Line data    Source code

       1             : /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
       2             :  * Copyright (c) 2007-2021, The Tor Project, Inc. */
       3             : /* See LICENSE for licensing information */
       4             : 
       5             : /**
       6             :  * \file qstring.c
       7             :  * \brief Implement QuotedString parsing.
       8             :  *
       9             :  * Note that this is only used for controller authentication; do not
      10             :  * create new users for this.  Instead, prefer the cstring.c functions.
      11             :  **/
      12             : 
      13             : #include "orconfig.h"
      14             : #include "lib/encoding/qstring.h"
      15             : #include "lib/malloc/malloc.h"
      16             : #include "lib/log/util_bug.h"
      17             : 
      18             : /** If the first <b>in_len_max</b> characters in <b>start</b> contain a
      19             :  * QuotedString, return the length of that
      20             :  * string (as encoded, including quotes).  Otherwise return -1. */
      21             : static inline int
      22           0 : get_qstring_length(const char *start, size_t in_len_max,
      23             :                           int *chars_out)
      24             : {
      25           0 :   const char *cp, *end;
      26           0 :   int chars = 0;
      27             : 
      28           0 :   if (*start != '\"')
      29             :     return -1;
      30             : 
      31           0 :   cp = start+1;
      32           0 :   end = start+in_len_max;
      33             : 
      34             :   /* Calculate length. */
      35           0 :   while (1) {
      36           0 :     if (cp >= end) {
      37             :       return -1; /* Too long. */
      38           0 :     } else if (*cp == '\\') {
      39           0 :       if (++cp == end)
      40             :         return -1; /* Can't escape EOS. */
      41           0 :       ++cp;
      42           0 :       ++chars;
      43           0 :     } else if (*cp == '\"') {
      44             :       break;
      45             :     } else {
      46           0 :       ++cp;
      47           0 :       ++chars;
      48             :     }
      49             :   }
      50           0 :   if (chars_out)
      51           0 :     *chars_out = chars;
      52           0 :   return (int)(cp - start+1);
      53             : }
      54             : 
      55             : /** Given a pointer to a string starting at <b>start</b> containing
      56             :  * <b>in_len_max</b> characters, decode a string beginning with one double
      57             :  * quote, containing any number of non-quote characters or characters escaped
      58             :  * with a backslash, and ending with a final double quote.  Place the resulting
      59             :  * string (unquoted, unescaped) into a newly allocated string in *<b>out</b>;
      60             :  * store its length in <b>out_len</b>.  On success, return a pointer to the
      61             :  * character immediately following the escaped string.  On failure, return
      62             :  * NULL. */
      63             : const char *
      64           0 : decode_qstring(const char *start, size_t in_len_max,
      65             :                char **out, size_t *out_len)
      66             : {
      67           0 :   const char *cp, *end;
      68           0 :   char *outp;
      69           0 :   int len, n_chars = 0;
      70             : 
      71           0 :   len = get_qstring_length(start, in_len_max, &n_chars);
      72           0 :   if (len<0)
      73             :     return NULL;
      74             : 
      75           0 :   end = start+len-1; /* Index of last quote. */
      76           0 :   tor_assert(*end == '\"');
      77           0 :   outp = *out = tor_malloc(len+1);
      78           0 :   *out_len = n_chars;
      79             : 
      80           0 :   cp = start+1;
      81           0 :   while (cp < end) {
      82           0 :     if (*cp == '\\')
      83           0 :       ++cp;
      84           0 :     *outp++ = *cp++;
      85             :   }
      86           0 :   *outp = '\0';
      87           0 :   tor_assert((outp - *out) == (int)*out_len);
      88             : 
      89           0 :   return end+1;
      90             : }