package/glibc/2.18-svnr23787/0001-CVE-2014-7817-eglibc.patch

   1 From https://bugzilla.redhat.com/show_bug.cgi?id=1157689
   2 Modified for eglibc.
   3
   4 Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
   5
   6 WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!! WARNING !!!
   7 EMBARGOED !!! EMBARGOED !!! EMARGOED !!! EMBARGOED !!! EMBARGOED !!!
   8 SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!! SECURITY !!!
   9
  10 CVE-2014-7817:
  11
  12 The function wordexp() fails to properly handle the WRDE_NOCMD
  13 flag when processing arithmetic inputs in the form of "$((... ``))"
  14 where "..." can be anything valid. The backticks in the arithmetic
  15 epxression are evaluated by in a shell even if WRDE_NOCMD forbade
  16 command substitution. This allows an attacker to attempt to pass
  17 dangerous commands via constructs of the above form, and bypass
  18 the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
  19 in parse_arith(). The patch also hardens parse_backticks() and
  20 parse_comm() to check for WRDE_NOCMD flag and return an error instead
  21 of ever running a shell.
  22
  23 We expand the testsuite and add 3 new regression tests of roughtly
  24 the same form but with a couple of nested levels.
  25
  26 On top of the 3 new tests we add fork validation to the WRDE_NOCMD
  27 testing. If any forks are detected during the execution of a wordexp()
  28 call with WRDE_NOCMD, the test is marked as failed. This is slightly
  29 heuristic since vfork might be used, but it provides a higher level
  30 of assurance that no shells were executed as part of command substitution
  31 with WRDE_NOCMD in effect. In addition it doesn't require libpthread or
  32 libdl, instead we use the public implementation namespace function
  33 __register_atfork (already part of the public ABI for libpthread).
  34
  35 Tested on x86_64 with no regressions.
  36
  37 2014-10-27  Carlos O'Donell  <carlos@redhat.com>
  38
  39         * wordexp-test.c (__dso_handle): Add prototype.
  40         (__register_atfork): Likewise.
  41         (__app_register_atfork): New function.
  42         (registered_forks): New global.
  43         (register_fork): New function.
  44         (test_case): Add 3 new tests for WRDE_CMDSUB.
  45         (main): Call __app_register_atfork.
  46         (testit): If WRDE_NOCMD set registered_forks to zero, run test, and
  47         if fork count is non-zero fail the test.
  48         * posix/wordexp.c (parse_arith): Return WRDE_NOCMD if WRDE_NOCMD flag
  49         is set and parsing '`'.
  50         (parse_comm): Return WRDE_NOCMD if WRDE_NOCMD flag is set.
  51         (parse_backtick): Return WRDE_NOCMD if WRDE_NOCMD flag is set and
  52         parsing '`'.
  53
  54 diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
  55 index 4957006..5ce2a1b 100644
  56 --- a/libc/posix/wordexp-test.c
  57 +++ b/libc/posix/wordexp-test.c
  58 @@ -27,6 +27,25 @@
  59
  60  #define IFS " \n\t"
  61
  62 +extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));
  63 +extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);
  64 +
  65 +static int __app_register_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))
  66 +{
  67 +  return __register_atfork (prepare, parent, child,
  68 +                           &__dso_handle == NULL ? NULL : __dso_handle);
  69 +}
  70 +
  71 +/* Number of forks seen.  */
  72 +static int registered_forks;
  73 +
  74 +/* For each fork increment the fork count.  */
  75 +static void
  76 +register_fork (void)
  77 +{
  78 +  registered_forks++;
  79 +}
  80 +
  81  struct test_case_struct
  82  {
  83    int retval;
  84 @@ -206,6 +225,12 @@ struct test_case_struct
  85      { WRDE_SYNTAX, NULL, "$((2+))", 0, 0, { NULL, }, IFS },
  86      { WRDE_SYNTAX, NULL, "`", 0, 0, { NULL, }, IFS },
  87      { WRDE_SYNTAX, NULL, "$((010+4+))", 0, 0, { NULL }, IFS },
  88 +    /* Test for CVE-2014-7817. We test 3 combinations of command
  89 +       substitution inside an arithmetic expression to make sure that
  90 +       no commands are executed and error is returned.  */
  91 +    { WRDE_CMDSUB, NULL, "$((`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
  92 +    { WRDE_CMDSUB, NULL, "$((1+`echo 1`))", WRDE_NOCMD, 0, { NULL, }, IFS },
  93 +    { WRDE_CMDSUB, NULL, "$((1+$((`echo 1`))))", WRDE_NOCMD, 0, { NULL, }, IFS },
  94
  95      { -1, NULL, NULL, 0, 0, { NULL, }, IFS },
  96    };
  97 @@ -258,6 +283,15 @@ main (int argc, char *argv[])
  98           return -1;
  99      }
 100
 101 +  /* If we are not allowed to do command substitution, we install
 102 +     fork handlers to verify that no forks happened.  No forks should
 103 +     happen at all if command substitution is disabled.  */
 104 +  if (__app_register_atfork (register_fork, NULL, NULL) != 0)
 105 +    {
 106 +      printf ("Failed to register fork handler.\n");
 107 +      return -1;
 108 +    }
 109 +
 110    for (test = 0; test_case[test].retval != -1; test++)
 111      if (testit (&test_case[test]))
 112        ++fail;
 113 @@ -367,6 +401,9 @@ testit (struct test_case_struct *tc)
 114
 115    printf ("Test %d (%s): ", ++tests, tc->words);
 116
 117 +  if (tc->flags & WRDE_NOCMD)
 118 +    registered_forks = 0;
 119 +
 120    if (tc->flags & WRDE_APPEND)
 121      {
 122        /* initial wordexp() call, to be appended to */
 123 @@ -378,6 +415,13 @@ testit (struct test_case_struct *tc)
 124      }
 125    retval = wordexp (tc->words, &we, tc->flags);
 126
 127 +  if ((tc->flags & WRDE_NOCMD)
 128 +      && (registered_forks > 0))
 129 +    {
 130 +      printf ("FAILED fork called for WRDE_NOCMD\n");
 131 +      return 1;
 132 +    }
 133 +
 134    if (tc->flags & WRDE_DOOFFS)
 135        start_offs = sav_we.we_offs;
 136
 137 diff --git a/posix/wordexp.c b/posix/wordexp.c
 138 index b6b65dd..d6a158f 100644
 139 --- a/libc/posix/wordexp.c
 140 +++ b/libc/posix/wordexp.c
 141 @@ -693,6 +693,12 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
 142           break;
 143
 144         case '`':
 145 +          if (flags & WRDE_NOCMD)
 146 +            {
 147 +              free (expr);
 148 +              return WRDE_NOCMD;
 149 +            }
 150 +
 151           (*offset)++;
 152           error = parse_backtick (&expr, &expr_length, &expr_maxlen,
 153                                   words, offset, flags, NULL, NULL, NULL);
 154 @@ -1144,6 +1150,10 @@ parse_comm (char **word, size_t *word_length, size_t *max_length,
 155    size_t comm_maxlen;
 156    char *comm = w_newword (&comm_length, &comm_maxlen);
 157
 158 +  /* Do nothing if command substitution should not succeed.  */
 159 +  if (flags & WRDE_NOCMD)
 160 +    return WRDE_CMDSUB;
 161 +
 162    for (; words[*offset]; ++(*offset))
 163      {
 164        switch (words[*offset])
 165 @@ -2121,6 +2131,9 @@ parse_backtick (char **word, size_t *word_length, size_t *max_length,
 166        switch (words[*offset])
 167         {
 168         case '`':
 169 +         if (flags & WRDE_NOCMD)
 170 +           return WRDE_NOCMD;
 171 +
 172           /* Go -- give the script to the shell */
 173           error = exec_comm (comm, word, word_length, max_length, flags,
 174                              pwordexp, ifs, ifs_white);