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973fe93a56
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>
57 lines
1.9 KiB
C
57 lines
1.9 KiB
C
/* NSS service provider that only provides gethostbyname2_r.
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Copyright The GNU Toolchain Authors.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <nss.h>
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#include <stdlib.h>
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#include <string.h>
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#include "nss/tst-nss-gai-hv2-canonname.h"
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/* Catch misnamed and functions. */
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#pragma GCC diagnostic error "-Wmissing-prototypes"
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NSS_DECLARE_MODULE_FUNCTIONS (test_gai_hv2_canonname)
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extern enum nss_status _nss_files_gethostbyname2_r (const char *, int,
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struct hostent *, char *,
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size_t, int *, int *);
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enum nss_status
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_nss_test_gai_hv2_canonname_gethostbyname2_r (const char *name, int af,
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struct hostent *result,
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char *buffer, size_t buflen,
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int *errnop, int *herrnop)
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{
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return _nss_files_gethostbyname2_r (name, af, result, buffer, buflen, errnop,
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herrnop);
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}
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enum nss_status
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_nss_test_gai_hv2_canonname_getcanonname_r (const char *name, char *buffer,
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size_t buflen, char **result,
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int *errnop, int *h_errnop)
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{
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/* We expect QUERYNAME, which is a small enough string that it shouldn't fail
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the test. */
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if (memcmp (QUERYNAME, name, sizeof (QUERYNAME))
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|| buflen < sizeof (QUERYNAME))
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abort ();
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strncpy (buffer, name, buflen);
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*result = buffer;
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return NSS_STATUS_SUCCESS;
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}
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