crypt_common.c

   1 /*
   2  * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file crypt_common.c Crypto functions independent of the implementation. */
   8
   9 #include <regex.h>
  10 #include <stdbool.h>
  11
  12 #include "para.h"
  13 #include "error.h"
  14 #include "string.h"
  15 #include "crypt_backend.h"
  16 #include "crypt.h"
  17
  18 #define KEY_TYPE_TXT "ssh-rsa"
  19
  20 /**
  21  * Check if given buffer starts with a ssh rsa key signature.
  22  *
  23  * \param data The buffer.
  24  * \param size Number of data bytes.
  25  *
  26  * \return Number of header bytes to be skipped on success, zero if
  27  * ssh rsa signature was not found.
  28  */
  29 size_t is_ssh_rsa_key(char *data, size_t size)
  30 {
  31         char *cp;
  32
  33         if (size < strlen(KEY_TYPE_TXT) + 2)
  34                 return 0;
  35         cp = memchr(data, ' ', size);
  36         if (cp == NULL)
  37                 return 0;
  38         if (strncmp(KEY_TYPE_TXT, data, strlen(KEY_TYPE_TXT)))
  39                 return 0;
  40         cp++;
  41         if (cp >= data + size)
  42                 return 0;
  43         if (*cp == '\0')
  44                 return 0;
  45         return cp - data;
  46 }
  47
  48 /*
  49  * This base64/uudecode stuff below is taken from openssh-5.2p1, Copyright (c)
  50  * 1996 by Internet Software Consortium.  Portions Copyright (c) 1995 by
  51  * International Business Machines, Inc.
  52  */
  53
  54 static const char Base64[] =
  55         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  56 static const char Pad64 = '=';
  57 /*
  58  * Skips all whitespace anywhere. Converts characters, four at a time, starting
  59  * at (or after) src from base - 64 numbers into three 8 bit bytes in the
  60  * target area. it returns the number of data bytes stored at the target, or -E_BASE64
  61  * on error.
  62  */
  63 int base64_decode(char const *src, unsigned char *target, size_t targsize)
  64 {
  65         unsigned int tarindex, state;
  66         int ch;
  67         char *pos;
  68
  69         state = 0;
  70         tarindex = 0;
  71
  72         while ((ch = *src++) != '\0') {
  73                 if (para_isspace(ch)) /* Skip whitespace anywhere. */
  74                         continue;
  75
  76                 if (ch == Pad64)
  77                         break;
  78
  79                 pos = strchr(Base64, ch);
  80                 if (pos == 0) /* A non-base64 character. */
  81                         return -E_BASE64;
  82
  83                 switch (state) {
  84                 case 0:
  85                         if (target) {
  86                                 if (tarindex >= targsize)
  87                                         return -E_BASE64;
  88                                 target[tarindex] = (pos - Base64) << 2;
  89                         }
  90                         state = 1;
  91                         break;
  92                 case 1:
  93                         if (target) {
  94                                 if (tarindex + 1 >= targsize)
  95                                         return -E_BASE64;
  96                                 target[tarindex]   |=  (pos - Base64) >> 4;
  97                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
  98                                                         << 4 ;
  99                         }
 100                         tarindex++;
 101                         state = 2;
 102                         break;
 103                 case 2:
 104                         if (target) {
 105                                 if (tarindex + 1 >= targsize)
 106                                         return -E_BASE64;
 107                                 target[tarindex]   |=  (pos - Base64) >> 2;
 108                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 109                                                         << 6;
 110                         }
 111                         tarindex++;
 112                         state = 3;
 113                         break;
 114                 case 3:
 115                         if (target) {
 116                                 if (tarindex >= targsize)
 117                                         return -E_BASE64;
 118                                 target[tarindex] |= (pos - Base64);
 119                         }
 120                         tarindex++;
 121                         state = 0;
 122                         break;
 123                 }
 124         }
 125
 126         /*
 127          * We are done decoding Base-64 chars.  Let's see if we ended
 128          * on a byte boundary, and/or with erroneous trailing characters.
 129          */
 130
 131         if (ch == Pad64) {              /* We got a pad char. */
 132                 ch = *src++;            /* Skip it, get next. */
 133                 switch (state) {
 134                 case 0:         /* Invalid = in first position */
 135                 case 1:         /* Invalid = in second position */
 136                         return -E_BASE64;
 137
 138                 case 2:         /* Valid, means one byte of info */
 139                         /* Skip any number of spaces. */
 140                         for (; ch != '\0'; ch = *src++)
 141                                 if (!isspace(ch))
 142                                         break;
 143                         /* Make sure there is another trailing = sign. */
 144                         if (ch != Pad64)
 145                                 return -E_BASE64;
 146                         ch = *src++;            /* Skip the = */
 147                         /* Fall through to "single trailing =" case. */
 148                         /* FALLTHROUGH */
 149
 150                 case 3:         /* Valid, means two bytes of info */
 151                         /*
 152                          * We know this char is an =.  Is there anything but
 153                          * whitespace after it?
 154                          */
 155                         for (; ch != '\0'; ch = *src++)
 156                                 if (!isspace(ch))
 157                                         return -E_BASE64;
 158
 159                         /*
 160                          * Now make sure for cases 2 and 3 that the "extra"
 161                          * bits that slopped past the last full byte were
 162                          * zeros.  If we don't check them, they become a
 163                          * subliminal channel.
 164                          */
 165                         if (target && target[tarindex] != 0)
 166                                 return -E_BASE64;
 167                 }
 168         } else {
 169                 /*
 170                  * We ended by seeing the end of the string.  Make sure we
 171                  * have no partial bytes lying around.
 172                  */
 173                 if (state != 0)
 174                         return -E_BASE64;
 175         }
 176
 177         return tarindex;
 178 }
 179
 180 int uudecode(const char *src, unsigned char *target, size_t targsize)
 181 {
 182         int len;
 183         char *encoded, *p;
 184
 185         /* copy the 'readonly' source */
 186         encoded = para_strdup(src);
 187         /* skip whitespace and data */
 188         for (p = encoded; *p == ' ' || *p == '\t'; p++)
 189                 ;
 190         for (; *p != '\0' && *p != ' ' && *p != '\t'; p++)
 191                 ;
 192         /* and remove trailing whitespace because base64_decode needs this */
 193         *p = '\0';
 194         len = base64_decode(encoded, target, targsize);
 195         free(encoded);
 196         return len;
 197 }
 198
 199 /*
 200  * Can not use the inline functions of portable_io.h here because the byte
 201  * order is different.
 202  */
 203 uint32_t read_ssh_u32(const void *vp)
 204 {
 205         const unsigned char *p = (const unsigned char *)vp;
 206         uint32_t v;
 207
 208         v  = (uint32_t)p[0] << 24;
 209         v |= (uint32_t)p[1] << 16;
 210         v |= (uint32_t)p[2] << 8;
 211         v |= (uint32_t)p[3];
 212
 213         return v;
 214 }
 215
 216 int check_ssh_key_header(const unsigned char *blob, int blen)
 217 {
 218         const unsigned char *p = blob, *end = blob + blen;
 219         uint32_t rlen;
 220
 221         if (p + 4 > end)
 222                 return -E_SSH_KEY_HEADER;
 223         rlen = read_ssh_u32(p);
 224         p += 4;
 225         if (p + rlen < p)
 226                 return -E_SSH_KEY_HEADER;
 227         if (p + rlen > end)
 228                 return -E_SSH_KEY_HEADER;
 229         if (rlen < strlen(KEY_TYPE_TXT))
 230                 return -E_SSH_KEY_HEADER;
 231         PARA_DEBUG_LOG("type: %s, rlen: %d\n", p, rlen);
 232         if (strncmp((char *)p, KEY_TYPE_TXT, strlen(KEY_TYPE_TXT)))
 233                 return -E_SSH_KEY_HEADER;
 234         return 4 + rlen;
 235 }
 236
 237 int check_key_file(const char *file, bool private_key)
 238 {
 239         struct stat st;
 240
 241         if (stat(file, &st) != 0)
 242                 return -ERRNO_TO_PARA_ERROR(errno);
 243         if (!private_key)
 244                 return 0;
 245         if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0)
 246                 return -E_KEY_PERM;
 247         return 1;
 248 }
 249
 250 void hash_to_asc(unsigned char *hash, char *asc)
 251 {
 252         int i;
 253         const char hexchar[] = "0123456789abcdef";
 254
 255         for (i = 0; i < HASH_SIZE; i++) {
 256                 asc[2 * i] = hexchar[hash[i] >> 4];
 257                 asc[2 * i + 1] = hexchar[hash[i] & 0xf];
 258         }
 259         asc[2 * HASH_SIZE] = '\0';
 260 }
 261
 262 int hash_compare(unsigned char *h1, unsigned char *h2)
 263 {
 264         int i;
 265
 266         for (i = 0; i < HASH_SIZE; i++) {
 267                 if (h1[i] < h2[i])
 268                         return -1;
 269                 if (h1[i] > h2[i])
 270                         return 1;
 271         }
 272         return 0;
 273 }
 274
 275 int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size)
 276 {
 277         int n;
 278
 279         assert(size);
 280         n = sc_recv_bin_buffer(scc, buf, size - 1);
 281         if (n >= 0)
 282                 buf[n] = '\0';
 283         else
 284                 *buf = '\0';
 285         return n;
 286 }
 287
 288 int sc_send_buffer(struct stream_cipher_context *scc, char *buf)
 289 {
 290         return sc_send_bin_buffer(scc, buf, strlen(buf));
 291 }
 292
 293 __printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
 294                 const char *fmt, ...)
 295 {
 296         char *msg;
 297         int ret;
 298
 299         PARA_VSPRINTF(fmt, msg);
 300         ret = sc_send_buffer(scc, msg);
 301         free(msg);
 302         return ret;
 303 }