tinc-vpn.org Git - tinc/blob - src/gcrypt/pem.c

   1 /*
   2     pem.c -- PEM encoding and decoding
   3     Copyright (C) 2007-2022 Guus Sliepen <guus@tinc-vpn.org>
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License along
  16     with this program; if not, write to the Free Software Foundation, Inc.,
  17     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #include "../system.h"
  21
  22 #include "pem.h"
  23 #include "../utils.h"
  24
  25 // Base64 decoding table
  26
  27 static const uint8_t b64dec[128] = {
  28         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  29         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  30         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  31         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  32         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  33         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  34         0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
  35         0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
  36         0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
  37         0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff,
  38         0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
  39         0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
  40         0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c,
  41         0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12,
  42         0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
  43         0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
  44         0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e,
  45         0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
  46         0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
  47         0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
  48         0x31, 0x32, 0x33, 0xff, 0xff, 0xff,
  49         0xff, 0xff
  50 };
  51
  52 static const char b64enc[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  53                              "abcdefghijklmnopqrstuvwxyz"
  54                              "0123456789+/";
  55
  56 // Heavily based on code by Jouni Malinen <j@w1.fi>
  57 // https://web.mit.edu/freebsd/head/contrib/wpa/src/utils/base64.c
  58 static size_t b64encode(char *dst, const void *src, const size_t length) {
  59         const uint8_t *end = (const uint8_t *)src + length;
  60         const uint8_t *in = src;
  61         char *pos = dst;
  62
  63         while(end - in >= 3) {
  64                 *pos++ = b64enc[in[0] >> 2];
  65                 *pos++ = b64enc[((in[0] & 0x03) << 4) | (in[1] >> 4)];
  66                 *pos++ = b64enc[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
  67                 *pos++ = b64enc[in[2] & 0x3f];
  68                 in += 3;
  69         }
  70
  71         if(end - in) {
  72                 *pos++ = b64enc[in[0] >> 2];
  73
  74                 if(end - in == 1) {
  75                         *pos++ = b64enc[(in[0] & 0x03) << 4];
  76                         *pos++ = '=';
  77                 } else {
  78                         *pos++ = b64enc[((in[0] & 0x03) << 4) | (in[1] >> 4)];
  79                         *pos++ = b64enc[(in[1] & 0x0f) << 2];
  80                 }
  81
  82                 *pos++ = '=';
  83         }
  84
  85         *pos = '\0';
  86
  87         return pos - dst;
  88 }
  89
  90
  91 bool pem_encode(FILE *fp, const char *header, uint8_t *buf, size_t size) {
  92         if(fprintf(fp, "-----BEGIN %s-----\n", header) <= 0) {
  93                 return false;
  94         }
  95
  96         char b64[B64_SIZE(size)];
  97         const size_t b64len = b64encode(b64, buf, size);
  98
  99         for(char *p = b64; p < b64 + b64len; p += 64) {
 100                 if(fprintf(fp, "%.64s\n", p) <= 0) {
 101                         return false;
 102                 }
 103         }
 104
 105         return fprintf(fp, "-----END %s-----\n", header) > 0;
 106 }
 107
 108 bool pem_decode(FILE *fp, const char *header, uint8_t *buf, size_t size, size_t *outsize) {
 109         bool decode = false;
 110         char line[1024];
 111         uint16_t word = 0;
 112         int shift = 10;
 113         size_t i, j = 0;
 114
 115         while(!feof(fp)) {
 116                 if(!fgets(line, sizeof(line), fp)) {
 117                         return false;
 118                 }
 119
 120                 if(!decode && !strncmp(line, "-----BEGIN ", 11)) {
 121                         if(!strncmp(line + 11, header, strlen(header))) {
 122                                 decode = true;
 123                         }
 124
 125                         continue;
 126                 }
 127
 128                 if(decode && !strncmp(line, "-----END", 8)) {
 129                         break;
 130                 }
 131
 132                 if(!decode) {
 133                         continue;
 134                 }
 135
 136                 for(i = 0; line[i] >= ' '; i++) {
 137                         if((signed char)line[i] < 0 || b64dec[(int)line[i]] == 0xff) {
 138                                 break;
 139                         }
 140
 141                         word |= b64dec[(int)line[i]] << shift;
 142                         shift -= 6;
 143
 144                         if(shift <= 2) {
 145                                 if(j > size) {
 146                                         errno = ENOMEM;
 147                                         return false;
 148                                 }
 149
 150                                 buf[j++] = word >> 8;
 151                                 word = (uint16_t)(word << 8);
 152                                 shift += 8;
 153                         }
 154                 }
 155         }
 156
 157         if(outsize) {
 158                 *outsize = j;
 159         }
 160
 161         return true;
 162 }