From 676599b36a92f3c201c5682ee7a5caddd9f370a4 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Fri, 2 Oct 2015 11:34:13 +0200 Subject: 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 '+'. --- gshadow/Makefile | 2 +- gshadow/putsgent.c | 11 ++++ gshadow/tst-putsgent.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 180 insertions(+), 1 deletion(-) create mode 100644 gshadow/tst-putsgent.c (limited to 'gshadow') diff --git a/gshadow/Makefile b/gshadow/Makefile index 883e1c8..c811041 100644 --- a/gshadow/Makefile +++ b/gshadow/Makefile @@ -26,7 +26,7 @@ headers = gshadow.h routines = getsgent getsgnam sgetsgent fgetsgent putsgent \ getsgent_r getsgnam_r sgetsgent_r fgetsgent_r -tests = tst-gshadow +tests = tst-gshadow tst-putsgent CFLAGS-getsgent_r.c = -fexceptions CFLAGS-getsgent.c = -fexceptions diff --git a/gshadow/putsgent.c b/gshadow/putsgent.c index 0b2cad6..c1cb921 100644 --- a/gshadow/putsgent.c +++ b/gshadow/putsgent.c @@ -15,9 +15,11 @@ License along with the GNU C Library; if not, see . */ +#include #include #include #include +#include #define _S(x) x ? x : "" @@ -29,6 +31,15 @@ putsgent (const struct sgrp *g, FILE *stream) { int errors = 0; + if (g->sg_namp == NULL || !__nss_valid_field (g->sg_namp) + || !__nss_valid_field (g->sg_passwd) + || !__nss_valid_list_field (g->sg_adm) + || !__nss_valid_list_field (g->sg_mem)) + { + __set_errno (EINVAL); + return -1; + } + _IO_flockfile (stream); if (fprintf (stream, "%s:%s:", g->sg_namp, _S (g->sg_passwd)) < 0) diff --git a/gshadow/tst-putsgent.c b/gshadow/tst-putsgent.c new file mode 100644 index 0000000..5b0f381 --- /dev/null +++ b/gshadow/tst-putsgent.c @@ -0,0 +1,168 @@ +/* Test for processing of invalid gshadow entries. [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 + . */ + +#include +#include +#include +#include +#include +#include + +static bool errors; + +static void +check (struct sgrp e, const char *expected) +{ + char *buf; + size_t buf_size; + FILE *f = open_memstream (&buf, &buf_size); + + if (f == NULL) + { + printf ("open_memstream: %m\n"); + errors = true; + return; + } + + int ret = putsgent (&e, f); + + if (expected == NULL) + { + if (ret == -1) + { + if (errno != EINVAL) + { + printf ("putsgent: unexpected error code: %m\n"); + errors = true; + } + } + else + { + printf ("putsgent: unexpected success (\"%s\")\n", e.sg_namp); + errors = true; + } + } + else + { + /* Expect success. */ + size_t expected_length = strlen (expected); + if (ret == 0) + { + long written = ftell (f); + + if (written <= 0 || fflush (f) < 0) + { + printf ("stream error: %m\n"); + errors = true; + } + else if (buf[written - 1] != '\n') + { + printf ("FAILED: \"%s\" without newline\n", expected); + errors = true; + } + else if (strncmp (buf, expected, written - 1) != 0 + || written - 1 != expected_length) + { + printf ("FAILED: \"%s\" (%ld), expected \"%s\" (%zu)\n", + buf, written - 1, expected, expected_length); + errors = true; + } + } + else + { + printf ("FAILED: putsgent (expected \"%s\"): %m\n", expected); + errors = true; + } + } + + fclose (f); + free (buf); +} + +static int +do_test (void) +{ + check ((struct sgrp) { + .sg_namp = (char *) "root", + }, + "root:::"); + check ((struct sgrp) { + .sg_namp = (char *) "root", + .sg_passwd = (char *) "password", + }, + "root:password::"); + check ((struct sgrp) { + .sg_namp = (char *) "root", + .sg_passwd = (char *) "password", + .sg_adm = (char *[]) {(char *) "adm1", (char *) "adm2", NULL}, + .sg_mem = (char *[]) {(char *) "mem1", (char *) "mem2", NULL}, + }, + "root:password:adm1,adm2:mem1,mem2"); + + /* Bad values. */ + { + static const char *const bad_strings[] = { + ":", + "\n", + ":bad", + "\nbad", + "b:ad", + "b\nad", + "bad:", + "bad\n", + "b:a\nd", + ",", + "\n,", + ":,", + ",bad", + "b,ad", + "bad,", + NULL + }; + for (const char *const *bad = bad_strings; *bad != NULL; ++bad) + { + char *members[] + = {(char *) "first", (char *) *bad, (char *) "last", NULL}; + if (strpbrk (*bad, ":\n") != NULL) + { + check ((struct sgrp) { + .sg_namp = (char *) *bad, + }, NULL); + check ((struct sgrp) { + .sg_namp = (char *) "root", + .sg_passwd = (char *) *bad, + }, NULL); + } + check ((struct sgrp) { + .sg_namp = (char *) "root", + .sg_passwd = (char *) "password", + .sg_adm = members + }, NULL); + check ((struct sgrp) { + .sg_namp = (char *) "root", + .sg_passwd = (char *) "password", + .sg_mem = members + }, NULL); + } + } + + return errors; +} + +#define TEST_FUNCTION do_test () +#include "../test-skeleton.c" -- cgit v1.1