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95 lines
2.9 KiB
Diff
95 lines
2.9 KiB
Diff
From 63437ffbb58837b214b4b92cb1c54bc5f3279928 Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Wed, 6 Sep 2017 22:34:21 +0100
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Subject: [PATCH] Fix CVE-2017-13704, which resulted in a crash on a large DNS
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query.
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A DNS query recieved by UDP which exceeds 512 bytes (or the EDNS0 packet size,
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if different.) is enough to cause SIGSEGV.
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---
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CHANGELOG | 7 +++++++
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src/auth.c | 5 -----
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src/forward.c | 8 ++++++++
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src/rfc1035.c | 5 -----
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4 files changed, 15 insertions(+), 10 deletions(-)
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diff --git a/CHANGELOG b/CHANGELOG
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index 3a640f3..7e65912 100644
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--- a/CHANGELOG
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+++ b/CHANGELOG
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@@ -17,6 +17,13 @@ version 2.78
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--strict-order active. Thanks to Hans Dedecker
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for the patch
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+ Fix regression in 2.77, ironically added as a security
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+ improvement, which resulted in a crash when a DNS
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+ query exceeded 512 bytes (or the EDNS0 packet size,
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+ if different.) Thanks to Christian Kujau, Arne Woerner
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+ Juan Manuel Fernandez and Kevin Darbyshire-Bryant for
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+ chasing this one down. CVE-2017-13704 applies.
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+
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version 2.77
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Generate an error when configured with a CNAME loop,
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diff --git a/src/auth.c b/src/auth.c
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index 2c24e16..7f95f98 100644
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--- a/src/auth.c
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+++ b/src/auth.c
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@@ -119,11 +119,6 @@ size_t answer_auth(struct dns_header *header, char *limit, size_t qlen, time_t n
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struct cname *a, *candidate;
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unsigned int wclen;
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- /* Clear buffer beyond request to avoid risk of
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- information disclosure. */
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- memset(((char *)header) + qlen, 0,
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- (limit - ((char *)header)) - qlen);
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-
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if (ntohs(header->qdcount) == 0 || OPCODE(header) != QUERY )
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return 0;
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diff --git a/src/forward.c b/src/forward.c
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index f22556a..e3fa94b 100644
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--- a/src/forward.c
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+++ b/src/forward.c
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@@ -1188,6 +1188,10 @@ void receive_query(struct listener *listen, time_t now)
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(msg.msg_flags & MSG_TRUNC) ||
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(header->hb3 & HB3_QR))
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return;
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+
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+ /* Clear buffer beyond request to avoid risk of
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+ information disclosure. */
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+ memset(daemon->packet + n, 0, daemon->edns_pktsz - n);
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source_addr.sa.sa_family = listen->family;
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@@ -1688,6 +1692,10 @@ unsigned char *tcp_request(int confd, time_t now,
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if (size < (int)sizeof(struct dns_header))
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continue;
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+
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+ /* Clear buffer beyond request to avoid risk of
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+ information disclosure. */
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+ memset(payload + size, 0, 65536 - size);
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query_count++;
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diff --git a/src/rfc1035.c b/src/rfc1035.c
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index 26f5301..af2fe46 100644
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--- a/src/rfc1035.c
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+++ b/src/rfc1035.c
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@@ -1223,11 +1223,6 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
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struct mx_srv_record *rec;
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size_t len;
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- /* Clear buffer beyond request to avoid risk of
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- information disclosure. */
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- memset(((char *)header) + qlen, 0,
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- (limit - ((char *)header)) - qlen);
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-
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if (ntohs(header->ancount) != 0 ||
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ntohs(header->nscount) != 0 ||
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ntohs(header->qdcount) == 0 ||
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--
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1.7.10.4
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