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Resolves: rhbz#2170867 - c-ares: buffer overflow in config_sortlist() due to missing string length check [rhel-8]

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This commit is contained in:
Alexey Tikhonov 2023-05-12 13:15:28 +02:00
parent 7170f1b111
commit 2067b47353
2 changed files with 70 additions and 1 deletions
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64
0003-Add-str-len-check-in-config_sortlist-to-avoid-stack-.patch Normal file
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@ -0,0 +1,64 @@
From 9903253c347f9e0bffd285ae3829aef251cc852d Mon Sep 17 00:00:00 2001
From: hopper-vul <118949689+hopper-vul@users.noreply.github.com>
Date: Wed, 18 Jan 2023 22:14:26 +0800
Subject: [PATCH] Add str len check in config_sortlist to avoid stack overflow
(#497)
In ares_set_sortlist, it calls config_sortlist(..., sortstr) to parse
the input str and initialize a sortlist configuration.
However, ares_set_sortlist has not any checks about the validity of the input str.
It is very easy to create an arbitrary length stack overflow with the unchecked
`memcpy(ipbuf, str, q-str);` and `memcpy(ipbufpfx, str, q-str);`
statements in the config_sortlist call, which could potentially cause severe
security impact in practical programs.
This commit add necessary check for `ipbuf` and `ipbufpfx` which avoid the
potential stack overflows.
fixes #496
Fix By: @hopper-vul
---
ares_init.c | 4 ++++
test/ares-test-init.cc | 2 ++
2 files changed, 6 insertions(+)
diff --git a/ares_init.c b/ares_init.c
index f7b700b..5aad7c8 100644
--- a/ares_init.c
+++ b/ares_init.c
@@ -2065,6 +2065,8 @@ static int config_sortlist(struct apattern **sortlist, int *nsort,
q = str;
while (*q && *q != '/' && *q != ';' && !ISSPACE(*q))
q++;
+ if (q-str >= 16)
+ return ARES_EBADSTR;
memcpy(ipbuf, str, q-str);
ipbuf[q-str] = '\0';
/* Find the prefix */
@@ -2073,6 +2075,8 @@ static int config_sortlist(struct apattern **sortlist, int *nsort,
const char *str2 = q+1;
while (*q && *q != ';' && !ISSPACE(*q))
q++;
+ if (q-str >= 32)
+ return ARES_EBADSTR;
memcpy(ipbufpfx, str, q-str);
ipbufpfx[q-str] = '\0';
str = str2;
diff --git a/test/ares-test-init.cc b/test/ares-test-init.cc
index 63c6a22..ee84518 100644
--- a/test/ares-test-init.cc
+++ b/test/ares-test-init.cc
@@ -275,6 +275,8 @@ TEST_F(DefaultChannelTest, SetAddresses) {
TEST_F(DefaultChannelTest, SetSortlistFailures) {
EXPECT_EQ(ARES_ENODATA, ares_set_sortlist(nullptr, "1.2.3.4"));
+ EXPECT_EQ(ARES_EBADSTR, ares_set_sortlist(channel_, "111.111.111.111*/16"));
+ EXPECT_EQ(ARES_EBADSTR, ares_set_sortlist(channel_, "111.111.111.111/255.255.255.240*"));
EXPECT_EQ(ARES_SUCCESS, ares_set_sortlist(channel_, "xyzzy ; lwk"));
EXPECT_EQ(ARES_SUCCESS, ares_set_sortlist(channel_, "xyzzy ; 0x123"));
}
--
2.37.3

7
c-ares.spec
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@ -1,7 +1,7 @@
Summary: A library that performs asynchronous DNS operations
Name: c-ares
Version: 1.13.0
Release: 6%{?dist}
Release: 7%{?dist}
License: MIT
Group: System Environment/Libraries
URL: http://c-ares.haxx.se/
@ -10,6 +10,7 @@ Source0: http://c-ares.haxx.se/download/%{name}-%{version}.tar.gz
Source1: LICENSE
Patch0: 0001-Use-RPM-compiler-options.patch
Patch1: 0002-fix-CVE-2021-3672.patch
Patch2: 0003-Add-str-len-check-in-config_sortlist-to-avoid-stack-.patch
BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
@ -36,6 +37,7 @@ compile applications or shared objects that use c-ares.
%setup -q
%patch0 -p1 -b .optflags
%patch1 -p1 -b .dns
%patch2 -p1 -b .sortlist
cp %{SOURCE1} .
f=CHANGES ; iconv -f iso-8859-1 -t utf-8 $f -o $f.utf8 ; mv $f.utf8 $f
@ -74,6 +76,9 @@ rm -rf $RPM_BUILD_ROOT
%{_mandir}/man3/ares_*
%changelog
* Fri May 12 2023 Alexey Tikhonov <atikhono@redhat.com> - 1.13.0-7
- Resolves: rhbz#2170867 - c-ares: buffer overflow in config_sortlist() due to missing string length check [rhel-8]
* Fri Oct 15 2021 Alexey Tikhonov <atikhono@redhat.com> - 1.13.0-6
- Resolves: rhbz#1989425 - CVE-2021-3672 c-ares: missing input validation of host names may lead to Domain Hijacking [rhel-8]