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
hex_to_bin(unsigned char c)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
percent_decode_in_place(char * str,int strict)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 }
70