(e)glibc: add security patches for CVE-2014-7817
Fixes: CVE-2014-7817 - command execution in wordexp() with WRDE_NOCMD specified Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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174
package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch
Normal file
174
package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch
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@ -0,0 +1,174 @@
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From https://bugzilla.redhat.com/show_bug.cgi?id=1157689
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Modified for eglibc.
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Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
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WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
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EMBARGOED !!! EMBARGOED !!! EMARGOED !!! EMBARGOED !!! EMBARGOED !!!
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SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!!
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CVE-2014-7817:
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The function wordexp() fails to properly handle the WRDE_NOCMD
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flag when processing arithmetic inputs in the form of "$((... ``))"
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where "..." can be anything valid. The backticks in the arithmetic
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epxression are evaluated by in a shell even if WRDE_NOCMD forbade
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command substitution. This allows an attacker to attempt to pass
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dangerous commands via constructs of the above form, and bypass
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the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
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in parse_arith(). The patch also hardens parse_backticks() and
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parse_comm() to check for WRDE_NOCMD flag and return an error instead
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of ever running a shell.
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We expand the testsuite and add 3 new regression tests of roughtly
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the same form but with a couple of nested levels.
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On top of the 3 new tests we add fork validation to the WRDE_NOCMD
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testing. If any forks are detected during the execution of a wordexp()
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call with WRDE_NOCMD, the test is marked as failed. This is slightly
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heuristic since vfork might be used, but it provides a higher level
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of assurance that no shells were executed as part of command substitution
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with WRDE_NOCMD in effect. In addition it doesn't require libpthread or
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libdl, instead we use the public implementation namespace function
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__register_atfork (already part of the public ABI for libpthread).
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Tested on x86_64 with no regressions.
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2014-10-27 Carlos O'Donell <carlos@redhat.com>
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* wordexp-test.c (__dso_handle): Add prototype.
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(__register_atfork): Likewise.
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(__app_register_atfork): New function.
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(registered_forks): New global.
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(register_fork): New function.
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(test_case): Add 3 new tests for WRDE_CMDSUB.
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(main): Call __app_register_atfork.
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(testit): If WRDE_NOCMD set registered_forks to zero, run test, and
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if fork count is non-zero fail the test.
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* posix/wordexp.c (parse_arith): Return WRDE_NOCMD if WRDE_NOCMD flag
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is set and parsing '`'.
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(parse_comm): Return WRDE_NOCMD if WRDE_NOCMD flag is set.
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(parse_backtick): Return WRDE_NOCMD if WRDE_NOCMD flag is set and
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parsing '`'.
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diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
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index 4957006..5ce2a1b 100644
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--- a/libc/posix/wordexp-test.c
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+++ b/libc/posix/wordexp-test.c
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@@ -27,6 +27,25 @@
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#define IFS " \n\t"
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+extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
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+extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
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+
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+static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
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+{
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+ return __register_atfork (prepare, parent, child,
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+ &__dso_handle == NULL ? NULL : __dso_handle);
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+}
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+
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+/* Number of forks seen. */
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+static int registered_forks;
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+
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+/* For each fork increment the fork count. */
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+static void
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+register_fork (void)
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+{
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+ registered_forks++;
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+}
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+
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struct test_case_struct
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{
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int retval;
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@@ -206,6 +225,12 @@ struct test_case_struct
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{ WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
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{ WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
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{ WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
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+ /* Test for CVE-2014-7817. We test 3 combinations of command
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+ substitution inside an arithmetic expression to make sure that
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+ no commands are executed and error is returned. */
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+ { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
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+ { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
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+ { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
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{ -1, NULL, NULL, 0, 0, { NULL, }, IFS },
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};
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@@ -258,6 +283,15 @@ main (int argc, char *argv[])
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return -1;
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}
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+ /* If we are not allowed to do command substitution, we install
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+ fork handlers to verify that no forks happened. No forks should
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+ happen at all if command substitution is disabled. */
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+ if (__app_register_atfork (register_fork, NULL, NULL) != 0)
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+ {
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+ printf ("Failed to register fork handler.\n");
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+ return -1;
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+ }
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+
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for (test = 0; test_case[test].retval != -1; test++)
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if (testit (&test_case[test]))
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++fail;
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@@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
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printf ("Test %d (%s): ", ++tests, tc->words);
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+ if (tc->flags & WRDE_NOCMD)
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+ registered_forks = 0;
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+
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if (tc->flags & WRDE_APPEND)
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{
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/* initial wordexp() call, to be appended to */
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@@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
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}
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retval = wordexp (tc->words, &we, tc->flags);
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+ if ((tc->flags & WRDE_NOCMD)
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+ && (registered_forks > 0))
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+ {
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+ printf ("FAILED fork called for WRDE_NOCMD\n");
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+ return 1;
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+ }
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+
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if (tc->flags & WRDE_DOOFFS)
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start_offs = sav_we.we_offs;
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diff --git a/posix/wordexp.c b/posix/wordexp.c
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index b6b65dd..d6a158f 100644
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--- a/libc/posix/wordexp.c
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+++ b/libc/posix/wordexp.c
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@@ -693,6 +693,12 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
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break;
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case '`':
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+ if (flags & WRDE_NOCMD)
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+ {
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+ free (expr);
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+ return WRDE_NOCMD;
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+ }
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+
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(*offset)++;
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error = parse_backtick (&expr, &expr_length, &expr_maxlen,
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words, offset, flags, NULL, NULL, NULL);
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@@ -1144,6 +1150,10 @@ parse_comm (char **word, size_t *word_length, size_t *max_length,
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size_t comm_maxlen;
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char *comm = w_newword (&comm_length, &comm_maxlen);
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+ /* Do nothing if command substitution should not succeed. */
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+ if (flags & WRDE_NOCMD)
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+ return WRDE_CMDSUB;
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+
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for (; words[*offset]; ++(*offset))
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{
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switch (words[*offset])
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@@ -2121,6 +2131,9 @@ parse_backtick (char **word, size_t *word_length, size_t *max_length,
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switch (words[*offset])
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{
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case '`':
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+ if (flags & WRDE_NOCMD)
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+ return WRDE_NOCMD;
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+
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/* Go -- give the script to the shell */
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error = exec_comm (comm, word, word_length, max_length, flags,
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pwordexp, ifs, ifs_white);
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174
package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch
Normal file
174
package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch
Normal file
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@ -0,0 +1,174 @@
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From https://bugzilla.redhat.com/show_bug.cgi?id=1157689
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Modified for eglibc.
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Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
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WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
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EMBARGOED !!! EMBARGOED !!! EMARGOED !!! EMBARGOED !!! EMBARGOED !!!
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SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!!
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CVE-2014-7817:
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The function wordexp() fails to properly handle the WRDE_NOCMD
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flag when processing arithmetic inputs in the form of "$((... ``))"
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where "..." can be anything valid. The backticks in the arithmetic
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epxression are evaluated by in a shell even if WRDE_NOCMD forbade
|
||||
command substitution. This allows an attacker to attempt to pass
|
||||
dangerous commands via constructs of the above form, and bypass
|
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the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
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in parse_arith(). The patch also hardens parse_backticks() and
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parse_comm() to check for WRDE_NOCMD flag and return an error instead
|
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of ever running a shell.
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We expand the testsuite and add 3 new regression tests of roughtly
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the same form but with a couple of nested levels.
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||||
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On top of the 3 new tests we add fork validation to the WRDE_NOCMD
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testing. If any forks are detected during the execution of a wordexp()
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call with WRDE_NOCMD, the test is marked as failed. This is slightly
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heuristic since vfork might be used, but it provides a higher level
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of assurance that no shells were executed as part of command substitution
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with WRDE_NOCMD in effect. In addition it doesn't require libpthread or
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libdl, instead we use the public implementation namespace function
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__register_atfork (already part of the public ABI for libpthread).
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Tested on x86_64 with no regressions.
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2014-10-27 Carlos O'Donell <carlos@redhat.com>
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* wordexp-test.c (__dso_handle): Add prototype.
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(__register_atfork): Likewise.
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(__app_register_atfork): New function.
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(registered_forks): New global.
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(register_fork): New function.
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(test_case): Add 3 new tests for WRDE_CMDSUB.
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(main): Call __app_register_atfork.
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(testit): If WRDE_NOCMD set registered_forks to zero, run test, and
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if fork count is non-zero fail the test.
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* posix/wordexp.c (parse_arith): Return WRDE_NOCMD if WRDE_NOCMD flag
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is set and parsing '`'.
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(parse_comm): Return WRDE_NOCMD if WRDE_NOCMD flag is set.
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(parse_backtick): Return WRDE_NOCMD if WRDE_NOCMD flag is set and
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parsing '`'.
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diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
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index 4957006..5ce2a1b 100644
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--- a/libc/posix/wordexp-test.c
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+++ b/libc/posix/wordexp-test.c
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@@ -27,6 +27,25 @@
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#define IFS " \n\t"
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+extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
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+extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
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+
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+static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
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+{
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+ return __register_atfork (prepare, parent, child,
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+ &__dso_handle == NULL ? NULL : __dso_handle);
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+}
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+
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+/* Number of forks seen. */
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+static int registered_forks;
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+
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+/* For each fork increment the fork count. */
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+static void
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+register_fork (void)
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+{
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+ registered_forks++;
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+}
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+
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struct test_case_struct
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{
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int retval;
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@@ -206,6 +225,12 @@ struct test_case_struct
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{ WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
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{ WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
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{ WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
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+ /* Test for CVE-2014-7817. We test 3 combinations of command
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+ substitution inside an arithmetic expression to make sure that
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+ no commands are executed and error is returned. */
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+ { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
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+ { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
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+ { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
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{ -1, NULL, NULL, 0, 0, { NULL, }, IFS },
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};
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@@ -258,6 +283,15 @@ main (int argc, char *argv[])
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return -1;
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}
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+ /* If we are not allowed to do command substitution, we install
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+ fork handlers to verify that no forks happened. No forks should
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+ happen at all if command substitution is disabled. */
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+ if (__app_register_atfork (register_fork, NULL, NULL) != 0)
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+ {
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+ printf ("Failed to register fork handler.\n");
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+ return -1;
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+ }
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+
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for (test = 0; test_case[test].retval != -1; test++)
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if (testit (&test_case[test]))
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++fail;
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@@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
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printf ("Test %d (%s): ", ++tests, tc->words);
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+ if (tc->flags & WRDE_NOCMD)
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+ registered_forks = 0;
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+
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if (tc->flags & WRDE_APPEND)
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{
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/* initial wordexp() call, to be appended to */
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@@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
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}
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retval = wordexp (tc->words, &we, tc->flags);
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+ if ((tc->flags & WRDE_NOCMD)
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+ && (registered_forks > 0))
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+ {
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+ printf ("FAILED fork called for WRDE_NOCMD\n");
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+ return 1;
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+ }
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+
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if (tc->flags & WRDE_DOOFFS)
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start_offs = sav_we.we_offs;
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diff --git a/posix/wordexp.c b/posix/wordexp.c
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index b6b65dd..d6a158f 100644
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--- a/libc/posix/wordexp.c
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+++ b/libc/posix/wordexp.c
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@@ -693,6 +693,12 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
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break;
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case '`':
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+ if (flags & WRDE_NOCMD)
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+ {
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+ free (expr);
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+ return WRDE_NOCMD;
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+ }
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+
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(*offset)++;
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error = parse_backtick (&expr, &expr_length, &expr_maxlen,
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words, offset, flags, NULL, NULL, NULL);
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@@ -1144,6 +1150,10 @@ parse_comm (char **word, size_t *word_length, size_t *max_length,
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size_t comm_maxlen;
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char *comm = w_newword (&comm_length, &comm_maxlen);
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+ /* Do nothing if command substitution should not succeed. */
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+ if (flags & WRDE_NOCMD)
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+ return WRDE_CMDSUB;
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+
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for (; words[*offset]; ++(*offset))
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{
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switch (words[*offset])
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@@ -2121,6 +2131,9 @@ parse_backtick (char **word, size_t *word_length, size_t *max_length,
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switch (words[*offset])
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{
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case '`':
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+ if (flags & WRDE_NOCMD)
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+ return WRDE_NOCMD;
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+
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/* Go -- give the script to the shell */
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error = exec_comm (comm, word, word_length, max_length, flags,
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pwordexp, ifs, ifs_white);
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173
package/glibc/2.19/0001-CVE-2014-7817.patch
Normal file
173
package/glibc/2.19/0001-CVE-2014-7817.patch
Normal file
|
@ -0,0 +1,173 @@
|
|||
Patch from https://bugzilla.redhat.com/show_bug.cgi?id=1157689
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Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
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|
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WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
|
||||
EMBARGOED !!! EMBARGOED !!! EMARGOED !!! EMBARGOED !!! EMBARGOED !!!
|
||||
SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!!
|
||||
|
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CVE-2014-7817:
|
||||
|
||||
The function wordexp() fails to properly handle the WRDE_NOCMD
|
||||
flag when processing arithmetic inputs in the form of "$((... ``))"
|
||||
where "..." can be anything valid. The backticks in the arithmetic
|
||||
epxression are evaluated by in a shell even if WRDE_NOCMD forbade
|
||||
command substitution. This allows an attacker to attempt to pass
|
||||
dangerous commands via constructs of the above form, and bypass
|
||||
the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
|
||||
in parse_arith(). The patch also hardens parse_backticks() and
|
||||
parse_comm() to check for WRDE_NOCMD flag and return an error instead
|
||||
of ever running a shell.
|
||||
|
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We expand the testsuite and add 3 new regression tests of roughtly
|
||||
the same form but with a couple of nested levels.
|
||||
|
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On top of the 3 new tests we add fork validation to the WRDE_NOCMD
|
||||
testing. If any forks are detected during the execution of a wordexp()
|
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call with WRDE_NOCMD, the test is marked as failed. This is slightly
|
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heuristic since vfork might be used, but it provides a higher level
|
||||
of assurance that no shells were executed as part of command substitution
|
||||
with WRDE_NOCMD in effect. In addition it doesn't require libpthread or
|
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libdl, instead we use the public implementation namespace function
|
||||
__register_atfork (already part of the public ABI for libpthread).
|
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|
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Tested on x86_64 with no regressions.
|
||||
|
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2014-10-27 Carlos O'Donell <carlos@redhat.com>
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|
||||
* wordexp-test.c (__dso_handle): Add prototype.
|
||||
(__register_atfork): Likewise.
|
||||
(__app_register_atfork): New function.
|
||||
(registered_forks): New global.
|
||||
(register_fork): New function.
|
||||
(test_case): Add 3 new tests for WRDE_CMDSUB.
|
||||
(main): Call __app_register_atfork.
|
||||
(testit): If WRDE_NOCMD set registered_forks to zero, run test, and
|
||||
if fork count is non-zero fail the test.
|
||||
* posix/wordexp.c (parse_arith): Return WRDE_NOCMD if WRDE_NOCMD flag
|
||||
is set and parsing '`'.
|
||||
(parse_comm): Return WRDE_NOCMD if WRDE_NOCMD flag is set.
|
||||
(parse_backtick): Return WRDE_NOCMD if WRDE_NOCMD flag is set and
|
||||
parsing '`'.
|
||||
|
||||
diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
|
||||
index 4957006..5ce2a1b 100644
|
||||
--- a/posix/wordexp-test.c
|
||||
+++ b/posix/wordexp-test.c
|
||||
@@ -27,6 +27,25 @@
|
||||
|
||||
#define IFS " \n\t"
|
||||
|
||||
+extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
|
||||
+extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
|
||||
+
|
||||
+static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
|
||||
+{
|
||||
+ return __register_atfork (prepare, parent, child,
|
||||
+ &__dso_handle == NULL ? NULL : __dso_handle);
|
||||
+}
|
||||
+
|
||||
+/* Number of forks seen. */
|
||||
+static int registered_forks;
|
||||
+
|
||||
+/* For each fork increment the fork count. */
|
||||
+static void
|
||||
+register_fork (void)
|
||||
+{
|
||||
+ registered_forks++;
|
||||
+}
|
||||
+
|
||||
struct test_case_struct
|
||||
{
|
||||
int retval;
|
||||
@@ -206,6 +225,12 @@ struct test_case_struct
|
||||
{ WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
|
||||
{ WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
|
||||
{ WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
|
||||
+ /* Test for CVE-2014-7817. We test 3 combinations of command
|
||||
+ substitution inside an arithmetic expression to make sure that
|
||||
+ no commands are executed and error is returned. */
|
||||
+ { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
+ { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
+ { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
|
||||
{ -1, NULL, NULL, 0, 0, { NULL, }, IFS },
|
||||
};
|
||||
@@ -258,6 +283,15 @@ main (int argc, char *argv[])
|
||||
return -1;
|
||||
}
|
||||
|
||||
+ /* If we are not allowed to do command substitution, we install
|
||||
+ fork handlers to verify that no forks happened. No forks should
|
||||
+ happen at all if command substitution is disabled. */
|
||||
+ if (__app_register_atfork (register_fork, NULL, NULL) != 0)
|
||||
+ {
|
||||
+ printf ("Failed to register fork handler.\n");
|
||||
+ return -1;
|
||||
+ }
|
||||
+
|
||||
for (test = 0; test_case[test].retval != -1; test++)
|
||||
if (testit (&test_case[test]))
|
||||
++fail;
|
||||
@@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
|
||||
|
||||
printf ("Test %d (%s): ", ++tests, tc->words);
|
||||
|
||||
+ if (tc->flags & WRDE_NOCMD)
|
||||
+ registered_forks = 0;
|
||||
+
|
||||
if (tc->flags & WRDE_APPEND)
|
||||
{
|
||||
/* initial wordexp() call, to be appended to */
|
||||
@@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
|
||||
}
|
||||
retval = wordexp (tc->words, &we, tc->flags);
|
||||
|
||||
+ if ((tc->flags & WRDE_NOCMD)
|
||||
+ && (registered_forks > 0))
|
||||
+ {
|
||||
+ printf ("FAILED fork called for WRDE_NOCMD\n");
|
||||
+ return 1;
|
||||
+ }
|
||||
+
|
||||
if (tc->flags & WRDE_DOOFFS)
|
||||
start_offs = sav_we.we_offs;
|
||||
|
||||
diff --git a/posix/wordexp.c b/posix/wordexp.c
|
||||
index b6b65dd..d6a158f 100644
|
||||
--- a/posix/wordexp.c
|
||||
+++ b/posix/wordexp.c
|
||||
@@ -693,6 +693,12 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
|
||||
break;
|
||||
|
||||
case '`':
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ {
|
||||
+ free (expr);
|
||||
+ return WRDE_NOCMD;
|
||||
+ }
|
||||
+
|
||||
(*offset)++;
|
||||
error = parse_backtick (&expr, &expr_length, &expr_maxlen,
|
||||
words, offset, flags, NULL, NULL, NULL);
|
||||
@@ -1144,6 +1150,10 @@ parse_comm (char **word, size_t *word_length, size_t *max_length,
|
||||
size_t comm_maxlen;
|
||||
char *comm = w_newword (&comm_length, &comm_maxlen);
|
||||
|
||||
+ /* Do nothing if command substitution should not succeed. */
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ return WRDE_CMDSUB;
|
||||
+
|
||||
for (; words[*offset]; ++(*offset))
|
||||
{
|
||||
switch (words[*offset])
|
||||
@@ -2121,6 +2131,9 @@ parse_backtick (char **word, size_t *word_length, size_t *max_length,
|
||||
switch (words[*offset])
|
||||
{
|
||||
case '`':
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ return WRDE_NOCMD;
|
||||
+
|
||||
/* Go -- give the script to the shell */
|
||||
error = exec_comm (comm, word, word_length, max_length, flags,
|
||||
pwordexp, ifs, ifs_white);
|
173
package/glibc/2.20/0001-CVE-2014-7817.patch
Normal file
173
package/glibc/2.20/0001-CVE-2014-7817.patch
Normal file
|
@ -0,0 +1,173 @@
|
|||
Patch from https://bugzilla.redhat.com/show_bug.cgi?id=1157689
|
||||
|
||||
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
|
||||
|
||||
WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
|
||||
EMBARGOED !!! EMBARGOED !!! EMARGOED !!! EMBARGOED !!! EMBARGOED !!!
|
||||
SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!!
|
||||
|
||||
CVE-2014-7817:
|
||||
|
||||
The function wordexp() fails to properly handle the WRDE_NOCMD
|
||||
flag when processing arithmetic inputs in the form of "$((... ``))"
|
||||
where "..." can be anything valid. The backticks in the arithmetic
|
||||
epxression are evaluated by in a shell even if WRDE_NOCMD forbade
|
||||
command substitution. This allows an attacker to attempt to pass
|
||||
dangerous commands via constructs of the above form, and bypass
|
||||
the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
|
||||
in parse_arith(). The patch also hardens parse_backticks() and
|
||||
parse_comm() to check for WRDE_NOCMD flag and return an error instead
|
||||
of ever running a shell.
|
||||
|
||||
We expand the testsuite and add 3 new regression tests of roughtly
|
||||
the same form but with a couple of nested levels.
|
||||
|
||||
On top of the 3 new tests we add fork validation to the WRDE_NOCMD
|
||||
testing. If any forks are detected during the execution of a wordexp()
|
||||
call with WRDE_NOCMD, the test is marked as failed. This is slightly
|
||||
heuristic since vfork might be used, but it provides a higher level
|
||||
of assurance that no shells were executed as part of command substitution
|
||||
with WRDE_NOCMD in effect. In addition it doesn't require libpthread or
|
||||
libdl, instead we use the public implementation namespace function
|
||||
__register_atfork (already part of the public ABI for libpthread).
|
||||
|
||||
Tested on x86_64 with no regressions.
|
||||
|
||||
2014-10-27 Carlos O'Donell <carlos@redhat.com>
|
||||
|
||||
* wordexp-test.c (__dso_handle): Add prototype.
|
||||
(__register_atfork): Likewise.
|
||||
(__app_register_atfork): New function.
|
||||
(registered_forks): New global.
|
||||
(register_fork): New function.
|
||||
(test_case): Add 3 new tests for WRDE_CMDSUB.
|
||||
(main): Call __app_register_atfork.
|
||||
(testit): If WRDE_NOCMD set registered_forks to zero, run test, and
|
||||
if fork count is non-zero fail the test.
|
||||
* posix/wordexp.c (parse_arith): Return WRDE_NOCMD if WRDE_NOCMD flag
|
||||
is set and parsing '`'.
|
||||
(parse_comm): Return WRDE_NOCMD if WRDE_NOCMD flag is set.
|
||||
(parse_backtick): Return WRDE_NOCMD if WRDE_NOCMD flag is set and
|
||||
parsing '`'.
|
||||
|
||||
diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
|
||||
index 4957006..5ce2a1b 100644
|
||||
--- a/posix/wordexp-test.c
|
||||
+++ b/posix/wordexp-test.c
|
||||
@@ -27,6 +27,25 @@
|
||||
|
||||
#define IFS " \n\t"
|
||||
|
||||
+extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
|
||||
+extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
|
||||
+
|
||||
+static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
|
||||
+{
|
||||
+ return __register_atfork (prepare, parent, child,
|
||||
+ &__dso_handle == NULL ? NULL : __dso_handle);
|
||||
+}
|
||||
+
|
||||
+/* Number of forks seen. */
|
||||
+static int registered_forks;
|
||||
+
|
||||
+/* For each fork increment the fork count. */
|
||||
+static void
|
||||
+register_fork (void)
|
||||
+{
|
||||
+ registered_forks++;
|
||||
+}
|
||||
+
|
||||
struct test_case_struct
|
||||
{
|
||||
int retval;
|
||||
@@ -206,6 +225,12 @@ struct test_case_struct
|
||||
{ WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
|
||||
{ WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
|
||||
{ WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
|
||||
+ /* Test for CVE-2014-7817. We test 3 combinations of command
|
||||
+ substitution inside an arithmetic expression to make sure that
|
||||
+ no commands are executed and error is returned. */
|
||||
+ { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
+ { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
+ { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
|
||||
|
||||
{ -1, NULL, NULL, 0, 0, { NULL, }, IFS },
|
||||
};
|
||||
@@ -258,6 +283,15 @@ main (int argc, char *argv[])
|
||||
return -1;
|
||||
}
|
||||
|
||||
+ /* If we are not allowed to do command substitution, we install
|
||||
+ fork handlers to verify that no forks happened. No forks should
|
||||
+ happen at all if command substitution is disabled. */
|
||||
+ if (__app_register_atfork (register_fork, NULL, NULL) != 0)
|
||||
+ {
|
||||
+ printf ("Failed to register fork handler.\n");
|
||||
+ return -1;
|
||||
+ }
|
||||
+
|
||||
for (test = 0; test_case[test].retval != -1; test++)
|
||||
if (testit (&test_case[test]))
|
||||
++fail;
|
||||
@@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
|
||||
|
||||
printf ("Test %d (%s): ", ++tests, tc->words);
|
||||
|
||||
+ if (tc->flags & WRDE_NOCMD)
|
||||
+ registered_forks = 0;
|
||||
+
|
||||
if (tc->flags & WRDE_APPEND)
|
||||
{
|
||||
/* initial wordexp() call, to be appended to */
|
||||
@@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
|
||||
}
|
||||
retval = wordexp (tc->words, &we, tc->flags);
|
||||
|
||||
+ if ((tc->flags & WRDE_NOCMD)
|
||||
+ && (registered_forks > 0))
|
||||
+ {
|
||||
+ printf ("FAILED fork called for WRDE_NOCMD\n");
|
||||
+ return 1;
|
||||
+ }
|
||||
+
|
||||
if (tc->flags & WRDE_DOOFFS)
|
||||
start_offs = sav_we.we_offs;
|
||||
|
||||
diff --git a/posix/wordexp.c b/posix/wordexp.c
|
||||
index b6b65dd..d6a158f 100644
|
||||
--- a/posix/wordexp.c
|
||||
+++ b/posix/wordexp.c
|
||||
@@ -693,6 +693,12 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
|
||||
break;
|
||||
|
||||
case '`':
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ {
|
||||
+ free (expr);
|
||||
+ return WRDE_NOCMD;
|
||||
+ }
|
||||
+
|
||||
(*offset)++;
|
||||
error = parse_backtick (&expr, &expr_length, &expr_maxlen,
|
||||
words, offset, flags, NULL, NULL, NULL);
|
||||
@@ -1144,6 +1150,10 @@ parse_comm (char **word, size_t *word_length, size_t *max_length,
|
||||
size_t comm_maxlen;
|
||||
char *comm = w_newword (&comm_length, &comm_maxlen);
|
||||
|
||||
+ /* Do nothing if command substitution should not succeed. */
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ return WRDE_CMDSUB;
|
||||
+
|
||||
for (; words[*offset]; ++(*offset))
|
||||
{
|
||||
switch (words[*offset])
|
||||
@@ -2121,6 +2131,9 @@ parse_backtick (char **word, size_t *word_length, size_t *max_length,
|
||||
switch (words[*offset])
|
||||
{
|
||||
case '`':
|
||||
+ if (flags & WRDE_NOCMD)
|
||||
+ return WRDE_NOCMD;
|
||||
+
|
||||
/* Go -- give the script to the shell */
|
||||
error = exec_comm (comm, word, word_length, max_length, flags,
|
||||
pwordexp, ifs, ifs_white);
|
Loading…
Reference in a new issue