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From 446225e54b4f23c08a07968433b39d62ed65afd1 Mon Sep 17 00:00:00 2001
From: Changqing Li <changqing.li@windriver.com>
Date: Tue, 14 Sep 2021 13:59:28 +0800
Subject: [PATCH 2/2] ares_expand_name(): fix formatting and handling of root
name response
Fixes issue introduced in prior commit with formatting and handling
of parsing a root name response which should not be escaped.
Fix By: Brad House
Upstream-Status: Backport [https://github.com/c-ares/c-ares/commit/44c009b8e62ea1929de68e3f438181bea469ec14]
CVE: CVE-2021-3672
Signed-off-by: Changqing Li <changqing.li@windriver.com>
---
ares_expand_name.c | 56 +++++++++++++++++++++++++++++-----------------
1 file changed, 35 insertions(+), 21 deletions(-)
diff --git a/ares_expand_name.c b/ares_expand_name.c
index 8604543..af0c2e8 100644
--- a/ares_expand_name.c
+++ b/ares_expand_name.c
@@ -133,22 +133,30 @@ int ares_expand_name(const unsigned char *encoded, const unsigned char *abuf,
}
else
{
- len = *p;
+ int name_len = *p;
+ len = name_len;
p++;
while (len--)
{
- if (!isprint(*p)) {
- /* Output as \DDD for consistency with RFC1035 5.1 */
- *q++ = '\\';
- *q++ = '0' + *p / 100;
- *q++ = '0' + (*p % 100) / 10;
- *q++ = '0' + (*p % 10);
- } else if (is_reservedch(*p)) {
- *q++ = '\\';
- *q++ = *p;
- } else {
- *q++ = *p;
- }
+ /* Output as \DDD for consistency with RFC1035 5.1, except
+ * for the special case of a root name response */
+ if (!isprint(*p) && !(name_len == 1 && *p == 0))
+ {
+
+ *q++ = '\\';
+ *q++ = '0' + *p / 100;
+ *q++ = '0' + (*p % 100) / 10;
+ *q++ = '0' + (*p % 10);
+ }
+ else if (is_reservedch(*p))
+ {
+ *q++ = '\\';
+ *q++ = *p;
+ }
+ else
+ {
+ *q++ = *p;
+ }
p++;
}
*q++ = '.';
@@ -200,19 +208,25 @@ static int name_length(const unsigned char *encoded, const unsigned char *abuf,
}
else if (top == 0x00)
{
- offset = *encoded;
+ int name_len = *encoded;
+ offset = name_len;
if (encoded + offset + 1 >= abuf + alen)
return -1;
encoded++;
while (offset--)
{
- if (!isprint(*encoded)) {
- n += 4;
- } else if (is_reservedch(*encoded)) {
- n += 2;
- } else {
- n += 1;
- }
+ if (!isprint(*encoded) && !(name_len == 1 && *encoded == 0))
+ {
+ n += 4;
+ }
+ else if (is_reservedch(*encoded))
+ {
+ n += 2;
+ }
+ else
+ {
+ n += 1;
+ }
encoded++;
}
n++;
--
2.17.1
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