From bbd3d847a3ad36d867275d1eed266ba362b4a420 Mon Sep 17 00:00:00 2001 From: Gustavo Zacarias Date: Thu, 27 Nov 2014 12:19:02 -0300 Subject: [PATCH] (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 Signed-off-by: Peter Korsgaard --- .../0001-CVE-2014-7817-eglibc.patch | 174 ++++++++++++++++++ ...pt-make4.patch => 0002-accept-make4.patch} | 0 .../0001-CVE-2014-7817-eglibc.patch | 174 ++++++++++++++++++ package/glibc/2.19/0001-CVE-2014-7817.patch | 173 +++++++++++++++++ package/glibc/2.20/0001-CVE-2014-7817.patch | 173 +++++++++++++++++ 5 files changed, 694 insertions(+) create mode 100644 package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch rename package/glibc/2.18-svnr23787/{glibc-0001-accept-make4.patch => 0002-accept-make4.patch} (100%) create mode 100644 package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch create mode 100644 package/glibc/2.19/0001-CVE-2014-7817.patch create mode 100644 package/glibc/2.20/0001-CVE-2014-7817.patch diff --git a/package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch b/package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch new file mode 100644 index 000000000..da2f49de1 --- /dev/null +++ b/package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch @@ -0,0 +1,174 @@ +From https://bugzilla.redhat.com/show_bug.cgi?id=1157689 +Modified for eglibc. + +Signed-off-by: Gustavo Zacarias + +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 + + * 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/libc/posix/wordexp-test.c ++++ b/libc/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/libc/posix/wordexp.c ++++ b/libc/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); diff --git a/package/glibc/2.18-svnr23787/glibc-0001-accept-make4.patch b/package/glibc/2.18-svnr23787/0002-accept-make4.patch similarity index 100% rename from package/glibc/2.18-svnr23787/glibc-0001-accept-make4.patch rename to package/glibc/2.18-svnr23787/0002-accept-make4.patch diff --git a/package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch b/package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch new file mode 100644 index 000000000..da2f49de1 --- /dev/null +++ b/package/glibc/2.19-svnr25243/0001-CVE-2014-7817-eglibc.patch @@ -0,0 +1,174 @@ +From https://bugzilla.redhat.com/show_bug.cgi?id=1157689 +Modified for eglibc. + +Signed-off-by: Gustavo Zacarias + +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 + + * 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/libc/posix/wordexp-test.c ++++ b/libc/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/libc/posix/wordexp.c ++++ b/libc/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); diff --git a/package/glibc/2.19/0001-CVE-2014-7817.patch b/package/glibc/2.19/0001-CVE-2014-7817.patch new file mode 100644 index 000000000..cd20c42c2 --- /dev/null +++ b/package/glibc/2.19/0001-CVE-2014-7817.patch @@ -0,0 +1,173 @@ +Patch from https://bugzilla.redhat.com/show_bug.cgi?id=1157689 + +Signed-off-by: Gustavo Zacarias + +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 + + * 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); diff --git a/package/glibc/2.20/0001-CVE-2014-7817.patch b/package/glibc/2.20/0001-CVE-2014-7817.patch new file mode 100644 index 000000000..cd20c42c2 --- /dev/null +++ b/package/glibc/2.20/0001-CVE-2014-7817.patch @@ -0,0 +1,173 @@ +Patch from https://bugzilla.redhat.com/show_bug.cgi?id=1157689 + +Signed-off-by: Gustavo Zacarias + +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 + + * 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);