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1 /* base64.c -- Encode binary data using printable characters. |
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2 Copyright (C) 1999, 2000, 2001, 2004, 2005, 2006 Free Software |
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3 Foundation, Inc. |
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4 |
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5 This program is free software; you can redistribute it and/or modify |
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6 it under the terms of the GNU General Public License as published by |
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7 the Free Software Foundation; either version 2, or (at your option) |
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8 any later version. |
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9 |
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10 This program is distributed in the hope that it will be useful, |
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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13 GNU General Public License for more details. |
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14 |
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15 You should have received a copy of the GNU General Public License |
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16 along with this program; if not, write to the Free Software Foundation, |
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17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ |
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18 |
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19 /* Written by Simon Josefsson. Partially adapted from GNU MailUtils |
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20 * (mailbox/filter_trans.c, as of 2004-11-28). Improved by review |
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21 * from Paul Eggert, Bruno Haible, and Stepan Kasal. |
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22 * |
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23 * See also RFC 3548 <http://www.ietf.org/rfc/rfc3548.txt>. |
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24 * |
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25 * Be careful with error checking. Here is how you would typically |
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26 * use these functions: |
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27 * |
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28 * bool ok = base64_decode_alloc (in, inlen, &out, &outlen); |
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29 * if (!ok) |
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30 * FAIL: input was not valid base64 |
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31 * if (out == NULL) |
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32 * FAIL: memory allocation error |
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33 * OK: data in OUT/OUTLEN |
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34 * |
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35 * size_t outlen = base64_encode_alloc (in, inlen, &out); |
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36 * if (out == NULL && outlen == 0 && inlen != 0) |
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37 * FAIL: input too long |
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38 * if (out == NULL) |
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39 * FAIL: memory allocation error |
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40 * OK: data in OUT/OUTLEN. |
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41 * |
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42 */ |
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43 |
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44 /* Get prototype. */ |
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45 #include "base64.h" |
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46 |
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47 /* Get malloc. */ |
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48 #include <stdlib.h> |
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49 |
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50 /* Get UCHAR_MAX. */ |
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51 #include <limits.h> |
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52 |
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53 /* C89 compliant way to cast 'char' to 'unsigned char'. */ |
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54 static inline unsigned char |
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55 to_uchar (char ch) |
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56 { |
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57 return ch; |
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58 } |
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59 |
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60 /* Base64 encode IN array of size INLEN into OUT array of size OUTLEN. |
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61 If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as |
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62 possible. If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero |
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63 terminate the output buffer. */ |
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64 void |
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65 base64_encode (const char *restrict in, size_t inlen, |
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66 char *restrict out, size_t outlen) |
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67 { |
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68 static const char b64str[64] = |
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69 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; |
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70 |
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71 while (inlen && outlen) |
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72 { |
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73 *out++ = b64str[(to_uchar (in[0]) >> 2) & 0x3f]; |
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74 if (!--outlen) |
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75 break; |
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76 *out++ = b64str[((to_uchar (in[0]) << 4) |
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77 + (--inlen ? to_uchar (in[1]) >> 4 : 0)) |
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78 & 0x3f]; |
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79 if (!--outlen) |
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80 break; |
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81 *out++ = |
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82 (inlen |
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83 ? b64str[((to_uchar (in[1]) << 2) |
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84 + (--inlen ? to_uchar (in[2]) >> 6 : 0)) |
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85 & 0x3f] |
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86 : '='); |
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87 if (!--outlen) |
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88 break; |
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89 *out++ = inlen ? b64str[to_uchar (in[2]) & 0x3f] : '='; |
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90 if (!--outlen) |
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91 break; |
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92 if (inlen) |
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93 inlen--; |
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94 if (inlen) |
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95 in += 3; |
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96 } |
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97 |
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98 if (outlen) |
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99 *out = '\0'; |
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100 } |
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101 |
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102 /* Allocate a buffer and store zero terminated base64 encoded data |
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103 from array IN of size INLEN, returning BASE64_LENGTH(INLEN), i.e., |
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104 the length of the encoded data, excluding the terminating zero. On |
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105 return, the OUT variable will hold a pointer to newly allocated |
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106 memory that must be deallocated by the caller. If output string |
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107 length would overflow, 0 is returned and OUT is set to NULL. If |
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108 memory allocation failed, OUT is set to NULL, and the return value |
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109 indicates length of the requested memory block, i.e., |
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110 BASE64_LENGTH(inlen) + 1. */ |
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111 size_t |
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112 base64_encode_alloc (const char *in, size_t inlen, char **out) |
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113 { |
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114 size_t outlen = 1 + BASE64_LENGTH (inlen); |
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115 |
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116 /* Check for overflow in outlen computation. |
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117 * |
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118 * If there is no overflow, outlen >= inlen. |
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119 * |
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120 * If the operation (inlen + 2) overflows then it yields at most +1, so |
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121 * outlen is 0. |
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122 * |
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123 * If the multiplication overflows, we lose at least half of the |
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124 * correct value, so the result is < ((inlen + 2) / 3) * 2, which is |
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125 * less than (inlen + 2) * 0.66667, which is less than inlen as soon as |
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126 * (inlen > 4). |
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127 */ |
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128 if (inlen > outlen) |
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129 { |
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130 *out = NULL; |
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131 return 0; |
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132 } |
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133 |
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134 *out = malloc (outlen); |
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135 if (!*out) |
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136 return outlen; |
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137 |
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138 base64_encode (in, inlen, *out, outlen); |
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139 |
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140 return outlen - 1; |
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141 } |
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142 |
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143 /* With this approach this file works independent of the charset used |
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144 (think EBCDIC). However, it does assume that the characters in the |
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145 Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255. POSIX |
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146 1003.1-2001 require that char and unsigned char are 8-bit |
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147 quantities, though, taking care of that problem. But this may be a |
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148 potential problem on non-POSIX C99 platforms. |
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149 |
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150 IBM C V6 for AIX mishandles "#define B64(x) ...'x'...", so use "_" |
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151 as the formal parameter rather than "x". */ |
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152 #define B64(_) \ |
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153 ((_) == 'A' ? 0 \ |
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154 : (_) == 'B' ? 1 \ |
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155 : (_) == 'C' ? 2 \ |
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156 : (_) == 'D' ? 3 \ |
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157 : (_) == 'E' ? 4 \ |
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158 : (_) == 'F' ? 5 \ |
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159 : (_) == 'G' ? 6 \ |
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160 : (_) == 'H' ? 7 \ |
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161 : (_) == 'I' ? 8 \ |
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162 : (_) == 'J' ? 9 \ |
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163 : (_) == 'K' ? 10 \ |
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164 : (_) == 'L' ? 11 \ |
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165 : (_) == 'M' ? 12 \ |
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166 : (_) == 'N' ? 13 \ |
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167 : (_) == 'O' ? 14 \ |
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168 : (_) == 'P' ? 15 \ |
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169 : (_) == 'Q' ? 16 \ |
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170 : (_) == 'R' ? 17 \ |
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171 : (_) == 'S' ? 18 \ |
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172 : (_) == 'T' ? 19 \ |
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173 : (_) == 'U' ? 20 \ |
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174 : (_) == 'V' ? 21 \ |
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175 : (_) == 'W' ? 22 \ |
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176 : (_) == 'X' ? 23 \ |
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177 : (_) == 'Y' ? 24 \ |
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178 : (_) == 'Z' ? 25 \ |
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179 : (_) == 'a' ? 26 \ |
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180 : (_) == 'b' ? 27 \ |
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181 : (_) == 'c' ? 28 \ |
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182 : (_) == 'd' ? 29 \ |
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183 : (_) == 'e' ? 30 \ |
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184 : (_) == 'f' ? 31 \ |
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185 : (_) == 'g' ? 32 \ |
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186 : (_) == 'h' ? 33 \ |
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187 : (_) == 'i' ? 34 \ |
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188 : (_) == 'j' ? 35 \ |
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189 : (_) == 'k' ? 36 \ |
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190 : (_) == 'l' ? 37 \ |
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191 : (_) == 'm' ? 38 \ |
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192 : (_) == 'n' ? 39 \ |
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193 : (_) == 'o' ? 40 \ |
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194 : (_) == 'p' ? 41 \ |
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195 : (_) == 'q' ? 42 \ |
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196 : (_) == 'r' ? 43 \ |
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197 : (_) == 's' ? 44 \ |
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198 : (_) == 't' ? 45 \ |
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199 : (_) == 'u' ? 46 \ |
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200 : (_) == 'v' ? 47 \ |
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201 : (_) == 'w' ? 48 \ |
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202 : (_) == 'x' ? 49 \ |
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203 : (_) == 'y' ? 50 \ |
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204 : (_) == 'z' ? 51 \ |
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205 : (_) == '0' ? 52 \ |
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206 : (_) == '1' ? 53 \ |
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207 : (_) == '2' ? 54 \ |
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208 : (_) == '3' ? 55 \ |
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209 : (_) == '4' ? 56 \ |
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210 : (_) == '5' ? 57 \ |
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211 : (_) == '6' ? 58 \ |
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212 : (_) == '7' ? 59 \ |
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213 : (_) == '8' ? 60 \ |
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214 : (_) == '9' ? 61 \ |
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215 : (_) == '+' ? 62 \ |
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216 : (_) == '/' ? 63 \ |
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217 : -1) |
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218 |
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219 static const signed char b64[0x100] = { |
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220 B64 (0), B64 (1), B64 (2), B64 (3), |
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221 B64 (4), B64 (5), B64 (6), B64 (7), |
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222 B64 (8), B64 (9), B64 (10), B64 (11), |
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223 B64 (12), B64 (13), B64 (14), B64 (15), |
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224 B64 (16), B64 (17), B64 (18), B64 (19), |
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225 B64 (20), B64 (21), B64 (22), B64 (23), |
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226 B64 (24), B64 (25), B64 (26), B64 (27), |
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227 B64 (28), B64 (29), B64 (30), B64 (31), |
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228 B64 (32), B64 (33), B64 (34), B64 (35), |
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229 B64 (36), B64 (37), B64 (38), B64 (39), |
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230 B64 (40), B64 (41), B64 (42), B64 (43), |
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231 B64 (44), B64 (45), B64 (46), B64 (47), |
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232 B64 (48), B64 (49), B64 (50), B64 (51), |
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233 B64 (52), B64 (53), B64 (54), B64 (55), |
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234 B64 (56), B64 (57), B64 (58), B64 (59), |
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235 B64 (60), B64 (61), B64 (62), B64 (63), |
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236 B64 (64), B64 (65), B64 (66), B64 (67), |
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237 B64 (68), B64 (69), B64 (70), B64 (71), |
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238 B64 (72), B64 (73), B64 (74), B64 (75), |
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239 B64 (76), B64 (77), B64 (78), B64 (79), |
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240 B64 (80), B64 (81), B64 (82), B64 (83), |
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241 B64 (84), B64 (85), B64 (86), B64 (87), |
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242 B64 (88), B64 (89), B64 (90), B64 (91), |
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243 B64 (92), B64 (93), B64 (94), B64 (95), |
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244 B64 (96), B64 (97), B64 (98), B64 (99), |
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245 B64 (100), B64 (101), B64 (102), B64 (103), |
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246 B64 (104), B64 (105), B64 (106), B64 (107), |
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247 B64 (108), B64 (109), B64 (110), B64 (111), |
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248 B64 (112), B64 (113), B64 (114), B64 (115), |
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249 B64 (116), B64 (117), B64 (118), B64 (119), |
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250 B64 (120), B64 (121), B64 (122), B64 (123), |
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251 B64 (124), B64 (125), B64 (126), B64 (127), |
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252 B64 (128), B64 (129), B64 (130), B64 (131), |
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253 B64 (132), B64 (133), B64 (134), B64 (135), |
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254 B64 (136), B64 (137), B64 (138), B64 (139), |
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255 B64 (140), B64 (141), B64 (142), B64 (143), |
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256 B64 (144), B64 (145), B64 (146), B64 (147), |
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257 B64 (148), B64 (149), B64 (150), B64 (151), |
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258 B64 (152), B64 (153), B64 (154), B64 (155), |
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259 B64 (156), B64 (157), B64 (158), B64 (159), |
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260 B64 (160), B64 (161), B64 (162), B64 (163), |
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261 B64 (164), B64 (165), B64 (166), B64 (167), |
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262 B64 (168), B64 (169), B64 (170), B64 (171), |
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263 B64 (172), B64 (173), B64 (174), B64 (175), |
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264 B64 (176), B64 (177), B64 (178), B64 (179), |
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265 B64 (180), B64 (181), B64 (182), B64 (183), |
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266 B64 (184), B64 (185), B64 (186), B64 (187), |
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267 B64 (188), B64 (189), B64 (190), B64 (191), |
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268 B64 (192), B64 (193), B64 (194), B64 (195), |
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269 B64 (196), B64 (197), B64 (198), B64 (199), |
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270 B64 (200), B64 (201), B64 (202), B64 (203), |
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271 B64 (204), B64 (205), B64 (206), B64 (207), |
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272 B64 (208), B64 (209), B64 (210), B64 (211), |
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273 B64 (212), B64 (213), B64 (214), B64 (215), |
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274 B64 (216), B64 (217), B64 (218), B64 (219), |
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275 B64 (220), B64 (221), B64 (222), B64 (223), |
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276 B64 (224), B64 (225), B64 (226), B64 (227), |
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277 B64 (228), B64 (229), B64 (230), B64 (231), |
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278 B64 (232), B64 (233), B64 (234), B64 (235), |
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279 B64 (236), B64 (237), B64 (238), B64 (239), |
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280 B64 (240), B64 (241), B64 (242), B64 (243), |
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281 B64 (244), B64 (245), B64 (246), B64 (247), |
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282 B64 (248), B64 (249), B64 (250), B64 (251), |
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283 B64 (252), B64 (253), B64 (254), B64 (255) |
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284 }; |
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285 |
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286 #if UCHAR_MAX == 255 |
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287 # define uchar_in_range(c) true |
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288 #else |
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289 # define uchar_in_range(c) ((c) <= 255) |
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290 #endif |
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291 |
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292 /* Return true if CH is a character from the Base64 alphabet, and |
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293 false otherwise. Note that '=' is padding and not considered to be |
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294 part of the alphabet. */ |
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295 bool |
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296 isbase64 (char ch) |
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297 { |
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298 return uchar_in_range (to_uchar (ch)) && 0 <= b64[to_uchar (ch)]; |
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299 } |
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300 |
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301 /* Decode base64 encoded input array IN of length INLEN to output |
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302 array OUT that can hold *OUTLEN bytes. Return true if decoding was |
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303 successful, i.e. if the input was valid base64 data, false |
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304 otherwise. If *OUTLEN is too small, as many bytes as possible will |
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305 be written to OUT. On return, *OUTLEN holds the length of decoded |
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306 bytes in OUT. Note that as soon as any non-alphabet characters are |
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307 encountered, decoding is stopped and false is returned. This means |
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308 that, when applicable, you must remove any line terminators that is |
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309 part of the data stream before calling this function. */ |
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310 bool |
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311 base64_decode (const char *restrict in, size_t inlen, |
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312 char *restrict out, size_t *outlen) |
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313 { |
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314 size_t outleft = *outlen; |
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315 |
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316 while (inlen >= 2) |
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317 { |
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318 if (!isbase64 (in[0]) || !isbase64 (in[1])) |
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319 break; |
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320 |
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321 if (outleft) |
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322 { |
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323 *out++ = ((b64[to_uchar (in[0])] << 2) |
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324 | (b64[to_uchar (in[1])] >> 4)); |
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325 outleft--; |
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326 } |
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327 |
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328 if (inlen == 2) |
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329 break; |
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330 |
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331 if (in[2] == '=') |
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332 { |
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333 if (inlen != 4) |
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334 break; |
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335 |
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336 if (in[3] != '=') |
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337 break; |
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338 |
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339 } |
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340 else |
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341 { |
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342 if (!isbase64 (in[2])) |
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343 break; |
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344 |
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345 if (outleft) |
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346 { |
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347 *out++ = (((b64[to_uchar (in[1])] << 4) & 0xf0) |
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348 | (b64[to_uchar (in[2])] >> 2)); |
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349 outleft--; |
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350 } |
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351 |
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352 if (inlen == 3) |
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353 break; |
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354 |
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355 if (in[3] == '=') |
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356 { |
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357 if (inlen != 4) |
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358 break; |
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359 } |
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360 else |
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361 { |
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362 if (!isbase64 (in[3])) |
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363 break; |
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364 |
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365 if (outleft) |
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366 { |
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367 *out++ = (((b64[to_uchar (in[2])] << 6) & 0xc0) |
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368 | b64[to_uchar (in[3])]); |
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369 outleft--; |
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370 } |
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371 } |
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372 } |
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373 |
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374 in += 4; |
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375 inlen -= 4; |
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376 } |
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377 |
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378 *outlen -= outleft; |
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379 |
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380 if (inlen != 0) |
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381 return false; |
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382 |
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383 return true; |
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384 } |
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385 |
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386 /* Allocate an output buffer in *OUT, and decode the base64 encoded |
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387 data stored in IN of size INLEN to the *OUT buffer. On return, the |
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388 size of the decoded data is stored in *OUTLEN. OUTLEN may be NULL, |
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389 if the caller is not interested in the decoded length. *OUT may be |
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390 NULL to indicate an out of memory error, in which case *OUTLEN |
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391 contains the size of the memory block needed. The function returns |
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392 true on successful decoding and memory allocation errors. (Use the |
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393 *OUT and *OUTLEN parameters to differentiate between successful |
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394 decoding and memory error.) The function returns false if the |
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395 input was invalid, in which case *OUT is NULL and *OUTLEN is |
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396 undefined. */ |
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397 bool |
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398 base64_decode_alloc (const char *in, size_t inlen, char **out, |
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399 size_t *outlen) |
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400 { |
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401 /* This may allocate a few bytes too much, depending on input, |
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402 but it's not worth the extra CPU time to compute the exact amount. |
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403 The exact amount is 3 * inlen / 4, minus 1 if the input ends |
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404 with "=" and minus another 1 if the input ends with "==". |
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405 Dividing before multiplying avoids the possibility of overflow. */ |
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406 size_t needlen = 3 * (inlen / 4) + 2; |
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407 |
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408 *out = malloc (needlen); |
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409 if (!*out) |
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410 return true; |
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411 |
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412 if (!base64_decode (in, inlen, *out, &needlen)) |
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413 { |
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414 free (*out); |
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415 *out = NULL; |
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416 return false; |
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417 } |
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418 |
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419 if (outlen) |
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420 *outlen = needlen; |
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421 |
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422 return true; |
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423 } |