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authorSona Sarmadi <sona.sarmadi@enea.com>2015-02-20 10:27:12 (GMT)
committerTudor Florea <tudor.florea@enea.com>2015-07-06 18:19:37 (GMT)
commitf48f7274bc47c526869eb347532d099f36d28b13 (patch)
tree84fb9443e971c379badd28af20b121fb259c4c8f
parentf5648403cc045b4bf549f824ec40aee64018c1e5 (diff)
downloadpoky-f48f7274bc47c526869eb347532d099f36d28b13.tar.gz
eglibc: CVE-2014-7817 wordexp fails to honour WRDE_NOCMD
Command execution in wordexp() with WRDE_NOCMD specified Changes in the NEWS and ChangeLog files from the original upstream commit have been ignored Reference https://sourceware.org/ml/libc-alpha/2014-11/msg00519.html Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
-rw-r--r--meta/recipes-core/eglibc/eglibc-2.19/CVE-2014-7817-wordexp-fails-to-honour-WRDE_NOCMD.patch164
-rw-r--r--meta/recipes-core/eglibc/eglibc_2.19.bb1
2 files changed, 165 insertions, 0 deletions
diff --git a/meta/recipes-core/eglibc/eglibc-2.19/CVE-2014-7817-wordexp-fails-to-honour-WRDE_NOCMD.patch b/meta/recipes-core/eglibc/eglibc-2.19/CVE-2014-7817-wordexp-fails-to-honour-WRDE_NOCMD.patch
new file mode 100644
index 0000000..6dc6b9e
--- /dev/null
+++ b/meta/recipes-core/eglibc/eglibc-2.19/CVE-2014-7817-wordexp-fails-to-honour-WRDE_NOCMD.patch
@@ -0,0 +1,164 @@
1From a39208bd7fb76c1b01c127b4c61f9bfd915bfe7c Mon Sep 17 00:00:00 2001
2From: Carlos O'Donell <carlos@redhat.com>
3Date: Wed, 19 Nov 2014 11:44:12 -0500
4Subject: [PATCH] CVE-2014-7817: wordexp fails to honour WRDE_NOCMD.
5
6The function wordexp() fails to properly handle the WRDE_NOCMD
7flag when processing arithmetic inputs in the form of "$((... ``))"
8where "..." can be anything valid. The backticks in the arithmetic
9epxression are evaluated by in a shell even if WRDE_NOCMD forbade
10command substitution. This allows an attacker to attempt to pass
11dangerous commands via constructs of the above form, and bypass
12the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
13in exec_comm(), the only place that can execute a shell. All other
14checks for WRDE_NOCMD are superfluous and removed.
15
16We expand the testsuite and add 3 new regression tests of roughly
17the same form but with a couple of nested levels.
18
19On top of the 3 new tests we add fork validation to the WRDE_NOCMD
20testing. If any forks are detected during the execution of a wordexp()
21call with WRDE_NOCMD, the test is marked as failed. This is slightly
22heuristic since vfork might be used in the future, but it provides a
23higher level of assurance that no shells were executed as part of
24command substitution with WRDE_NOCMD in effect. In addition it doesn't
25require libpthread or libdl, instead we use the public implementation
26namespace function __register_atfork (already part of the public ABI
27for libpthread).
28
29Tested on x86_64 with no regressions.
30---
31 posix/wordexp-test.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
32 posix/wordexp.c | 16 ++++------------
33
34Index: git/posix/wordexp-test.c
35===================================================================
36--- git.orig/posix/wordexp-test.c
37+++ git/posix/wordexp-test.c
38@@ -27,6 +27,25 @@
39
40 #define IFS " \n\t"
41
42+extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
43+extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
44+
45+static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
46+{
47+ return __register_atfork (prepare, parent, child,
48+ &__dso_handle == NULL ? NULL : __dso_handle);
49+}
50+
51+/* Number of forks seen. */
52+static int registered_forks;
53+
54+/* For each fork increment the fork count. */
55+static void
56+register_fork (void)
57+{
58+ registered_forks++;
59+}
60+
61 struct test_case_struct
62 {
63 int retval;
64@@ -206,6 +225,12 @@ struct test_case_struct
65 { WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
66 { WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
67 { WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
68+ /* Test for CVE-2014-7817. We test 3 combinations of command
69+ substitution inside an arithmetic expression to make sure that
70+ no commands are executed and error is returned. */
71+ { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
72+ { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
73+ { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
74
75 { -1, NULL, NULL, 0, 0, { NULL, }, IFS },
76 };
77@@ -258,6 +283,15 @@ main (int argc, char *argv[])
78 return -1;
79 }
80
81+ /* If we are not allowed to do command substitution, we install
82+ fork handlers to verify that no forks happened. No forks should
83+ happen at all if command substitution is disabled. */
84+ if (__app_register_atfork (register_fork, NULL, NULL) != 0)
85+ {
86+ printf ("Failed to register fork handler.\n");
87+ return -1;
88+ }
89+
90 for (test = 0; test_case[test].retval != -1; test++)
91 if (testit (&test_case[test]))
92 ++fail;
93@@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
94
95 printf ("Test %d (%s): ", ++tests, tc->words);
96
97+ if (tc->flags & WRDE_NOCMD)
98+ registered_forks = 0;
99+
100 if (tc->flags & WRDE_APPEND)
101 {
102 /* initial wordexp() call, to be appended to */
103@@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
104 }
105 retval = wordexp (tc->words, &we, tc->flags);
106
107+ if ((tc->flags & WRDE_NOCMD)
108+ && (registered_forks > 0))
109+ {
110+ printf ("FAILED fork called for WRDE_NOCMD\n");
111+ return 1;
112+ }
113+
114 if (tc->flags & WRDE_DOOFFS)
115 start_offs = sav_we.we_offs;
116
117Index: git/posix/wordexp.c
118===================================================================
119--- git.orig/posix/wordexp.c
120+++ git/posix/wordexp.c
121@@ -893,6 +893,10 @@ exec_comm (char *comm, char **word, size
122 pid_t pid;
123 int noexec = 0;
124
125+ /* Do nothing if command substitution should not succeed. */
126+ if (flags & WRDE_NOCMD)
127+ return WRDE_CMDSUB;
128+
129 /* Don't fork() unless necessary */
130 if (!comm || !*comm)
131 return 0;
132@@ -2082,9 +2086,6 @@ parse_dollars (char **word, size_t *word
133 }
134 }
135
136- if (flags & WRDE_NOCMD)
137- return WRDE_CMDSUB;
138-
139 (*offset) += 2;
140 return parse_comm (word, word_length, max_length, words, offset, flags,
141 quoted? NULL : pwordexp, ifs, ifs_white);
142@@ -2196,9 +2197,6 @@ parse_dquote (char **word, size_t *word_
143 break;
144
145 case '`':
146- if (flags & WRDE_NOCMD)
147- return WRDE_CMDSUB;
148-
149 ++(*offset);
150 error = parse_backtick (word, word_length, max_length, words,
151 offset, flags, NULL, NULL, NULL);
152@@ -2357,12 +2355,6 @@ wordexp (const char *words, wordexp_t *p
153 break;
154
155 case '`':
156- if (flags & WRDE_NOCMD)
157- {
158- error = WRDE_CMDSUB;
159- goto do_error;
160- }
161-
162 ++words_offset;
163 error = parse_backtick (&word, &word_length, &max_length, words,
164 &words_offset, flags, pwordexp, ifs,
diff --git a/meta/recipes-core/eglibc/eglibc_2.19.bb b/meta/recipes-core/eglibc/eglibc_2.19.bb
index b9e43a1..ba79f27 100644
--- a/meta/recipes-core/eglibc/eglibc_2.19.bb
+++ b/meta/recipes-core/eglibc/eglibc_2.19.bb
@@ -26,6 +26,7 @@ SRC_URI = "http://downloads.yoctoproject.org/releases/eglibc/eglibc-${PV}-svnr25
26 file://fix-tibetian-locales.patch \ 26 file://fix-tibetian-locales.patch \
27 file://ppce6500-32b_slow_ieee754_sqrt.patch \ 27 file://ppce6500-32b_slow_ieee754_sqrt.patch \
28 file://CVE-2014-5119.patch \ 28 file://CVE-2014-5119.patch \
29 file://CVE-2014-7817-wordexp-fails-to-honour-WRDE_NOCMD.patch \
29 " 30 "
30SRC_URI[md5sum] = "197836c2ba42fb146e971222647198dd" 31SRC_URI[md5sum] = "197836c2ba42fb146e971222647198dd"
31SRC_URI[sha256sum] = "baaa030531fc308f7820c46acdf8e1b2f8e3c1f40bcd28b6e440d1c95d170d4c" 32SRC_URI[sha256sum] = "baaa030531fc308f7820c46acdf8e1b2f8e3c1f40bcd28b6e440d1c95d170d4c"