net/asterisk-11.x/patches/025-AST-2017-006-11.diff

   1 From 31676ce058596b57e10fbf83ff1817ca7907c3b1 Mon Sep 17 00:00:00 2001
   2 From: Corey Farrell <git@cfware.com>
   3 Date: Sat, 01 Jul 2017 20:24:27 -0400
   4 Subject: [PATCH] AST-2017-006: Fix app_minivm application MinivmNotify command injection
   5
   6 An admin can configure app_minivm with an externnotify program to be run
   7 when a voicemail is received.  The app_minivm application MinivmNotify
   8 uses ast_safe_system() for this purpose which is vulnerable to command
   9 injection since the Caller-ID name and number values given to externnotify
  10 can come from an external untrusted source.
  11
  12 * Add ast_safe_execvp() function.  This gives modules the ability to run
  13 external commands with greater safety compared to ast_safe_system().
  14 Specifically when some parameters are filled by untrusted sources the new
  15 function does not allow malicious input to break argument encoding.  This
  16 may be of particular concern where CALLERID(name) or CALLERID(num) may be
  17 used as a parameter to a script run by ast_safe_system() which could
  18 potentially allow arbitrary command execution.
  19
  20 * Changed app_minivm.c:run_externnotify() to use the new ast_safe_execvp()
  21 instead of ast_safe_system() to avoid command injection.
  22
  23 * Document code injection potential from untrusted data sources for other
  24 shell commands that are under user control.
  25
  26 ASTERISK-27103
  27
  28 Change-Id: I7552472247a84cde24e1358aaf64af160107aef1
  29 ---
  30
  31 diff --git a/README-SERIOUSLY.bestpractices.txt b/README-SERIOUSLY.bestpractices.txt
  32 index 281d0d3..d63f1df 100644
  33 --- a/README-SERIOUSLY.bestpractices.txt
  34 +++ b/README-SERIOUSLY.bestpractices.txt
  35 @@ -94,6 +94,13 @@
  36  ways in which you can mitigate this impact: stricter pattern matching, or using
  37  the FILTER() dialplan function.
  38
  39 +The CALLERID(num) and CALLERID(name) values are other commonly used values that
  40 +are sources of data potentially supplied by outside sources.  If you use these
  41 +values as parameters to the System(), MixMonitor(), or Monitor() applications
  42 +or the SHELL() dialplan function, you can allow injection of arbitrary operating
  43 +system command execution.  The FILTER() dialplan function is available to remove
  44 +dangerous characters from untrusted strings to block the command injection.
  45 +
  46  Strict Pattern Matching
  47  -----------------------
  48
  49 diff --git a/apps/app_minivm.c b/apps/app_minivm.c
  50 index ecdf9c6..8edc132 100644
  51 --- a/apps/app_minivm.c
  52 +++ b/apps/app_minivm.c
  53 @@ -1741,21 +1741,35 @@
  54  /*! \brief Run external notification for voicemail message */
  55  static void run_externnotify(struct ast_channel *chan, struct minivm_account *vmu)
  56  {
  57 -       char arguments[BUFSIZ];
  58 +       char fquser[AST_MAX_CONTEXT * 2];
  59 +       char *argv[5] = { NULL };
  60 +       struct ast_party_caller *caller;
  61 +       char *cid;
  62 +       int idx;
  63
  64 -       if (ast_strlen_zero(vmu->externnotify) && ast_strlen_zero(global_externnotify))
  65 +       if (ast_strlen_zero(vmu->externnotify) && ast_strlen_zero(global_externnotify)) {
  66                 return;
  67 +       }
  68
  69 -       snprintf(arguments, sizeof(arguments), "%s %s@%s %s %s&",
  70 -               ast_strlen_zero(vmu->externnotify) ? global_externnotify : vmu->externnotify,
  71 -               vmu->username, vmu->domain,
  72 -               (ast_channel_caller(chan)->id.name.valid && ast_channel_caller(chan)->id.name.str)
  73 -                       ? ast_channel_caller(chan)->id.name.str : "",
  74 -               (ast_channel_caller(chan)->id.number.valid && ast_channel_caller(chan)->id.number.str)
  75 -                       ? ast_channel_caller(chan)->id.number.str : "");
  76 +       snprintf(fquser, sizeof(fquser), "%s@%s", vmu->username, vmu->domain);
  77
  78 -       ast_debug(1, "Executing: %s\n", arguments);
  79 -       ast_safe_system(arguments);
  80 +       caller = ast_channel_caller(chan);
  81 +       idx = 0;
  82 +       argv[idx++] = ast_strlen_zero(vmu->externnotify) ? global_externnotify : vmu->externnotify;
  83 +       argv[idx++] = fquser;
  84 +       cid = S_COR(caller->id.name.valid, caller->id.name.str, NULL);
  85 +       if (cid) {
  86 +               argv[idx++] = cid;
  87 +       }
  88 +       cid = S_COR(caller->id.number.valid, caller->id.number.str, NULL);
  89 +       if (cid) {
  90 +               argv[idx++] = cid;
  91 +       }
  92 +       argv[idx] = NULL;
  93 +
  94 +       ast_debug(1, "Executing: %s %s %s %s\n",
  95 +               argv[0], argv[1], argv[2] ?: "", argv[3] ?: "");
  96 +       ast_safe_execvp(1, argv[0], argv);
  97  }
  98
  99  /*!\internal
 100 diff --git a/apps/app_mixmonitor.c b/apps/app_mixmonitor.c
 101 index 89a1d8c..96adb9a 100644
 102 --- a/apps/app_mixmonitor.c
 103 +++ b/apps/app_mixmonitor.c
 104 @@ -127,6 +127,11 @@
 105                                 <para>Will be executed when the recording is over.</para>
 106                                 <para>Any strings matching <literal>^{X}</literal> will be unescaped to <variable>X</variable>.</para>
 107                                 <para>All variables will be evaluated at the time MixMonitor is called.</para>
 108 +                               <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
 109 +                               or <variable>CALLERID(name)</variable> as part of the command parameters.  You
 110 +                               risk a command injection attack executing arbitrary commands if the untrusted
 111 +                               strings aren't filtered to remove dangerous characters.  See function
 112 +                               <variable>FILTER()</variable>.</para></warning>
 113                         </parameter>
 114                 </syntax>
 115                 <description>
 116 @@ -143,6 +148,11 @@
 117                                         <para>Will contain the filename used to record.</para>
 118                                 </variable>
 119                         </variablelist>
 120 +                       <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
 121 +                       or <variable>CALLERID(name)</variable> as part of ANY of the application's
 122 +                       parameters.  You risk a command injection attack executing arbitrary commands
 123 +                       if the untrusted strings aren't filtered to remove dangerous characters.  See
 124 +                       function <variable>FILTER()</variable>.</para></warning>
 125                 </description>
 126                 <see-also>
 127                         <ref type="application">Monitor</ref>
 128 diff --git a/apps/app_system.c b/apps/app_system.c
 129 index 7fe453d..e868a07 100644
 130 --- a/apps/app_system.c
 131 +++ b/apps/app_system.c
 132 @@ -48,6 +48,11 @@
 133                 <syntax>
 134                         <parameter name="command" required="true">
 135                                 <para>Command to execute</para>
 136 +                               <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
 137 +                               or <variable>CALLERID(name)</variable> as part of the command parameters.  You
 138 +                               risk a command injection attack executing arbitrary commands if the untrusted
 139 +                               strings aren't filtered to remove dangerous characters.  See function
 140 +                               <variable>FILTER()</variable>.</para></warning>
 141                         </parameter>
 142                 </syntax>
 143                 <description>
 144 @@ -73,6 +78,11 @@
 145                 <syntax>
 146                         <parameter name="command" required="true">
 147                                 <para>Command to execute</para>
 148 +                               <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
 149 +                               or <variable>CALLERID(name)</variable> as part of the command parameters.  You
 150 +                               risk a command injection attack executing arbitrary commands if the untrusted
 151 +                               strings aren't filtered to remove dangerous characters.  See function
 152 +                               <variable>FILTER()</variable>.</para></warning>
 153                         </parameter>
 154                 </syntax>
 155                 <description>
 156 diff --git a/configs/minivm.conf.sample b/configs/minivm.conf.sample
 157 index 55a39c8..3dcd59d 100644
 158 --- a/configs/minivm.conf.sample
 159 +++ b/configs/minivm.conf.sample
 160 @@ -51,7 +51,7 @@
 161  ; If you need to have an external program, i.e. /usr/bin/myapp called when a
 162  ; voicemail is received by the server. The arguments are
 163  ;
 164 -;      <app> <username@domain> <callerid-number> <callerid-name>
 165 +;      <app> <username@domain> <callerid-name> <callerid-number>
 166  ;
 167  ;externnotify=/usr/bin/myapp
 168  ; The character set for voicemail messages can be specified here
 169 diff --git a/funcs/func_shell.c b/funcs/func_shell.c
 170 index e403efc..79b7f99 100644
 171 --- a/funcs/func_shell.c
 172 +++ b/funcs/func_shell.c
 173 @@ -84,6 +84,11 @@
 174                 <syntax>
 175                         <parameter name="command" required="true">
 176                                 <para>The command that the shell should execute.</para>
 177 +                               <warning><para>Do not use untrusted strings such as <variable>CALLERID(num)</variable>
 178 +                               or <variable>CALLERID(name)</variable> as part of the command parameters.  You
 179 +                               risk a command injection attack executing arbitrary commands if the untrusted
 180 +                               strings aren't filtered to remove dangerous characters.  See function
 181 +                               <variable>FILTER()</variable>.</para></warning>
 182                         </parameter>
 183                 </syntax>
 184                 <description>
 185 diff --git a/include/asterisk/app.h b/include/asterisk/app.h
 186 index d10a0a6..8cdaea1 100644
 187 --- a/include/asterisk/app.h
 188 +++ b/include/asterisk/app.h
 189 @@ -577,9 +577,34 @@
 190  int ast_vm_test_create_user(const char *context, const char *mailbox);
 191  #endif
 192
 193 -/*! \brief Safely spawn an external program while closing file descriptors
 194 -       \note This replaces the \b system call in all Asterisk modules
 195 -*/
 196 +/*!
 197 + * \brief Safely spawn an external program while closing file descriptors
 198 + *
 199 + * \note This replaces the \b execvp call in all Asterisk modules
 200 + *
 201 + * \param dualfork Non-zero to simulate running the program in the
 202 + * background by forking twice.  The option provides similar
 203 + * functionality to the '&' in the OS shell command "cmd &".  The
 204 + * option allows Asterisk to run a reaper loop to watch the first fork
 205 + * which immediately exits after spaning the second fork.  The actual
 206 + * program is run in the second fork.
 207 + * \param file execvp(file, argv) file parameter
 208 + * \param argv execvp(file, argv) argv parameter
 209 + */
 210 +int ast_safe_execvp(int dualfork, const char *file, char *const argv[]);
 211 +
 212 +/*!
 213 + * \brief Safely spawn an OS shell command while closing file descriptors
 214 + *
 215 + * \note This replaces the \b system call in all Asterisk modules
 216 + *
 217 + * \param s - OS shell command string to execute.
 218 + *
 219 + * \warning Command injection can happen using this call if the passed
 220 + * in string is created using untrusted data from an external source.
 221 + * It is best not to use untrusted data.  However, the caller could
 222 + * filter out dangerous characters to avoid command injection.
 223 + */
 224  int ast_safe_system(const char *s);
 225
 226  /*!
 227 diff --git a/main/asterisk.c b/main/asterisk.c
 228 index ce1d153..92256bd 100644
 229 --- a/main/asterisk.c
 230 +++ b/main/asterisk.c
 231 @@ -1102,12 +1102,10 @@
 232         ast_mutex_unlock(&safe_system_lock);
 233  }
 234
 235 -int ast_safe_system(const char *s)
 236 +/*! \brief fork and perform other preparations for spawning applications */
 237 +static pid_t safe_exec_prep(int dualfork)
 238  {
 239         pid_t pid;
 240 -       int res;
 241 -       struct rusage rusage;
 242 -       int status;
 243
 244  #if defined(HAVE_WORKING_FORK) || defined(HAVE_WORKING_VFORK)
 245         ast_replace_sigchld();
 246 @@ -1129,35 +1127,102 @@
 247                 cap_free(cap);
 248  #endif
 249  #ifdef HAVE_WORKING_FORK
 250 -               if (ast_opt_high_priority)
 251 +               if (ast_opt_high_priority) {
 252                         ast_set_priority(0);
 253 +               }
 254                 /* Close file descriptors and launch system command */
 255                 ast_close_fds_above_n(STDERR_FILENO);
 256  #endif
 257 -               execl("/bin/sh", "/bin/sh", "-c", s, (char *) NULL);
 258 -               _exit(1);
 259 -       } else if (pid > 0) {
 260 +               if (dualfork) {
 261 +#ifdef HAVE_WORKING_FORK
 262 +                       pid = fork();
 263 +#else
 264 +                       pid = vfork();
 265 +#endif
 266 +                       if (pid < 0) {
 267 +                               /* Second fork failed. */
 268 +                               /* No logger available. */
 269 +                               _exit(1);
 270 +                       }
 271 +
 272 +                       if (pid > 0) {
 273 +                               /* This is the first fork, exit so the reaper finishes right away. */
 274 +                               _exit(0);
 275 +                       }
 276 +
 277 +                       /* This is the second fork.  The first fork will exit immediately so
 278 +                        * Asterisk doesn't have to wait for completion.
 279 +                        * ast_safe_system("cmd &") would run in the background, but the '&'
 280 +                        * cannot be added with ast_safe_execvp, so we have to double fork.
 281 +                        */
 282 +               }
 283 +       }
 284 +
 285 +       if (pid < 0) {
 286 +               ast_log(LOG_WARNING, "Fork failed: %s\n", strerror(errno));
 287 +       }
 288 +#else
 289 +       ast_log(LOG_WARNING, "Fork failed: %s\n", strerror(ENOTSUP));
 290 +       pid = -1;
 291 +#endif
 292 +
 293 +       return pid;
 294 +}
 295 +
 296 +/*! \brief wait for spawned application to complete and unreplace sigchld */
 297 +static int safe_exec_wait(pid_t pid)
 298 +{
 299 +       int res = -1;
 300 +
 301 +#if defined(HAVE_WORKING_FORK) || defined(HAVE_WORKING_VFORK)
 302 +       if (pid > 0) {
 303                 for (;;) {
 304 +                       struct rusage rusage;
 305 +                       int status;
 306 +
 307                         res = wait4(pid, &status, 0, &rusage);
 308                         if (res > -1) {
 309                                 res = WIFEXITED(status) ? WEXITSTATUS(status) : -1;
 310                                 break;
 311 -                       } else if (errno != EINTR)
 312 +                       }
 313 +                       if (errno != EINTR) {
 314                                 break;
 315 +                       }
 316                 }
 317 -       } else {
 318 -               ast_log(LOG_WARNING, "Fork failed: %s\n", strerror(errno));
 319 -               res = -1;
 320         }
 321
 322         ast_unreplace_sigchld();
 323 -#else /* !defined(HAVE_WORKING_FORK) && !defined(HAVE_WORKING_VFORK) */
 324 -       res = -1;
 325  #endif
 326
 327         return res;
 328  }
 329
 330 +int ast_safe_execvp(int dualfork, const char *file, char *const argv[])
 331 +{
 332 +       pid_t pid = safe_exec_prep(dualfork);
 333 +
 334 +       if (pid == 0) {
 335 +               execvp(file, argv);
 336 +               _exit(1);
 337 +               /* noreturn from _exit */
 338 +       }
 339 +
 340 +       return safe_exec_wait(pid);
 341 +}
 342 +
 343 +int ast_safe_system(const char *s)
 344 +{
 345 +       pid_t pid = safe_exec_prep(0);
 346 +
 347 +       if (pid == 0) {
 348 +               execl("/bin/sh", "/bin/sh", "-c", s, (char *) NULL);
 349 +               _exit(1);
 350 +               /* noreturn from _exit */
 351 +       }
 352 +
 353 +       return safe_exec_wait(pid);
 354 +}
 355 +
 356  /*!
 357   * \brief enable or disable a logging level to a specified console
 358   */
 359 diff --git a/res/res_monitor.c b/res/res_monitor.c
 360 index 76c43e1..12f478a 100644
 361 --- a/res/res_monitor.c
 362 +++ b/res/res_monitor.c
 363 @@ -57,17 +57,17 @@
 364                 <syntax>
 365                         <parameter name="file_format" argsep=":">
 366                                 <argument name="file_format" required="true">
 367 -                                       <para>optional, if not set, defaults to <literal>wav</literal></para>
 368 +                                       <para>Optional.  If not set, defaults to <literal>wav</literal></para>
 369                                 </argument>
 370                                 <argument name="urlbase" />
 371                         </parameter>
 372                         <parameter name="fname_base">
 373 -                               <para>if set, changes the filename used to the one specified.</para>
 374 +                               <para>If set, changes the filename used to the one specified.</para>
 375                         </parameter>
 376                         <parameter name="options">
 377                                 <optionlist>
 378                                         <option name="m">
 379 -                                               <para>when the recording ends mix the two leg files into one and
 380 +                                               <para>When the recording ends mix the two leg files into one and
 381                                                 delete the two leg files. If the variable <variable>MONITOR_EXEC</variable>
 382                                                 is set, the application referenced in it will be executed instead of
 383                                                 soxmix/sox and the raw leg files will NOT be deleted automatically.
 384 @@ -78,6 +78,13 @@
 385                                                 will be passed on as additional arguments to <variable>MONITOR_EXEC</variable>.
 386                                                 Both <variable>MONITOR_EXEC</variable> and the Mix flag can be set from the
 387                                                 administrator interface.</para>
 388 +                                               <warning><para>Do not use untrusted strings such as
 389 +                                               <variable>CALLERID(num)</variable> or <variable>CALLERID(name)</variable>
 390 +                                               as part of <variable>MONITOR_EXEC</variable> or
 391 +                                               <variable>MONITOR_EXEC_ARGS</variable>.  You risk a command injection
 392 +                                               attack executing arbitrary commands if the untrusted strings aren't
 393 +                                               filtered to remove dangerous characters.  See function
 394 +                                               <variable>FILTER()</variable>.</para></warning>
 395                                         </option>
 396                                         <option name="b">
 397                                                 <para>Don't begin recording unless a call is bridged to another channel.</para>