+++ b/src/forward.c |
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@@ -1408,6 +1408,8 @@ void receive_query(struct listener *listen, time_t now) |
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defaults to 512 */ |
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if (udp_size > daemon->edns_pktsz) |
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udp_size = daemon->edns_pktsz; |
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+ else if (udp_size < PACKETSZ) |
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+ udp_size = PACKETSZ; /* Sanity check - can't reduce below default. RFC 6891 6.2.3 */ |
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} |
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#ifdef HAVE_AUTH |
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-- |
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2.9.5 |
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