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glibc/glibc-RHEL-2423.patch
Siddhesh Poyarekar 1c55a2977c CVE-2023-4806 glibc: potential use-after-free in getaddrinfo 
Resolves: RHEL-2423
2023-09-19 13:52:14 -04:00

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Avoid UAF in getcanonname (CVE-2023-4806)
When an NSS plugin only implements the _gethostbyname2_r and
_getcanonname_r callbacks, getaddrinfo could use memory that was freed
during tmpbuf resizing, through h_name in a previous query response.
The backing store for res->at->name when doing a query with
gethostbyname3_r or gethostbyname2_r is tmpbuf, which is reallocated in
gethosts during the query. For AF_INET6 lookup with AI_ALL |
AI_V4MAPPED, gethosts gets called twice, once for a v6 lookup and second
for a v4 lookup. In this case, if the first call reallocates tmpbuf
enough number of times, resulting in a malloc, th->h_name (that
res->at->name refers to) ends up on a heap allocated storage in tmpbuf.
Now if the second call to gethosts also causes the plugin callback to
return NSS_STATUS_TRYAGAIN, tmpbuf will get freed, resulting in a UAF
reference in res->at->name. This then gets dereferenced in the
getcanonname_r plugin call, resulting in the use after free.
Fix this by copying h_name over and freeing it at the end. This
resolves BZ #30843, which is assigned CVE-2023-4806. This is a minimal
RHEL-8-specific fix. Test case differences from upstream:
- The test module needs to explicitly link against libnss_files on
RHEL-8; upstream libnss_files is built into libc.so.
- Test module code was adapted to not use the upstream NSS module
convenience macros.
This change is adapted from the following commit from upstream:
commit 973fe93a5675c42798b2161c6f29c01b0e243994
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Fri Sep 15 13:51:12 2023 -0400
getaddrinfo: Fix use after free in getcanonname (CVE-2023-4806)
When an NSS plugin only implements the _gethostbyname2_r and
_getcanonname_r callbacks, getaddrinfo could use memory that was freed
during tmpbuf resizing, through h_name in a previous query response.
The backing store for res->at->name when doing a query with
gethostbyname3_r or gethostbyname2_r is tmpbuf, which is reallocated in
gethosts during the query. For AF_INET6 lookup with AI_ALL |
AI_V4MAPPED, gethosts gets called twice, once for a v6 lookup and second
for a v4 lookup. In this case, if the first call reallocates tmpbuf
enough number of times, resulting in a malloc, th->h_name (that
res->at->name refers to) ends up on a heap allocated storage in tmpbuf.
Now if the second call to gethosts also causes the plugin callback to
return NSS_STATUS_TRYAGAIN, tmpbuf will get freed, resulting in a UAF
reference in res->at->name. This then gets dereferenced in the
getcanonname_r plugin call, resulting in the use after free.
Fix this by copying h_name over and freeing it at the end. This
resolves BZ #30843, which is assigned CVE-2023-4806.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
diff --git a/nss/Makefile b/nss/Makefile
index cfb255c6e7a3a4de..5829a2539306ddb5 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -66,7 +66,8 @@ xtests = bug-erange
tests-container = \
tst-nss-db-endpwent \
tst-nss-db-endgrent \
- tst-nss-gai-actions
+ tst-nss-gai-actions \
+ tst-nss-gai-hv2-canonname
# Tests which need libdl
ifeq (yes,$(build-shared))
@@ -132,7 +133,8 @@ routines += $(libnss_files-routines)
static-only-routines += $(libnss_files-routines)
tests-static += tst-nss-static
endif
-extra-test-objs += nss_test1.os nss_test2.os nss_test_errno.os
+extra-test-objs += nss_test1.os nss_test2.os nss_test_errno.os \
+ nss_test_gai_hv2_canonname.os
include ../Rules
@@ -169,12 +171,17 @@ rtld-tests-LDFLAGS += -Wl,--dynamic-list=nss_test.ver
libof-nss_test1 = extramodules
libof-nss_test2 = extramodules
libof-nss_test_errno = extramodules
+libof-nss_test_gai_hv2_canonname = extramodules
$(objpfx)/libnss_test1.so: $(objpfx)nss_test1.os $(link-libc-deps)
$(build-module)
$(objpfx)/libnss_test2.so: $(objpfx)nss_test2.os $(link-libc-deps)
$(build-module)
$(objpfx)/libnss_test_errno.so: $(objpfx)nss_test_errno.os $(link-libc-deps)
$(build-module)
+$(objpfx)/libnss_test_gai_hv2_canonname.so: \
+ $(objpfx)nss_test_gai_hv2_canonname.os $(link-libc-deps) \
+ $(objpfx)/libnss_files.so
+ $(build-module)
$(objpfx)nss_test2.os : nss_test1.c
ifdef libnss_test1.so-version
$(objpfx)/libnss_test1.so$(libnss_test1.so-version): $(objpfx)/libnss_test1.so
@@ -187,10 +194,14 @@ endif
$(objpfx)/libnss_test_errno.so$(libnss_files.so-version): \
$(objpfx)/libnss_test_errno.so
$(make-link)
+$(objpfx)/libnss_test_gai_hv2_canonname.so$(libnss_files.so-version): \
+ $(objpfx)/libnss_test_gai_hv2_canonname.so
+ $(make-link)
$(patsubst %,$(objpfx)%.out,$(tests)) : \
$(objpfx)/libnss_test1.so$(libnss_test1.so-version) \
$(objpfx)/libnss_test2.so$(libnss_test2.so-version) \
- $(objpfx)/libnss_test_errno.so$(libnss_files.so-version)
+ $(objpfx)/libnss_test_errno.so$(libnss_files.so-version) \
+ $(objpfx)/libnss_test_gai_hv2_canonname.so$(libnss_files.so-version)
ifeq (yes,$(have-thread-library))
$(objpfx)tst-cancel-getpwuid_r: $(shared-thread-library)
diff --git a/nss/nss_test_gai_hv2_canonname.c b/nss/nss_test_gai_hv2_canonname.c
new file mode 100644
index 0000000000000000..4195d7d24fdd5f6d
--- /dev/null
+++ b/nss/nss_test_gai_hv2_canonname.c
@@ -0,0 +1,64 @@
+/* NSS service provider that only provides gethostbyname2_r.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <netdb.h>
+#include <nss.h>
+#include <stdlib.h>
+#include <string.h>
+#include "nss/tst-nss-gai-hv2-canonname.h"
+
+/* Catch misnamed and functions. */
+#pragma GCC diagnostic error "-Wmissing-prototypes"
+
+extern enum nss_status _nss_files_gethostbyname2_r (const char *, int,
+ struct hostent *, char *,
+ size_t, int *, int *);
+
+enum nss_status
+_nss_test_gai_hv2_canonname_gethostbyname2_r (const char *, int, struct hostent
+ *, char *, size_t, int *, int *);
+
+enum nss_status
+_nss_test_gai_hv2_canonname_getcanonname_r (const char *, char *, size_t, char
+ **, int *, int *);
+
+enum nss_status
+_nss_test_gai_hv2_canonname_gethostbyname2_r (const char *name, int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *herrnop)
+{
+ return _nss_files_gethostbyname2_r (name, af, result, buffer, buflen, errnop,
+ herrnop);
+}
+
+enum nss_status
+_nss_test_gai_hv2_canonname_getcanonname_r (const char *name, char *buffer,
+ size_t buflen, char **result,
+ int *errnop, int *h_errnop)
+{
+ /* We expect QUERYNAME, which is a small enough string that it shouldn't fail
+ the test. */
+ if (memcmp (QUERYNAME, name, sizeof (QUERYNAME))
+ || buflen < sizeof (QUERYNAME))
+ abort ();
+
+ strncpy (buffer, name, buflen);
+ *result = buffer;
+ return NSS_STATUS_SUCCESS;
+}
diff --git a/nss/tst-nss-gai-hv2-canonname.c b/nss/tst-nss-gai-hv2-canonname.c
new file mode 100644
index 0000000000000000..d5f10c07d6a90773
--- /dev/null
+++ b/nss/tst-nss-gai-hv2-canonname.c
@@ -0,0 +1,63 @@
+/* Test NSS query path for plugins that only implement gethostbyname2
+ (#30843).
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <nss.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/xstdio.h>
+#include "nss/tst-nss-gai-hv2-canonname.h"
+
+#define PREPARE do_prepare
+
+static void do_prepare (int a, char **av)
+{
+ FILE *hosts = xfopen ("/etc/hosts", "w");
+ for (unsigned i = 2; i < 255; i++)
+ {
+ fprintf (hosts, "ff01::ff02:ff03:%u:2\ttest.example.com\n", i);
+ fprintf (hosts, "192.168.0.%u\ttest.example.com\n", i);
+ }
+ xfclose (hosts);
+}
+
+static int
+do_test (void)
+{
+ __nss_configure_lookup ("hosts", "test_gai_hv2_canonname");
+
+ struct addrinfo hints = {};
+ struct addrinfo *result = NULL;
+
+ hints.ai_family = AF_INET6;
+ hints.ai_flags = AI_ALL | AI_V4MAPPED | AI_CANONNAME;
+
+ int ret = getaddrinfo (QUERYNAME, NULL, &hints, &result);
+
+ if (ret != 0)
+ FAIL_EXIT1 ("getaddrinfo failed: %s\n", gai_strerror (ret));
+
+ TEST_COMPARE_STRING (result->ai_canonname, QUERYNAME);
+
+ freeaddrinfo(result);
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/nss/tst-nss-gai-hv2-canonname.h b/nss/tst-nss-gai-hv2-canonname.h
new file mode 100644
index 0000000000000000..14f2a9cb0867dff9
--- /dev/null
+++ b/nss/tst-nss-gai-hv2-canonname.h
@@ -0,0 +1 @@
+#define QUERYNAME "test.example.com"
diff --git a/nss/tst-nss-gai-hv2-canonname.root/postclean.req b/nss/tst-nss-gai-hv2-canonname.root/postclean.req
new file mode 100644
index 0000000000000000..e69de29bb2d1d643
diff --git a/nss/tst-nss-gai-hv2-canonname.root/tst-nss-gai-hv2-canonname.script b/nss/tst-nss-gai-hv2-canonname.root/tst-nss-gai-hv2-canonname.script
new file mode 100644
index 0000000000000000..31848b4a28524af6
--- /dev/null
+++ b/nss/tst-nss-gai-hv2-canonname.root/tst-nss-gai-hv2-canonname.script
@@ -0,0 +1,2 @@
+cp $B/nss/libnss_test_gai_hv2_canonname.so $L/libnss_test_gai_hv2_canonname.so.2
+su
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 4fa963644af8b7d5..46046504a6858f2e 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -233,7 +233,6 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req,
}
array[i].next = array + i + 1;
}
- array[0].name = h->h_name;
array[count - 1].next = NULL;
*result = array;
@@ -287,6 +286,18 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req,
} \
*pat = addrmem; \
\
+ /* Store h_name so that it survives accidental deallocation when \
+ gethosts is called again and tmpbuf gets reallocated. */ \
+ if (h_name == NULL && th.h_name != NULL) \
+ { \
+ h_name = __strdup (th.h_name); \
+ if (h_name == NULL) \
+ { \
+ __resolv_context_put (res_ctx); \
+ result = -EAI_SYSTEM; \
+ goto free_and_return; \
+ } \
+ } \
if (localcanon != NULL && canon == NULL) \
{ \
canonbuf = __strdup (localcanon); \
@@ -323,15 +334,15 @@ typedef enum nss_status (*nss_getcanonname_r)
memory allocation failure. The returned string is allocated on the
heap; the caller has to free it. */
static char *
-getcanonname (service_user *nip, struct gaih_addrtuple *at, const char *name)
+getcanonname (service_user *nip, const char *hname, const char *name)
{
nss_getcanonname_r cfct = __nss_lookup_function (nip, "getcanonname_r");
char *s = (char *) name;
if (cfct != NULL)
{
char buf[256];
- if (DL_CALL_FCT (cfct, (at->name ?: name, buf, sizeof (buf),
- &s, &errno, &h_errno)) != NSS_STATUS_SUCCESS)
+ if (DL_CALL_FCT (cfct, (hname ?: name, buf, sizeof (buf), &s, &errno,
+ &h_errno)) != NSS_STATUS_SUCCESS)
/* If the canonical name cannot be determined, use the passed
string. */
s = (char *) name;
@@ -349,6 +360,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
struct gaih_addrtuple *at = NULL;
bool got_ipv6 = false;
const char *canon = NULL;
+ char *h_name = NULL;
const char *orig_name = name;
/* Reserve stack memory for the scratch buffer in the getaddrinfo
@@ -919,7 +931,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
if ((req->ai_flags & AI_CANONNAME) != 0
&& canon == NULL)
{
- canonbuf = getcanonname (nip, at, name);
+ canonbuf = getcanonname (nip, h_name, name);
if (canonbuf == NULL)
{
__resolv_context_enable_inet6
@@ -1169,6 +1181,7 @@ gaih_inet (const char *name, const struct gaih_service *service,
free ((char *) name);
free (addrmem);
free (canonbuf);
+ free (h_name);
return result;
}
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