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
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * TrIPE is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with TrIPE; if not, write to the Free Software Foundation,
  24  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25  */
  26
  27 /*----- Header files ------------------------------------------------------*/
  28
  29 #include "tripe.h"
  30
  31 /*----- Algswitch stuff ---------------------------------------------------*/
  32
  33 /* --- @algs_get@ --- *
  34  *
  35  * Arguments:   @algswitch *a@ = where to put the algorithms
  36  *              @dstr *e@ = where to write error tokens
  37  *              @key_file *kf@ = key file
  38  *              @key *k@ = key to inspect
  39  *
  40  * Returns:     Zero if OK; nonzero on error.
  41  *
  42  * Use:         Extracts an algorithm choice from a key.
  43  */
  44
  45 static int algs_get(algswitch *a, dstr *e, key_file *kf, key *k)
  46 {
  47   const char *p;
  48   const bulkops *bops;
  49   dstr d = DSTR_INIT, dd = DSTR_INIT;
  50   int rc = -1;
  51
  52   /* --- Hash function --- */
  53
  54   if ((p = key_getattr(kf, k, "hash")) == 0) p = "rmd160";
  55   if ((a->h = ghash_byname(p)) == 0) {
  56     a_format(e, "unknown-hash", "%s", p, A_END);
  57     goto done;
  58   }
  59
  60   /* --- Symmetric encryption for key derivation --- */
  61
  62   if ((p = key_getattr(kf, k, "mgf")) == 0) {
  63     dstr_reset(&d);
  64     dstr_putf(&d, "%s-mgf", a->h->name);
  65     p = d.buf;
  66   }
  67   if ((a->mgf = gcipher_byname(p)) == 0) {
  68     a_format(e, "unknown-mgf-cipher", "%s", p, A_END);
  69     goto done;
  70   }
  71
  72   /* --- Bulk crypto transform --- */
  73
  74   if ((p = key_getattr(kf, k, "bulk")) == 0) p = "v0";
  75   for (bops = bulktab; bops->name && strcmp(p, bops->name) != 0; bops++);
  76   if (!bops->name) {
  77     a_format(e, "unknown-bulk-transform", "%s", p, A_END);
  78     goto done;
  79   }
  80   if ((a->bulk = bops->getalgs(a, e, kf, k)) == 0) goto done;
  81   a->bulk->ops = bops;
  82
  83   /* --- All done --- */
  84
  85   rc = 0;
  86 done:
  87   dstr_destroy(&d);
  88   dstr_destroy(&dd);
  89   return (rc);
  90 }
  91
  92 /* --- @algs_check@ --- *
  93  *
  94  * Arguments:   @algswitch *a@ = a choice of algorithms
  95  *              @dstr *e@ = where to write error tokens
  96  *              @const dhgrp *grp@ = the group we're working in
  97  *
  98  * Returns:     Zero if OK; nonzero on error.
  99  *
 100  * Use:         Checks an algorithm choice for sensibleness.  This also
 101  *              derives some useful information from the choices, and you
 102  *              must call this before committing the algorithm selection
 103  *              for use by @keyset@ functions.
 104  */
 105
 106 static int algs_check(algswitch *a, dstr *e, const dhgrp *grp)
 107 {
 108   a->hashsz = a->h->hashsz;
 109
 110   if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz) {
 111     a_format(e, "mgf", "%s", a->mgf->name,
 112              "restrictive-key-schedule",
 113              A_END);
 114     return (-1);
 115   }
 116
 117   if (a->bulk->ops->checkalgs(a->bulk, a, e)) return (-1);
 118
 119   return (0);
 120 }
 121
 122 /* --- @km_samealgsp@ --- *
 123  *
 124  * Arguments:   @const kdata *kdx, *kdy@ = two key data objects
 125  *
 126  * Returns:     Nonzero if their two algorithm selections are the same.
 127  *
 128  * Use:         Checks sameness of algorithm selections: used to ensure that
 129  *              peers are using sensible algorithms.
 130  */
 131
 132 int km_samealgsp(const kdata *kdx, const kdata *kdy)
 133 {
 134   const algswitch *a = &kdx->algs, *aa = &kdy->algs;
 135
 136   return (kdx->grp->ops == kdy->grp->ops &&
 137           kdx->grp->ops->samegrpp(kdx->grp, kdy->grp) &&
 138           a->mgf == aa->mgf && a->h == aa->h &&
 139           a->bulk->ops == aa->bulk->ops &&
 140           a->bulk->ops->samealgsp(a->bulk, aa->bulk));
 141 }
 142
 143 /*----- Key data and key nodes --------------------------------------------*/
 144
 145 typedef struct keyhalf {
 146   const char *kind;
 147   int (*load)(key_file *, key *, key_data *,
 148               const dhops *, kdata *, dstr *, dstr *);
 149   const char *kr;
 150   key_file *kf;
 151   fwatch w;
 152   sym_table tab;
 153 } keyhalf;
 154
 155 /* --- @kh_loadpub@, @kh_loadpriv@ --- *
 156  *
 157  * Arguments:   @const dhops *dh@ = Diffie--Hellman operations for key type
 158  *              @key_file *kf@ = key file from which the key was loaded
 159  *              @key *k@ = the key object we're loading
 160  *              @key_data *d@ = the key data to load
 161  *              @kdata *kd@ = our key-data object to fill in
 162  *              @dstr *t@ = the key tag name
 163  *              @dstr *e@ = a string to write error tokens to
 164  *
 165  * Returns:     Zero on success, @-1@ on error.
 166  *
 167  * Use:         These functions handle the main difference between public and
 168  *              private key halves.  They are responsible for setting @grp@,
 169  *              @k@ and @K@ appropriately in all keys, handling the mismatch
 170  *              between the largely half-indifferent calling code and the
 171  *              group-specific loading functions.
 172  *
 173  *              The function @kh_loadpriv@ is also responsible for checking
 174  *              the group for goodness.  We don't bother checking public
 175  *              keys, because each public key we actually end up using must
 176  *              share a group with a private key which we'll already have
 177  *              checked.
 178  */
 179
 180 static int kh_loadpub(key_file *kf, key *k, key_data *d,
 181                       const dhops *dh, kdata *kd, dstr *t, dstr *e)
 182 {
 183   int rc;
 184
 185   if ((rc = dh->ldpub(kf, k, d, kd, t, e)) != 0)
 186     goto fail_0;
 187   kd->grp->ops = dh;
 188   if (kd->grp->ops->checkge(kd->grp, kd->K)) {
 189     a_format(e, "bad-public-group-element", A_END);
 190     goto fail_1;
 191   }
 192   return (0);
 193
 194 fail_1:
 195   kd->grp->ops->freege(kd->grp, kd->K);
 196   kd->grp->ops->freegrp(kd->grp);
 197 fail_0:
 198   return (-1);
 199 }
 200
 201 static int kh_loadpriv(key_file *kf, key *k, key_data *d,
 202                        const dhops *dh, kdata *kd, dstr *t, dstr *e)
 203 {
 204   int rc;
 205   const char *err;
 206   dhge *K;
 207   int ok;
 208
 209   if ((rc = dh->ldpriv(kf, k, d, kd, t, e)) != 0)
 210     goto fail_0;
 211   kd->grp->ops = dh;
 212   if ((err = kd->grp->ops->checkgrp(kd->grp)) != 0) {
 213     a_format(e, "bad-group", "%s", err, A_END);
 214     goto fail_1;
 215   }
 216   K = kd->grp->ops->mul(kd->grp, kd->k, 0);
 217   ok = kd->grp->ops->eq(kd->grp, kd->K, K);
 218   kd->grp->ops->freege(kd->grp, K);
 219   if (!ok) {
 220     a_format(e, "incorrect-public-key", A_END);
 221     goto fail_1;
 222   }
 223   return (0);
 224
 225 fail_1:
 226   kd->grp->ops->freesc(kd->grp, kd->k);
 227   kd->grp->ops->freege(kd->grp, kd->K);
 228   kd->grp->ops->freegrp(kd->grp);
 229 fail_0:
 230   return (-1);
 231 }
 232
 233 static struct keyhalf
 234   priv = { "private", kh_loadpriv },
 235   pub = { "public", kh_loadpub };
 236
 237 /* --- @keymoan@ --- *
 238  *
 239  * Arguments:   @const char *file@ = name of the file
 240  *              @int line@ = line number in file
 241  *              @const char *msg@ = error message
 242  *              @void *p@ = argument pointer (indicates which keyring)
 243  *
 244  * Returns:     ---
 245  *
 246  * Use:         Reports an error message about loading a key file.
 247  */
 248
 249 static void keymoan(const char *file, int line, const char *msg, void *p)
 250 {
 251   keyhalf *kh = p;
 252
 253   if (!line) {
 254     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file,
 255            "io-error", "?ERRNO", A_END);
 256   } else {
 257     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file, "line", "%d", line,
 258            "%s", msg, A_END);
 259   }
 260 }
 261
 262 /* --- @kh_reopen@ --- *
 263  *
 264  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure
 265  *
 266  * Returns:     Zero on success, @-1@ on error.
 267  *
 268  * Use:         Reopens the key file for the appropriate key half.  If this
 269  *              fails, everything is left as it was; if it succeeds, then the
 270  *              old file is closed (if it was non-null) and the new one put
 271  *              in its place.
 272  */
 273
 274 static int kh_reopen(keyhalf *kh)
 275 {
 276   key_file *kf = CREATE(key_file);
 277
 278   if (key_open(kf, kh->kr, KOPEN_READ, keymoan, kh)) {
 279     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 280            "io-error", "?ERRNO", A_END);
 281     DESTROY(kf);
 282     return (-1);
 283   } else {
 284     if (kh->kf) {
 285       key_close(kh->kf);
 286       DESTROY(kh->kf);
 287     }
 288     kh->kf = kf;
 289     return (0);
 290   }
 291 }
 292
 293 /* --- @kh_init@ --- *
 294  *
 295  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure to set up
 296  *              @const char *kr@ = name of the keyring file
 297  *
 298  * Returns:     ---
 299  *
 300  * Use:         Initialize a keyhalf structure, maintaining the private or
 301  *              public keys.  Intended to be called during initialization:
 302  *              exits if there's some kind of problem.
 303  */
 304
 305 static void kh_init(keyhalf *kh, const char *kr)
 306 {
 307   kh->kr = kr;
 308   fwatch_init(&kh->w, kr);
 309   sym_create(&kh->tab);
 310   kh->kf = 0;
 311
 312   if (kh_reopen(kh))
 313     die(EXIT_FAILURE, "failed to load %s keyring `%s'", kh->kind, kr);
 314 }
 315
 316 /* --- @kh_load@ --- *
 317  *
 318  * Arguments:   @keyhalf *kh@ = pointer to keyhalf
 319  *              @const char *tag@ = key tag to be loaded
 320  *              @int complainp@ = whether to complain about missing keys
 321  *
 322  * Returns:     Pointer to a @kdata@ structure if successful, or null on
 323  *              failure.
 324  *
 325  * Use:         Attempts to load a key from the current key file.  This
 326  *              function always reads data from the file: it's used when
 327  *              there's a cache miss from @kh_find@, and when refreshing the
 328  *              known keys in @kh_refresh@.  The returned kdata has a
 329  *              reference count of exactly 1, and has no home knode.
 330  */
 331
 332 static kdata *kh_load(keyhalf *kh, const char *tag, int complainp)
 333 {
 334   dstr t = DSTR_INIT;
 335   dstr e = DSTR_INIT;
 336   key *k;
 337   key_data **d;
 338   kdata *kd;
 339   const char *ty;
 340   const dhops *dh;
 341   T( const dhgrp *g; )
 342
 343   /* --- Find the key and grab its tag --- */
 344
 345   if (key_qtag(kh->kf, tag, &t, &k, &d)) {
 346     if (complainp) {
 347       a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 348              "key-not-found", "%s", tag, A_END);
 349     }
 350     goto fail_0;
 351   }
 352
 353   /* --- Find the key's group type and the appropriate operations --- *
 354    *
 355    * There are several places to look for the key type.  The most obvious is
 356    * the `kx-group' key attribute.  But there's also the key type itself, for
 357    * compatibility reasons.
 358    */
 359
 360   ty = key_getattr(kh->kf, k, "kx-group");
 361   if (!ty && strncmp(k->type, "tripe-", 6) == 0) ty = k->type + 6;
 362   if (!ty) ty = "dh";
 363
 364   for (dh = dhtab; dh->name; dh++)
 365     if (strcmp(dh->name, ty) == 0) goto founddh;
 366   a_warn("KEYMGMT", "%s-keyring", kh->kind,
 367          "%s", kh->kr, "key", "%s", t.buf,
 368          "unknown-group-type", "%s", ty, A_END);
 369   goto fail_0;
 370
 371 founddh:
 372   kd = CREATE(kdata);
 373   if (kh->load(kh->kf, k, *d, dh, kd, &t, &e)) {
 374     a_warn("KEYMGMT", "%s-keyring", kh->kind,
 375            "%s", kh->kr, "key", "%s", t.buf,
 376            "*%s", e.buf, A_END);
 377     goto fail_1;
 378   }
 379
 380   if (algs_get(&kd->algs, &e, kh->kf, k) ||
 381       (kd->k && algs_check(&kd->algs, &e, kd->grp))) {
 382     a_warn("KEYMGMT", "%s-keyring", kh->kind,
 383            "%s", kh->kr, "key", "%s", t.buf,
 384            "*%s", e.buf, A_END);
 385     goto fail_2;
 386   }
 387
 388   kd->tag = xstrdup(t.buf);
 389   kd->ref = 1;
 390   kd->kn = 0;
 391   kd->t_exp = k->exp;
 392
 393   IF_TRACING(T_KEYMGMT, {
 394     trace(T_KEYMGMT, "keymgmt: loaded %s key `%s'", kh->kind, t.buf);
 395     IF_TRACING(T_CRYPTO, {
 396       g = kd->grp;
 397       g->ops->tracegrp(g);
 398       if (kd->k)
 399         trace(T_CRYPTO, "crypto: k = %s", g->ops->scstr(g, kd->k));
 400       trace(T_CRYPTO, "crypto: K = %s", g->ops->gestr(g, kd->K));
 401       kd->algs.bulk->ops->tracealgs(kd->algs.bulk);
 402     })
 403   })
 404
 405   goto done;
 406
 407 fail_2:
 408   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 409   kd->grp->ops->freege(kd->grp, kd->K);
 410   kd->grp->ops->freegrp(kd->grp);
 411 fail_1:
 412   DESTROY(kd);
 413 fail_0:
 414   kd = 0;
 415 done:
 416   dstr_destroy(&t);
 417   dstr_destroy(&e);
 418   return (kd);
 419 }
 420
 421 /* --- @kh_find@ --- *
 422  *
 423  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 424  *              @const char *tag@ = key to be obtained
 425  *              @int complainp@ = whether to complain about missing keys
 426  *
 427  * Returns:     A pointer to the kdata, or null on error.
 428  *
 429  * Use:         Obtains kdata, maybe from the cache.  This won't update a
 430  *              stale cache entry, though @kh_refresh@ ought to have done
 431  *              that already.  The returned kdata object may be shared with
 432  *              other users.  (One of this function's responsibilities, over
 433  *              @kh_load@, is to set the home knode of a freshly loaded
 434  *              kdata.)
 435  */
 436
 437 static kdata *kh_find(keyhalf *kh, const char *tag, int complainp)
 438 {
 439   knode *kn;
 440   kdata *kd;
 441   unsigned f;
 442
 443   kn = sym_find(&kh->tab, tag, -1, sizeof(knode), &f);
 444
 445   if (f) {
 446     if (kn->f & KNF_BROKEN) {
 447       T( if (complainp)
 448            trace(T_KEYMGMT, "keymgmt: key `%s' marked as broken", tag); )
 449       return (0);
 450     }
 451
 452     kd = kn->kd;
 453     if (kd) kd->ref++;
 454     T( trace(T_KEYMGMT, "keymgmt: %scache hit for key `%s'",
 455              kd ? "" : "negative ", tag); )
 456     return (kd);
 457   } else {
 458     kd = kh_load(kh, tag, complainp);
 459     kn->kd = kd;
 460     kn->kh = kh;
 461     kn->f = 0;
 462     if (!kd)
 463       kn->f |= KNF_BROKEN;
 464     else {
 465       kd->kn = kn;
 466       kd->ref++;
 467     }
 468     return (kd);
 469   }
 470 }
 471
 472 /* --- @kh_refresh@ --- *
 473  *
 474  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 475  *
 476  * Returns:     Zero if nothing needs to be done; nonzero if peers should
 477  *              refresh their keys.
 478  *
 479  * Use:         Refreshes cached keys from files.
 480  *
 481  *              Each active knode is examined to see if a new key is
 482  *              available: the return value is nonzero if any new keys are.
 483  *              A key is considered new if its algorithms, public key, or
 484  *              expiry time are/is different.
 485  *
 486  *              Stub knodes (with no kdata attached) are removed, so that a
 487  *              later retry can succeed if the file has been fixed.  (This
 488  *              doesn't count as a change, since no peers should be relying
 489  *              on a nonexistent key.)
 490  */
 491
 492 static int kh_refresh(keyhalf *kh)
 493 {
 494   knode *kn;
 495   kdata *kd;
 496   sym_iter i;
 497   int changep = 0;
 498
 499   if (!fwatch_update(&kh->w, kh->kr) || kh_reopen(kh))
 500     return (0);
 501
 502   T( trace(T_KEYMGMT, "keymgmt: rescan %s keyring `%s'", kh->kind, kh->kr); )
 503   for (sym_mkiter(&i, &kh->tab); (kn = sym_next(&i)) != 0; ) {
 504     if (!kn->kd) {
 505       T( trace(T_KEYMGMT, "keymgmt: discard stub entry for key `%s'",
 506                SYM_NAME(kn)); )
 507       sym_remove(&kh->tab, kn);
 508       continue;
 509     }
 510     if ((kd = kh_load(kh, SYM_NAME(kn), 1)) == 0) {
 511       if (!(kn->f & KNF_BROKEN)) {
 512         T( trace(T_KEYMGMT, "keymgmt: failed to load new key `%s': "
 513                  "marking it as broken",
 514                  SYM_NAME(kn)); )
 515         kn->f |= KNF_BROKEN;
 516       }
 517       continue;
 518     }
 519     kn->f &= ~KNF_BROKEN;
 520     if (kd->t_exp == kn->kd->t_exp &&
 521         km_samealgsp(kd, kn->kd) &&
 522         kd->grp->ops->eq(kd->grp, kd->K, kn->kd->K)) {
 523       T( trace(T_KEYMGMT, "keymgmt: key `%s' unchanged", SYM_NAME(kn)); )
 524       continue;
 525     }
 526     T( trace(T_KEYMGMT, "keymgmt: loaded new version of key `%s'",
 527              SYM_NAME(kn)); )
 528     km_unref(kn->kd);
 529     kd->kn = kn;
 530     kn->kd = kd;
 531     changep = 1;
 532   }
 533
 534   return (changep);
 535 }
 536
 537 /*----- Main code ---------------------------------------------------------*/
 538
 539 const char *tag_priv;
 540 kdata *master;
 541
 542 /* --- @km_init@ --- *
 543  *
 544  * Arguments:   @const char *privkr@ = private keyring file
 545  *              @const char *pubkr@ = public keyring file
 546  *              @const char *ptag@ = default private-key tag
 547  *
 548  * Returns:     ---
 549  *
 550  * Use:         Initializes the key-management machinery, loading the
 551  *              keyrings and so on.
 552  */
 553
 554 void km_init(const char *privkr, const char *pubkr, const char *ptag)
 555 {
 556   const gchash *const *hh;
 557
 558   for (hh = ghashtab; *hh; hh++) {
 559     if ((*hh)->hashsz > MAXHASHSZ) {
 560       die(EXIT_FAILURE, "INTERNAL ERROR: %s hash length %lu > MAXHASHSZ %d",
 561           (*hh)->name, (unsigned long)(*hh)->hashsz, MAXHASHSZ);
 562     }
 563   }
 564
 565   kh_init(&priv, privkr);
 566   kh_init(&pub, pubkr);
 567
 568   tag_priv = ptag;
 569   if ((master = km_findpriv(ptag)) == 0) exit(EXIT_FAILURE);
 570 }
 571
 572 /* --- @km_reload@ --- *
 573  *
 574  * Arguments:   ---
 575  *
 576  * Returns:     Zero if OK, nonzero to force reloading of keys.
 577  *
 578  * Use:         Checks the keyrings to see if they need reloading.
 579  */
 580
 581 int km_reload(void)
 582 {
 583   int changep = 0;
 584   kdata *kd;
 585
 586   if (kh_refresh(&priv)) {
 587     changep = 1;
 588     kd = master->kn->kd;
 589     if (kd != master) {
 590       km_unref(master);
 591       km_ref(kd);
 592       master = kd;
 593     }
 594   }
 595   if (kh_refresh(&pub))
 596     changep = 1;
 597   return (changep);
 598 }
 599
 600 /* --- @km_findpub@, @km_findpriv@ --- *
 601  *
 602  * Arguments:   @const char *tag@ = key tag to load
 603  *
 604  * Returns:     Pointer to the kdata object if successful, or null on error.
 605  *
 606  * Use:         Fetches a public or private key from the keyring.
 607  */
 608
 609 kdata *km_findpub(const char *tag) { return (kh_find(&pub, tag, 1)); }
 610
 611 kdata *km_findpriv(const char *tag)
 612 {
 613   kdata *kd;
 614
 615   /* Unpleasantness for the sake of compatibility. */
 616   if (!tag && (kd = kh_find(&priv, "tripe", 0)) != 0) return (kd);
 617   else return (kh_find(&priv, tag ? tag : "tripe-dh", 1));
 618 }
 619
 620 /* --- @km_tag@ --- *
 621  *
 622  * Arguments:   @kdata *kd@ - pointer to the kdata object
 623  *
 624  * Returns:     A pointer to the short tag by which the kdata was loaded.
 625  */
 626
 627 const char *km_tag(kdata *kd) { return (SYM_NAME(kd->kn)); }
 628
 629 /* --- @km_ref@ --- *
 630  *
 631  * Arguments:   @kdata *kd@ = pointer to the kdata object
 632  *
 633  * Returns:     ---
 634  *
 635  * Use:         Claim a new reference to a kdata object.
 636  */
 637
 638 void km_ref(kdata *kd) { kd->ref++; }
 639
 640 /* --- @km_unref@ --- *
 641  *
 642  * Arguments:   @kdata *kd@ = pointer to the kdata object
 643  *
 644  * Returns:     ---
 645  *
 646  * Use:         Releases a reference to a kdata object.
 647  */
 648
 649 void km_unref(kdata *kd)
 650 {
 651   if (--kd->ref) return;
 652   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 653   kd->grp->ops->freege(kd->grp, kd->K);
 654   kd->grp->ops->freegrp(kd->grp);
 655   xfree(kd->tag);
 656   DESTROY(kd);
 657 }
 658
 659 /*----- That's all, folks -------------------------------------------------*/