crypto/asymmetric_keys/x509_cert_parser.c

   1 /* X.509 certificate parser
   2  *
   3  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) "X.509: "fmt
  13 #include <linux/kernel.h>
  14 #include <linux/slab.h>
  15 #include <linux/err.h>
  16 #include <linux/oid_registry.h>
  17 #include "public_key.h"
  18 #include "x509_parser.h"
  19 #include "x509-asn1.h"
  20 #include "x509_rsakey-asn1.h"
  21
  22 struct x509_parse_context {
  23         struct x509_certificate *cert;          /* Certificate being constructed */
  24         unsigned long   data;                   /* Start of data */
  25         const void      *cert_start;            /* Start of cert content */
  26         const void      *key;                   /* Key data */
  27         size_t          key_size;               /* Size of key data */
  28         enum OID        last_oid;               /* Last OID encountered */
  29         enum OID        algo_oid;               /* Algorithm OID */
  30         unsigned char   nr_mpi;                 /* Number of MPIs stored */
  31         u8              o_size;                 /* Size of organizationName (O) */
  32         u8              cn_size;                /* Size of commonName (CN) */
  33         u8              email_size;             /* Size of emailAddress */
  34         u16             o_offset;               /* Offset of organizationName (O) */
  35         u16             cn_offset;              /* Offset of commonName (CN) */
  36         u16             email_offset;           /* Offset of emailAddress */
  37 };
  38
  39 /*
  40  * Free an X.509 certificate
  41  */
  42 void x509_free_certificate(struct x509_certificate *cert)
  43 {
  44         if (cert) {
  45                 public_key_destroy(cert->pub);
  46                 kfree(cert->issuer);
  47                 kfree(cert->subject);
  48                 kfree(cert->fingerprint);
  49                 kfree(cert->authority);
  50                 kfree(cert->sig.digest);
  51                 mpi_free(cert->sig.rsa.s);
  52                 kfree(cert);
  53         }
  54 }
  55
  56 /*
  57  * Parse an X.509 certificate
  58  */
  59 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  60 {
  61         struct x509_certificate *cert;
  62         struct x509_parse_context *ctx;
  63         long ret;
  64
  65         ret = -ENOMEM;
  66         cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  67         if (!cert)
  68                 goto error_no_cert;
  69         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  70         if (!cert->pub)
  71                 goto error_no_ctx;
  72         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  73         if (!ctx)
  74                 goto error_no_ctx;
  75
  76         ctx->cert = cert;
  77         ctx->data = (unsigned long)data;
  78
  79         /* Attempt to decode the certificate */
  80         ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  81         if (ret < 0)
  82                 goto error_decode;
  83
  84         /* Decode the public key */
  85         ret = asn1_ber_decoder(&x509_rsakey_decoder, ctx,
  86                                ctx->key, ctx->key_size);
  87         if (ret < 0)
  88                 goto error_decode;
  89
  90         kfree(ctx);
  91         return cert;
  92
  93 error_decode:
  94         kfree(ctx);
  95 error_no_ctx:
  96         x509_free_certificate(cert);
  97 error_no_cert:
  98         return ERR_PTR(ret);
  99 }
 100
 101 /*
 102  * Note an OID when we find one for later processing when we know how
 103  * to interpret it.
 104  */
 105 int x509_note_OID(void *context, size_t hdrlen,
 106              unsigned char tag,
 107              const void *value, size_t vlen)
 108 {
 109         struct x509_parse_context *ctx = context;
 110
 111         ctx->last_oid = look_up_OID(value, vlen);
 112         if (ctx->last_oid == OID__NR) {
 113                 char buffer[50];
 114                 sprint_oid(value, vlen, buffer, sizeof(buffer));
 115                 pr_debug("Unknown OID: [%lu] %s\n",
 116                          (unsigned long)value - ctx->data, buffer);
 117         }
 118         return 0;
 119 }
 120
 121 /*
 122  * Save the position of the TBS data so that we can check the signature over it
 123  * later.
 124  */
 125 int x509_note_tbs_certificate(void *context, size_t hdrlen,
 126                               unsigned char tag,
 127                               const void *value, size_t vlen)
 128 {
 129         struct x509_parse_context *ctx = context;
 130
 131         pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 132                  hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 133
 134         ctx->cert->tbs = value - hdrlen;
 135         ctx->cert->tbs_size = vlen + hdrlen;
 136         return 0;
 137 }
 138
 139 /*
 140  * Record the public key algorithm
 141  */
 142 int x509_note_pkey_algo(void *context, size_t hdrlen,
 143                         unsigned char tag,
 144                         const void *value, size_t vlen)
 145 {
 146         struct x509_parse_context *ctx = context;
 147
 148         pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 149
 150         switch (ctx->last_oid) {
 151         case OID_md2WithRSAEncryption:
 152         case OID_md3WithRSAEncryption:
 153         default:
 154                 return -ENOPKG; /* Unsupported combination */
 155
 156         case OID_md4WithRSAEncryption:
 157                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_MD5;
 158                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 159                 break;
 160
 161         case OID_sha1WithRSAEncryption:
 162                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA1;
 163                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 164                 break;
 165
 166         case OID_sha256WithRSAEncryption:
 167                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA256;
 168                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 169                 break;
 170
 171         case OID_sha384WithRSAEncryption:
 172                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA384;
 173                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 174                 break;
 175
 176         case OID_sha512WithRSAEncryption:
 177                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA512;
 178                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 179                 break;
 180
 181         case OID_sha224WithRSAEncryption:
 182                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA224;
 183                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 184                 break;
 185         }
 186
 187         ctx->algo_oid = ctx->last_oid;
 188         return 0;
 189 }
 190
 191 /*
 192  * Note the whereabouts and type of the signature.
 193  */
 194 int x509_note_signature(void *context, size_t hdrlen,
 195                         unsigned char tag,
 196                         const void *value, size_t vlen)
 197 {
 198         struct x509_parse_context *ctx = context;
 199
 200         pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 201
 202         if (ctx->last_oid != ctx->algo_oid) {
 203                 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 204                         ctx->algo_oid, ctx->last_oid);
 205                 return -EINVAL;
 206         }
 207
 208         ctx->cert->raw_sig = value;
 209         ctx->cert->raw_sig_size = vlen;
 210         return 0;
 211 }
 212
 213 /*
 214  * Note some of the name segments from which we'll fabricate a name.
 215  */
 216 int x509_extract_name_segment(void *context, size_t hdrlen,
 217                               unsigned char tag,
 218                               const void *value, size_t vlen)
 219 {
 220         struct x509_parse_context *ctx = context;
 221
 222         switch (ctx->last_oid) {
 223         case OID_commonName:
 224                 ctx->cn_size = vlen;
 225                 ctx->cn_offset = (unsigned long)value - ctx->data;
 226                 break;
 227         case OID_organizationName:
 228                 ctx->o_size = vlen;
 229                 ctx->o_offset = (unsigned long)value - ctx->data;
 230                 break;
 231         case OID_email_address:
 232                 ctx->email_size = vlen;
 233                 ctx->email_offset = (unsigned long)value - ctx->data;
 234                 break;
 235         default:
 236                 break;
 237         }
 238
 239         return 0;
 240 }
 241
 242 /*
 243  * Fabricate and save the issuer and subject names
 244  */
 245 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 246                                unsigned char tag,
 247                                char **_name, size_t vlen)
 248 {
 249         const void *name, *data = (const void *)ctx->data;
 250         size_t namesize;
 251         char *buffer;
 252
 253         if (*_name)
 254                 return -EINVAL;
 255
 256         /* Empty name string if no material */
 257         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 258                 buffer = kmalloc(1, GFP_KERNEL);
 259                 if (!buffer)
 260                         return -ENOMEM;
 261                 buffer[0] = 0;
 262                 goto done;
 263         }
 264
 265         if (ctx->cn_size && ctx->o_size) {
 266                 /* Consider combining O and CN, but use only the CN if it is
 267                  * prefixed by the O, or a significant portion thereof.
 268                  */
 269                 namesize = ctx->cn_size;
 270                 name = data + ctx->cn_offset;
 271                 if (ctx->cn_size >= ctx->o_size &&
 272                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 273                            ctx->o_size) == 0)
 274                         goto single_component;
 275                 if (ctx->cn_size >= 7 &&
 276                     ctx->o_size >= 7 &&
 277                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 278                         goto single_component;
 279
 280                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 281                                  GFP_KERNEL);
 282                 if (!buffer)
 283                         return -ENOMEM;
 284
 285                 memcpy(buffer,
 286                        data + ctx->o_offset, ctx->o_size);
 287                 buffer[ctx->o_size + 0] = ':';
 288                 buffer[ctx->o_size + 1] = ' ';
 289                 memcpy(buffer + ctx->o_size + 2,
 290                        data + ctx->cn_offset, ctx->cn_size);
 291                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 292                 goto done;
 293
 294         } else if (ctx->cn_size) {
 295                 namesize = ctx->cn_size;
 296                 name = data + ctx->cn_offset;
 297         } else if (ctx->o_size) {
 298                 namesize = ctx->o_size;
 299                 name = data + ctx->o_offset;
 300         } else {
 301                 namesize = ctx->email_size;
 302                 name = data + ctx->email_offset;
 303         }
 304
 305 single_component:
 306         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 307         if (!buffer)
 308                 return -ENOMEM;
 309         memcpy(buffer, name, namesize);
 310         buffer[namesize] = 0;
 311
 312 done:
 313         *_name = buffer;
 314         ctx->cn_size = 0;
 315         ctx->o_size = 0;
 316         ctx->email_size = 0;
 317         return 0;
 318 }
 319
 320 int x509_note_issuer(void *context, size_t hdrlen,
 321                      unsigned char tag,
 322                      const void *value, size_t vlen)
 323 {
 324         struct x509_parse_context *ctx = context;
 325         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 326 }
 327
 328 int x509_note_subject(void *context, size_t hdrlen,
 329                       unsigned char tag,
 330                       const void *value, size_t vlen)
 331 {
 332         struct x509_parse_context *ctx = context;
 333         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 334 }
 335
 336 /*
 337  * Extract the data for the public key algorithm
 338  */
 339 int x509_extract_key_data(void *context, size_t hdrlen,
 340                           unsigned char tag,
 341                           const void *value, size_t vlen)
 342 {
 343         struct x509_parse_context *ctx = context;
 344
 345         if (ctx->last_oid != OID_rsaEncryption)
 346                 return -ENOPKG;
 347
 348         ctx->cert->pub->pkey_algo = PKEY_ALGO_RSA;
 349
 350         /* Discard the BIT STRING metadata */
 351         ctx->key = value + 1;
 352         ctx->key_size = vlen - 1;
 353         return 0;
 354 }
 355
 356 /*
 357  * Extract a RSA public key value
 358  */
 359 int rsa_extract_mpi(void *context, size_t hdrlen,
 360                     unsigned char tag,
 361                     const void *value, size_t vlen)
 362 {
 363         struct x509_parse_context *ctx = context;
 364         MPI mpi;
 365
 366         if (ctx->nr_mpi >= ARRAY_SIZE(ctx->cert->pub->mpi)) {
 367                 pr_err("Too many public key MPIs in certificate\n");
 368                 return -EBADMSG;
 369         }
 370
 371         mpi = mpi_read_raw_data(value, vlen);
 372         if (!mpi)
 373                 return -ENOMEM;
 374
 375         ctx->cert->pub->mpi[ctx->nr_mpi++] = mpi;
 376         return 0;
 377 }
 378
 379 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
 380 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
 381
 382 /*
 383  * Process certificate extensions that are used to qualify the certificate.
 384  */
 385 int x509_process_extension(void *context, size_t hdrlen,
 386                            unsigned char tag,
 387                            const void *value, size_t vlen)
 388 {
 389         struct x509_parse_context *ctx = context;
 390         const unsigned char *v = value;
 391         char *f;
 392         int i;
 393
 394         pr_debug("Extension: %u\n", ctx->last_oid);
 395
 396         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 397                 /* Get hold of the key fingerprint */
 398                 if (vlen < 3)
 399                         return -EBADMSG;
 400                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 401                         return -EBADMSG;
 402                 v += 2;
 403                 vlen -= 2;
 404
 405                 f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
 406                 if (!f)
 407                         return -ENOMEM;
 408                 for (i = 0; i < vlen; i++)
 409                         sprintf(f + i * 2, "%02x", v[i]);
 410                 pr_debug("fingerprint %s\n", f);
 411                 ctx->cert->fingerprint = f;
 412                 return 0;
 413         }
 414
 415         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 416                 size_t key_len;
 417
 418                 /* Get hold of the CA key fingerprint */
 419                 if (vlen < 5)
 420                         return -EBADMSG;
 421
 422                 /* Authority Key Identifier must be a Constructed SEQUENCE */
 423                 if (v[0] != (ASN1_SEQ | (ASN1_CONS << 5)))
 424                         return -EBADMSG;
 425
 426                 /* Authority Key Identifier is not indefinite length */
 427                 if (unlikely(vlen == ASN1_INDEFINITE_LENGTH))
 428                         return -EBADMSG;
 429
 430                 if (vlen < ASN1_INDEFINITE_LENGTH) {
 431                         /* Short Form length */
 432                         if (v[1] != vlen - 2 ||
 433                             v[2] != SEQ_TAG_KEYID ||
 434                             v[3] > vlen - 4)
 435                                 return -EBADMSG;
 436
 437                         key_len = v[3];
 438                         v += 4;
 439                 } else {
 440                         /* Long Form length */
 441                         size_t seq_len = 0;
 442                         size_t sub = v[1] - ASN1_INDEFINITE_LENGTH;
 443
 444                         if (sub > 2)
 445                                 return -EBADMSG;
 446
 447                         /* calculate the length from subsequent octets */
 448                         v += 2;
 449                         for (i = 0; i < sub; i++) {
 450                                 seq_len <<= 8;
 451                                 seq_len |= v[i];
 452                         }
 453
 454                         if (seq_len != vlen - 2 - sub ||
 455                             v[sub] != SEQ_TAG_KEYID ||
 456                             v[sub + 1] > vlen - 4 - sub)
 457                                 return -EBADMSG;
 458
 459                         key_len = v[sub + 1];
 460                         v += (sub + 2);
 461                 }
 462
 463                 f = kmalloc(key_len * 2 + 1, GFP_KERNEL);
 464                 if (!f)
 465                         return -ENOMEM;
 466                 for (i = 0; i < key_len; i++)
 467                         sprintf(f + i * 2, "%02x", v[i]);
 468                 pr_debug("authority   %s\n", f);
 469                 ctx->cert->authority = f;
 470                 return 0;
 471         }
 472
 473         return 0;
 474 }
 475
 476 /*
 477  * Record a certificate time.
 478  */
 479 static int x509_note_time(struct tm *tm,  size_t hdrlen,
 480                           unsigned char tag,
 481                           const unsigned char *value, size_t vlen)
 482 {
 483         const unsigned char *p = value;
 484
 485 #define dec2bin(X) ((X) - '0')
 486 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 487
 488         if (tag == ASN1_UNITIM) {
 489                 /* UTCTime: YYMMDDHHMMSSZ */
 490                 if (vlen != 13)
 491                         goto unsupported_time;
 492                 tm->tm_year = DD2bin(p);
 493                 if (tm->tm_year >= 50)
 494                         tm->tm_year += 1900;
 495                 else
 496                         tm->tm_year += 2000;
 497         } else if (tag == ASN1_GENTIM) {
 498                 /* GenTime: YYYYMMDDHHMMSSZ */
 499                 if (vlen != 15)
 500                         goto unsupported_time;
 501                 tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
 502         } else {
 503                 goto unsupported_time;
 504         }
 505
 506         tm->tm_year -= 1900;
 507         tm->tm_mon  = DD2bin(p) - 1;
 508         tm->tm_mday = DD2bin(p);
 509         tm->tm_hour = DD2bin(p);
 510         tm->tm_min  = DD2bin(p);
 511         tm->tm_sec  = DD2bin(p);
 512
 513         if (*p != 'Z')
 514                 goto unsupported_time;
 515
 516         return 0;
 517
 518 unsupported_time:
 519         pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n",
 520                  tag, (int)vlen, (int)vlen, value);
 521         return -EBADMSG;
 522 }
 523
 524 int x509_note_not_before(void *context, size_t hdrlen,
 525                          unsigned char tag,
 526                          const void *value, size_t vlen)
 527 {
 528         struct x509_parse_context *ctx = context;
 529         return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 530 }
 531
 532 int x509_note_not_after(void *context, size_t hdrlen,
 533                         unsigned char tag,
 534                         const void *value, size_t vlen)
 535 {
 536         struct x509_parse_context *ctx = context;
 537         return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 538 }