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

0003-Add-str-len-check-in-config_sortlist-to-avoid-stack-.patch

@@ -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
+

c-ares.spec

@@ -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]