mdw@git.distorted.org.uk Git - tripe/blob - server/keymgmt.c

   1 /* -*-c-*-
   2  *
   3  * Key loading and storing
   4  *
   5  * (c) 2001 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Trivial IP Encryption (TrIPE).
  11  *
  12  * TrIPE is free software: you can redistribute it and/or modify it under
  13  * the terms of the GNU General Public License as published by the Free
  14  * Software Foundation; either version 3 of the License, or (at your
  15  * option) any later version.
  16  *
  17  * TrIPE is distributed in the hope that it will be useful, but WITHOUT
  18  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20  * for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with TrIPE.  If not, see <https://www.gnu.org/licenses/>.
  24  */
  25
  26 /*----- Header files ------------------------------------------------------*/
  27
  28 #include "tripe.h"
  29
  30 /*----- Algswitch stuff ---------------------------------------------------*/
  31
  32 /* --- @algs_get@ --- *
  33  *
  34  * Arguments:   @algswitch *a@ = where to put the algorithms
  35  *              @dstr *e@ = where to write error tokens
  36  *              @key_file *kf@ = key file
  37  *              @key *k@ = key to inspect
  38  *
  39  * Returns:     Zero if OK; nonzero on error.
  40  *
  41  * Use:         Extracts an algorithm choice from a key.
  42  */
  43
  44 static int algs_get(algswitch *a, dstr *e, key_file *kf, key *k)
  45 {
  46   const char *p;
  47   const bulkops *bops;
  48   dstr d = DSTR_INIT, dd = DSTR_INIT;
  49   int rc = -1;
  50
  51   /* --- Hash function --- */
  52
  53   if ((p = key_getattr(kf, k, "hash")) == 0) p = "rmd160";
  54   if ((a->h = ghash_byname(p)) == 0) {
  55     a_format(e, "unknown-hash", "%s", p, A_END);
  56     goto done;
  57   }
  58
  59   /* --- Symmetric encryption for key derivation --- */
  60
  61   if ((p = key_getattr(kf, k, "mgf")) == 0) {
  62     dstr_reset(&d);
  63     dstr_putf(&d, "%s-mgf", a->h->name);
  64     p = d.buf;
  65   }
  66   if ((a->mgf = gcipher_byname(p)) == 0) {
  67     a_format(e, "unknown-mgf-cipher", "%s", p, A_END);
  68     goto done;
  69   }
  70
  71   /* --- Bulk crypto transform --- */
  72
  73   if ((p = key_getattr(kf, k, "bulk")) == 0) p = "v0";
  74   for (bops = bulktab; bops->name && strcmp(p, bops->name) != 0; bops++);
  75   if (!bops->name) {
  76     a_format(e, "unknown-bulk-transform", "%s", p, A_END);
  77     goto done;
  78   }
  79   if ((a->bulk = bops->getalgs(a, e, kf, k)) == 0) goto done;
  80   a->bulk->ops = bops;
  81
  82   /* --- All done --- */
  83
  84   rc = 0;
  85 done:
  86   dstr_destroy(&d);
  87   dstr_destroy(&dd);
  88   return (rc);
  89 }
  90
  91 /* --- @algs_check@ --- *
  92  *
  93  * Arguments:   @algswitch *a@ = a choice of algorithms
  94  *              @dstr *e@ = where to write error tokens
  95  *              @const dhgrp *grp@ = the group we're working in
  96  *
  97  * Returns:     Zero if OK; nonzero on error.
  98  *
  99  * Use:         Checks an algorithm choice for sensibleness.  This also
 100  *              derives some useful information from the choices, and you
 101  *              must call this before committing the algorithm selection
 102  *              for use by @keyset@ functions.
 103  */
 104
 105 static int algs_check(algswitch *a, dstr *e, const dhgrp *grp)
 106 {
 107   a->hashsz = a->h->hashsz;
 108
 109   if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz) {
 110     a_format(e, "mgf", "%s", a->mgf->name,
 111              "restrictive-key-schedule",
 112              A_END);
 113     return (-1);
 114   }
 115
 116   if (a->bulk->ops->checkalgs(a->bulk, a, e)) return (-1);
 117
 118   return (0);
 119 }
 120
 121 /* --- @km_samealgsp@ --- *
 122  *
 123  * Arguments:   @const kdata *kdx, *kdy@ = two key data objects
 124  *
 125  * Returns:     Nonzero if their two algorithm selections are the same.
 126  *
 127  * Use:         Checks sameness of algorithm selections: used to ensure that
 128  *              peers are using sensible algorithms.
 129  */
 130
 131 int km_samealgsp(const kdata *kdx, const kdata *kdy)
 132 {
 133   const algswitch *a = &kdx->algs, *aa = &kdy->algs;
 134
 135   return (kdx->grp->ops == kdy->grp->ops &&
 136           kdx->grp->ops->samegrpp(kdx->grp, kdy->grp) &&
 137           a->mgf == aa->mgf && a->h == aa->h &&
 138           a->bulk->ops == aa->bulk->ops &&
 139           a->bulk->ops->samealgsp(a->bulk, aa->bulk));
 140 }
 141
 142 /*----- Key data and key nodes --------------------------------------------*/
 143
 144 typedef struct keyhalf {
 145   const char *kind;
 146   int (*load)(key_file *, key *, key_data *,
 147               const dhops *, kdata *, dstr *, dstr *);
 148   const char *kr;
 149   key_file *kf;
 150   fwatch w;
 151   sym_table tab;
 152 } keyhalf;
 153
 154 /* --- @kh_loadpub@, @kh_loadpriv@ --- *
 155  *
 156  * Arguments:   @const dhops *dh@ = Diffie--Hellman operations for key type
 157  *              @key_file *kf@ = key file from which the key was loaded
 158  *              @key *k@ = the key object we're loading
 159  *              @key_data *d@ = the key data to load
 160  *              @kdata *kd@ = our key-data object to fill in
 161  *              @dstr *t@ = the key tag name
 162  *              @dstr *e@ = a string to write error tokens to
 163  *
 164  * Returns:     Zero on success, @-1@ on error.
 165  *
 166  * Use:         These functions handle the main difference between public and
 167  *              private key halves.  They are responsible for setting @grp@,
 168  *              @k@ and @K@ appropriately in all keys, handling the mismatch
 169  *              between the largely half-indifferent calling code and the
 170  *              group-specific loading functions.
 171  *
 172  *              The function @kh_loadpriv@ is also responsible for checking
 173  *              the group for goodness.  We don't bother checking public
 174  *              keys, because each public key we actually end up using must
 175  *              share a group with a private key which we'll already have
 176  *              checked.
 177  */
 178
 179 static int kh_loadpub(key_file *kf, key *k, key_data *d,
 180                       const dhops *dh, kdata *kd, dstr *t, dstr *e)
 181 {
 182   int rc;
 183
 184   if ((rc = dh->ldpub(kf, k, d, kd, t, e)) != 0)
 185     goto fail_0;
 186   kd->grp->ops = dh;
 187   if (kd->grp->ops->checkge(kd->grp, kd->K)) {
 188     a_format(e, "bad-public-group-element", A_END);
 189     goto fail_1;
 190   }
 191   return (0);
 192
 193 fail_1:
 194   kd->grp->ops->freege(kd->grp, kd->K);
 195   kd->grp->ops->freegrp(kd->grp);
 196 fail_0:
 197   return (-1);
 198 }
 199
 200 static int kh_loadpriv(key_file *kf, key *k, key_data *d,
 201                        const dhops *dh, kdata *kd, dstr *t, dstr *e)
 202 {
 203   int rc;
 204   const char *err;
 205   dhge *K;
 206   int ok;
 207
 208   if ((rc = dh->ldpriv(kf, k, d, kd, t, e)) != 0)
 209     goto fail_0;
 210   kd->grp->ops = dh;
 211   if ((err = kd->grp->ops->checkgrp(kd->grp)) != 0) {
 212     a_format(e, "bad-group", "%s", err, A_END);
 213     goto fail_1;
 214   }
 215   K = kd->grp->ops->mul(kd->grp, kd->k, 0);
 216   ok = kd->grp->ops->eq(kd->grp, kd->K, K);
 217   kd->grp->ops->freege(kd->grp, K);
 218   if (!ok) {
 219     a_format(e, "incorrect-public-key", A_END);
 220     goto fail_1;
 221   }
 222   return (0);
 223
 224 fail_1:
 225   kd->grp->ops->freesc(kd->grp, kd->k);
 226   kd->grp->ops->freege(kd->grp, kd->K);
 227   kd->grp->ops->freegrp(kd->grp);
 228 fail_0:
 229   return (-1);
 230 }
 231
 232 static struct keyhalf
 233   priv = { "private", kh_loadpriv },
 234   pub = { "public", kh_loadpub };
 235
 236 /* --- @keymoan@ --- *
 237  *
 238  * Arguments:   @const char *file@ = name of the file
 239  *              @int line@ = line number in file
 240  *              @const char *msg@ = error message
 241  *              @void *p@ = argument pointer (indicates which keyring)
 242  *
 243  * Returns:     ---
 244  *
 245  * Use:         Reports an error message about loading a key file.
 246  */
 247
 248 static void keymoan(const char *file, int line, const char *msg, void *p)
 249 {
 250   keyhalf *kh = p;
 251
 252   if (!line) {
 253     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file,
 254            "io-error", "?ERRNO", A_END);
 255   } else {
 256     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file, "line", "%d", line,
 257            "%s", msg, A_END);
 258   }
 259 }
 260
 261 /* --- @kh_reopen@ --- *
 262  *
 263  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure
 264  *
 265  * Returns:     Zero on success, @-1@ on error.
 266  *
 267  * Use:         Reopens the key file for the appropriate key half.  If this
 268  *              fails, everything is left as it was; if it succeeds, then the
 269  *              old file is closed (if it was non-null) and the new one put
 270  *              in its place.
 271  */
 272
 273 static int kh_reopen(keyhalf *kh)
 274 {
 275   key_file *kf = CREATE(key_file);
 276
 277   if (key_open(kf, kh->kr, KOPEN_READ, keymoan, kh)) {
 278     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 279            "io-error", "?ERRNO", A_END);
 280     DESTROY(kf);
 281     return (-1);
 282   } else {
 283     if (kh->kf) {
 284       key_close(kh->kf);
 285       DESTROY(kh->kf);
 286     }
 287     kh->kf = kf;
 288     return (0);
 289   }
 290 }
 291
 292 /* --- @kh_init@ --- *
 293  *
 294  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure to set up
 295  *              @const char *kr@ = name of the keyring file
 296  *
 297  * Returns:     ---
 298  *
 299  * Use:         Initialize a keyhalf structure, maintaining the private or
 300  *              public keys.  Intended to be called during initialization:
 301  *              exits if there's some kind of problem.
 302  */
 303
 304 static void kh_init(keyhalf *kh, const char *kr)
 305 {
 306   kh->kr = kr;
 307   fwatch_init(&kh->w, kr);
 308   sym_create(&kh->tab);
 309   kh->kf = 0;
 310
 311   if (kh_reopen(kh))
 312     die(EXIT_FAILURE, "failed to load %s keyring `%s'", kh->kind, kr);
 313 }
 314
 315 /* --- @kh_load@ --- *
 316  *
 317  * Arguments:   @keyhalf *kh@ = pointer to keyhalf
 318  *              @const char *tag@ = key tag to be loaded
 319  *              @int complainp@ = whether to complain about missing keys
 320  *
 321  * Returns:     Pointer to a @kdata@ structure if successful, or null on
 322  *              failure.
 323  *
 324  * Use:         Attempts to load a key from the current key file.  This
 325  *              function always reads data from the file: it's used when
 326  *              there's a cache miss from @kh_find@, and when refreshing the
 327  *              known keys in @kh_refresh@.  The returned kdata has a
 328  *              reference count of exactly 1, and has no home knode.
 329  */
 330
 331 static kdata *kh_load(keyhalf *kh, const char *tag, int complainp)
 332 {
 333   dstr t = DSTR_INIT;
 334   dstr e = DSTR_INIT;
 335   key *k;
 336   key_data **d;
 337   kdata *kd;
 338   const char *ty;
 339   const dhops *dh;
 340   T( const dhgrp *g; )
 341
 342   /* --- Find the key and grab its tag --- */
 343
 344   if (key_qtag(kh->kf, tag, &t, &k, &d)) {
 345     if (complainp) {
 346       a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 347              "key-not-found", "%s", tag, A_END);
 348     }
 349     goto fail_0;
 350   }
 351
 352   /* --- Find the key's group type and the appropriate operations --- *
 353    *
 354    * There are several places to look for the key type.  The most obvious is
 355    * the `kx-group' key attribute.  But there's also the key type itself, for
 356    * compatibility reasons.
 357    */
 358
 359   ty = key_getattr(kh->kf, k, "kx-group");
 360   if (!ty && strncmp(k->type, "tripe-", 6) == 0) ty = k->type + 6;
 361   if (!ty) ty = "dh";
 362
 363   for (dh = dhtab; dh->name; dh++)
 364     if (strcmp(dh->name, ty) == 0) goto founddh;
 365   a_warn("KEYMGMT", "%s-keyring", kh->kind,
 366          "%s", kh->kr, "key", "%s", t.buf,
 367          "unknown-group-type", "%s", ty, A_END);
 368   goto fail_0;
 369
 370 founddh:
 371   kd = CREATE(kdata);
 372   if (kh->load(kh->kf, k, *d, dh, kd, &t, &e)) {
 373     a_warn("KEYMGMT", "%s-keyring", kh->kind,
 374            "%s", kh->kr, "key", "%s", t.buf,
 375            "*%s", e.buf, A_END);
 376     goto fail_1;
 377   }
 378
 379   if (algs_get(&kd->algs, &e, kh->kf, k) ||
 380       algs_check(&kd->algs, &e, kd->grp)) {
 381     a_warn("KEYMGMT", "%s-keyring", kh->kind,
 382            "%s", kh->kr, "key", "%s", t.buf,
 383            "*%s", e.buf, A_END);
 384     goto fail_2;
 385   }
 386
 387   kd->tag = xstrdup(t.buf);
 388   kd->ref = 1;
 389   kd->kn = 0;
 390   kd->t_exp = k->exp;
 391
 392   IF_TRACING(T_KEYMGMT, {
 393     trace(T_KEYMGMT, "keymgmt: loaded %s key `%s'", kh->kind, t.buf);
 394     IF_TRACING(T_CRYPTO, {
 395       g = kd->grp;
 396       g->ops->tracegrp(g);
 397       if (kd->k)
 398         trace(T_CRYPTO, "crypto: k = %s", g->ops->scstr(g, kd->k));
 399       trace(T_CRYPTO, "crypto: K = %s", g->ops->gestr(g, kd->K));
 400       kd->algs.bulk->ops->tracealgs(kd->algs.bulk);
 401     })
 402   })
 403
 404   goto done;
 405
 406 fail_2:
 407   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 408   kd->grp->ops->freege(kd->grp, kd->K);
 409   kd->grp->ops->freegrp(kd->grp);
 410 fail_1:
 411   DESTROY(kd);
 412 fail_0:
 413   kd = 0;
 414 done:
 415   dstr_destroy(&t);
 416   dstr_destroy(&e);
 417   return (kd);
 418 }
 419
 420 /* --- @kh_find@ --- *
 421  *
 422  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 423  *              @const char *tag@ = key to be obtained
 424  *              @int complainp@ = whether to complain about missing keys
 425  *
 426  * Returns:     A pointer to the kdata, or null on error.
 427  *
 428  * Use:         Obtains kdata, maybe from the cache.  This won't update a
 429  *              stale cache entry, though @kh_refresh@ ought to have done
 430  *              that already.  The returned kdata object may be shared with
 431  *              other users.  (One of this function's responsibilities, over
 432  *              @kh_load@, is to set the home knode of a freshly loaded
 433  *              kdata.)
 434  */
 435
 436 static kdata *kh_find(keyhalf *kh, const char *tag, int complainp)
 437 {
 438   knode *kn;
 439   kdata *kd;
 440   unsigned f;
 441
 442   kn = sym_find(&kh->tab, tag, -1, sizeof(knode), &f);
 443
 444   if (f) {
 445     if (kn->f & KNF_BROKEN) {
 446       T( if (complainp)
 447            trace(T_KEYMGMT, "keymgmt: key `%s' marked as broken", tag); )
 448       return (0);
 449     }
 450
 451     kd = kn->kd;
 452     if (kd) kd->ref++;
 453     T( trace(T_KEYMGMT, "keymgmt: %scache hit for key `%s'",
 454              kd ? "" : "negative ", tag); )
 455     return (kd);
 456   } else {
 457     kd = kh_load(kh, tag, complainp);
 458     kn->kd = kd;
 459     kn->kh = kh;
 460     kn->f = 0;
 461     if (!kd)
 462       kn->f |= KNF_BROKEN;
 463     else {
 464       kd->kn = kn;
 465       kd->ref++;
 466     }
 467     return (kd);
 468   }
 469 }
 470
 471 /* --- @kh_refresh@ --- *
 472  *
 473  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 474  *
 475  * Returns:     Zero if nothing needs to be done; nonzero if peers should
 476  *              refresh their keys.
 477  *
 478  * Use:         Refreshes cached keys from files.
 479  *
 480  *              Each active knode is examined to see if a new key is
 481  *              available: the return value is nonzero if any new keys are.
 482  *              A key is considered new if its algorithms, public key, or
 483  *              expiry time are/is different.
 484  *
 485  *              Stub knodes (with no kdata attached) are removed, so that a
 486  *              later retry can succeed if the file has been fixed.  (This
 487  *              doesn't count as a change, since no peers should be relying
 488  *              on a nonexistent key.)
 489  */
 490
 491 static int kh_refresh(keyhalf *kh)
 492 {
 493   knode *kn;
 494   kdata *kd;
 495   sym_iter i;
 496   int changep = 0;
 497
 498   if (!fwatch_update(&kh->w, kh->kr) || kh_reopen(kh))
 499     return (0);
 500
 501   T( trace(T_KEYMGMT, "keymgmt: rescan %s keyring `%s'", kh->kind, kh->kr); )
 502   for (sym_mkiter(&i, &kh->tab); (kn = sym_next(&i)) != 0; ) {
 503     if (!kn->kd) {
 504       T( trace(T_KEYMGMT, "keymgmt: discard stub entry for key `%s'",
 505                SYM_NAME(kn)); )
 506       sym_remove(&kh->tab, kn);
 507       continue;
 508     }
 509     if ((kd = kh_load(kh, SYM_NAME(kn), 1)) == 0) {
 510       if (!(kn->f & KNF_BROKEN)) {
 511         T( trace(T_KEYMGMT, "keymgmt: failed to load new key `%s': "
 512                  "marking it as broken",
 513                  SYM_NAME(kn)); )
 514         kn->f |= KNF_BROKEN;
 515       }
 516       continue;
 517     }
 518     kn->f &= ~KNF_BROKEN;
 519     if (kd->t_exp == kn->kd->t_exp &&
 520         km_samealgsp(kd, kn->kd) &&
 521         kd->grp->ops->eq(kd->grp, kd->K, kn->kd->K)) {
 522       T( trace(T_KEYMGMT, "keymgmt: key `%s' unchanged", SYM_NAME(kn)); )
 523       continue;
 524     }
 525     T( trace(T_KEYMGMT, "keymgmt: loaded new version of key `%s'",
 526              SYM_NAME(kn)); )
 527     km_unref(kn->kd);
 528     kd->kn = kn;
 529     kn->kd = kd;
 530     changep = 1;
 531   }
 532
 533   return (changep);
 534 }
 535
 536 /*----- Main code ---------------------------------------------------------*/
 537
 538 const char *tag_priv;
 539 kdata *master;
 540
 541 /* --- @km_init@ --- *
 542  *
 543  * Arguments:   @const char *privkr@ = private keyring file
 544  *              @const char *pubkr@ = public keyring file
 545  *              @const char *ptag@ = default private-key tag
 546  *
 547  * Returns:     ---
 548  *
 549  * Use:         Initializes the key-management machinery, loading the
 550  *              keyrings and so on.
 551  */
 552
 553 void km_init(const char *privkr, const char *pubkr, const char *ptag)
 554 {
 555   const gchash *const *hh;
 556
 557   for (hh = ghashtab; *hh; hh++) {
 558     if ((*hh)->hashsz > MAXHASHSZ) {
 559       die(EXIT_FAILURE, "INTERNAL ERROR: %s hash length %lu > MAXHASHSZ %d",
 560           (*hh)->name, (unsigned long)(*hh)->hashsz, MAXHASHSZ);
 561     }
 562   }
 563
 564   kh_init(&priv, privkr);
 565   kh_init(&pub, pubkr);
 566
 567   tag_priv = ptag;
 568   if ((master = km_findpriv(ptag)) == 0) exit(EXIT_FAILURE);
 569 }
 570
 571 /* --- @km_reload@ --- *
 572  *
 573  * Arguments:   ---
 574  *
 575  * Returns:     Zero if OK, nonzero to force reloading of keys.
 576  *
 577  * Use:         Checks the keyrings to see if they need reloading.
 578  */
 579
 580 int km_reload(void)
 581 {
 582   int changep = 0;
 583   kdata *kd;
 584
 585   if (kh_refresh(&priv)) {
 586     changep = 1;
 587     kd = master->kn->kd;
 588     if (kd != master) {
 589       km_unref(master);
 590       km_ref(kd);
 591       master = kd;
 592     }
 593   }
 594   if (kh_refresh(&pub))
 595     changep = 1;
 596   return (changep);
 597 }
 598
 599 /* --- @km_findpub@, @km_findpriv@ --- *
 600  *
 601  * Arguments:   @const char *tag@ = key tag to load
 602  *
 603  * Returns:     Pointer to the kdata object if successful, or null on error.
 604  *
 605  * Use:         Fetches a public or private key from the keyring.
 606  */
 607
 608 kdata *km_findpub(const char *tag) { return (kh_find(&pub, tag, 1)); }
 609
 610 kdata *km_findpriv(const char *tag)
 611 {
 612   kdata *kd;
 613
 614   /* Unpleasantness for the sake of compatibility. */
 615   if (!tag && (kd = kh_find(&priv, "tripe", 0)) != 0) return (kd);
 616   else return (kh_find(&priv, tag ? tag : "tripe-dh", 1));
 617 }
 618
 619 /* --- @km_tag@ --- *
 620  *
 621  * Arguments:   @kdata *kd@ - pointer to the kdata object
 622  *
 623  * Returns:     A pointer to the short tag by which the kdata was loaded.
 624  */
 625
 626 const char *km_tag(kdata *kd) { return (SYM_NAME(kd->kn)); }
 627
 628 /* --- @km_ref@ --- *
 629  *
 630  * Arguments:   @kdata *kd@ = pointer to the kdata object
 631  *
 632  * Returns:     ---
 633  *
 634  * Use:         Claim a new reference to a kdata object.
 635  */
 636
 637 void km_ref(kdata *kd) { kd->ref++; }
 638
 639 /* --- @km_unref@ --- *
 640  *
 641  * Arguments:   @kdata *kd@ = pointer to the kdata object
 642  *
 643  * Returns:     ---
 644  *
 645  * Use:         Releases a reference to a kdata object.
 646  */
 647
 648 void km_unref(kdata *kd)
 649 {
 650   if (--kd->ref) return;
 651   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 652   kd->grp->ops->freege(kd->grp, kd->K);
 653   kd->grp->ops->freegrp(kd->grp);
 654   xfree(kd->tag);
 655   DESTROY(kd);
 656 }
 657
 658 /*----- That's all, folks -------------------------------------------------*/