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authorFlorian Weimer <fweimer@redhat.com>2015-10-02 11:34:13 +0200
committerFlorian Weimer <fweimer@redhat.com>2015-10-02 11:34:13 +0200
commit676599b36a92f3c201c5682ee7a5caddd9f370a4 (patch)
tree6860752c26ccab76ee9db5e60ff465d1edf25feb /nss
parentb0f81637d5bda47be93bac34b68f429a12979321 (diff)
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Harden putpwent, putgrent, putspent, putspent against injection [BZ #18724]
This prevents injection of ':' and '\n' into output functions which use the NSS files database syntax. Critical fields (user/group names and file system paths) are checked strictly. For backwards compatibility, the GECOS field is rewritten instead. The getent program is adjusted to use the put*ent functions in libc, instead of local copies. This changes the behavior of getent if user names start with '-' or '+'.
Diffstat (limited to 'nss')
-rw-r--r--nss/Makefile8
-rw-r--r--nss/getent.c76
-rw-r--r--nss/rewrite_field.c51
-rw-r--r--nss/tst-field.c101
-rw-r--r--nss/valid_field.c31
-rw-r--r--nss/valid_list_field.c35
6 files changed, 231 insertions, 71 deletions
diff --git a/nss/Makefile b/nss/Makefile
index 02a5016..bbbad85 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -26,6 +26,7 @@ headers := nss.h
# This is the trivial part which goes into libc itself.
routines = nsswitch getnssent getnssent_r digits_dots \
+ valid_field valid_list_field rewrite_field \
$(addsuffix -lookup,$(databases))
# These are the databases that go through nss dispatch.
@@ -47,8 +48,10 @@ install-bin := getent makedb
makedb-modules = xmalloc hash-string
extra-objs += $(makedb-modules:=.o)
+tests-static = tst-field
tests = test-netdb tst-nss-test1 test-digits-dots \
- tst-nss-getpwent bug17079
+ tst-nss-getpwent bug17079 \
+ $(tests-static)
xtests = bug-erange
# Specify rules for the nss_* modules. We have some services.
@@ -83,8 +86,7 @@ libnss_db-inhibit-o = $(filter-out .os,$(object-suffixes))
ifeq ($(build-static-nss),yes)
routines += $(libnss_files-routines)
static-only-routines += $(libnss_files-routines)
-tests-static = tst-nss-static
-tests += $(tests-static)
+tests-static += tst-nss-static
endif
include ../Rules
diff --git a/nss/getent.c b/nss/getent.c
index 34df848..996d378 100644
--- a/nss/getent.c
+++ b/nss/getent.c
@@ -184,20 +184,8 @@ ethers_keys (int number, char *key[])
static void
print_group (struct group *grp)
{
- unsigned int i = 0;
-
- printf ("%s:%s:%lu:", grp->gr_name ? grp->gr_name : "",
- grp->gr_passwd ? grp->gr_passwd : "",
- (unsigned long int) grp->gr_gid);
-
- while (grp->gr_mem[i] != NULL)
- {
- fputs_unlocked (grp->gr_mem[i], stdout);
- ++i;
- if (grp->gr_mem[i] != NULL)
- putchar_unlocked (',');
- }
- putchar_unlocked ('\n');
+ if (putgrent (grp, stdout) != 0)
+ fprintf (stderr, "error writing group entry: %m\n");
}
static int
@@ -241,32 +229,8 @@ group_keys (int number, char *key[])
static void
print_gshadow (struct sgrp *sg)
{
- unsigned int i = 0;
-
- printf ("%s:%s:",
- sg->sg_namp ? sg->sg_namp : "",
- sg->sg_passwd ? sg->sg_passwd : "");
-
- while (sg->sg_adm[i] != NULL)
- {
- fputs_unlocked (sg->sg_adm[i], stdout);
- ++i;
- if (sg->sg_adm[i] != NULL)
- putchar_unlocked (',');
- }
-
- putchar_unlocked (':');
-
- i = 0;
- while (sg->sg_mem[i] != NULL)
- {
- fputs_unlocked (sg->sg_mem[i], stdout);
- ++i;
- if (sg->sg_mem[i] != NULL)
- putchar_unlocked (',');
- }
-
- putchar_unlocked ('\n');
+ if (putsgent (sg, stdout) != 0)
+ fprintf (stderr, "error writing gshadow entry: %m\n");
}
static int
@@ -603,14 +567,8 @@ networks_keys (int number, char *key[])
static void
print_passwd (struct passwd *pwd)
{
- printf ("%s:%s:%lu:%lu:%s:%s:%s\n",
- pwd->pw_name ? pwd->pw_name : "",
- pwd->pw_passwd ? pwd->pw_passwd : "",
- (unsigned long int) pwd->pw_uid,
- (unsigned long int) pwd->pw_gid,
- pwd->pw_gecos ? pwd->pw_gecos : "",
- pwd->pw_dir ? pwd->pw_dir : "",
- pwd->pw_shell ? pwd->pw_shell : "");
+ if (putpwent (pwd, stdout) != 0)
+ fprintf (stderr, "error writing passwd entry: %m\n");
}
static int
@@ -812,26 +770,8 @@ services_keys (int number, char *key[])
static void
print_shadow (struct spwd *sp)
{
- printf ("%s:%s:",
- sp->sp_namp ? sp->sp_namp : "",
- sp->sp_pwdp ? sp->sp_pwdp : "");
-
-#define SHADOW_FIELD(n) \
- if (sp->n == -1) \
- putchar_unlocked (':'); \
- else \
- printf ("%ld:", sp->n)
-
- SHADOW_FIELD (sp_lstchg);
- SHADOW_FIELD (sp_min);
- SHADOW_FIELD (sp_max);
- SHADOW_FIELD (sp_warn);
- SHADOW_FIELD (sp_inact);
- SHADOW_FIELD (sp_expire);
- if (sp->sp_flag == ~0ul)
- putchar_unlocked ('\n');
- else
- printf ("%lu\n", sp->sp_flag);
+ if (putspent (sp, stdout) != 0)
+ fprintf (stderr, "error writing shadow entry: %m\n");
}
static int
diff --git a/nss/rewrite_field.c b/nss/rewrite_field.c
new file mode 100644
index 0000000..fb9d274
--- /dev/null
+++ b/nss/rewrite_field.c
@@ -0,0 +1,51 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <nss.h>
+#include <string.h>
+
+/* Rewrite VALUE to a valid field value in the NSS database. Invalid
+ characters are replaced with a single space character ' '. If
+ VALUE is NULL, the empty string is returned. *TO_BE_FREED is
+ overwritten with a pointer the caller has to free if the function
+ returns successfully. On failure, return NULL. */
+const char *
+__nss_rewrite_field (const char *value, char **to_be_freed)
+{
+ *to_be_freed = NULL;
+ if (value == NULL)
+ return "";
+
+ /* Search for non-allowed characters. */
+ const char *p = strpbrk (value, __nss_invalid_field_characters);
+ if (p == NULL)
+ return value;
+ *to_be_freed = __strdup (value);
+ if (*to_be_freed == NULL)
+ return NULL;
+
+ /* Switch pointer to freshly-allocated buffer. */
+ char *bad = *to_be_freed + (p - value);
+ do
+ {
+ *bad = ' ';
+ bad = strpbrk (bad + 1, __nss_invalid_field_characters);
+ }
+ while (bad != NULL);
+
+ return *to_be_freed;
+}
diff --git a/nss/tst-field.c b/nss/tst-field.c
new file mode 100644
index 0000000..f97d3ae
--- /dev/null
+++ b/nss/tst-field.c
@@ -0,0 +1,101 @@
+/* Test for invalid field handling in file-style NSS databases. [BZ #18724]
+ Copyright (C) 2015 Free Software Foundation, Inc.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+/* This test needs to be statically linked because it access hidden
+ functions. */
+
+#include <nss.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static bool errors;
+
+static void
+check (const char *what, bool expr)
+{
+ if (!expr)
+ {
+ printf ("FAIL: %s\n", what);
+ errors = true;
+ }
+}
+
+#define CHECK(expr) check (#expr, (expr))
+
+static void
+check_rewrite (const char *input, const char *expected)
+{
+ char *to_free;
+ const char *result = __nss_rewrite_field (input, &to_free);
+ CHECK (result != NULL);
+ if (result != NULL && strcmp (result, expected) != 0)
+ {
+ printf ("FAIL: rewrite \"%s\" -> \"%s\", expected \"%s\"\n",
+ input, result, expected);
+ errors = true;
+ }
+ free (to_free);
+}
+
+static int
+do_test (void)
+{
+ CHECK (__nss_valid_field (NULL));
+ CHECK (__nss_valid_field (""));
+ CHECK (__nss_valid_field ("+"));
+ CHECK (__nss_valid_field ("-"));
+ CHECK (__nss_valid_field (" "));
+ CHECK (__nss_valid_field ("abcdef"));
+ CHECK (__nss_valid_field ("abc def"));
+ CHECK (__nss_valid_field ("abc\tdef"));
+ CHECK (!__nss_valid_field ("abcdef:"));
+ CHECK (!__nss_valid_field ("abcde:f"));
+ CHECK (!__nss_valid_field (":abcdef"));
+ CHECK (!__nss_valid_field ("abcdef\n"));
+ CHECK (!__nss_valid_field ("\nabcdef"));
+ CHECK (!__nss_valid_field (":"));
+ CHECK (!__nss_valid_field ("\n"));
+
+ CHECK (__nss_valid_list_field (NULL));
+ CHECK (__nss_valid_list_field ((char *[]) {(char *) "good", NULL}));
+ CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g,ood", NULL}));
+ CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g\nood", NULL}));
+ CHECK (!__nss_valid_list_field ((char *[]) {(char *) "g:ood", NULL}));
+
+ check_rewrite (NULL, "");
+ check_rewrite ("", "");
+ check_rewrite ("abc", "abc");
+ check_rewrite ("abc\n", "abc ");
+ check_rewrite ("abc:", "abc ");
+ check_rewrite ("\nabc", " abc");
+ check_rewrite (":abc", " abc");
+ check_rewrite (":", " ");
+ check_rewrite ("\n", " ");
+ check_rewrite ("a:b:c", "a b c");
+ check_rewrite ("a\nb\nc", "a b c");
+ check_rewrite ("a\nb:c", "a b c");
+ check_rewrite ("aa\nbb\ncc", "aa bb cc");
+ check_rewrite ("aa\nbb:cc", "aa bb cc");
+
+ return errors;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/nss/valid_field.c b/nss/valid_field.c
new file mode 100644
index 0000000..5fcddc5
--- /dev/null
+++ b/nss/valid_field.c
@@ -0,0 +1,31 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <nss.h>
+#include <string.h>
+
+const char __nss_invalid_field_characters[] = NSS_INVALID_FIELD_CHARACTERS;
+
+/* Check that VALUE is either NULL or a NUL-terminated string which
+ does not contain characters not permitted in NSS database
+ fields. */
+_Bool
+__nss_valid_field (const char *value)
+{
+ return value == NULL
+ || strpbrk (value, __nss_invalid_field_characters) == NULL;
+}
diff --git a/nss/valid_list_field.c b/nss/valid_list_field.c
new file mode 100644
index 0000000..98ab93b
--- /dev/null
+++ b/nss/valid_list_field.c
@@ -0,0 +1,35 @@
+/* Copyright (C) 2015 Free Software Foundation, Inc.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <nss.h>
+#include <stdbool.h>
+#include <string.h>
+
+static const char invalid_characters[] = NSS_INVALID_FIELD_CHARACTERS ",";
+
+/* Check that all list members match the field syntax requirements and
+ do not contain the character ','. */
+_Bool
+__nss_valid_list_field (char **list)
+{
+ if (list == NULL)
+ return true;
+ for (; *list != NULL; ++list)
+ if (strpbrk (*list, invalid_characters) != NULL)
+ return false;
+ return true;
+}