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
 207   if ((rc = dh->ldpriv(kf, k, d, kd, t, e)) != 0)
 208     goto fail_0;
 209   kd->grp->ops = dh;
 210   if ((err = kd->grp->ops->checkgrp(kd->grp)) != 0) {
 211     a_format(e, "bad-group", "%s", err, A_END);
 212     goto fail_1;
 213   }
 214   return (0);
 215
 216 fail_1:
 217   kd->grp->ops->freesc(kd->grp, kd->k);
 218   kd->grp->ops->freege(kd->grp, kd->K);
 219   kd->grp->ops->freegrp(kd->grp);
 220 fail_0:
 221   return (-1);
 222 }
 223
 224 static struct keyhalf
 225   priv = { "private", kh_loadpriv },
 226   pub = { "public", kh_loadpub };
 227
 228 /* --- @keymoan@ --- *
 229  *
 230  * Arguments:   @const char *file@ = name of the file
 231  *              @int line@ = line number in file
 232  *              @const char *msg@ = error message
 233  *              @void *p@ = argument pointer (indicates which keyring)
 234  *
 235  * Returns:     ---
 236  *
 237  * Use:         Reports an error message about loading a key file.
 238  */
 239
 240 static void keymoan(const char *file, int line, const char *msg, void *p)
 241 {
 242   keyhalf *kh = p;
 243
 244   if (!line) {
 245     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file,
 246            "io-error", "?ERRNO", A_END);
 247   } else {
 248     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", file, "line", "%d", line,
 249            "%s", msg, A_END);
 250   }
 251 }
 252
 253 /* --- @kh_reopen@ --- *
 254  *
 255  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure
 256  *
 257  * Returns:     Zero on success, @-1@ on error.
 258  *
 259  * Use:         Reopens the key file for the appropriate key half.  If this
 260  *              fails, everything is left as it was; if it succeeds, then the
 261  *              old file is closed (if it was non-null) and the new one put
 262  *              in its place.
 263  */
 264
 265 static int kh_reopen(keyhalf *kh)
 266 {
 267   key_file *kf = CREATE(key_file);
 268
 269   if (key_open(kf, kh->kr, KOPEN_READ, keymoan, kh)) {
 270     a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 271            "io-error", "?ERRNO", A_END);
 272     DESTROY(kf);
 273     return (-1);
 274   } else {
 275     if (kh->kf) {
 276       key_close(kh->kf);
 277       DESTROY(kh->kf);
 278     }
 279     kh->kf = kf;
 280     return (0);
 281   }
 282 }
 283
 284 /* --- @kh_init@ --- *
 285  *
 286  * Arguments:   @keyhalf *kh@ = pointer to keyhalf structure to set up
 287  *              @const char *kr@ = name of the keyring file
 288  *
 289  * Returns:     ---
 290  *
 291  * Use:         Initialize a keyhalf structure, maintaining the private or
 292  *              public keys.  Intended to be called during initialization:
 293  *              exits if there's some kind of problem.
 294  */
 295
 296 static void kh_init(keyhalf *kh, const char *kr)
 297 {
 298   kh->kr = kr;
 299   fwatch_init(&kh->w, kr);
 300   sym_create(&kh->tab);
 301   kh->kf = 0;
 302
 303   if (kh_reopen(kh))
 304     die(EXIT_FAILURE, "failed to load %s keyring `%s'", kh->kind, kr);
 305 }
 306
 307 /* --- @kh_load@ --- *
 308  *
 309  * Arguments:   @keyhalf *kh@ = pointer to keyhalf
 310  *              @const char *tag@ = key tag to be loaded
 311  *              @int complainp@ = whether to complain about missing keys
 312  *
 313  * Returns:     Pointer to a @kdata@ structure if successful, or null on
 314  *              failure.
 315  *
 316  * Use:         Attempts to load a key from the current key file.  This
 317  *              function always reads data from the file: it's used when
 318  *              there's a cache miss from @kh_find@, and when refreshing the
 319  *              known keys in @kh_refresh@.  The returned kdata has a
 320  *              reference count of exactly 1, and has no home knode.
 321  */
 322
 323 static kdata *kh_load(keyhalf *kh, const char *tag, int complainp)
 324 {
 325   dstr t = DSTR_INIT;
 326   dstr e = DSTR_INIT;
 327   key *k;
 328   key_data **d;
 329   kdata *kd;
 330   const char *ty;
 331   const dhops *dh;
 332   T( const dhgrp *g; )
 333
 334   /* --- Find the key and grab its tag --- */
 335
 336   if (key_qtag(kh->kf, tag, &t, &k, &d)) {
 337     if (complainp) {
 338       a_warn("KEYMGMT", "%s-keyring", kh->kind, "%s", kh->kr,
 339              "key-not-found", "%s", tag, A_END);
 340     }
 341     goto fail_0;
 342   }
 343
 344   /* --- Find the key's group type and the appropriate operations --- *
 345    *
 346    * There are several places to look for the key type.  The most obvious is
 347    * the `kx-group' key attribute.  But there's also the key type itself, for
 348    * compatibility reasons.
 349    */
 350
 351   ty = key_getattr(kh->kf, k, "kx-group");
 352   if (!ty && strncmp(k->type, "tripe-", 6) == 0) ty = k->type + 6;
 353   if (!ty) ty = "dh";
 354
 355   for (dh = dhtab; dh->name; dh++)
 356     if (strcmp(dh->name, ty) == 0) goto founddh;
 357   a_warn("KEYMGMT", "%s-keyring", kh->kind,
 358          "%s", kh->kr, "key", "%s", t.buf,
 359          "unknown-group-type", "%s", ty, A_END);
 360   goto fail_0;
 361
 362 founddh:
 363   kd = CREATE(kdata);
 364   if (kh->load(kh->kf, k, *d, dh, kd, &t, &e)) {
 365     a_warn("KEYMGMT", "%s-keyring", kh->kind,
 366            "%s", kh->kr, "key", "%s", t.buf,
 367            "*%s", e.buf, A_END);
 368     goto fail_1;
 369   }
 370
 371   if (algs_get(&kd->algs, &e, kh->kf, k) ||
 372       (kd->k && algs_check(&kd->algs, &e, kd->grp))) {
 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_2;
 377   }
 378
 379   kd->tag = xstrdup(t.buf);
 380   kd->ref = 1;
 381   kd->kn = 0;
 382   kd->t_exp = k->exp;
 383
 384   IF_TRACING(T_KEYMGMT, {
 385     trace(T_KEYMGMT, "keymgmt: loaded %s key `%s'", kh->kind, t.buf);
 386     IF_TRACING(T_CRYPTO, {
 387       g = kd->grp;
 388       g->ops->tracegrp(g);
 389       if (kd->k)
 390         trace(T_CRYPTO, "crypto: k = %s", g->ops->scstr(g, kd->k));
 391       trace(T_CRYPTO, "crypto: K = %s", g->ops->gestr(g, kd->K));
 392       kd->algs.bulk->ops->tracealgs(kd->algs.bulk);
 393     })
 394   })
 395
 396   goto done;
 397
 398 fail_2:
 399   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 400   kd->grp->ops->freege(kd->grp, kd->K);
 401   kd->grp->ops->freegrp(kd->grp);
 402 fail_1:
 403   DESTROY(kd);
 404 fail_0:
 405   kd = 0;
 406 done:
 407   dstr_destroy(&t);
 408   dstr_destroy(&e);
 409   return (kd);
 410 }
 411
 412 /* --- @kh_find@ --- *
 413  *
 414  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 415  *              @const char *tag@ = key to be obtained
 416  *              @int complainp@ = whether to complain about missing keys
 417  *
 418  * Returns:     A pointer to the kdata, or null on error.
 419  *
 420  * Use:         Obtains kdata, maybe from the cache.  This won't update a
 421  *              stale cache entry, though @kh_refresh@ ought to have done
 422  *              that already.  The returned kdata object may be shared with
 423  *              other users.  (One of this function's responsibilities, over
 424  *              @kh_load@, is to set the home knode of a freshly loaded
 425  *              kdata.)
 426  */
 427
 428 static kdata *kh_find(keyhalf *kh, const char *tag, int complainp)
 429 {
 430   knode *kn;
 431   kdata *kd;
 432   unsigned f;
 433
 434   kn = sym_find(&kh->tab, tag, -1, sizeof(knode), &f);
 435
 436   if (f) {
 437     if (kn->f & KNF_BROKEN) {
 438       T( if (complainp)
 439            trace(T_KEYMGMT, "keymgmt: key `%s' marked as broken", tag); )
 440       return (0);
 441     }
 442
 443     kd = kn->kd;
 444     if (kd) kd->ref++;
 445     T( trace(T_KEYMGMT, "keymgmt: %scache hit for key `%s'",
 446              kd ? "" : "negative ", tag); )
 447     return (kd);
 448   } else {
 449     kd = kh_load(kh, tag, complainp);
 450     kn->kd = kd;
 451     kn->kh = kh;
 452     kn->f = 0;
 453     if (!kd)
 454       kn->f |= KNF_BROKEN;
 455     else {
 456       kd->kn = kn;
 457       kd->ref++;
 458     }
 459     return (kd);
 460   }
 461 }
 462
 463 /* --- @kh_refresh@ --- *
 464  *
 465  * Arguments:   @keyhalf *kh@ = pointer to the keyhalf
 466  *
 467  * Returns:     Zero if nothing needs to be done; nonzero if peers should
 468  *              refresh their keys.
 469  *
 470  * Use:         Refreshes cached keys from files.
 471  *
 472  *              Each active knode is examined to see if a new key is
 473  *              available: the return value is nonzero if any new keys are.
 474  *              A key is considered new if its algorithms, public key, or
 475  *              expiry time are/is different.
 476  *
 477  *              Stub knodes (with no kdata attached) are removed, so that a
 478  *              later retry can succeed if the file has been fixed.  (This
 479  *              doesn't count as a change, since no peers should be relying
 480  *              on a nonexistent key.)
 481  */
 482
 483 static int kh_refresh(keyhalf *kh)
 484 {
 485   knode *kn;
 486   kdata *kd;
 487   sym_iter i;
 488   int changep = 0;
 489
 490   if (!fwatch_update(&kh->w, kh->kr) || kh_reopen(kh))
 491     return (0);
 492
 493   T( trace(T_KEYMGMT, "keymgmt: rescan %s keyring `%s'", kh->kind, kh->kr); )
 494   for (sym_mkiter(&i, &kh->tab); (kn = sym_next(&i)) != 0; ) {
 495     if (!kn->kd) {
 496       T( trace(T_KEYMGMT, "keymgmt: discard stub entry for key `%s'",
 497                SYM_NAME(kn)); )
 498       sym_remove(&kh->tab, kn);
 499       continue;
 500     }
 501     if ((kd = kh_load(kh, SYM_NAME(kn), 1)) == 0) {
 502       if (!(kn->f & KNF_BROKEN)) {
 503         T( trace(T_KEYMGMT, "keymgmt: failed to load new key `%s': "
 504                  "marking it as broken",
 505                  SYM_NAME(kn)); )
 506         kn->f |= KNF_BROKEN;
 507       }
 508       continue;
 509     }
 510     kn->f &= ~KNF_BROKEN;
 511     if (kd->t_exp == kn->kd->t_exp &&
 512         km_samealgsp(kd, kn->kd) &&
 513         kd->grp->ops->eq(kd->grp, kd->K, kn->kd->K)) {
 514       T( trace(T_KEYMGMT, "keymgmt: key `%s' unchanged", SYM_NAME(kn)); )
 515       continue;
 516     }
 517     T( trace(T_KEYMGMT, "keymgmt: loaded new version of key `%s'",
 518              SYM_NAME(kn)); )
 519     km_unref(kn->kd);
 520     kd->kn = kn;
 521     kn->kd = kd;
 522     changep = 1;
 523   }
 524
 525   return (changep);
 526 }
 527
 528 /*----- Main code ---------------------------------------------------------*/
 529
 530 const char *tag_priv;
 531 kdata *master;
 532
 533 /* --- @km_init@ --- *
 534  *
 535  * Arguments:   @const char *privkr@ = private keyring file
 536  *              @const char *pubkr@ = public keyring file
 537  *              @const char *ptag@ = default private-key tag
 538  *
 539  * Returns:     ---
 540  *
 541  * Use:         Initializes the key-management machinery, loading the
 542  *              keyrings and so on.
 543  */
 544
 545 void km_init(const char *privkr, const char *pubkr, const char *ptag)
 546 {
 547   const gchash *const *hh;
 548
 549   for (hh = ghashtab; *hh; hh++) {
 550     if ((*hh)->hashsz > MAXHASHSZ) {
 551       die(EXIT_FAILURE, "INTERNAL ERROR: %s hash length %lu > MAXHASHSZ %d",
 552           (*hh)->name, (unsigned long)(*hh)->hashsz, MAXHASHSZ);
 553     }
 554   }
 555
 556   kh_init(&priv, privkr);
 557   kh_init(&pub, pubkr);
 558
 559   tag_priv = ptag;
 560   if ((master = km_findpriv(ptag)) == 0) exit(EXIT_FAILURE);
 561 }
 562
 563 /* --- @km_reload@ --- *
 564  *
 565  * Arguments:   ---
 566  *
 567  * Returns:     Zero if OK, nonzero to force reloading of keys.
 568  *
 569  * Use:         Checks the keyrings to see if they need reloading.
 570  */
 571
 572 int km_reload(void)
 573 {
 574   int changep = 0;
 575   kdata *kd;
 576
 577   if (kh_refresh(&priv)) {
 578     changep = 1;
 579     kd = master->kn->kd;
 580     if (kd != master) {
 581       km_unref(master);
 582       km_ref(kd);
 583       master = kd;
 584     }
 585   }
 586   if (kh_refresh(&pub))
 587     changep = 1;
 588   return (changep);
 589 }
 590
 591 /* --- @km_findpub@, @km_findpriv@ --- *
 592  *
 593  * Arguments:   @const char *tag@ = key tag to load
 594  *
 595  * Returns:     Pointer to the kdata object if successful, or null on error.
 596  *
 597  * Use:         Fetches a public or private key from the keyring.
 598  */
 599
 600 kdata *km_findpub(const char *tag) { return (kh_find(&pub, tag, 1)); }
 601
 602 kdata *km_findpriv(const char *tag)
 603 {
 604   kdata *kd;
 605
 606   /* Unpleasantness for the sake of compatibility. */
 607   if (!tag && (kd = kh_find(&priv, "tripe", 0)) != 0) return (kd);
 608   else return (kh_find(&priv, tag ? tag : "tripe-dh", 1));
 609 }
 610
 611 /* --- @km_tag@ --- *
 612  *
 613  * Arguments:   @kdata *kd@ - pointer to the kdata object
 614  *
 615  * Returns:     A pointer to the short tag by which the kdata was loaded.
 616  */
 617
 618 const char *km_tag(kdata *kd) { return (SYM_NAME(kd->kn)); }
 619
 620 /* --- @km_ref@ --- *
 621  *
 622  * Arguments:   @kdata *kd@ = pointer to the kdata object
 623  *
 624  * Returns:     ---
 625  *
 626  * Use:         Claim a new reference to a kdata object.
 627  */
 628
 629 void km_ref(kdata *kd) { kd->ref++; }
 630
 631 /* --- @km_unref@ --- *
 632  *
 633  * Arguments:   @kdata *kd@ = pointer to the kdata object
 634  *
 635  * Returns:     ---
 636  *
 637  * Use:         Releases a reference to a kdata object.
 638  */
 639
 640 void km_unref(kdata *kd)
 641 {
 642   if (--kd->ref) return;
 643   if (kd->k) kd->grp->ops->freesc(kd->grp, kd->k);
 644   kd->grp->ops->freege(kd->grp, kd->K);
 645   kd->grp->ops->freegrp(kd->grp);
 646   xfree(kd->tag);
 647   DESTROY(kd);
 648 }
 649
 650 /*----- That's all, folks -------------------------------------------------*/