Implement "TOR_PT_EXIT_ON_STDIN_CLOSE".

Background processes spawned by Tor now will have a valid stdin. Pluggable transports can detect this behavior with the aformentioned enviornment variable, and exit if stdin ever gets closed.
2024-12-06 19:41:15 +01:00 · 2015-03-26 12:55:12 +00:00
parent 732322b710
commit fda61e030e
5 changed files with 82 additions and 14 deletions
@@ -3939,9 +3939,11 @@ process_handle_new(void)
  process_handle_t *out = tor_malloc_zero(sizeof(process_handle_t));

 #ifdef _WIN32
+  out->stdin_pipe = INVALID_HANDLE_VALUE;
  out->stdout_pipe = INVALID_HANDLE_VALUE;
  out->stderr_pipe = INVALID_HANDLE_VALUE;
 #else
+  out->stdin_pipe = -1;
  out->stdout_pipe = -1;
  out->stderr_pipe = -1;
 #endif
@@ -3981,7 +3983,7 @@ process_handle_waitpid_cb(int status, void *arg)
 #define CHILD_STATE_FORK 3
 #define CHILD_STATE_DUPOUT 4
 #define CHILD_STATE_DUPERR 5
-#define CHILD_STATE_REDIRECT 6
+#define CHILD_STATE_DUPIN 6
 #define CHILD_STATE_CLOSEFD 7
 #define CHILD_STATE_EXEC 8
 #define CHILD_STATE_FAILEXEC 9
@@ -4015,6 +4017,8 @@ tor_spawn_background(const char *const filename, const char **argv,
  HANDLE stdout_pipe_write = NULL;
  HANDLE stderr_pipe_read = NULL;
  HANDLE stderr_pipe_write = NULL;
+  HANDLE stdin_pipe_read = NULL;
+  HANDLE stdin_pipe_write = NULL;
  process_handle_t *process_handle;
  int status;

@@ -4060,6 +4064,20 @@ tor_spawn_background(const char *const filename, const char **argv,
    return status;
  }

+  /* Set up pipe for stdin */
+  if (!CreatePipe(&stdin_pipe_read, &stdin_pipe_write, &saAttr, 0)) {
+    log_warn(LD_GENERAL,
+      "Failed to create pipe for stdin communication with child process: %s",
+      format_win32_error(GetLastError()));
+    return status;
+  }
+  if (!SetHandleInformation(stderr_pipe_write, HANDLE_FLAG_INHERIT, 0)) {
+    log_warn(LD_GENERAL,
+      "Failed to configure pipe for stdin communication with child "
+      "process: %s", format_win32_error(GetLastError()));
+    return status;
+  }
+
  /* Create the child process */

  /* Windows expects argv to be a whitespace delimited string, so join argv up
@@ -4074,7 +4092,7 @@ tor_spawn_background(const char *const filename, const char **argv,
  siStartInfo.cb = sizeof(STARTUPINFO);
  siStartInfo.hStdError = stderr_pipe_write;
  siStartInfo.hStdOutput = stdout_pipe_write;
-  siStartInfo.hStdInput = NULL;
+  siStartInfo.hStdInput = stdin_pipe_read;
  siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

  /* Create the child process */
@@ -4104,6 +4122,7 @@ tor_spawn_background(const char *const filename, const char **argv,
    /* TODO: Close hProcess and hThread in process_handle->pid? */
    process_handle->stdout_pipe = stdout_pipe_read;
    process_handle->stderr_pipe = stderr_pipe_read;
+    process_handle->stdin_pipe = stdin_pipe_write;
    status = process_handle->status = PROCESS_STATUS_RUNNING;
  }

@@ -4114,6 +4133,7 @@ tor_spawn_background(const char *const filename, const char **argv,
  pid_t pid;
  int stdout_pipe[2];
  int stderr_pipe[2];
+  int stdin_pipe[2];
  int fd, retval;
  ssize_t nbytes;
  process_handle_t *process_handle;
@@ -4138,7 +4158,7 @@ tor_spawn_background(const char *const filename, const char **argv,

  child_state = CHILD_STATE_PIPE;

-  /* Set up pipe for redirecting stdout and stderr of child */
+  /* Set up pipe for redirecting stdout, stderr, and stdin of child */
  retval = pipe(stdout_pipe);
  if (-1 == retval) {
    log_warn(LD_GENERAL,
@@ -4159,6 +4179,20 @@ tor_spawn_background(const char *const filename, const char **argv,
    return status;
  }

+  retval = pipe(stdin_pipe);
+  if (-1 == retval) {
+    log_warn(LD_GENERAL,
+      "Failed to set up pipe for stdin communication with child process: %s",
+       strerror(errno));
+
+    close(stdout_pipe[0]);
+    close(stdout_pipe[1]);
+    close(stderr_pipe[0]);
+    close(stderr_pipe[1]);
+
+    return status;
+  }
+
  child_state = CHILD_STATE_MAXFD;

 #ifdef _SC_OPEN_MAX
@@ -4194,13 +4228,11 @@ tor_spawn_background(const char *const filename, const char **argv,
    if (-1 == retval)
        goto error;

-    child_state = CHILD_STATE_REDIRECT;
+    child_state = CHILD_STATE_DUPIN;

-    /* Link stdin to /dev/null */
-    fd = open("/dev/null", O_RDONLY); /* NOT cloexec, obviously. */
-    if (fd != -1)
-      dup2(fd, STDIN_FILENO);
-    else
+    /* Link child stdin to the read end of the pipe */
+    retval = dup2(stdin_pipe[0], STDIN_FILENO);
+    if (-1 == retval)
      goto error;

    child_state = CHILD_STATE_CLOSEFD;
@@ -4209,7 +4241,8 @@ tor_spawn_background(const char *const filename, const char **argv,
    close(stderr_pipe[1]);
    close(stdout_pipe[0]);
    close(stdout_pipe[1]);
-    close(fd);
+    close(stdin_pipe[0]);
+    close(stdin_pipe[1]);

    /* Close all other fds, including the read end of the pipe */
    /* XXX: We should now be doing enough FD_CLOEXEC setting to make
@@ -4259,6 +4292,8 @@ tor_spawn_background(const char *const filename, const char **argv,

  if (-1 == pid) {
    log_warn(LD_GENERAL, "Failed to fork child process: %s", strerror(errno));
+    close(stdin_pipe[0]);
+    close(stdin_pipe[1]);
    close(stdout_pipe[0]);
    close(stdout_pipe[1]);
    close(stderr_pipe[0]);
@@ -4295,16 +4330,28 @@ tor_spawn_background(const char *const filename, const char **argv,
            strerror(errno));
  }

+  /* Return write end of the stdin pipe to caller, and close the read end */
+  process_handle->stdin_pipe = stdin_pipe[1];
+  retval = close(stdin_pipe[0]);
+
+  if (-1 == retval) {
+    log_warn(LD_GENERAL,
+            "Failed to close read end of stdin pipe in parent process: %s",
+            strerror(errno));
+  }
+
  status = process_handle->status = PROCESS_STATUS_RUNNING;
-  /* Set stdout/stderr pipes to be non-blocking */
+  /* Set stdin/stdout/stderr pipes to be non-blocking */
  if (fcntl(process_handle->stdout_pipe, F_SETFL, O_NONBLOCK) < 0 ||
-      fcntl(process_handle->stderr_pipe, F_SETFL, O_NONBLOCK) < 0) {
-    log_warn(LD_GENERAL, "Failed to set stderror/stdout pipes nonblocking "
-             "in parent process: %s", strerror(errno));
+      fcntl(process_handle->stderr_pipe, F_SETFL, O_NONBLOCK) < 0 ||
+      fcntl(process_handle->stdin_pipe, F_SETFL, O_NONBLOCK) < 0) {
+    log_warn(LD_GENERAL, "Failed to set stderror/stdout/stdin pipes "
+             "nonblocking in parent process: %s", strerror(errno));
  }
  /* Open the buffered IO streams */
  process_handle->stdout_handle = fdopen(process_handle->stdout_pipe, "r");
  process_handle->stderr_handle = fdopen(process_handle->stderr_pipe, "r");
+  process_handle->stdin_handle = fdopen(process_handle->stdin_pipe, "r");

  *process_handle_out = process_handle;
  return process_handle->status;
@@ -4347,6 +4394,9 @@ tor_process_handle_destroy,(process_handle_t *process_handle,

  if (process_handle->stderr_pipe)
    CloseHandle(process_handle->stderr_pipe);
+
+  if (process_handle->stdin_pipe)
+    CloseHandle(process_handle->stdin_pipe);
 #else
  if (process_handle->stdout_handle)
    fclose(process_handle->stdout_handle);
@@ -4354,6 +4404,9 @@ tor_process_handle_destroy,(process_handle_t *process_handle,
  if (process_handle->stderr_handle)
    fclose(process_handle->stderr_handle);

+  if (process_handle->stdin_handle)
+    fclose(process_handle->stdin_handle);
+
  clear_waitpid_callback(process_handle->waitpid_cb);
 #endif

@@ -474,12 +474,15 @@ struct process_handle_t {
  /** One of the PROCESS_STATUS_* values */
  int status;
 #ifdef _WIN32
+  HANDLE stdin_pipe;
  HANDLE stdout_pipe;
  HANDLE stderr_pipe;
  PROCESS_INFORMATION pid;
 #else
+  int stdin_pipe;
  int stdout_pipe;
  int stderr_pipe;
+  FILE *stdin_handle;
  FILE *stdout_handle;
  FILE *stderr_handle;
  pid_t pid;