release/src/router/busybox/libbb/percent_decode.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   4  */
   5
   6 //kbuild:lib-y += percent_decode.o
   7
   8 #include "libbb.h"
   9
  10 static unsigned hex_to_bin(unsigned char c)
  11 {
  12         unsigned v;
  13
  14         v = c - '0';
  15         if (v <= 9)
  16                 return v;
  17         /* c | 0x20: letters to lower case, non-letters
  18          * to (potentially different) non-letters */
  19         v = (unsigned)(c | 0x20) - 'a';
  20         if (v <= 5)
  21                 return v + 10;
  22         return ~0;
  23 /* For testing:
  24 void t(char c) { printf("'%c'(%u) %u\n", c, c, hex_to_bin(c)); }
  25 int main() { t(0x10); t(0x20); t('0'); t('9'); t('A'); t('F'); t('a'); t('f');
  26 t('0'-1); t('9'+1); t('A'-1); t('F'+1); t('a'-1); t('f'+1); return 0; }
  27 */
  28 }
  29
  30 char* FAST_FUNC percent_decode_in_place(char *str, int strict)
  31 {
  32         /* note that decoded string is always shorter than original */
  33         char *src = str;
  34         char *dst = str;
  35         char c;
  36
  37         while ((c = *src++) != '\0') {
  38                 unsigned v;
  39
  40                 if (!strict && c == '+') {
  41                         *dst++ = ' ';
  42                         continue;
  43                 }
  44                 if (c != '%') {
  45                         *dst++ = c;
  46                         continue;
  47                 }
  48                 v = hex_to_bin(src[0]);
  49                 if (v > 15) {
  50  bad_hex:
  51                         if (strict)
  52                                 return NULL;
  53                         *dst++ = '%';
  54                         continue;
  55                 }
  56                 v = (v * 16) | hex_to_bin(src[1]);
  57                 if (v > 255)
  58                         goto bad_hex;
  59                 if (strict && (v == '/' || v == '\0')) {
  60                         /* caller takes it as indication of invalid
  61                          * (dangerous wrt exploits) chars */
  62                         return str + 1;
  63                 }
  64                 *dst++ = v;
  65                 src += 2;
  66         }
  67         *dst = '\0';
  68         return str;
  69 }