cleankey.c

   1 /*
   2  * cleankey.c - Routines to look for common key problems and clean them up.
   3  *
   4  * Copyright 2004,2012 Jonathan McDowell <noodles@earth.li>
   5  *
   6  * This program is free software: you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  13  * more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along with
  16  * this program.  If not, see <https://www.gnu.org/licenses/>.
  17  */
  18
  19 #include <stdbool.h>
  20 #include <stdlib.h>
  21
  22 #include "build-config.h"
  23 #include "cleankey.h"
  24 #include "decodekey.h"
  25 #include "keyid.h"
  26 #include "keystructs.h"
  27 #include "log.h"
  28 #include "mem.h"
  29 #include "merge.h"
  30 #include "openpgp.h"
  31 #include "sigcheck.h"
  32
  33 /**
  34  *      dedupuids - Merge duplicate uids on a key.
  35  *      @key: The key to de-dup uids on.
  36  *
  37  *      This function attempts to merge duplicate IDs on a key. It returns 0
  38  *      if the key is unchanged, otherwise the number of dups merged.
  39  */
  40 int dedupuids(struct openpgp_publickey *key)
  41 {
  42         struct openpgp_signedpacket_list *curuid = NULL;
  43         struct openpgp_signedpacket_list *dup = NULL;
  44         struct openpgp_signedpacket_list *tmp = NULL;
  45         int                               merged = 0;
  46
  47         log_assert(key != NULL);
  48         curuid = key->uids;
  49         while (curuid != NULL) {
  50                 dup = find_signed_packet(curuid->next, curuid->packet);
  51                 while (dup != NULL) {
  52                         logthing(LOGTHING_INFO, "Found duplicate uid: %.*s",
  53                                         curuid->packet->length,
  54                                         curuid->packet->data);
  55                         merged++;
  56                         merge_packet_sigs(curuid, dup);
  57                         /*
  58                          * Remove the duplicate uid.
  59                          */
  60                         tmp = curuid;
  61                         while (tmp != NULL && tmp->next != dup) {
  62                                 tmp = tmp->next;
  63                         }
  64                         log_assert(tmp != NULL);
  65                         tmp->next = dup->next;
  66                         dup->next = NULL;
  67                         free_signedpacket_list(dup);
  68
  69                         dup = find_signed_packet(curuid->next, curuid->packet);
  70                 }
  71                 curuid = curuid->next;
  72         }
  73
  74         return merged;
  75 }
  76
  77 /**
  78  *      dedupsubkeys - Merge duplicate subkeys on a key.
  79  *      @key: The key to de-dup subkeys on.
  80  *
  81  *      This function attempts to merge duplicate subkeys on a key. It returns
  82  *      0 if the key is unchanged, otherwise the number of dups merged.
  83  */
  84 int dedupsubkeys(struct openpgp_publickey *key)
  85 {
  86         struct openpgp_signedpacket_list *cursubkey = NULL;
  87         struct openpgp_signedpacket_list *dup = NULL;
  88         struct openpgp_signedpacket_list *tmp = NULL;
  89         int                               merged = 0;
  90         uint64_t                          subkeyid;
  91
  92         log_assert(key != NULL);
  93         cursubkey = key->subkeys;
  94         while (cursubkey != NULL) {
  95                 dup = find_signed_packet(cursubkey->next, cursubkey->packet);
  96                 while (dup != NULL) {
  97                         get_packetid(cursubkey->packet, &subkeyid);
  98                         logthing(LOGTHING_INFO,
  99                                 "Found duplicate subkey: 0x%016" PRIX64,
 100                                 subkeyid);
 101                         merged++;
 102                         merge_packet_sigs(cursubkey, dup);
 103                         /*
 104                          * Remove the duplicate uid.
 105                          */
 106                         tmp = cursubkey;
 107                         while (tmp != NULL && tmp->next != dup) {
 108                                 tmp = tmp->next;
 109                         }
 110                         log_assert(tmp != NULL);
 111                         tmp->next = dup->next;
 112                         dup->next = NULL;
 113                         free_signedpacket_list(dup);
 114
 115                         dup = find_signed_packet(cursubkey->next,
 116                                 cursubkey->packet);
 117                 }
 118                 cursubkey = cursubkey->next;
 119         }
 120
 121         return merged;
 122 }
 123
 124 /**
 125  *      check_sighashes - Check that sig hashes are correct.
 126  *      @key - the check to check the sig hashes of.
 127  *
 128  *      Given an OpenPGP key confirm that all of the sigs on it have the
 129  *      appropriate 2 octet hash beginning, as stored as part of the sig.
 130  *      This is a simple way to remove junk sigs and, for example, catches
 131  *      subkey sig corruption as produced by old pksd implementations.
 132  *      Any sig that has an incorrect hash is removed from the key. If the
 133  *      hash cannot be checked (eg we don't support that hash type) we err
 134  *      on the side of caution and keep it.
 135  */
 136 int clean_sighashes(struct onak_dbctx *dbctx,
 137                 struct openpgp_publickey *key,
 138                 struct openpgp_packet *sigdata,
 139                 struct openpgp_packet_list **sigs,
 140                 bool fullverify,
 141                 bool *selfsig, bool *othersig)
 142 {
 143         struct openpgp_packet_list *tmpsig;
 144         struct openpgp_publickey *sigkeys = NULL, *curkey;
 145         onak_status_t ret;
 146         uint8_t hashtype;
 147         uint8_t hash[64];
 148         uint8_t *sighash;
 149         int removed = 0;
 150         uint64_t keyid, sigid;
 151         bool remove;
 152
 153         get_keyid(key, &keyid);
 154         if (selfsig != NULL) {
 155                 *selfsig = false;
 156         }
 157         while (*sigs != NULL) {
 158                 remove = false;
 159                 ret = calculate_packet_sighash(key, sigdata, (*sigs)->packet,
 160                                 &hashtype, hash, &sighash);
 161
 162                 if (ret == ONAK_E_UNSUPPORTED_FEATURE) {
 163                         get_keyid(key, &keyid);
 164                         logthing(LOGTHING_ERROR,
 165                                 "Unsupported signature hash type %d on 0x%016"
 166                                 PRIX64,
 167                                 hashtype,
 168                                 keyid);
 169                         if (fullverify) {
 170                                 remove = true;
 171                         }
 172                 } else if (ret != ONAK_E_OK || (!fullverify &&
 173                                 !(hash[0] == sighash[0] &&
 174                                         hash[1] == sighash[1]))) {
 175                         remove = true;
 176                 }
 177
 178 #if HAVE_CRYPTO
 179                 if (fullverify && !remove) {
 180                         sig_info((*sigs)->packet, &sigid, NULL);
 181
 182                         /* Start by assuming it's a bad sig */
 183
 184                         remove = true;
 185                         if (sigid == keyid) {
 186                                 ret = onak_check_hash_sig(key, (*sigs)->packet,
 187                                                 hash, hashtype);
 188
 189                                 /* We have a valid self signature */
 190                                 if (ret == ONAK_E_OK) {
 191                                         remove = false;
 192                                         if (selfsig != NULL) {
 193                                                 *selfsig = true;
 194                                         }
 195                                 }
 196                         }
 197
 198                         if (remove) {
 199                                 dbctx->fetch_key_id(dbctx, sigid,
 200                                                 &sigkeys, false);
 201                         }
 202
 203                         /*
 204                          * A 64 bit collision is probably a sign of something
 205                          * sneaky happening, but if the signature verifies we
 206                          * should keep it.
 207                          */
 208                         for (curkey = sigkeys; curkey != NULL;
 209                                         curkey = curkey->next) {
 210
 211                                 ret = onak_check_hash_sig(curkey,
 212                                                 (*sigs)->packet,
 213                                                 hash, hashtype);
 214
 215                                 /* Got a valid signature */
 216                                 if (ret == ONAK_E_OK) {
 217                                         remove = false;
 218                                         if (othersig != NULL) {
 219                                                 *othersig = true;
 220                                         }
 221                                         break;
 222                                 }
 223                         }
 224
 225                         free_publickey(sigkeys);
 226                         sigkeys = NULL;
 227                 }
 228 #endif
 229
 230                 if (remove) {
 231                         tmpsig = *sigs;
 232                         *sigs = (*sigs)->next;
 233                         tmpsig->next = NULL;
 234                         free_packet_list(tmpsig);
 235                         removed++;
 236                 } else {
 237                         sigs = &(*sigs)->next;
 238                 }
 239         }
 240
 241         return removed;
 242 }
 243
 244 int clean_list_sighashes(struct onak_dbctx *dbctx,
 245                         struct openpgp_publickey *key,
 246                         struct openpgp_signedpacket_list **siglist,
 247                         bool fullverify, bool needother)
 248 {
 249         struct openpgp_signedpacket_list **orig, *tmp = NULL;
 250         bool selfsig, othersig;
 251         int removed = 0;
 252
 253         othersig = false;
 254         orig = siglist;
 255         while (siglist != NULL && *siglist != NULL) {
 256                 selfsig = false;
 257
 258                 removed += clean_sighashes(dbctx, key, (*siglist)->packet,
 259                         &(*siglist)->sigs, fullverify, &selfsig, &othersig);
 260
 261                 if (fullverify && !selfsig) {
 262                         /* Remove the UID/subkey if there's no selfsig */
 263                         tmp = *siglist;
 264                         *siglist = (*siglist)->next;
 265                         tmp->next = NULL;
 266                         free_signedpacket_list(tmp);
 267                 } else {
 268                         siglist = &(*siglist)->next;
 269                 }
 270         }
 271
 272         /*
 273          * We need at least one UID to have a signature from another key,
 274          * otherwise we remove all of them if needother is set.
 275          */
 276         if (needother && fullverify && !othersig) {
 277                 siglist = orig;
 278                 while (siglist != NULL && *siglist != NULL) {
 279                         tmp = *siglist;
 280                         *siglist = (*siglist)->next;
 281                         tmp->next = NULL;
 282                         free_signedpacket_list(tmp);
 283                 }
 284         }
 285
 286         return removed;
 287 }
 288
 289 int clean_key_signatures(struct onak_dbctx *dbctx,
 290                 struct openpgp_publickey *key, bool fullverify, bool needother)
 291 {
 292         int removed;
 293
 294         removed = clean_sighashes(dbctx, key, NULL, &key->sigs, fullverify,
 295                         NULL, NULL);
 296         removed += clean_list_sighashes(dbctx, key, &key->uids, fullverify,
 297                         needother);
 298         removed += clean_list_sighashes(dbctx, key, &key->subkeys, fullverify,
 299                         false);
 300
 301         return removed;
 302 }
 303
 304 #define UAT_LIMIT       0xFFFF
 305 #define UID_LIMIT       1024
 306 #define PACKET_LIMIT    8383            /* Fits in 2 byte packet length */
 307 int clean_large_packets(struct openpgp_publickey *key)
 308 {
 309         struct openpgp_signedpacket_list **curuid = NULL;
 310         struct openpgp_signedpacket_list *tmp = NULL;
 311         bool                              drop;
 312         int                               dropped = 0;
 313
 314         log_assert(key != NULL);
 315         curuid = &key->uids;
 316         while (*curuid != NULL) {
 317                 drop = false;
 318                 switch ((*curuid)->packet->tag) {
 319                 case OPENPGP_PACKET_UID:
 320                         if ((*curuid)->packet->length > UID_LIMIT)
 321                                 drop = true;
 322                         break;
 323                 case OPENPGP_PACKET_UAT:
 324                         if ((*curuid)->packet->length > UAT_LIMIT)
 325                                 drop = true;
 326                         break;
 327                 default:
 328                         if ((*curuid)->packet->length > PACKET_LIMIT)
 329                                 drop = true;
 330                         break;
 331                 }
 332
 333                 if (drop) {
 334                         logthing(LOGTHING_INFO,
 335                                         "Dropping large (%d) packet, type %d",
 336                                         (*curuid)->packet->length,
 337                                         (*curuid)->packet->tag);
 338                         /* Remove the entire large signed packet list */
 339                         tmp = *curuid;
 340                         *curuid = (*curuid)->next;
 341                         tmp->next = NULL;
 342                         free_signedpacket_list(tmp);
 343                         dropped++;
 344                 } else {
 345                         curuid = &(*curuid)->next;
 346                 }
 347         }
 348
 349         return dropped;
 350 }
 351
 352 /**
 353  *      cleankeys - Apply all available cleaning options on a list of keys.
 354  *      @policies: The cleaning policies to apply.
 355  *
 356  *      Applies the requested cleaning policies to a list of keys. These are
 357  *      specified from the ONAK_CLEAN_* set of flags, or ONAK_CLEAN_ALL to
 358  *      apply all available cleaning options. Returns 0 if no changes were
 359  *      made, otherwise the number of keys cleaned. Note that some options
 360  *      may result in keys being removed entirely from the list.
 361  */
 362 int cleankeys(struct onak_dbctx *dbctx, struct openpgp_publickey **keys,
 363                 uint64_t policies)
 364 {
 365         struct openpgp_publickey **curkey, *tmp;
 366         struct openpgp_fingerprint fp;
 367         int changed = 0, count = 0;
 368         bool needother;
 369
 370         if (keys == NULL)
 371                 return 0;
 372
 373         curkey = keys;
 374         while (*curkey != NULL) {
 375                 if (policies & ONAK_CLEAN_DROP_V3_KEYS) {
 376                         if ((*curkey)->publickey->data[0] < 4) {
 377                                 /* Remove the key from the list if it's < v4 */
 378                                 tmp = *curkey;
 379                                 *curkey = tmp->next;
 380                                 tmp->next = NULL;
 381                                 free_publickey(tmp);
 382                                 changed++;
 383                                 continue;
 384                         }
 385                 }
 386                 if (policies & ONAK_CLEAN_LARGE_PACKETS) {
 387                         count += clean_large_packets(*curkey);
 388                 }
 389                 count += dedupuids(*curkey);
 390                 count += dedupsubkeys(*curkey);
 391                 if (policies & (ONAK_CLEAN_CHECK_SIGHASH |
 392                                         ONAK_CLEAN_VERIFY_SIGNATURES)) {
 393
 394                         needother = policies & ONAK_CLEAN_NEED_OTHER_SIG;
 395                         if (needother) {
 396                                 /*
 397                                  * Check if we already have the key; if we do
 398                                  * then we can skip the check to make sure we
 399                                  * have signatures from other keys.
 400                                  */
 401                                 get_fingerprint((*curkey)->publickey, &fp);
 402                                 tmp = NULL;
 403                                 needother = dbctx->fetch_key(dbctx, &fp,
 404                                                 &tmp, false) == 0;
 405                                 free_publickey(tmp);
 406                         }
 407
 408                         count += clean_key_signatures(dbctx, *curkey,
 409                                 policies & ONAK_CLEAN_VERIFY_SIGNATURES,
 410                                 needother);
 411                 }
 412                 if (count > 0) {
 413                         changed++;
 414                 }
 415                 if ((*curkey)->uids == NULL) {
 416                         /* No valid UIDS so remove the key from the list */
 417                         tmp = *curkey;
 418                         *curkey = tmp->next;
 419                         tmp->next = NULL;
 420                         free_publickey(tmp);
 421                 } else {
 422                         curkey = &(*curkey)->next;
 423                 }
 424         }
 425
 426         return changed;
 427 }