src/lib/base64.c

   1 #include <stdlib.h>
   2 #include <string.h>
   3 #include <ctype.h>
   4
   5 #include "base64.h"
   6
   7 #define DEFAULT_CHARLIST "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
   8
   9 #define BASE64_PADDING 0x40
  10 #define BASE64_INVALID 0x80
  11
  12 struct base64_s {
  13         char charlist[65];
  14         char charmap[256];
  15         int charmap_inited;
  16
  17         int use_padding;
  18         int skip_spaces;
  19 };
  20
  21 static base64_t default_base64 =
  22         { .charlist = DEFAULT_CHARLIST,
  23           .use_padding = 1 };
  24
  25 static void
  26 initialize_charmap(base64_t *base64)
  27 {
  28         int i;
  29
  30         memset(base64->charmap, BASE64_INVALID, sizeof(base64->charmap));
  31         for (i=0; i<64; i++) {
  32                 base64->charmap[(int)base64->charlist[i]] = i;
  33         }
  34         base64->charmap['='] = BASE64_PADDING;
  35         base64->charmap_inited = 1;
  36 }
  37
  38 base64_t *
  39 base64_init(const char *charlist, int use_padding, int skip_spaces)
  40 {
  41         base64_t *base64;
  42         int i;
  43
  44         if (!charlist) {
  45                 charlist = DEFAULT_CHARLIST;
  46         }
  47         if (strlen(charlist) != 64) {
  48                 return NULL;
  49         }
  50         for (i=0; i<64; i++) {
  51                 switch (charlist[i]) {
  52                 case '\r':
  53                 case '\n':
  54                 case '=':
  55                         return NULL;
  56                 }
  57         }
  58
  59         base64 = calloc(1, sizeof(base64_t));
  60         if (!base64) {
  61                 return NULL;
  62         }
  63         strncpy(base64->charlist, charlist, sizeof(base64->charlist)-1);
  64         base64->use_padding = use_padding;
  65         base64->skip_spaces = skip_spaces;
  66
  67         return base64;
  68 }
  69
  70 void
  71 base64_destroy(base64_t *base64)
  72 {
  73         free(base64);
  74 }
  75
  76 int
  77 base64_encoded_length(base64_t *base64, int srclen)
  78 {
  79         if (!base64) {
  80                 base64 = &default_base64;
  81         }
  82
  83         if (base64->use_padding) {
  84                 return ((srclen+2)/3*4)+1;
  85         } else {
  86                 int strlen = 0;
  87                 switch (srclen % 3) {
  88                 case 2:
  89                         strlen += 1;
  90                 case 1:
  91                         strlen += 2;
  92                 default:
  93                         strlen += srclen/3*4;
  94                         break;
  95                 }
  96                 return strlen+1;
  97         }
  98 }
  99
 100 int
 101 base64_encode(base64_t *base64, char *dst, const unsigned char *src, int srclen)
 102 {
 103         int src_idx, dst_idx;
 104         int residue;
 105
 106         if (!base64) {
 107                 base64 = &default_base64;
 108         }
 109
 110         residue = 0;
 111         for (src_idx=dst_idx=0; src_idx<srclen; src_idx++) {
 112                 residue |= src[src_idx];
 113
 114                 switch (src_idx%3) {
 115                 case 0:
 116                         dst[dst_idx++] = base64->charlist[(residue>>2)%64];
 117                         residue &= 0x03;
 118                         break;
 119                 case 1:
 120                         dst[dst_idx++] = base64->charlist[residue>>4];
 121                         residue &= 0x0f;
 122                         break;
 123                 case 2:
 124                         dst[dst_idx++] = base64->charlist[residue>>6];
 125                         dst[dst_idx++] = base64->charlist[residue&0x3f];
 126                         residue = 0;
 127                         break;
 128                 }
 129                 residue <<= 8;
 130         }
 131
 132         /* Add padding */
 133         if (src_idx%3 == 1) {
 134                 dst[dst_idx++] = base64->charlist[residue>>4];
 135                 if (base64->use_padding) {
 136                         dst[dst_idx++] = '=';
 137                         dst[dst_idx++] = '=';
 138                 }
 139         } else if (src_idx%3 == 2) {
 140                 dst[dst_idx++] = base64->charlist[residue>>6];
 141                 if (base64->use_padding) {
 142                         dst[dst_idx++] = '=';
 143                 }
 144         }
 145         dst[dst_idx] = '\0';
 146         return dst_idx;
 147 }
 148
 149 int
 150 base64_decode(base64_t *base64, unsigned char **dst, const char *src, int srclen)
 151 {
 152         char *inbuf;
 153         int inbuflen;
 154         unsigned char *outbuf;
 155         int outbuflen;
 156         char *srcptr;
 157         int index;
 158
 159         if (!base64) {
 160                 base64 = &default_base64;
 161         }
 162         if (!base64->charmap_inited) {
 163                 initialize_charmap(base64);
 164         }
 165
 166         inbuf = malloc(srclen+4);
 167         if (!inbuf) {
 168                 return -1;
 169         }
 170         memcpy(inbuf, src, srclen);
 171         inbuf[srclen] = '\0';
 172
 173         /* Remove all whitespaces from inbuf */
 174         if (base64->skip_spaces) {
 175                 int i, inbuflen = strlen(inbuf);
 176                 for (i=0; i<inbuflen; i++) {
 177                         if (inbuf[i] == '\0') {
 178                                 break;
 179                         } else if (isspace(inbuf[i])) {
 180                                 memmove(inbuf+i, inbuf+i+1, inbuflen-i);
 181                                 inbuflen -= 1;
 182                                 i -= 1;
 183                         }
 184                 }
 185         }
 186
 187         /* Add padding to inbuf if required */
 188         inbuflen = strlen(inbuf);
 189         if (!base64->use_padding) {
 190                 if (inbuflen%4 == 1) {
 191                         free(inbuf);
 192                         return -2;
 193                 }
 194                 if (inbuflen%4 == 2) {
 195                         inbuf[inbuflen] = '=';
 196                         inbuf[inbuflen+1] = '=';
 197                         inbuf[inbuflen+2] = '\0';
 198                         inbuflen += 2;
 199                 } else if (inbuflen%4 == 3) {
 200                         inbuf[inbuflen] = '=';
 201                         inbuf[inbuflen+1] = '\0';
 202                         inbuflen += 1;
 203                 }
 204         }
 205
 206         /* Make sure data is divisible by 4 */
 207         if (inbuflen%4 != 0) {
 208                 free(inbuf);
 209                 return -3;
 210         }
 211
 212         /* Calculate the output length without padding */
 213         outbuflen = inbuflen/4*3;
 214         if (inbuflen >= 4 && inbuf[inbuflen-1] == '=') {
 215                 outbuflen -= 1;
 216                 if (inbuf[inbuflen-2] == '=') {
 217                         outbuflen -= 1;
 218                 }
 219         }
 220
 221         /* Allocate buffer for outputting data */
 222         outbuf = malloc(outbuflen);
 223         if (!outbuf) {
 224                 free(inbuf);
 225                 return -4;
 226         }
 227
 228         index = 0;
 229         srcptr = inbuf;
 230         while (*srcptr) {
 231                 unsigned char a = base64->charmap[(unsigned char)*(srcptr++)];
 232                 unsigned char b = base64->charmap[(unsigned char)*(srcptr++)];
 233                 unsigned char c = base64->charmap[(unsigned char)*(srcptr++)];
 234                 unsigned char d = base64->charmap[(unsigned char)*(srcptr++)];
 235
 236                 if (a == BASE64_INVALID || b == BASE64_INVALID ||
 237                     c == BASE64_INVALID || d == BASE64_INVALID) {
 238                         return -5;
 239                 }
 240                 if (a == BASE64_PADDING || b == BASE64_PADDING) {
 241                         return -6;
 242                 }
 243
 244                 /* Update the first byte */
 245                 outbuf[index++] = (a << 2) | ((b & 0x30) >> 4);
 246
 247                 /* Update the second byte */
 248                 if (c == BASE64_PADDING) {
 249                         break;
 250                 }
 251                 outbuf[index++] = ((b & 0x0f) << 4) | ((c & 0x3c) >> 2);
 252
 253                 /* Update the third byte */
 254                 if (d == BASE64_PADDING) {
 255                         break;
 256                 }
 257                 outbuf[index++] = ((c & 0x03) << 6) | d;
 258         }
 259         if (index != outbuflen) {
 260                 free(inbuf);
 261                 free(outbuf);
 262                 return -7;
 263         }
 264
 265         free(inbuf);
 266         *dst = outbuf;
 267         return outbuflen;
 268 }