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From: Mark Johnston <markj@FreeBSD.org>
Subject: git: 1af332a7d8f8 - main - rtsold: Fix validation of RDNSS options
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The branch main has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=1af332a7d8f86b6fcc1f0f575fe5b06021b54f4c
commit 1af332a7d8f86b6fcc1f0f575fe5b06021b54f4c
Author: Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2021-03-21 18:18:10 +0000
Commit: Mark Johnston <markj@FreeBSD.org>
CommitDate: 2021-03-21 18:19:42 +0000
rtsold: Fix validation of RDNSS options
The header specifies the size of the option in multiples of eight bytes.
The option consists of an eight-byte header followed by one or more IPv6
addresses, so the option is invalid if the size is not equal to 1+2n for
some n>0. Check this.
The bug can cause random stack data to be formatted as an IPv6 address
and passed to resolvconf(8), but a host able to trigger the bug may also
specify arbitrary addresses this way.
Reported by: Q C <cq674350529@gmail.com>
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
---
usr.sbin/rtsold/rtsol.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/usr.sbin/rtsold/rtsol.c b/usr.sbin/rtsold/rtsol.c
index 30027fc65ac9..76756bfd8393 100644
--- a/usr.sbin/rtsold/rtsol.c
+++ b/usr.sbin/rtsold/rtsol.c
@@ -363,13 +363,19 @@ rtsol_input(int sock)
case ND_OPT_RDNSS:
rdnss = (struct nd_opt_rdnss *)raoptp;
- /* Optlen sanity check (Section 5.3.1 in RFC 6106) */
- if (rdnss->nd_opt_rdnss_len < 3) {
+ /*
+ * The option header is 8 bytes long and each address
+ * occupies 16 bytes, so the option length must be
+ * greater than or equal to 24 bytes and an odd multiple
+ * of 8 bytes. See section 5.1 in RFC 6106.
+ */
+ if (rdnss->nd_opt_rdnss_len < 3 ||
+ rdnss->nd_opt_rdnss_len % 2 == 0) {
warnmsg(LOG_INFO, __func__,
- "too short RDNSS option"
- "in RA from %s was ignored.",
- inet_ntop(AF_INET6, &from.sin6_addr,
- ntopbuf, sizeof(ntopbuf)));
+ "too short RDNSS option in RA from %s "
+ "was ignored.",
+ inet_ntop(AF_INET6, &from.sin6_addr, ntopbuf,
+ sizeof(ntopbuf)));
break;
}