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/export.h>
  15 #include <linux/slab.h>
  16 #include <linux/err.h>
  17 #include <linux/oid_registry.h>
  18 #include "public_key.h"
  19 #include "x509_parser.h"
  20 #include "x509-asn1.h"
  21 #include "x509_rsakey-asn1.h"
  22
  23 struct x509_parse_context {
  24         struct x509_certificate *cert;          /* Certificate being constructed */
  25         unsigned long   data;                   /* Start of data */
  26         const void      *cert_start;            /* Start of cert content */
  27         const void      *key;                   /* Key data */
  28         size_t          key_size;               /* Size of key data */
  29         enum OID        last_oid;               /* Last OID encountered */
  30         enum OID        algo_oid;               /* Algorithm OID */
  31         unsigned char   nr_mpi;                 /* Number of MPIs stored */
  32         u8              o_size;                 /* Size of organizationName (O) */
  33         u8              cn_size;                /* Size of commonName (CN) */
  34         u8              email_size;             /* Size of emailAddress */
  35         u16             o_offset;               /* Offset of organizationName (O) */
  36         u16             cn_offset;              /* Offset of commonName (CN) */
  37         u16             email_offset;           /* Offset of emailAddress */
  38 };
  39
  40 /*
  41  * Free an X.509 certificate
  42  */
  43 void x509_free_certificate(struct x509_certificate *cert)
  44 {
  45         if (cert) {
  46                 public_key_destroy(cert->pub);
  47                 kfree(cert->issuer);
  48                 kfree(cert->subject);
  49                 kfree(cert->id);
  50                 kfree(cert->skid);
  51                 kfree(cert->authority);
  52                 kfree(cert->sig.digest);
  53                 mpi_free(cert->sig.rsa.s);
  54                 kfree(cert);
  55         }
  56 }
  57 EXPORT_SYMBOL_GPL(x509_free_certificate);
  58
  59 /*
  60  * Parse an X.509 certificate
  61  */
  62 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  63 {
  64         struct x509_certificate *cert;
  65         struct x509_parse_context *ctx;
  66         struct asymmetric_key_id *kid;
  67         long ret;
  68
  69         ret = -ENOMEM;
  70         cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  71         if (!cert)
  72                 goto error_no_cert;
  73         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  74         if (!cert->pub)
  75                 goto error_no_ctx;
  76         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  77         if (!ctx)
  78                 goto error_no_ctx;
  79
  80         ctx->cert = cert;
  81         ctx->data = (unsigned long)data;
  82
  83         /* Attempt to decode the certificate */
  84         ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  85         if (ret < 0)
  86                 goto error_decode;
  87
  88         /* Decode the public key */
  89         ret = asn1_ber_decoder(&x509_rsakey_decoder, ctx,
  90                                ctx->key, ctx->key_size);
  91         if (ret < 0)
  92                 goto error_decode;
  93
  94         /* Generate cert issuer + serial number key ID */
  95         kid = asymmetric_key_generate_id(cert->raw_serial,
  96                                          cert->raw_serial_size,
  97                                          cert->raw_issuer,
  98                                          cert->raw_issuer_size);
  99         if (IS_ERR(kid)) {
 100                 ret = PTR_ERR(kid);
 101                 goto error_decode;
 102         }
 103         cert->id = kid;
 104
 105         kfree(ctx);
 106         return cert;
 107
 108 error_decode:
 109         kfree(ctx);
 110 error_no_ctx:
 111         x509_free_certificate(cert);
 112 error_no_cert:
 113         return ERR_PTR(ret);
 114 }
 115 EXPORT_SYMBOL_GPL(x509_cert_parse);
 116
 117 /*
 118  * Note an OID when we find one for later processing when we know how
 119  * to interpret it.
 120  */
 121 int x509_note_OID(void *context, size_t hdrlen,
 122              unsigned char tag,
 123              const void *value, size_t vlen)
 124 {
 125         struct x509_parse_context *ctx = context;
 126
 127         ctx->last_oid = look_up_OID(value, vlen);
 128         if (ctx->last_oid == OID__NR) {
 129                 char buffer[50];
 130                 sprint_oid(value, vlen, buffer, sizeof(buffer));
 131                 pr_debug("Unknown OID: [%lu] %s\n",
 132                          (unsigned long)value - ctx->data, buffer);
 133         }
 134         return 0;
 135 }
 136
 137 /*
 138  * Save the position of the TBS data so that we can check the signature over it
 139  * later.
 140  */
 141 int x509_note_tbs_certificate(void *context, size_t hdrlen,
 142                               unsigned char tag,
 143                               const void *value, size_t vlen)
 144 {
 145         struct x509_parse_context *ctx = context;
 146
 147         pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 148                  hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 149
 150         ctx->cert->tbs = value - hdrlen;
 151         ctx->cert->tbs_size = vlen + hdrlen;
 152         return 0;
 153 }
 154
 155 /*
 156  * Record the public key algorithm
 157  */
 158 int x509_note_pkey_algo(void *context, size_t hdrlen,
 159                         unsigned char tag,
 160                         const void *value, size_t vlen)
 161 {
 162         struct x509_parse_context *ctx = context;
 163
 164         pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 165
 166         switch (ctx->last_oid) {
 167         case OID_md2WithRSAEncryption:
 168         case OID_md3WithRSAEncryption:
 169         default:
 170                 return -ENOPKG; /* Unsupported combination */
 171
 172         case OID_md4WithRSAEncryption:
 173                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_MD5;
 174                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 175                 break;
 176
 177         case OID_sha1WithRSAEncryption:
 178                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA1;
 179                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 180                 break;
 181
 182         case OID_sha256WithRSAEncryption:
 183                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA256;
 184                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 185                 break;
 186
 187         case OID_sha384WithRSAEncryption:
 188                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA384;
 189                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 190                 break;
 191
 192         case OID_sha512WithRSAEncryption:
 193                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA512;
 194                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 195                 break;
 196
 197         case OID_sha224WithRSAEncryption:
 198                 ctx->cert->sig.pkey_hash_algo = HASH_ALGO_SHA224;
 199                 ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
 200                 break;
 201         }
 202
 203         ctx->algo_oid = ctx->last_oid;
 204         return 0;
 205 }
 206
 207 /*
 208  * Note the whereabouts and type of the signature.
 209  */
 210 int x509_note_signature(void *context, size_t hdrlen,
 211                         unsigned char tag,
 212                         const void *value, size_t vlen)
 213 {
 214         struct x509_parse_context *ctx = context;
 215
 216         pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 217
 218         if (ctx->last_oid != ctx->algo_oid) {
 219                 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 220                         ctx->algo_oid, ctx->last_oid);
 221                 return -EINVAL;
 222         }
 223
 224         ctx->cert->raw_sig = value;
 225         ctx->cert->raw_sig_size = vlen;
 226         return 0;
 227 }
 228
 229 /*
 230  * Note the certificate serial number
 231  */
 232 int x509_note_serial(void *context, size_t hdrlen,
 233                      unsigned char tag,
 234                      const void *value, size_t vlen)
 235 {
 236         struct x509_parse_context *ctx = context;
 237         ctx->cert->raw_serial = value;
 238         ctx->cert->raw_serial_size = vlen;
 239         return 0;
 240 }
 241
 242 /*
 243  * Note some of the name segments from which we'll fabricate a name.
 244  */
 245 int x509_extract_name_segment(void *context, size_t hdrlen,
 246                               unsigned char tag,
 247                               const void *value, size_t vlen)
 248 {
 249         struct x509_parse_context *ctx = context;
 250
 251         switch (ctx->last_oid) {
 252         case OID_commonName:
 253                 ctx->cn_size = vlen;
 254                 ctx->cn_offset = (unsigned long)value - ctx->data;
 255                 break;
 256         case OID_organizationName:
 257                 ctx->o_size = vlen;
 258                 ctx->o_offset = (unsigned long)value - ctx->data;
 259                 break;
 260         case OID_email_address:
 261                 ctx->email_size = vlen;
 262                 ctx->email_offset = (unsigned long)value - ctx->data;
 263                 break;
 264         default:
 265                 break;
 266         }
 267
 268         return 0;
 269 }
 270
 271 /*
 272  * Fabricate and save the issuer and subject names
 273  */
 274 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 275                                unsigned char tag,
 276                                char **_name, size_t vlen)
 277 {
 278         const void *name, *data = (const void *)ctx->data;
 279         size_t namesize;
 280         char *buffer;
 281
 282         if (*_name)
 283                 return -EINVAL;
 284
 285         /* Empty name string if no material */
 286         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 287                 buffer = kmalloc(1, GFP_KERNEL);
 288                 if (!buffer)
 289                         return -ENOMEM;
 290                 buffer[0] = 0;
 291                 goto done;
 292         }
 293
 294         if (ctx->cn_size && ctx->o_size) {
 295                 /* Consider combining O and CN, but use only the CN if it is
 296                  * prefixed by the O, or a significant portion thereof.
 297                  */
 298                 namesize = ctx->cn_size;
 299                 name = data + ctx->cn_offset;
 300                 if (ctx->cn_size >= ctx->o_size &&
 301                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 302                            ctx->o_size) == 0)
 303                         goto single_component;
 304                 if (ctx->cn_size >= 7 &&
 305                     ctx->o_size >= 7 &&
 306                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 307                         goto single_component;
 308
 309                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 310                                  GFP_KERNEL);
 311                 if (!buffer)
 312                         return -ENOMEM;
 313
 314                 memcpy(buffer,
 315                        data + ctx->o_offset, ctx->o_size);
 316                 buffer[ctx->o_size + 0] = ':';
 317                 buffer[ctx->o_size + 1] = ' ';
 318                 memcpy(buffer + ctx->o_size + 2,
 319                        data + ctx->cn_offset, ctx->cn_size);
 320                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 321                 goto done;
 322
 323         } else if (ctx->cn_size) {
 324                 namesize = ctx->cn_size;
 325                 name = data + ctx->cn_offset;
 326         } else if (ctx->o_size) {
 327                 namesize = ctx->o_size;
 328                 name = data + ctx->o_offset;
 329         } else {
 330                 namesize = ctx->email_size;
 331                 name = data + ctx->email_offset;
 332         }
 333
 334 single_component:
 335         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 336         if (!buffer)
 337                 return -ENOMEM;
 338         memcpy(buffer, name, namesize);
 339         buffer[namesize] = 0;
 340
 341 done:
 342         *_name = buffer;
 343         ctx->cn_size = 0;
 344         ctx->o_size = 0;
 345         ctx->email_size = 0;
 346         return 0;
 347 }
 348
 349 int x509_note_issuer(void *context, size_t hdrlen,
 350                      unsigned char tag,
 351                      const void *value, size_t vlen)
 352 {
 353         struct x509_parse_context *ctx = context;
 354         ctx->cert->raw_issuer = value;
 355         ctx->cert->raw_issuer_size = vlen;
 356         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 357 }
 358
 359 int x509_note_subject(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         ctx->cert->raw_subject = value;
 365         ctx->cert->raw_subject_size = vlen;
 366         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 367 }
 368
 369 /*
 370  * Extract the data for the public key algorithm
 371  */
 372 int x509_extract_key_data(void *context, size_t hdrlen,
 373                           unsigned char tag,
 374                           const void *value, size_t vlen)
 375 {
 376         struct x509_parse_context *ctx = context;
 377
 378         if (ctx->last_oid != OID_rsaEncryption)
 379                 return -ENOPKG;
 380
 381         ctx->cert->pub->pkey_algo = PKEY_ALGO_RSA;
 382
 383         /* Discard the BIT STRING metadata */
 384         ctx->key = value + 1;
 385         ctx->key_size = vlen - 1;
 386         return 0;
 387 }
 388
 389 /*
 390  * Extract a RSA public key value
 391  */
 392 int rsa_extract_mpi(void *context, size_t hdrlen,
 393                     unsigned char tag,
 394                     const void *value, size_t vlen)
 395 {
 396         struct x509_parse_context *ctx = context;
 397         MPI mpi;
 398
 399         if (ctx->nr_mpi >= ARRAY_SIZE(ctx->cert->pub->mpi)) {
 400                 pr_err("Too many public key MPIs in certificate\n");
 401                 return -EBADMSG;
 402         }
 403
 404         mpi = mpi_read_raw_data(value, vlen);
 405         if (!mpi)
 406                 return -ENOMEM;
 407
 408         ctx->cert->pub->mpi[ctx->nr_mpi++] = mpi;
 409         return 0;
 410 }
 411
 412 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
 413 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
 414
 415 /*
 416  * Process certificate extensions that are used to qualify the certificate.
 417  */
 418 int x509_process_extension(void *context, size_t hdrlen,
 419                            unsigned char tag,
 420                            const void *value, size_t vlen)
 421 {
 422         struct x509_parse_context *ctx = context;
 423         struct asymmetric_key_id *kid;
 424         const unsigned char *v = value;
 425         int i;
 426
 427         pr_debug("Extension: %u\n", ctx->last_oid);
 428
 429         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 430                 /* Get hold of the key fingerprint */
 431                 if (ctx->cert->skid || vlen < 3)
 432                         return -EBADMSG;
 433                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 434                         return -EBADMSG;
 435                 v += 2;
 436                 vlen -= 2;
 437
 438                 ctx->cert->raw_skid_size = vlen;
 439                 ctx->cert->raw_skid = v;
 440                 kid = asymmetric_key_generate_id(ctx->cert->raw_subject,
 441                                                  ctx->cert->raw_subject_size,
 442                                                  v, vlen);
 443                 if (IS_ERR(kid))
 444                         return PTR_ERR(kid);
 445                 ctx->cert->skid = kid;
 446                 pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
 447                 return 0;
 448         }
 449
 450         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 451                 /* Get hold of the CA key fingerprint */
 452                 if (ctx->cert->authority || vlen < 5)
 453                         return -EBADMSG;
 454
 455                 /* Authority Key Identifier must be a Constructed SEQUENCE */
 456                 if (v[0] != (ASN1_SEQ | (ASN1_CONS << 5)))
 457                         return -EBADMSG;
 458
 459                 /* Authority Key Identifier is not indefinite length */
 460                 if (unlikely(vlen == ASN1_INDEFINITE_LENGTH))
 461                         return -EBADMSG;
 462
 463                 if (vlen < ASN1_INDEFINITE_LENGTH) {
 464                         /* Short Form length */
 465                         if (v[1] != vlen - 2 ||
 466                             v[2] != SEQ_TAG_KEYID ||
 467                             v[3] > vlen - 4)
 468                                 return -EBADMSG;
 469
 470                         vlen = v[3];
 471                         v += 4;
 472                 } else {
 473                         /* Long Form length */
 474                         size_t seq_len = 0;
 475                         size_t sub = v[1] - ASN1_INDEFINITE_LENGTH;
 476
 477                         if (sub > 2)
 478                                 return -EBADMSG;
 479
 480                         /* calculate the length from subsequent octets */
 481                         v += 2;
 482                         for (i = 0; i < sub; i++) {
 483                                 seq_len <<= 8;
 484                                 seq_len |= v[i];
 485                         }
 486
 487                         if (seq_len != vlen - 2 - sub ||
 488                             v[sub] != SEQ_TAG_KEYID ||
 489                             v[sub + 1] > vlen - 4 - sub)
 490                                 return -EBADMSG;
 491
 492                         vlen = v[sub + 1];
 493                         v += (sub + 2);
 494                 }
 495
 496                 kid = asymmetric_key_generate_id(ctx->cert->raw_issuer,
 497                                                  ctx->cert->raw_issuer_size,
 498                                                  v, vlen);
 499                 if (IS_ERR(kid))
 500                         return PTR_ERR(kid);
 501                 pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 502                 ctx->cert->authority = kid;
 503                 return 0;
 504         }
 505
 506         return 0;
 507 }
 508
 509 /*
 510  * Record a certificate time.
 511  */
 512 static int x509_note_time(struct tm *tm,  size_t hdrlen,
 513                           unsigned char tag,
 514                           const unsigned char *value, size_t vlen)
 515 {
 516         const unsigned char *p = value;
 517
 518 #define dec2bin(X) ((X) - '0')
 519 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 520
 521         if (tag == ASN1_UNITIM) {
 522                 /* UTCTime: YYMMDDHHMMSSZ */
 523                 if (vlen != 13)
 524                         goto unsupported_time;
 525                 tm->tm_year = DD2bin(p);
 526                 if (tm->tm_year >= 50)
 527                         tm->tm_year += 1900;
 528                 else
 529                         tm->tm_year += 2000;
 530         } else if (tag == ASN1_GENTIM) {
 531                 /* GenTime: YYYYMMDDHHMMSSZ */
 532                 if (vlen != 15)
 533                         goto unsupported_time;
 534                 tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
 535         } else {
 536                 goto unsupported_time;
 537         }
 538
 539         tm->tm_year -= 1900;
 540         tm->tm_mon  = DD2bin(p) - 1;
 541         tm->tm_mday = DD2bin(p);
 542         tm->tm_hour = DD2bin(p);
 543         tm->tm_min  = DD2bin(p);
 544         tm->tm_sec  = DD2bin(p);
 545
 546         if (*p != 'Z')
 547                 goto unsupported_time;
 548
 549         return 0;
 550
 551 unsupported_time:
 552         pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n",
 553                  tag, (int)vlen, (int)vlen, value);
 554         return -EBADMSG;
 555 }
 556
 557 int x509_note_not_before(void *context, size_t hdrlen,
 558                          unsigned char tag,
 559                          const void *value, size_t vlen)
 560 {
 561         struct x509_parse_context *ctx = context;
 562         return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 563 }
 564
 565 int x509_note_not_after(void *context, size_t hdrlen,
 566                         unsigned char tag,
 567                         const void *value, size_t vlen)
 568 {
 569         struct x509_parse_context *ctx = context;
 570         return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 571 }