1 #include "first.h" 2 3 #include "base64.h" 4 5 /* reverse mapping: 6 * >= 0: base64 value 7 * -1: invalid character 8 * -2: skip character (whitespace/control) 9 * -3: padding 10 */ 11 12 /* BASE64_STANDARD: "A-Z a-z 0-9 + /" maps to 0-63, pad with "=" */ 13 static const char base64_standard_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; 14 static const signed char base64_standard_reverse_table[] = { 15 /* 0 1 2 3 4 5 6 7 8 9 A B C D E F */ 16 -1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, /* 0x00 - 0x0F */ 17 -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, /* 0x10 - 0x1F */ 18 -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /* 0x20 - 0x2F */ 19 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -3, -1, -1, /* 0x30 - 0x3F */ 20 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 0x40 - 0x4F */ 21 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 0x50 - 0x5F */ 22 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 0x60 - 0x6F */ 23 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, /* 0x70 - 0x7F */ 24 }; 25 26 /* BASE64_URL: "A-Z a-z 0-9 - _" maps to 0-63, pad with "." */ 27 static const char base64_url_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_."; 28 static const signed char base64_url_reverse_table[] = { 29 /* 0 1 2 3 4 5 6 7 8 9 A B C D E F */ 30 -1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, /* 0x00 - 0x0F */ 31 -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, /* 0x10 - 0x1F */ 32 -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -3, -1, /* 0x20 - 0x2F */ 33 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, /* 0x30 - 0x3F */ 34 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 0x40 - 0x4F */ 35 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, /* 0x50 - 0x5F */ 36 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 0x60 - 0x6F */ 37 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, /* 0x70 - 0x7F */ 38 }; 39 40 unsigned char* buffer_append_base64_decode(buffer *out, const char* in, size_t in_length, base64_charset charset) { 41 unsigned char *result; 42 size_t out_pos = 0; /* current output character (position) that is decoded. can contain partial result */ 43 unsigned int group = 0; /* how many base64 digits in the current group were decoded already. each group has up to 4 digits */ 44 size_t i; 45 const signed char *base64_reverse_table; 46 47 switch (charset) { 48 case BASE64_STANDARD: 49 base64_reverse_table = base64_standard_reverse_table; 50 break; 51 case BASE64_URL: 52 base64_reverse_table = base64_url_reverse_table; 53 break; 54 default: 55 return NULL; 56 } 57 58 result = (unsigned char *) buffer_string_prepare_append(out, 3*(in_length / 4) + 3); 59 60 /* run through the whole string, converting as we go */ 61 for (i = 0; i < in_length; i++) { 62 unsigned char c = (unsigned char) in[i]; 63 int ch; 64 65 if (c == '\0') break; 66 if (c >= 128) return NULL; /* only 7-bit characters allowed */ 67 68 ch = base64_reverse_table[c]; 69 if (-3 == ch) { 70 /* pad character; can only come after 2 base64 digits in a group */ 71 if (group < 2) return NULL; 72 break; 73 } else if (-2 == ch) { 74 continue; /* skip character */ 75 } else if (ch < 0) { 76 return NULL; /* invalid character, abort */ 77 } 78 79 switch(group) { 80 case 0: 81 result[out_pos] = ch << 2; 82 group = 1; 83 break; 84 case 1: 85 result[out_pos++] |= ch >> 4; 86 result[out_pos] = (ch & 0x0f) << 4; 87 group = 2; 88 break; 89 case 2: 90 result[out_pos++] |= ch >>2; 91 result[out_pos] = (ch & 0x03) << 6; 92 group = 3; 93 break; 94 case 3: 95 result[out_pos++] |= ch; 96 group = 0; 97 break; 98 } 99 } 100 101 switch(group) { 102 case 0: 103 /* ended on boundary */ 104 break; 105 case 1: 106 /* need at least 2 base64 digits per group */ 107 return NULL; 108 case 2: 109 /* have 2 base64 digits in last group => one real octet, two zeroes padded */ 110 case 3: 111 /* have 3 base64 digits in last group => two real octects, one zero padded */ 112 113 /* for both cases the current index already is on the first zero padded octet 114 * - check it really is zero (overlapping bits) */ 115 if (0 != result[out_pos]) return NULL; 116 break; 117 } 118 119 buffer_commit(out, out_pos); 120 121 return result; 122 } 123 124 size_t li_to_base64_no_padding(char* out, size_t out_length, const unsigned char* in, size_t in_length, base64_charset charset) { 125 const size_t full_tuples = in_length / 3; 126 const size_t in_tuple_remainder = in_length % 3; 127 const size_t out_tuple_remainder = in_tuple_remainder ? 1 + in_tuple_remainder : 0; 128 const size_t require_space = 4 * full_tuples + out_tuple_remainder; 129 const char* base64_table; 130 size_t i; 131 size_t out_pos = 0; 132 133 switch (charset) { 134 case BASE64_STANDARD: 135 base64_table = base64_standard_table; 136 break; 137 case BASE64_URL: 138 base64_table = base64_url_table; 139 break; 140 default: 141 force_assert(0 && "invalid charset"); 142 } 143 144 /* check overflows */ 145 force_assert(full_tuples <= 2*full_tuples); 146 force_assert(full_tuples <= 4*full_tuples); 147 force_assert(4*full_tuples <= 4*full_tuples + out_tuple_remainder); 148 force_assert(require_space <= out_length); 149 150 for (i = 2; i < in_length; i += 3) { 151 unsigned int v = (in[i-2] << 16) | (in[i-1] << 8) | in[i]; 152 out[out_pos+3] = base64_table[v & 0x3f]; v >>= 6; 153 out[out_pos+2] = base64_table[v & 0x3f]; v >>= 6; 154 out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6; 155 out[out_pos+0] = base64_table[v & 0x3f]; 156 out_pos += 4; 157 } 158 switch (in_tuple_remainder) { 159 case 0: 160 break; 161 case 1: 162 { 163 /* pretend in[i-1] = in[i] = 0, don't write last two (out_pos+3, out_pos+2) characters */ 164 unsigned int v = (in[i-2] << 4); 165 out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6; 166 out[out_pos+0] = base64_table[v & 0x3f]; 167 out_pos += 2; 168 } 169 break; 170 case 2: 171 { 172 /* pretend in[i] = 0, don't write last (out_pos+3) character */ 173 unsigned int v = (in[i-2] << 10) | (in[i-1] << 2); 174 out[out_pos+2] = base64_table[v & 0x3f]; v >>= 6; 175 out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6; 176 out[out_pos+0] = base64_table[v & 0x3f]; 177 out_pos += 3; 178 } 179 break; 180 } 181 force_assert(out_pos <= out_length); 182 return out_pos; 183 } 184 185 size_t li_to_base64(char* out, size_t out_length, const unsigned char* in, size_t in_length, base64_charset charset) { 186 const size_t in_tuple_remainder = in_length % 3; 187 size_t padding_length = in_tuple_remainder ? 3 - in_tuple_remainder : 0; 188 189 char padding; 190 size_t out_pos; 191 192 switch (charset) { 193 case BASE64_STANDARD: 194 padding = base64_standard_table[64]; 195 break; 196 case BASE64_URL: 197 padding = base64_url_table[64]; 198 break; 199 default: 200 force_assert(0 && "invalid charset"); 201 } 202 203 force_assert(out_length >= padding_length); 204 out_pos = li_to_base64_no_padding(out, out_length - padding_length, in, in_length, charset); 205 206 while (padding_length > 0) { 207 out[out_pos++] = padding; 208 padding_length--; 209 } 210 211 force_assert(out_pos <= out_length); 212 213 return out_pos; 214 } 215 216 217 char* buffer_append_base64_encode_no_padding(buffer *out, const unsigned char* in, size_t in_length, base64_charset charset) { 218 size_t reserve = 4*(in_length/3) + 4; 219 char* result = buffer_string_prepare_append(out, reserve); 220 size_t out_pos = li_to_base64_no_padding(result, reserve, in, in_length, charset); 221 222 buffer_commit(out, out_pos); 223 224 return result; 225 } 226 227 char* buffer_append_base64_encode(buffer *out, const unsigned char* in, size_t in_length, base64_charset charset) { 228 size_t reserve = 4*(in_length/3) + 4; 229 char* result = buffer_string_prepare_append(out, reserve); 230 size_t out_pos = li_to_base64(result, reserve, in, in_length, charset); 231 232 buffer_commit(out, out_pos); 233 234 return result; 235 } 236