Refactor out command line formatting

Now correctly handles whitespace, quotes and backslashes. Passes all unit tests.

1 files changed, 100 insertions, 8 deletions

diff --git a/src/common/util.c b/src/common/util.c
index dd2d1110e..87c6fb5c1 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -2953,6 +2953,105 @@ load_windows_system_library(const TCHAR *library_name)
 }
 #endif
 
+/* Format a single argument for being put on a Windows command line.
+ * Returns a newly allocated string */
+static char *
+format_cmdline_argument(const char *arg)
+{
+  char *formatted_arg;
+  char need_quotes;
+  const char *c;
+  int i;
+  int bs_counter = 0;
+  /* Backslash we can point to when one is inserted into the string */
+  const char backslash = '\\';
+
+  /* Smartlist of *char */
+  smartlist_t *arg_chars;
+  arg_chars = smartlist_create();
+
+  /* Quote string if it contains whitespace or is empty */
+  need_quotes = (strchr(arg, ' ') || strchr(arg, '\t') || '\0' == arg[0]);
+
+  /* Build up smartlist of *chars */
+  for (c=arg; *c != '\0'; c++) {
+    if ('"' == *c) {
+      /* Double up backslashes preceding a quote */
+      for (i=0; i<(bs_counter*2); i++)
+        smartlist_add(arg_chars, (void*)&backslash);
+      bs_counter = 0;
+      /* Escape the quote */
+      smartlist_add(arg_chars, (void*)&backslash);
+      smartlist_add(arg_chars, (void*)c);
+    } else if ('\\' == *c) {
+      /* Count backslashes until we know whether to double up */
+      bs_counter++;
+    } else {
+      /* Don't double up slashes preceding a non-quote */
+      for (i=0; i<bs_counter; i++)
+        smartlist_add(arg_chars, (void*)&backslash);
+      bs_counter = 0;
+      smartlist_add(arg_chars, (void*)c);
+    }
+  }
+  /* Don't double up trailing backslashes */
+  for (i=0; i<bs_counter; i++)
+    smartlist_add(arg_chars, (void*)&backslash);
+
+  /* Allocate space for argument, quotes (if needed), and terminator */
+  formatted_arg = tor_malloc(sizeof(char) *
+      (smartlist_len(arg_chars) + (need_quotes?2:0) + 1));
+
+  /* Add leading quote */
+  i=0;
+  if (need_quotes)
+    formatted_arg[i++] = '"';
+
+  /* Add characters */
+  SMARTLIST_FOREACH(arg_chars, char*, c,
+  {
+    formatted_arg[i++] = *c;
+  });
+
+  /* Add trailing quote */
+  if (need_quotes)
+    formatted_arg[i++] = '"';
+  formatted_arg[i] = '\0';
+
+  smartlist_free(arg_chars);
+  return formatted_arg;
+}
+
+/* Format a command line for use on Windows, which takes the command as a
+ * string rather than string array. Follows the rules from "Parsing C++
+ * Command-Line Arguments" in MSDN. Algorithm based on list2cmdline in the
+ * Python subprocess module. Returns a newly allocated string */
+char *
+tor_join_cmdline(const char *argv[])
+{
+  smartlist_t *argv_list;
+  char *joined_argv;
+  int i;
+
+  /* Format each argument and put the result in a smartlist */
+  argv_list = smartlist_create();
+  for (i=0; argv[i] != NULL; i++) {
+    smartlist_add(argv_list, (void *)format_cmdline_argument(argv[i]));
+  }
+
+  /* Join the arguments with whitespace */
+  joined_argv = smartlist_join_strings(argv_list, " ", 0, NULL);
+
+  /* Free the newly allocated arguments, and the smartlist */
+  SMARTLIST_FOREACH(argv_list, char *, arg,
+  {
+    tor_free(arg);
+  });
+  smartlist_free(argv_list);
+
+  return joined_argv;
+}
+
 /** Format <b>child_state</b> and <b>saved_errno</b> as a hex string placed in
  * <b>hex_errno</b>.  Called between fork and _exit, so must be signal-handler
  * safe.
@@ -3068,9 +3167,7 @@ tor_spawn_background(const char *const filename, const char **argv,
   BOOL retval = FALSE;
 
   SECURITY_ATTRIBUTES saAttr;
-  smartlist_t *argv_list;
   char *joined_argv;
-  int i;
 
   /* process_handle must not be NULL */
   tor_assert(process_handle != NULL);
@@ -3116,12 +3213,7 @@ tor_spawn_background(const char *const filename, const char **argv,
 
   /* Windows expects argv to be a whitespace delimited string, so join argv up
    */
-  argv_list = smartlist_create();
-  for (i=0; argv[i] != NULL; i++) {
-    smartlist_add(argv_list, (void *)argv[i]);
-  }
-
-  joined_argv = smartlist_join_strings(argv_list, " ", 0, NULL);
+  joined_argv = tor_join_cmdline(argv);
 
   ZeroMemory(&(process_handle->pid), sizeof(PROCESS_INFORMATION));
   ZeroMemory(&siStartInfo, sizeof(STARTUPINFO));