kbx/keybox-openpgp.c

   1 /* keybox-openpgp.c - OpenPGP key parsing
   2  *      Copyright (C) 2001, 2003 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 /* This is a simple OpenPGP parser suitable for all OpenPGP key
  21    material.  It just provides the functionality required to build and
  22    parse an KBX OpenPGP key blob.  Thus it is not a complete parser.
  23    However it is self-contained and optimized for fast in-memory
  24    parsing.  Note that we don't support old ElGamal v3 keys
  25    anymore. */
  26
  27 #include <config.h>
  28 #include <stdlib.h>
  29 #include <stdio.h>
  30 #include <string.h>
  31 #include <errno.h>
  32 #include <assert.h>
  33
  34 #include "keybox-defs.h"
  35
  36 #include <gcrypt.h>
  37
  38
  39 enum packet_types
  40   {
  41     PKT_NONE               =0,
  42     PKT_PUBKEY_ENC         =1, /* public key encrypted packet */
  43     PKT_SIGNATURE          =2, /* secret key encrypted packet */
  44     PKT_SYMKEY_ENC         =3, /* session key packet (OpenPGP)*/
  45     PKT_ONEPASS_SIG        =4, /* one pass sig packet (OpenPGP)*/
  46     PKT_SECRET_KEY         =5, /* secret key */
  47     PKT_PUBLIC_KEY         =6, /* public key */
  48     PKT_SECRET_SUBKEY      =7, /* secret subkey (OpenPGP) */
  49     PKT_COMPRESSED         =8, /* compressed data packet */
  50     PKT_ENCRYPTED          =9, /* conventional encrypted data */
  51     PKT_MARKER            =10, /* marker packet (OpenPGP) */
  52     PKT_PLAINTEXT         =11, /* plaintext data with filename and mode */
  53     PKT_RING_TRUST        =12, /* keyring trust packet */
  54     PKT_USER_ID           =13, /* user id packet */
  55     PKT_PUBLIC_SUBKEY     =14, /* public subkey (OpenPGP) */
  56     PKT_OLD_COMMENT       =16, /* comment packet from an OpenPGP draft */
  57     PKT_ATTRIBUTE         =17, /* PGP's attribute packet */
  58     PKT_ENCRYPTED_MDC     =18, /* integrity protected encrypted data */
  59     PKT_MDC               =19, /* manipulation detection code packet */
  60     PKT_COMMENT           =61, /* new comment packet (private) */
  61     PKT_GPG_CONTROL       =63  /* internal control packet */
  62   };
  63
  64
  65
  66 /* Assume a valid OpenPGP packet at the address pointed to by BUFBTR
  67    which is of amaximum length as stored at BUFLEN.  Return the header
  68    information of that packet and advance the pointer stored at BUFPTR
  69    to the next packet; also adjust the length stored at BUFLEN to
  70    match the remaining bytes. If there are no more packets, store NULL
  71    at BUFPTR.  Return an non-zero error code on failure or the
  72    follwing data on success:
  73
  74    R_DATAPKT = Pointer to the begin of the packet data.
  75    R_DATALEN = Length of this data.  This has already been checked to fit
  76                into the buffer.
  77    R_PKTTYPE = The packet type.
  78    R_NTOTAL  = The total number of bytes of this packet
  79
  80    Note that these values are only updated on success.
  81 */
  82 static gpg_error_t
  83 next_packet (unsigned char const **bufptr, size_t *buflen,
  84              unsigned char const **r_data, size_t *r_datalen, int *r_pkttype,
  85              size_t *r_ntotal)
  86 {
  87   const unsigned char *buf = *bufptr;
  88   size_t len = *buflen;
  89   int c, ctb, pkttype;
  90   unsigned long pktlen;
  91
  92   if (!len)
  93     return gpg_error (GPG_ERR_NO_DATA);
  94
  95   ctb = *buf++; len--;
  96   if ( !(ctb & 0x80) )
  97     return gpg_error (GPG_ERR_INV_PACKET); /* Invalid CTB. */
  98
  99   pktlen = 0;
 100   if ((ctb & 0x40))  /* New style (OpenPGP) CTB.  */
 101     {
 102       pkttype = (ctb & 0x3f);
 103       if (!len)
 104         return gpg_error (GPG_ERR_INV_PACKET); /* No 1st length byte. */
 105       c = *buf++; len--;
 106       if (pkttype == PKT_COMPRESSED)
 107         return gpg_error (GPG_ERR_UNEXPECTED); /* ... packet in a keyblock. */
 108       if ( c < 192 )
 109         pktlen = c;
 110       else if ( c < 224 )
 111         {
 112           pktlen = (c - 192) * 256;
 113           if (!len)
 114             return gpg_error (GPG_ERR_INV_PACKET); /* No 2nd length byte. */
 115           c = *buf++; len--;
 116           pktlen += c + 192;
 117         }
 118       else if (c == 255)
 119         {
 120           if (len <4 )
 121             return gpg_error (GPG_ERR_INV_PACKET); /* No length bytes. */
 122           pktlen  = (*buf++) << 24;
 123           pktlen |= (*buf++) << 16;
 124           pktlen |= (*buf++) << 8;
 125           pktlen |= (*buf++);
 126           len -= 4;
 127       }
 128       else /* Partial length encoding is not allowed for key packets. */
 129         return gpg_error (GPG_ERR_UNEXPECTED);
 130     }
 131   else /* Old style CTB.  */
 132     {
 133       int lenbytes;
 134
 135       pktlen = 0;
 136       pkttype = (ctb>>2)&0xf;
 137       lenbytes = ((ctb&3)==3)? 0 : (1<<(ctb & 3));
 138       if (!lenbytes) /* Not allowed in key packets.  */
 139         return gpg_error (GPG_ERR_UNEXPECTED);
 140       if (len < lenbytes)
 141         return gpg_error (GPG_ERR_INV_PACKET); /* Not enough length bytes.  */
 142       for (; lenbytes; lenbytes--)
 143         {
 144           pktlen <<= 8;
 145           pktlen |= *buf++; len--;
 146         }
 147     }
 148
 149   /* Do some basic sanity check.  */
 150   switch (pkttype)
 151     {
 152     case PKT_SIGNATURE:
 153     case PKT_SECRET_KEY:
 154     case PKT_PUBLIC_KEY:
 155     case PKT_SECRET_SUBKEY:
 156     case PKT_MARKER:
 157     case PKT_RING_TRUST:
 158     case PKT_USER_ID:
 159     case PKT_PUBLIC_SUBKEY:
 160     case PKT_OLD_COMMENT:
 161     case PKT_ATTRIBUTE:
 162     case PKT_COMMENT:
 163     case PKT_GPG_CONTROL:
 164       break; /* Okay these are allowed packets. */
 165     default:
 166       return gpg_error (GPG_ERR_UNEXPECTED);
 167     }
 168
 169   if (pktlen == 0xffffffff)
 170       return gpg_error (GPG_ERR_INV_PACKET);
 171
 172   if (pktlen > len)
 173     return gpg_error (GPG_ERR_INV_PACKET); /* Packet length header too long. */
 174
 175   *r_data = buf;
 176   *r_datalen = pktlen;
 177   *r_pkttype = pkttype;
 178   *r_ntotal = (buf - *bufptr) + pktlen;
 179
 180   *bufptr = buf + pktlen;
 181   *buflen = len - pktlen;
 182   if (!*buflen)
 183     *bufptr = NULL;
 184
 185   return 0;
 186 }
 187
 188
 189 /* Parse a key packet and store the ionformation in KI. */
 190 static gpg_error_t
 191 parse_key (const unsigned char *data, size_t datalen,
 192            struct _keybox_openpgp_key_info *ki)
 193 {
 194   gpg_error_t err;
 195   const unsigned char *data_start = data;
 196   int i, version, algorithm;
 197   size_t n;
 198   unsigned long timestamp, expiredate;
 199   int npkey;
 200   unsigned char hashbuffer[768];
 201   const unsigned char *mpi_n = NULL;
 202   size_t mpi_n_len = 0, mpi_e_len = 0;
 203   gcry_md_hd_t md;
 204
 205   if (datalen < 5)
 206     return gpg_error (GPG_ERR_INV_PACKET);
 207   version = *data++; datalen--;
 208   if (version < 2 || version > 4 )
 209     return gpg_error (GPG_ERR_INV_PACKET); /* Invalid version. */
 210
 211   timestamp = ((data[0]<<24)|(data[1]<<16)|(data[2]<<8)|(data[3]));
 212   data +=4; datalen -=4;
 213
 214   if (version < 4)
 215     {
 216       unsigned short ndays;
 217
 218       if (datalen < 2)
 219         return gpg_error (GPG_ERR_INV_PACKET);
 220       ndays = ((data[0]<<8)|(data[1]));
 221       data +=2; datalen -= 2;
 222       if (ndays)
 223       expiredate = ndays? (timestamp + ndays * 86400L) : 0;
 224     }
 225   else
 226     expiredate = 0; /* This is stored in the self-signature. */
 227
 228   if (!datalen)
 229     return gpg_error (GPG_ERR_INV_PACKET);
 230   algorithm = *data++; datalen--;
 231
 232   switch (algorithm)
 233     {
 234     case 1:
 235     case 2:
 236     case 3: /* RSA */
 237       npkey = 2;
 238       break;
 239     case 16:
 240     case 20: /* Elgamal */
 241       npkey = 3;
 242       break;
 243     case 17: /* DSA */
 244       npkey = 4;
 245       break;
 246     default: /* Unknown algorithm. */
 247       return gpg_error (GPG_ERR_UNKNOWN_ALGORITHM);
 248     }
 249
 250   for (i=0; i < npkey; i++ )
 251     {
 252       unsigned int nbits, nbytes;
 253
 254       if (datalen < 2)
 255         return gpg_error (GPG_ERR_INV_PACKET);
 256       nbits = ((data[0]<<8)|(data[1]));
 257       data += 2; datalen -=2;
 258       nbytes = (nbits+7) / 8;
 259       if (datalen < nbytes)
 260         return gpg_error (GPG_ERR_INV_PACKET);
 261       /* For use by v3 fingerprint calculation we need to know the RSA
 262          modulus and exponent. */
 263       if (i==0)
 264         {
 265           mpi_n = data;
 266           mpi_n_len = nbytes;
 267         }
 268       else if (i==1)
 269         mpi_e_len = nbytes;
 270
 271       data += nbytes; datalen -= nbytes;
 272     }
 273   n = data - data_start;
 274
 275   if (version < 4)
 276     {
 277       /* We do not support any other algorithm than RSA in v3
 278          packets. */
 279       if (algorithm < 1 || algorithm > 3)
 280         return gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
 281
 282       err = gcry_md_open (&md, GCRY_MD_MD5, 0);
 283       if (err)
 284         return err; /* Oops */
 285       gcry_md_write (md, mpi_n, mpi_n_len);
 286       gcry_md_write (md, mpi_n+mpi_n_len+2, mpi_e_len);
 287       memcpy (ki->fpr, gcry_md_read (md, 0), 16);
 288       gcry_md_close (md);
 289       ki->fprlen = 16;
 290
 291       if (mpi_n_len < 8)
 292         {
 293           /* Moduli less than 64 bit are out of the specs scope.  Zero
 294              them out becuase this is what gpg does too. */
 295           memset (ki->keyid, 0, 8);
 296         }
 297       else
 298         memcpy (ki->keyid, mpi_n + mpi_n_len - 8, 8);
 299     }
 300   else
 301     {
 302       /* Its a pitty that we need to prefix the buffer with the tag
 303          and a length header: We can't simply pass it to the fast
 304          hashing fucntion for that reason.  It might be a good idea to
 305          have a scatter-gather enabled hash function. What we do here
 306          is to use a static buffer if this one is large enough and
 307          only use the regular hash fucntions if this buffer is not
 308          large enough. */
 309       if ( 3 + n < sizeof hashbuffer )
 310         {
 311           hashbuffer[0] = 0x99;     /* CTB */
 312           hashbuffer[1] = (n >> 8); /* 2 byte length header. */
 313           hashbuffer[2] = n;
 314           memcpy (hashbuffer + 3, data_start, n);
 315           gcry_md_hash_buffer (GCRY_MD_SHA1, ki->fpr, hashbuffer, 3 + n);
 316         }
 317       else
 318         {
 319           err = gcry_md_open (&md, GCRY_MD_SHA1, 0);
 320           if (err)
 321             return err; /* Oops */
 322           gcry_md_putc (md, 0x99 );     /* CTB */
 323           gcry_md_putc (md, (n >> 8) ); /* 2 byte length header. */
 324           gcry_md_putc (md, n );
 325           gcry_md_write (md, data_start, n);
 326           memcpy (ki->fpr, gcry_md_read (md, 0), 20);
 327           gcry_md_close (md);
 328         }
 329       ki->fprlen = 20;
 330       memcpy (ki->keyid, ki->fpr+12, 8);
 331     }
 332
 333   return 0;
 334 }
 335
 336
 337
 338 /* The caller must pass the address of an INFO structure which will
 339    get filled on success with information pertaining to the OpenPGP
 340    keyblock IMAGE of length IMAGELEN.  Note that a caller does only
 341    need to release this INFO structure when the function returns
 342    success.  If NPARSED is not NULL the actual number of bytes parsed
 343    will be stored at this address.  */
 344 gpg_error_t
 345 _keybox_parse_openpgp (const unsigned char *image, size_t imagelen,
 346                        size_t *nparsed,
 347                        keybox_openpgp_info_t info)
 348 {
 349   gpg_error_t err = 0;
 350   const unsigned char *image_start, *data;
 351   size_t n, datalen;
 352   int pkttype;
 353   int first = 1;
 354   struct _keybox_openpgp_key_info *k, **ktail = NULL;
 355   struct _keybox_openpgp_uid_info *u, **utail = NULL;
 356
 357   memset (info, 0, sizeof *info);
 358   if (nparsed)
 359     *nparsed = 0;
 360
 361   image_start = image;
 362   while (image)
 363     {
 364       err = next_packet (&image, &imagelen, &data, &datalen, &pkttype, &n);
 365       if (err)
 366         break;
 367
 368       if (first)
 369         {
 370           if (pkttype == PKT_PUBLIC_KEY)
 371             ;
 372           else if (pkttype == PKT_SECRET_KEY)
 373             info->is_secret = 1;
 374           else
 375             {
 376               err = gpg_error (GPG_ERR_UNEXPECTED);
 377               break;
 378             }
 379           first = 0;
 380         }
 381       else if (pkttype == PKT_PUBLIC_KEY || pkttype == PKT_SECRET_KEY)
 382         break; /* Next keyblock encountered - ready. */
 383
 384       if (nparsed)
 385         *nparsed += n;
 386
 387       if (pkttype == PKT_SIGNATURE)
 388         {
 389           /* For now we only count the total number of signatures. */
 390           info->nsigs++;
 391         }
 392       else if (pkttype == PKT_USER_ID)
 393         {
 394           info->nuids++;
 395           if (info->nuids == 1)
 396             {
 397               info->uids.off = data - image_start;
 398               info->uids.len = datalen;
 399               utail = &info->uids.next;
 400             }
 401           else
 402             {
 403               u = xtrycalloc (1, sizeof *u);
 404               if (!u)
 405                 {
 406                   err = gpg_error_from_syserror ();
 407                   break;
 408                 }
 409               u->off = data - image_start;
 410               u->len = datalen;
 411               *utail = u;
 412               utail = &u->next;
 413             }
 414         }
 415       else if (pkttype == PKT_PUBLIC_KEY || pkttype == PKT_SECRET_KEY)
 416         {
 417           err = parse_key (data, datalen, &info->primary);
 418           if (err)
 419             break;
 420         }
 421       else if( pkttype == PKT_PUBLIC_SUBKEY && datalen && *data == '#' )
 422         {
 423           /* Early versions of GnuPG used old PGP comment packets;
 424            * luckily all those comments are prefixed by a hash
 425            * sign - ignore these packets. */
 426         }
 427       else if (pkttype == PKT_PUBLIC_SUBKEY || pkttype == PKT_SECRET_SUBKEY)
 428         {
 429           info->nsubkeys++;
 430           if (info->nsubkeys == 1)
 431             {
 432               err = parse_key (data, datalen, &info->subkeys);
 433               if (err)
 434                 {
 435                   info->nsubkeys--;
 436                   if (gpg_err_code (err) != GPG_ERR_UNKNOWN_ALGORITHM)
 437                     break;
 438                   /* We ignore subkeys with unknown algorithms. */
 439                 }
 440               else
 441                 ktail = &info->subkeys.next;
 442             }
 443           else
 444             {
 445               k = xtrycalloc (1, sizeof *k);
 446               if (!k)
 447                 {
 448                   err = gpg_error_from_syserror ();
 449                   break;
 450                 }
 451               err = parse_key (data, datalen, k);
 452               if (err)
 453                 {
 454                   xfree (k);
 455                   info->nsubkeys--;
 456                   if (gpg_err_code (err) != GPG_ERR_UNKNOWN_ALGORITHM)
 457                     break;
 458                   /* We ignore subkeys with unknown algorithms. */
 459                 }
 460               else
 461                 {
 462                   *ktail = k;
 463                   ktail = &k->next;
 464                 }
 465             }
 466         }
 467     }
 468
 469   if (err)
 470     {
 471       _keybox_destroy_openpgp_info (info);
 472       if (!first
 473           && (gpg_err_code (err) == GPG_ERR_UNSUPPORTED_ALGORITHM
 474               || gpg_err_code (err) == GPG_ERR_UNKNOWN_ALGORITHM))
 475         {
 476           /* We are able to skip to the end of this keyblock. */
 477           while (image)
 478             {
 479               if (next_packet (&image, &imagelen,
 480                                &data, &datalen, &pkttype, &n) )
 481                 break; /* Another error - stop here. */
 482
 483               if (pkttype == PKT_PUBLIC_KEY || pkttype == PKT_SECRET_KEY)
 484                 break; /* Next keyblock encountered - ready. */
 485
 486               if (nparsed)
 487                 *nparsed += n;
 488             }
 489         }
 490     }
 491
 492   return err;
 493 }
 494
 495
 496 /* Release any malloced data in INFO but not INFO itself! */
 497 void
 498 _keybox_destroy_openpgp_info (keybox_openpgp_info_t info)
 499 {
 500   struct _keybox_openpgp_key_info *k, *k2;
 501   struct _keybox_openpgp_uid_info *u, *u2;
 502
 503   assert (!info->primary.next);
 504   for (k=info->subkeys.next; k; k = k2)
 505     {
 506       k2 = k->next;
 507       xfree (k);
 508     }
 509
 510   for (u=info->uids.next; u; u = u2)
 511     {
 512       u2 = u->next;
 513       xfree (u);
 514     }
 515 }