base64.c

   1 /*
   2 cencoder.c - c source to a base64 encoding algorithm implementation
   3
   4 This is part of the libb64 project, and has been placed in the public domain.
   5 For details, see http://sourceforge.net/projects/libb64
   6 */
   7
   8 /*
   9   Modified by Eugene Crosser to fit pam_pcsc_cr project, 2013
  10 */
  11
  12 #include <string.h>
  13 #include <base64.h>
  14 /*
  15 cencode.h - c header for a base64 encoding algorithm
  16
  17 This is part of the libb64 project, and has been placed in the public domain.
  18 For details, see http://sourceforge.net/projects/libb64
  19 */
  20
  21 /*
  22   Modified by Eugene Crosser to fit pam_pcsc_cr project, 2013
  23 */
  24
  25 typedef enum
  26 {
  27         step_A, step_B, step_C
  28 } base64_encodestep;
  29
  30 typedef struct
  31 {
  32         base64_encodestep step;
  33         char result;
  34         int stepcount;
  35 } base64_encodestate;
  36
  37 /*
  38 cdecode.h - c header for a base64 decoding algorithm
  39
  40 This is part of the libb64 project, and has been placed in the public domain.
  41 For details, see http://sourceforge.net/projects/libb64
  42 */
  43
  44 typedef enum
  45 {
  46         step_a, step_b, step_c, step_d
  47 } base64_decodestep;
  48
  49 typedef struct
  50 {
  51         base64_decodestep step;
  52         char plainchar;
  53 } base64_decodestate;
  54
  55 static void base64_init_encodestate(base64_encodestate* state_in)
  56 {
  57         state_in->step = step_A;
  58         state_in->result = 0;
  59         state_in->stepcount = 0;
  60 }
  61
  62 static char base64_encode_value(char value_in)
  63 {
  64         static const char* encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  65         if (value_in > 63) return '=';
  66         return encoding[(int)value_in];
  67 }
  68
  69 static int base64_encode_block(const unsigned char* plaintext_in, int length_in, char* code_out, base64_encodestate* state_in)
  70 {
  71         const unsigned char* plainchar = plaintext_in;
  72         const unsigned char* const plaintextend = plaintext_in + length_in;
  73         char* codechar = code_out;
  74         char result;
  75         char fragment;
  76
  77         result = state_in->result;
  78
  79         switch (state_in->step)
  80         {
  81                 while (1)
  82                 {
  83         case step_A:
  84                         if (plainchar == plaintextend)
  85                         {
  86                                 state_in->result = result;
  87                                 state_in->step = step_A;
  88                                 return codechar - code_out;
  89                         }
  90                         fragment = *plainchar++;
  91                         result = (fragment & 0x0fc) >> 2;
  92                         *codechar++ = base64_encode_value(result);
  93                         result = (fragment & 0x003) << 4;
  94         case step_B:
  95                         if (plainchar == plaintextend)
  96                         {
  97                                 state_in->result = result;
  98                                 state_in->step = step_B;
  99                                 return codechar - code_out;
 100                         }
 101                         fragment = *plainchar++;
 102                         result |= (fragment & 0x0f0) >> 4;
 103                         *codechar++ = base64_encode_value(result);
 104                         result = (fragment & 0x00f) << 2;
 105         case step_C:
 106                         if (plainchar == plaintextend)
 107                         {
 108                                 state_in->result = result;
 109                                 state_in->step = step_C;
 110                                 return codechar - code_out;
 111                         }
 112                         fragment = *plainchar++;
 113                         result |= (fragment & 0x0c0) >> 6;
 114                         *codechar++ = base64_encode_value(result);
 115                         result  = (fragment & 0x03f) >> 0;
 116                         *codechar++ = base64_encode_value(result);
 117
 118                         ++(state_in->stepcount);
 119                 }
 120         }
 121         /* control should not reach here */
 122         return codechar - code_out;
 123 }
 124
 125 static int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
 126 {
 127         char* codechar = code_out;
 128
 129         switch (state_in->step)
 130         {
 131         case step_B:
 132                 *codechar++ = base64_encode_value(state_in->result);
 133                 *codechar++ = '=';
 134                 *codechar++ = '=';
 135                 break;
 136         case step_C:
 137                 *codechar++ = base64_encode_value(state_in->result);
 138                 *codechar++ = '=';
 139                 break;
 140         case step_A:
 141                 break;
 142         }
 143
 144         return codechar - code_out;
 145 }
 146
 147 /*
 148 cdecoder.c - c source to a base64 decoding algorithm implementation
 149
 150 This is part of the libb64 project, and has been placed in the public domain.
 151 For details, see http://sourceforge.net/projects/libb64
 152 */
 153
 154 static int base64_decode_value(char value_in)
 155 {
 156         static const char decoding[] = {62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51};
 157         static const char decoding_size = sizeof(decoding);
 158         value_in -= 43;
 159         if (value_in < 0 || value_in >= decoding_size) return -1;
 160         return decoding[(int)value_in];
 161 }
 162
 163 static void base64_init_decodestate(base64_decodestate* state_in)
 164 {
 165         state_in->step = step_a;
 166         state_in->plainchar = 0;
 167 }
 168
 169 static int base64_decode_block(const char* code_in, const int length_in, unsigned char* plaintext_out, base64_decodestate* state_in)
 170 {
 171         const char* codechar = code_in;
 172         unsigned char* plainchar = plaintext_out;
 173         char fragment;
 174
 175         *plainchar = state_in->plainchar;
 176
 177         switch (state_in->step)
 178         {
 179                 while (1)
 180                 {
 181         case step_a:
 182                         do {
 183                                 if (codechar == code_in+length_in)
 184                                 {
 185                                         state_in->step = step_a;
 186                                         state_in->plainchar = *plainchar;
 187                                         return plainchar - plaintext_out;
 188                                 }
 189                                 fragment = (char)base64_decode_value(*codechar++);
 190                         } while (fragment < 0);
 191                         *plainchar    = (fragment & 0x03f) << 2;
 192         case step_b:
 193                         do {
 194                                 if (codechar == code_in+length_in)
 195                                 {
 196                                         state_in->step = step_b;
 197                                         state_in->plainchar = *plainchar;
 198                                         return plainchar - plaintext_out;
 199                                 }
 200                                 fragment = (char)base64_decode_value(*codechar++);
 201                         } while (fragment < 0);
 202                         *plainchar++ |= (fragment & 0x030) >> 4;
 203                         *plainchar    = (fragment & 0x00f) << 4;
 204         case step_c:
 205                         do {
 206                                 if (codechar == code_in+length_in)
 207                                 {
 208                                         state_in->step = step_c;
 209                                         state_in->plainchar = *plainchar;
 210                                         return plainchar - plaintext_out;
 211                                 }
 212                                 fragment = (char)base64_decode_value(*codechar++);
 213                         } while (fragment < 0);
 214                         *plainchar++ |= (fragment & 0x03c) >> 2;
 215                         *plainchar    = (fragment & 0x003) << 6;
 216         case step_d:
 217                         do {
 218                                 if (codechar == code_in+length_in)
 219                                 {
 220                                         state_in->step = step_d;
 221                                         state_in->plainchar = *plainchar;
 222                                         return plainchar - plaintext_out;
 223                                 }
 224                                 fragment = (char)base64_decode_value(*codechar++);
 225                         } while (fragment < 0);
 226                         *plainchar++   |= (fragment & 0x03f);
 227                 }
 228         }
 229         /* control should not reach here */
 230         return plainchar - plaintext_out;
 231 }
 232
 233 int b64_encode(const unsigned char *src, const int ssize,
 234                 char *const b64, int *const bsize)
 235 {
 236         base64_encodestate s;
 237         int cnt1, cnt2;
 238         char *c = b64;
 239
 240         if (*bsize < ((ssize-1)/3+1)*4+1) return 1;
 241         base64_init_encodestate(&s);
 242         cnt1 = base64_encode_block(src, ssize, c, &s);
 243         c += cnt1;
 244         cnt2 = base64_encode_blockend(c, &s);
 245         c += cnt2;
 246         *c = 0;
 247         *bsize = cnt1 + cnt2;
 248         return 0;
 249 }
 250
 251 int b64_decode(const char *b64, unsigned char *const dst, int *const dsize)
 252 {
 253         base64_decodestate s;
 254         int cnt;
 255         int bsize = strlen(b64);
 256
 257         if (*dsize < (bsize*3/4)) return 1;
 258         base64_init_decodestate(&s);
 259         cnt = base64_decode_block(b64, bsize, dst, &s);
 260         *dsize = cnt;
 261         return 0;
 262 }