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 <crypto/public_key.h>
  19 #include "x509_parser.h"
  20 #include "x509.asn1.h"
  21 #include "x509_akid.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         unsigned        raw_akid_size;
  39         const void      *raw_akid;              /* Raw authorityKeyId in ASN.1 */
  40         const void      *akid_raw_issuer;       /* Raw directoryName in authorityKeyId */
  41         unsigned        akid_raw_issuer_size;
  42 };
  43
  44 /*
  45  * Free an X.509 certificate
  46  */
  47 void x509_free_certificate(struct x509_certificate *cert)
  48 {
  49         if (cert) {
  50                 public_key_free(cert->pub);
  51                 public_key_signature_free(cert->sig);
  52                 kfree(cert->issuer);
  53                 kfree(cert->subject);
  54                 kfree(cert->id);
  55                 kfree(cert->skid);
  56                 kfree(cert);
  57         }
  58 }
  59 EXPORT_SYMBOL_GPL(x509_free_certificate);
  60
  61 /*
  62  * Parse an X.509 certificate
  63  */
  64 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  65 {
  66         struct x509_certificate *cert;
  67         struct x509_parse_context *ctx;
  68         struct asymmetric_key_id *kid;
  69         long ret;
  70
  71         ret = -ENOMEM;
  72         cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  73         if (!cert)
  74                 goto error_no_cert;
  75         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  76         if (!cert->pub)
  77                 goto error_no_ctx;
  78         cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
  79         if (!cert->sig)
  80                 goto error_no_ctx;
  81         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  82         if (!ctx)
  83                 goto error_no_ctx;
  84
  85         ctx->cert = cert;
  86         ctx->data = (unsigned long)data;
  87
  88         /* Attempt to decode the certificate */
  89         ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  90         if (ret < 0)
  91                 goto error_decode;
  92
  93         /* Decode the AuthorityKeyIdentifier */
  94         if (ctx->raw_akid) {
  95                 pr_devel("AKID: %u %*phN\n",
  96                          ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
  97                 ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
  98                                        ctx->raw_akid, ctx->raw_akid_size);
  99                 if (ret < 0) {
 100                         pr_warn("Couldn't decode AuthKeyIdentifier\n");
 101                         goto error_decode;
 102                 }
 103         }
 104
 105         ret = -ENOMEM;
 106         cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
 107         if (!cert->pub->key)
 108                 goto error_decode;
 109
 110         cert->pub->keylen = ctx->key_size;
 111
 112         /* Grab the signature bits */
 113         ret = x509_get_sig_params(cert);
 114         if (ret < 0)
 115                 goto error_decode;
 116
 117         /* Generate cert issuer + serial number key ID */
 118         kid = asymmetric_key_generate_id(cert->raw_serial,
 119                                          cert->raw_serial_size,
 120                                          cert->raw_issuer,
 121                                          cert->raw_issuer_size);
 122         if (IS_ERR(kid)) {
 123                 ret = PTR_ERR(kid);
 124                 goto error_decode;
 125         }
 126         cert->id = kid;
 127
 128         /* Detect self-signed certificates */
 129         ret = x509_check_for_self_signed(cert);
 130         if (ret < 0)
 131                 goto error_decode;
 132
 133         kfree(ctx);
 134         return cert;
 135
 136 error_decode:
 137         kfree(ctx);
 138 error_no_ctx:
 139         x509_free_certificate(cert);
 140 error_no_cert:
 141         return ERR_PTR(ret);
 142 }
 143 EXPORT_SYMBOL_GPL(x509_cert_parse);
 144
 145 /*
 146  * Note an OID when we find one for later processing when we know how
 147  * to interpret it.
 148  */
 149 int x509_note_OID(void *context, size_t hdrlen,
 150              unsigned char tag,
 151              const void *value, size_t vlen)
 152 {
 153         struct x509_parse_context *ctx = context;
 154
 155         ctx->last_oid = look_up_OID(value, vlen);
 156         if (ctx->last_oid == OID__NR) {
 157                 char buffer[50];
 158                 sprint_oid(value, vlen, buffer, sizeof(buffer));
 159                 pr_debug("Unknown OID: [%lu] %s\n",
 160                          (unsigned long)value - ctx->data, buffer);
 161         }
 162         return 0;
 163 }
 164
 165 /*
 166  * Save the position of the TBS data so that we can check the signature over it
 167  * later.
 168  */
 169 int x509_note_tbs_certificate(void *context, size_t hdrlen,
 170                               unsigned char tag,
 171                               const void *value, size_t vlen)
 172 {
 173         struct x509_parse_context *ctx = context;
 174
 175         pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 176                  hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 177
 178         ctx->cert->tbs = value - hdrlen;
 179         ctx->cert->tbs_size = vlen + hdrlen;
 180         return 0;
 181 }
 182
 183 /*
 184  * Record the public key algorithm
 185  */
 186 int x509_note_pkey_algo(void *context, size_t hdrlen,
 187                         unsigned char tag,
 188                         const void *value, size_t vlen)
 189 {
 190         struct x509_parse_context *ctx = context;
 191
 192         pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 193
 194         switch (ctx->last_oid) {
 195         case OID_md2WithRSAEncryption:
 196         case OID_md3WithRSAEncryption:
 197         default:
 198                 return -ENOPKG; /* Unsupported combination */
 199
 200         case OID_md4WithRSAEncryption:
 201                 ctx->cert->sig->hash_algo = "md4";
 202                 goto rsa_pkcs1;
 203
 204         case OID_sha1WithRSAEncryption:
 205                 ctx->cert->sig->hash_algo = "sha1";
 206                 goto rsa_pkcs1;
 207
 208         case OID_sha256WithRSAEncryption:
 209                 ctx->cert->sig->hash_algo = "sha256";
 210                 goto rsa_pkcs1;
 211
 212         case OID_sha384WithRSAEncryption:
 213                 ctx->cert->sig->hash_algo = "sha384";
 214                 goto rsa_pkcs1;
 215
 216         case OID_sha512WithRSAEncryption:
 217                 ctx->cert->sig->hash_algo = "sha512";
 218                 goto rsa_pkcs1;
 219
 220         case OID_sha224WithRSAEncryption:
 221                 ctx->cert->sig->hash_algo = "sha224";
 222                 goto rsa_pkcs1;
 223         }
 224
 225 rsa_pkcs1:
 226         ctx->cert->sig->pkey_algo = "rsa";
 227         ctx->cert->sig->encoding = "pkcs1";
 228         ctx->algo_oid = ctx->last_oid;
 229         return 0;
 230 }
 231
 232 /*
 233  * Note the whereabouts and type of the signature.
 234  */
 235 int x509_note_signature(void *context, size_t hdrlen,
 236                         unsigned char tag,
 237                         const void *value, size_t vlen)
 238 {
 239         struct x509_parse_context *ctx = context;
 240
 241         pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 242
 243         if (ctx->last_oid != ctx->algo_oid) {
 244                 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 245                         ctx->algo_oid, ctx->last_oid);
 246                 return -EINVAL;
 247         }
 248
 249         if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0) {
 250                 /* Discard the BIT STRING metadata */
 251                 if (vlen < 1 || *(const u8 *)value != 0)
 252                         return -EBADMSG;
 253
 254                 value++;
 255                 vlen--;
 256         }
 257
 258         ctx->cert->raw_sig = value;
 259         ctx->cert->raw_sig_size = vlen;
 260         return 0;
 261 }
 262
 263 /*
 264  * Note the certificate serial number
 265  */
 266 int x509_note_serial(void *context, size_t hdrlen,
 267                      unsigned char tag,
 268                      const void *value, size_t vlen)
 269 {
 270         struct x509_parse_context *ctx = context;
 271         ctx->cert->raw_serial = value;
 272         ctx->cert->raw_serial_size = vlen;
 273         return 0;
 274 }
 275
 276 /*
 277  * Note some of the name segments from which we'll fabricate a name.
 278  */
 279 int x509_extract_name_segment(void *context, size_t hdrlen,
 280                               unsigned char tag,
 281                               const void *value, size_t vlen)
 282 {
 283         struct x509_parse_context *ctx = context;
 284
 285         switch (ctx->last_oid) {
 286         case OID_commonName:
 287                 ctx->cn_size = vlen;
 288                 ctx->cn_offset = (unsigned long)value - ctx->data;
 289                 break;
 290         case OID_organizationName:
 291                 ctx->o_size = vlen;
 292                 ctx->o_offset = (unsigned long)value - ctx->data;
 293                 break;
 294         case OID_email_address:
 295                 ctx->email_size = vlen;
 296                 ctx->email_offset = (unsigned long)value - ctx->data;
 297                 break;
 298         default:
 299                 break;
 300         }
 301
 302         return 0;
 303 }
 304
 305 /*
 306  * Fabricate and save the issuer and subject names
 307  */
 308 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 309                                unsigned char tag,
 310                                char **_name, size_t vlen)
 311 {
 312         const void *name, *data = (const void *)ctx->data;
 313         size_t namesize;
 314         char *buffer;
 315
 316         if (*_name)
 317                 return -EINVAL;
 318
 319         /* Empty name string if no material */
 320         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 321                 buffer = kmalloc(1, GFP_KERNEL);
 322                 if (!buffer)
 323                         return -ENOMEM;
 324                 buffer[0] = 0;
 325                 goto done;
 326         }
 327
 328         if (ctx->cn_size && ctx->o_size) {
 329                 /* Consider combining O and CN, but use only the CN if it is
 330                  * prefixed by the O, or a significant portion thereof.
 331                  */
 332                 namesize = ctx->cn_size;
 333                 name = data + ctx->cn_offset;
 334                 if (ctx->cn_size >= ctx->o_size &&
 335                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 336                            ctx->o_size) == 0)
 337                         goto single_component;
 338                 if (ctx->cn_size >= 7 &&
 339                     ctx->o_size >= 7 &&
 340                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 341                         goto single_component;
 342
 343                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 344                                  GFP_KERNEL);
 345                 if (!buffer)
 346                         return -ENOMEM;
 347
 348                 memcpy(buffer,
 349                        data + ctx->o_offset, ctx->o_size);
 350                 buffer[ctx->o_size + 0] = ':';
 351                 buffer[ctx->o_size + 1] = ' ';
 352                 memcpy(buffer + ctx->o_size + 2,
 353                        data + ctx->cn_offset, ctx->cn_size);
 354                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 355                 goto done;
 356
 357         } else if (ctx->cn_size) {
 358                 namesize = ctx->cn_size;
 359                 name = data + ctx->cn_offset;
 360         } else if (ctx->o_size) {
 361                 namesize = ctx->o_size;
 362                 name = data + ctx->o_offset;
 363         } else {
 364                 namesize = ctx->email_size;
 365                 name = data + ctx->email_offset;
 366         }
 367
 368 single_component:
 369         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 370         if (!buffer)
 371                 return -ENOMEM;
 372         memcpy(buffer, name, namesize);
 373         buffer[namesize] = 0;
 374
 375 done:
 376         *_name = buffer;
 377         ctx->cn_size = 0;
 378         ctx->o_size = 0;
 379         ctx->email_size = 0;
 380         return 0;
 381 }
 382
 383 int x509_note_issuer(void *context, size_t hdrlen,
 384                      unsigned char tag,
 385                      const void *value, size_t vlen)
 386 {
 387         struct x509_parse_context *ctx = context;
 388         ctx->cert->raw_issuer = value;
 389         ctx->cert->raw_issuer_size = vlen;
 390         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 391 }
 392
 393 int x509_note_subject(void *context, size_t hdrlen,
 394                       unsigned char tag,
 395                       const void *value, size_t vlen)
 396 {
 397         struct x509_parse_context *ctx = context;
 398         ctx->cert->raw_subject = value;
 399         ctx->cert->raw_subject_size = vlen;
 400         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 401 }
 402
 403 /*
 404  * Extract the data for the public key algorithm
 405  */
 406 int x509_extract_key_data(void *context, size_t hdrlen,
 407                           unsigned char tag,
 408                           const void *value, size_t vlen)
 409 {
 410         struct x509_parse_context *ctx = context;
 411
 412         if (ctx->last_oid != OID_rsaEncryption)
 413                 return -ENOPKG;
 414
 415         ctx->cert->pub->pkey_algo = "rsa";
 416
 417         /* Discard the BIT STRING metadata */
 418         if (vlen < 1 || *(const u8 *)value != 0)
 419                 return -EBADMSG;
 420         ctx->key = value + 1;
 421         ctx->key_size = vlen - 1;
 422         return 0;
 423 }
 424
 425 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
 426 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
 427
 428 /*
 429  * Process certificate extensions that are used to qualify the certificate.
 430  */
 431 int x509_process_extension(void *context, size_t hdrlen,
 432                            unsigned char tag,
 433                            const void *value, size_t vlen)
 434 {
 435         struct x509_parse_context *ctx = context;
 436         struct asymmetric_key_id *kid;
 437         const unsigned char *v = value;
 438
 439         pr_debug("Extension: %u\n", ctx->last_oid);
 440
 441         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 442                 /* Get hold of the key fingerprint */
 443                 if (ctx->cert->skid || vlen < 3)
 444                         return -EBADMSG;
 445                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 446                         return -EBADMSG;
 447                 v += 2;
 448                 vlen -= 2;
 449
 450                 ctx->cert->raw_skid_size = vlen;
 451                 ctx->cert->raw_skid = v;
 452                 kid = asymmetric_key_generate_id(v, vlen, "", 0);
 453                 if (IS_ERR(kid))
 454                         return PTR_ERR(kid);
 455                 ctx->cert->skid = kid;
 456                 pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
 457                 return 0;
 458         }
 459
 460         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 461                 /* Get hold of the CA key fingerprint */
 462                 ctx->raw_akid = v;
 463                 ctx->raw_akid_size = vlen;
 464                 return 0;
 465         }
 466
 467         return 0;
 468 }
 469
 470 /**
 471  * x509_decode_time - Decode an X.509 time ASN.1 object
 472  * @_t: The time to fill in
 473  * @hdrlen: The length of the object header
 474  * @tag: The object tag
 475  * @value: The object value
 476  * @vlen: The size of the object value
 477  *
 478  * Decode an ASN.1 universal time or generalised time field into a struct the
 479  * kernel can handle and check it for validity.  The time is decoded thus:
 480  *
 481  *      [RFC5280 §4.1.2.5]
 482  *      CAs conforming to this profile MUST always encode certificate validity
 483  *      dates through the year 2049 as UTCTime; certificate validity dates in
 484  *      2050 or later MUST be encoded as GeneralizedTime.  Conforming
 485  *      applications MUST be able to process validity dates that are encoded in
 486  *      either UTCTime or GeneralizedTime.
 487  */
 488 int x509_decode_time(time64_t *_t,  size_t hdrlen,
 489                      unsigned char tag,
 490                      const unsigned char *value, size_t vlen)
 491 {
 492         static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
 493                                                        31, 31, 30, 31, 30, 31 };
 494         const unsigned char *p = value;
 495         unsigned year, mon, day, hour, min, sec, mon_len;
 496
 497 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
 498 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 499
 500         if (tag == ASN1_UNITIM) {
 501                 /* UTCTime: YYMMDDHHMMSSZ */
 502                 if (vlen != 13)
 503                         goto unsupported_time;
 504                 year = DD2bin(p);
 505                 if (year >= 50)
 506                         year += 1900;
 507                 else
 508                         year += 2000;
 509         } else if (tag == ASN1_GENTIM) {
 510                 /* GenTime: YYYYMMDDHHMMSSZ */
 511                 if (vlen != 15)
 512                         goto unsupported_time;
 513                 year = DD2bin(p) * 100 + DD2bin(p);
 514                 if (year >= 1950 && year <= 2049)
 515                         goto invalid_time;
 516         } else {
 517                 goto unsupported_time;
 518         }
 519
 520         mon  = DD2bin(p);
 521         day = DD2bin(p);
 522         hour = DD2bin(p);
 523         min  = DD2bin(p);
 524         sec  = DD2bin(p);
 525
 526         if (*p != 'Z')
 527                 goto unsupported_time;
 528
 529         if (year < 1970 ||
 530             mon < 1 || mon > 12)
 531                 goto invalid_time;
 532
 533         mon_len = month_lengths[mon - 1];
 534         if (mon == 2) {
 535                 if (year % 4 == 0) {
 536                         mon_len = 29;
 537                         if (year % 100 == 0) {
 538                                 mon_len = 28;
 539                                 if (year % 400 == 0)
 540                                         mon_len = 29;
 541                         }
 542                 }
 543         }
 544
 545         if (day < 1 || day > mon_len ||
 546             hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
 547             min > 59 ||
 548             sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
 549                 goto invalid_time;
 550
 551         *_t = mktime64(year, mon, day, hour, min, sec);
 552         return 0;
 553
 554 unsupported_time:
 555         pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
 556                  tag, (int)vlen, value);
 557         return -EBADMSG;
 558 invalid_time:
 559         pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
 560                  tag, (int)vlen, value);
 561         return -EBADMSG;
 562 }
 563 EXPORT_SYMBOL_GPL(x509_decode_time);
 564
 565 int x509_note_not_before(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_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 571 }
 572
 573 int x509_note_not_after(void *context, size_t hdrlen,
 574                         unsigned char tag,
 575                         const void *value, size_t vlen)
 576 {
 577         struct x509_parse_context *ctx = context;
 578         return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 579 }
 580
 581 /*
 582  * Note a key identifier-based AuthorityKeyIdentifier
 583  */
 584 int x509_akid_note_kid(void *context, size_t hdrlen,
 585                        unsigned char tag,
 586                        const void *value, size_t vlen)
 587 {
 588         struct x509_parse_context *ctx = context;
 589         struct asymmetric_key_id *kid;
 590
 591         pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
 592
 593         if (ctx->cert->sig->auth_ids[1])
 594                 return 0;
 595
 596         kid = asymmetric_key_generate_id(value, vlen, "", 0);
 597         if (IS_ERR(kid))
 598                 return PTR_ERR(kid);
 599         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 600         ctx->cert->sig->auth_ids[1] = kid;
 601         return 0;
 602 }
 603
 604 /*
 605  * Note a directoryName in an AuthorityKeyIdentifier
 606  */
 607 int x509_akid_note_name(void *context, size_t hdrlen,
 608                         unsigned char tag,
 609                         const void *value, size_t vlen)
 610 {
 611         struct x509_parse_context *ctx = context;
 612
 613         pr_debug("AKID: name: %*phN\n", (int)vlen, value);
 614
 615         ctx->akid_raw_issuer = value;
 616         ctx->akid_raw_issuer_size = vlen;
 617         return 0;
 618 }
 619
 620 /*
 621  * Note a serial number in an AuthorityKeyIdentifier
 622  */
 623 int x509_akid_note_serial(void *context, size_t hdrlen,
 624                           unsigned char tag,
 625                           const void *value, size_t vlen)
 626 {
 627         struct x509_parse_context *ctx = context;
 628         struct asymmetric_key_id *kid;
 629
 630         pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
 631
 632         if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
 633                 return 0;
 634
 635         kid = asymmetric_key_generate_id(value,
 636                                          vlen,
 637                                          ctx->akid_raw_issuer,
 638                                          ctx->akid_raw_issuer_size);
 639         if (IS_ERR(kid))
 640                 return PTR_ERR(kid);
 641
 642         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 643         ctx->cert->sig->auth_ids[0] = kid;
 644         return 0;
 645 }