git.ozlabs.org Git - ccan/blob - ccan/base64/base64.c

   1 /* Licensed under BSD-MIT - see LICENSE file for details */
   2 #include "base64.h"
   3
   4 #include <errno.h>
   5 #include <string.h>
   6 #include <assert.h>
   7 #include <stdint.h>
   8
   9 /**
  10  * sixbit_to_b64 - maps a 6-bit value to the base64 alphabet
  11  * @param map A base 64 map (see base64_init_map)
  12  * @param sixbit Six-bit value to map
  13  * @return a base 64 character
  14  */
  15 static char sixbit_to_b64(const base64_maps_t *maps, const uint8_t sixbit)
  16 {
  17         assert(sixbit <= 63);
  18
  19         return maps->encode_map[(unsigned char)sixbit];
  20 }
  21
  22 /**
  23  * sixbit_from_b64 - maps a base64-alphabet character to its 6-bit value
  24  * @param maps A base 64 maps structure (see base64_init_maps)
  25  * @param sixbit Six-bit value to map
  26  * @return a six-bit value
  27  */
  28 static int8_t sixbit_from_b64(const base64_maps_t *maps,
  29                               const unsigned char b64letter)
  30 {
  31         int8_t ret;
  32
  33         ret = maps->decode_map[(unsigned char)b64letter];
  34         if (ret == (char)0xff) {
  35                 errno = EDOM;
  36                 return -1;
  37         }
  38
  39         return ret;
  40 }
  41
  42 bool base64_char_in_alphabet(const base64_maps_t *maps, const char b64char)
  43 {
  44         return (maps->decode_map[(const unsigned char)b64char] != (char)0xff);
  45 }
  46
  47 void base64_init_maps(base64_maps_t *dest, const char src[64])
  48 {
  49         unsigned char i;
  50
  51         memcpy(dest->encode_map,src,64);
  52         memset(dest->decode_map,0xff,256);
  53         for (i=0; i<64; i++) {
  54                 dest->decode_map[(unsigned char)src[i]] = i;
  55         }
  56 }
  57
  58 size_t base64_encoded_length(size_t srclen)
  59 {
  60         return ((srclen + 2) / 3) * 4;
  61 }
  62
  63 void base64_encode_triplet_using_maps(const base64_maps_t *maps,
  64                                       char dest[4], const char src[3])
  65 {
  66         char a = src[0];
  67         char b = src[1];
  68         char c = src[2];
  69
  70         dest[0] = sixbit_to_b64(maps, (a & 0xfc) >> 2);
  71         dest[1] = sixbit_to_b64(maps, ((a & 0x3) << 4) | ((b & 0xf0) >> 4));
  72         dest[2] = sixbit_to_b64(maps, ((c & 0xc0) >> 6) | ((b & 0xf) << 2));
  73         dest[3] = sixbit_to_b64(maps, c & 0x3f);
  74 }
  75
  76 void base64_encode_tail_using_maps(const base64_maps_t *maps, char dest[4],
  77                                    const char *src, const size_t srclen)
  78 {
  79         char longsrc[3] = { 0 };
  80
  81         assert(srclen <= 3);
  82
  83         memcpy(longsrc, src, srclen);
  84         base64_encode_triplet_using_maps(maps, dest, longsrc);
  85         memset(dest+1+srclen, '=', 3-srclen);
  86 }
  87
  88 ssize_t base64_encode_using_maps(const base64_maps_t *maps,
  89                                  char *dest, const size_t destlen,
  90                                  const char *src, const size_t srclen)
  91 {
  92         size_t src_offset = 0;
  93         size_t dest_offset = 0;
  94
  95         if (destlen < base64_encoded_length(srclen)) {
  96                 errno = EOVERFLOW;
  97                 return -1;
  98         }
  99
 100         while (srclen - src_offset >= 3) {
 101                 base64_encode_triplet_using_maps(maps, &dest[dest_offset], &src[src_offset]);
 102                 src_offset += 3;
 103                 dest_offset += 4;
 104         }
 105
 106         if (src_offset < srclen) {
 107                 base64_encode_tail_using_maps(maps, &dest[dest_offset], &src[src_offset], srclen-src_offset);
 108                 dest_offset += 4;
 109         }
 110
 111         memset(&dest[dest_offset], '\0', destlen-dest_offset);
 112
 113         return dest_offset;
 114 }
 115
 116 size_t base64_decoded_length(size_t srclen)
 117 {
 118         return ((srclen+3)/4*3);
 119 }
 120
 121 int base64_decode_quartet_using_maps(const base64_maps_t *maps, char dest[3],
 122                                      const char src[4])
 123 {
 124         signed char a;
 125         signed char b;
 126         signed char c;
 127         signed char d;
 128
 129         a = sixbit_from_b64(maps, src[0]);
 130         b = sixbit_from_b64(maps, src[1]);
 131         c = sixbit_from_b64(maps, src[2]);
 132         d = sixbit_from_b64(maps, src[3]);
 133
 134         if ((a == -1) || (b == -1) || (c == -1) || (d == -1)) {
 135                 return -1;
 136         }
 137
 138         dest[0] = (a << 2) | (b >> 4);
 139         dest[1] = ((b & 0xf) << 4) | (c >> 2);
 140         dest[2] = ((c & 0x3) << 6) | d;
 141
 142         return 0;
 143 }
 144
 145
 146 int base64_decode_tail_using_maps(const base64_maps_t *maps, char dest[3],
 147                                   const char * src, const size_t srclen)
 148 {
 149         char longsrc[4];
 150         int quartet_result;
 151         size_t insize = srclen;
 152
 153         while (insize != 0 &&
 154                src[insize-1] == '=') { /* throw away padding symbols */
 155                 insize--;
 156         }
 157         if (insize == 0) {
 158                 return 0;
 159         }
 160         if (insize == 1) {
 161                 /* the input is malformed.... */
 162                 errno = EINVAL;
 163                 return -1;
 164         }
 165         memcpy(longsrc, src, insize);
 166         memset(longsrc+insize, 'A', 4-insize);
 167         quartet_result = base64_decode_quartet_using_maps(maps, dest, longsrc);
 168         if (quartet_result == -1) {
 169                 return -1;
 170         }
 171
 172         return insize - 1;
 173 }
 174
 175 ssize_t base64_decode_using_maps(const base64_maps_t *maps,
 176                                  char *dest, const size_t destlen,
 177                                  const char *src, const size_t srclen)
 178 {
 179         ssize_t dest_offset = 0;
 180         ssize_t i;
 181         size_t more;
 182
 183         if (destlen < base64_decoded_length(srclen)) {
 184                 errno = EOVERFLOW;
 185                 return -1;
 186         }
 187
 188         for(i=0; srclen - i > 4; i+=4) {
 189                 if (base64_decode_quartet_using_maps(maps, &dest[dest_offset], &src[i]) == -1) {
 190                         return -1;
 191                 }
 192                 dest_offset += 3;
 193         }
 194
 195         more = base64_decode_tail_using_maps(maps, &dest[dest_offset], &src[i], srclen - i);
 196         if (more == -1) {
 197                 return -1;
 198         }
 199         dest_offset += more;
 200
 201         memset(&dest[dest_offset], '\0', destlen-dest_offset);
 202
 203         return dest_offset;
 204 }
 205
 206
 207
 208
 209 /**
 210  * base64_maps_rfc4648 - pregenerated maps struct for rfc4648
 211  */
 212 const base64_maps_t base64_maps_rfc4648 = {
 213   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
 214
 215   "\xff\xff\xff\xff\xff" /* 0 */                                        \
 216   "\xff\xff\xff\xff\xff" /* 5 */                                        \
 217   "\xff\xff\xff\xff\xff" /* 10 */                                       \
 218   "\xff\xff\xff\xff\xff" /* 15 */                                       \
 219   "\xff\xff\xff\xff\xff" /* 20 */                                       \
 220   "\xff\xff\xff\xff\xff" /* 25 */                                       \
 221   "\xff\xff\xff\xff\xff" /* 30 */                                       \
 222   "\xff\xff\xff\xff\xff" /* 35 */                                       \
 223   "\xff\xff\xff\x3e\xff" /* 40 */                                       \
 224   "\xff\xff\x3f\x34\x35" /* 45 */                                       \
 225   "\x36\x37\x38\x39\x3a" /* 50 */                                       \
 226   "\x3b\x3c\x3d\xff\xff" /* 55 */                                       \
 227   "\xff\xff\xff\xff\xff" /* 60 */                                       \
 228   "\x00\x01\x02\x03\x04" /* 65 A */                                     \
 229   "\x05\x06\x07\x08\x09" /* 70 */                                       \
 230   "\x0a\x0b\x0c\x0d\x0e" /* 75 */                                       \
 231   "\x0f\x10\x11\x12\x13" /* 80 */                                       \
 232   "\x14\x15\x16\x17\x18" /* 85 */                                       \
 233   "\x19\xff\xff\xff\xff" /* 90 */                                       \
 234   "\xff\xff\x1a\x1b\x1c" /* 95 */                                       \
 235   "\x1d\x1e\x1f\x20\x21" /* 100 */                                      \
 236   "\x22\x23\x24\x25\x26" /* 105 */                                      \
 237   "\x27\x28\x29\x2a\x2b" /* 110 */                                      \
 238   "\x2c\x2d\x2e\x2f\x30" /* 115 */                                      \
 239   "\x31\x32\x33\xff\xff" /* 120 */                                      \
 240   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 125 */                  \
 241   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 242   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 243   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 155 */                  \
 244   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 245   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 246   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 185 */                  \
 247   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 248   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 249   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 215 */                  \
 250   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 251   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"                            \
 252   "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" /* 245 */
 253 };