crypto_ed25519.c 25 KB

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  1. /* Copyright (c) 2013-2017, The Tor Project, Inc. */
  2. /* See LICENSE for licensing information */
  3. /**
  4. * \file crypto_ed25519.c
  5. *
  6. * \brief Wrapper code for an ed25519 implementation.
  7. *
  8. * Ed25519 is a Schnorr signature on a Twisted Edwards curve, defined
  9. * by Dan Bernstein. For more information, see https://ed25519.cr.yp.to/
  10. *
  11. * This module wraps our choice of Ed25519 backend, and provides a few
  12. * convenience functions for checking and generating signatures. It also
  13. * provides Tor-specific tools for key blinding and for converting Ed25519
  14. * keys to and from the corresponding Curve25519 keys.
  15. */
  16. #define CRYPTO_ED25519_PRIVATE
  17. #include "orconfig.h"
  18. #ifdef HAVE_SYS_STAT_H
  19. #include <sys/stat.h>
  20. #endif
  21. #include "crypto.h"
  22. #include "crypto_curve25519.h"
  23. #include "crypto_ed25519.h"
  24. #include "crypto_format.h"
  25. #include "torlog.h"
  26. #include "util.h"
  27. #include "util_format.h"
  28. #include "ed25519/ref10/ed25519_ref10.h"
  29. #include "ed25519/donna/ed25519_donna_tor.h"
  30. static void pick_ed25519_impl(void);
  31. /** An Ed25519 implementation, as a set of function pointers. */
  32. typedef struct {
  33. int (*selftest)(void);
  34. int (*seckey)(unsigned char *);
  35. int (*seckey_expand)(unsigned char *, const unsigned char *);
  36. int (*pubkey)(unsigned char *, const unsigned char *);
  37. int (*keygen)(unsigned char *, unsigned char *);
  38. int (*open)(const unsigned char *, const unsigned char *, size_t, const
  39. unsigned char *);
  40. int (*sign)(unsigned char *, const unsigned char *, size_t,
  41. const unsigned char *, const unsigned char *);
  42. int (*open_batch)(const unsigned char **, size_t *, const unsigned char **,
  43. const unsigned char **, size_t, int *);
  44. int (*blind_secret_key)(unsigned char *, const unsigned char *,
  45. const unsigned char *);
  46. int (*blind_public_key)(unsigned char *, const unsigned char *,
  47. const unsigned char *);
  48. int (*pubkey_from_curve25519_pubkey)(unsigned char *, const unsigned char *,
  49. int);
  50. int (*ed25519_scalarmult_with_group_order)(unsigned char *,
  51. const unsigned char *);
  52. } ed25519_impl_t;
  53. /** The Ref10 Ed25519 implementation. This one is pure C and lightly
  54. * optimized. */
  55. static const ed25519_impl_t impl_ref10 = {
  56. NULL,
  57. ed25519_ref10_seckey,
  58. ed25519_ref10_seckey_expand,
  59. ed25519_ref10_pubkey,
  60. ed25519_ref10_keygen,
  61. ed25519_ref10_open,
  62. ed25519_ref10_sign,
  63. NULL,
  64. ed25519_ref10_blind_secret_key,
  65. ed25519_ref10_blind_public_key,
  66. ed25519_ref10_pubkey_from_curve25519_pubkey,
  67. ed25519_ref10_scalarmult_with_group_order,
  68. };
  69. /** The Ref10 Ed25519 implementation. This one is heavily optimized, but still
  70. * mostly C. The C still tends to be heavily platform-specific. */
  71. static const ed25519_impl_t impl_donna = {
  72. ed25519_donna_selftest,
  73. ed25519_donna_seckey,
  74. ed25519_donna_seckey_expand,
  75. ed25519_donna_pubkey,
  76. ed25519_donna_keygen,
  77. ed25519_donna_open,
  78. ed25519_donna_sign,
  79. ed25519_sign_open_batch_donna,
  80. ed25519_donna_blind_secret_key,
  81. ed25519_donna_blind_public_key,
  82. ed25519_donna_pubkey_from_curve25519_pubkey,
  83. ed25519_donna_scalarmult_with_group_order,
  84. };
  85. /** Which Ed25519 implementation are we using? NULL if we haven't decided
  86. * yet. */
  87. static const ed25519_impl_t *ed25519_impl = NULL;
  88. /** Helper: Return our chosen Ed25519 implementation.
  89. *
  90. * This should only be called after we've picked an implementation, but
  91. * it _does_ recover if you forget this.
  92. **/
  93. static inline const ed25519_impl_t *
  94. get_ed_impl(void)
  95. {
  96. if (BUG(ed25519_impl == NULL)) {
  97. pick_ed25519_impl(); // LCOV_EXCL_LINE - We always call ed25519_init().
  98. }
  99. return ed25519_impl;
  100. }
  101. #ifdef TOR_UNIT_TESTS
  102. /** For testing: used to remember our actual choice of Ed25519
  103. * implementation */
  104. static const ed25519_impl_t *saved_ed25519_impl = NULL;
  105. /** For testing: Use the Ed25519 implementation called <b>name</b> until
  106. * crypto_ed25519_testing_restore_impl is called. Recognized names are
  107. * "donna" and "ref10". */
  108. void
  109. crypto_ed25519_testing_force_impl(const char *name)
  110. {
  111. tor_assert(saved_ed25519_impl == NULL);
  112. saved_ed25519_impl = ed25519_impl;
  113. if (! strcmp(name, "donna")) {
  114. ed25519_impl = &impl_donna;
  115. } else {
  116. tor_assert(!strcmp(name, "ref10"));
  117. ed25519_impl = &impl_ref10;
  118. }
  119. }
  120. /** For testing: go back to whatever Ed25519 implementation we had picked
  121. * before crypto_ed25519_testing_force_impl was called.
  122. */
  123. void
  124. crypto_ed25519_testing_restore_impl(void)
  125. {
  126. ed25519_impl = saved_ed25519_impl;
  127. saved_ed25519_impl = NULL;
  128. }
  129. #endif /* defined(TOR_UNIT_TESTS) */
  130. /**
  131. * Initialize a new ed25519 secret key in <b>seckey_out</b>. If
  132. * <b>extra_strong</b>, take the RNG inputs directly from the operating
  133. * system. Return 0 on success, -1 on failure.
  134. */
  135. int
  136. ed25519_secret_key_generate(ed25519_secret_key_t *seckey_out,
  137. int extra_strong)
  138. {
  139. int r;
  140. uint8_t seed[32];
  141. if (extra_strong)
  142. crypto_strongest_rand(seed, sizeof(seed));
  143. else
  144. crypto_rand((char*)seed, sizeof(seed));
  145. r = get_ed_impl()->seckey_expand(seckey_out->seckey, seed);
  146. memwipe(seed, 0, sizeof(seed));
  147. return r < 0 ? -1 : 0;
  148. }
  149. /**
  150. * Given a 32-byte random seed in <b>seed</b>, expand it into an ed25519
  151. * secret key in <b>seckey_out</b>. Return 0 on success, -1 on failure.
  152. */
  153. int
  154. ed25519_secret_key_from_seed(ed25519_secret_key_t *seckey_out,
  155. const uint8_t *seed)
  156. {
  157. if (get_ed_impl()->seckey_expand(seckey_out->seckey, seed) < 0)
  158. return -1;
  159. return 0;
  160. }
  161. /**
  162. * Given a secret key in <b>seckey</b>, expand it into an
  163. * ed25519 public key. Return 0 on success, -1 on failure.
  164. */
  165. int
  166. ed25519_public_key_generate(ed25519_public_key_t *pubkey_out,
  167. const ed25519_secret_key_t *seckey)
  168. {
  169. if (get_ed_impl()->pubkey(pubkey_out->pubkey, seckey->seckey) < 0)
  170. return -1;
  171. return 0;
  172. }
  173. /** Generate a new ed25519 keypair in <b>keypair_out</b>. If
  174. * <b>extra_strong</b> is set, try to mix some system entropy into the key
  175. * generation process. Return 0 on success, -1 on failure. */
  176. int
  177. ed25519_keypair_generate(ed25519_keypair_t *keypair_out, int extra_strong)
  178. {
  179. if (ed25519_secret_key_generate(&keypair_out->seckey, extra_strong) < 0)
  180. return -1;
  181. if (ed25519_public_key_generate(&keypair_out->pubkey,
  182. &keypair_out->seckey)<0)
  183. return -1;
  184. return 0;
  185. }
  186. /** Return true iff 'pubkey' is set to zero (eg to indicate that it is not
  187. * set). */
  188. int
  189. ed25519_public_key_is_zero(const ed25519_public_key_t *pubkey)
  190. {
  191. return tor_mem_is_zero((char*)pubkey->pubkey, ED25519_PUBKEY_LEN);
  192. }
  193. /* Return a heap-allocated array that contains <b>msg</b> prefixed by the
  194. * string <b>prefix_str</b>. Set <b>final_msg_len_out</b> to the size of the
  195. * final array. If an error occured, return NULL. It's the resonsibility of the
  196. * caller to free the returned array. */
  197. static uint8_t *
  198. get_prefixed_msg(const uint8_t *msg, size_t msg_len,
  199. const char *prefix_str,
  200. size_t *final_msg_len_out)
  201. {
  202. size_t prefixed_msg_len, prefix_len;
  203. uint8_t *prefixed_msg;
  204. tor_assert(prefix_str);
  205. tor_assert(final_msg_len_out);
  206. prefix_len = strlen(prefix_str);
  207. /* msg_len + strlen(prefix_str) must not overflow. */
  208. if (msg_len > SIZE_T_CEILING - prefix_len) {
  209. return NULL;
  210. }
  211. prefixed_msg_len = msg_len + prefix_len;
  212. prefixed_msg = tor_malloc_zero(prefixed_msg_len);
  213. memcpy(prefixed_msg, prefix_str, prefix_len);
  214. memcpy(prefixed_msg + prefix_len, msg, msg_len);
  215. *final_msg_len_out = prefixed_msg_len;
  216. return prefixed_msg;
  217. }
  218. /**
  219. * Set <b>signature_out</b> to a signature of the <b>len</b>-byte message
  220. * <b>msg</b>, using the secret and public key in <b>keypair</b>.
  221. *
  222. * Return 0 if we successfuly signed the message, otherwise return -1.
  223. */
  224. int
  225. ed25519_sign(ed25519_signature_t *signature_out,
  226. const uint8_t *msg, size_t len,
  227. const ed25519_keypair_t *keypair)
  228. {
  229. if (get_ed_impl()->sign(signature_out->sig, msg, len,
  230. keypair->seckey.seckey,
  231. keypair->pubkey.pubkey) < 0) {
  232. return -1;
  233. }
  234. return 0;
  235. }
  236. /**
  237. * Like ed25519_sign(), but also prefix <b>msg</b> with <b>prefix_str</b>
  238. * before signing. <b>prefix_str</b> must be a NUL-terminated string.
  239. */
  240. MOCK_IMPL(int,
  241. ed25519_sign_prefixed,(ed25519_signature_t *signature_out,
  242. const uint8_t *msg, size_t msg_len,
  243. const char *prefix_str,
  244. const ed25519_keypair_t *keypair))
  245. {
  246. int retval;
  247. size_t prefixed_msg_len;
  248. uint8_t *prefixed_msg;
  249. tor_assert(prefix_str);
  250. prefixed_msg = get_prefixed_msg(msg, msg_len, prefix_str,
  251. &prefixed_msg_len);
  252. if (BUG(!prefixed_msg)) {
  253. /* LCOV_EXCL_START -- only possible when the message and prefix are
  254. * ridiculously huge */
  255. log_warn(LD_GENERAL, "Failed to get prefixed msg.");
  256. return -1;
  257. /* LCOV_EXCL_STOP */
  258. }
  259. retval = ed25519_sign(signature_out,
  260. prefixed_msg, prefixed_msg_len,
  261. keypair);
  262. tor_free(prefixed_msg);
  263. return retval;
  264. }
  265. /**
  266. * Check whether if <b>signature</b> is a valid signature for the
  267. * <b>len</b>-byte message in <b>msg</b> made with the key <b>pubkey</b>.
  268. *
  269. * Return 0 if the signature is valid; -1 if it isn't.
  270. */
  271. MOCK_IMPL(int,
  272. ed25519_checksig,(const ed25519_signature_t *signature,
  273. const uint8_t *msg, size_t len,
  274. const ed25519_public_key_t *pubkey))
  275. {
  276. return
  277. get_ed_impl()->open(signature->sig, msg, len, pubkey->pubkey) < 0 ? -1 : 0;
  278. }
  279. /**
  280. * Like ed2519_checksig(), but also prefix <b>msg</b> with <b>prefix_str</b>
  281. * before verifying signature. <b>prefix_str</b> must be a NUL-terminated
  282. * string.
  283. */
  284. int
  285. ed25519_checksig_prefixed(const ed25519_signature_t *signature,
  286. const uint8_t *msg, size_t msg_len,
  287. const char *prefix_str,
  288. const ed25519_public_key_t *pubkey)
  289. {
  290. int retval;
  291. size_t prefixed_msg_len;
  292. uint8_t *prefixed_msg;
  293. prefixed_msg = get_prefixed_msg(msg, msg_len, prefix_str,
  294. &prefixed_msg_len);
  295. if (BUG(!prefixed_msg)) {
  296. /* LCOV_EXCL_START -- only possible when the message and prefix are
  297. * ridiculously huge */
  298. log_warn(LD_GENERAL, "Failed to get prefixed msg.");
  299. return -1;
  300. /* LCOV_EXCL_STOP */
  301. }
  302. retval = ed25519_checksig(signature,
  303. prefixed_msg, prefixed_msg_len,
  304. pubkey);
  305. tor_free(prefixed_msg);
  306. return retval;
  307. }
  308. /** Validate every signature among those in <b>checkable</b>, which contains
  309. * exactly <b>n_checkable</b> elements. If <b>okay_out</b> is non-NULL, set
  310. * the i'th element of <b>okay_out</b> to 1 if the i'th element of
  311. * <b>checkable</b> is valid, and to 0 otherwise. Return 0 if every signature
  312. * was valid. Otherwise return -N, where N is the number of invalid
  313. * signatures.
  314. */
  315. MOCK_IMPL(int,
  316. ed25519_checksig_batch,(int *okay_out,
  317. const ed25519_checkable_t *checkable,
  318. int n_checkable))
  319. {
  320. int i, res;
  321. const ed25519_impl_t *impl = get_ed_impl();
  322. if (impl->open_batch == NULL) {
  323. /* No batch verification implementation available, fake it by checking the
  324. * each signature individually.
  325. */
  326. res = 0;
  327. for (i = 0; i < n_checkable; ++i) {
  328. const ed25519_checkable_t *ch = &checkable[i];
  329. int r = ed25519_checksig(&ch->signature, ch->msg, ch->len, ch->pubkey);
  330. if (r < 0)
  331. --res;
  332. if (okay_out)
  333. okay_out[i] = (r == 0);
  334. }
  335. } else {
  336. /* ed25519-donna style batch verification available.
  337. *
  338. * Theoretically, this should only be called if n_checkable >= 3, since
  339. * that's the threshold where the batch verification actually kicks in,
  340. * but the only difference is a few mallocs/frees.
  341. */
  342. const uint8_t **ms;
  343. size_t *lens;
  344. const uint8_t **pks;
  345. const uint8_t **sigs;
  346. int *oks;
  347. int all_ok;
  348. ms = tor_calloc(n_checkable, sizeof(uint8_t*));
  349. lens = tor_calloc(n_checkable, sizeof(size_t));
  350. pks = tor_calloc(n_checkable, sizeof(uint8_t*));
  351. sigs = tor_calloc(n_checkable, sizeof(uint8_t*));
  352. oks = okay_out ? okay_out : tor_calloc(n_checkable, sizeof(int));
  353. for (i = 0; i < n_checkable; ++i) {
  354. ms[i] = checkable[i].msg;
  355. lens[i] = checkable[i].len;
  356. pks[i] = checkable[i].pubkey->pubkey;
  357. sigs[i] = checkable[i].signature.sig;
  358. oks[i] = 0;
  359. }
  360. res = 0;
  361. all_ok = impl->open_batch(ms, lens, pks, sigs, n_checkable, oks);
  362. for (i = 0; i < n_checkable; ++i) {
  363. if (!oks[i])
  364. --res;
  365. }
  366. /* XXX: For now sanity check oks with the return value. Once we have
  367. * more confidence in the code, if `all_ok == 0` we can skip iterating
  368. * over oks since all the signatures were found to be valid.
  369. */
  370. tor_assert(((res == 0) && !all_ok) || ((res < 0) && all_ok));
  371. tor_free(ms);
  372. tor_free(lens);
  373. tor_free(pks);
  374. tor_free(sigs);
  375. if (! okay_out)
  376. tor_free(oks);
  377. }
  378. return res;
  379. }
  380. /**
  381. * Given a curve25519 keypair in <b>inp</b>, generate a corresponding
  382. * ed25519 keypair in <b>out</b>, and set <b>signbit_out</b> to the
  383. * sign bit of the X coordinate of the ed25519 key.
  384. *
  385. * NOTE THAT IT IS PROBABLY NOT SAFE TO USE THE GENERATED KEY FOR ANYTHING
  386. * OUTSIDE OF WHAT'S PRESENTED IN PROPOSAL 228. In particular, it's probably
  387. * not a great idea to use it to sign attacker-supplied anything.
  388. */
  389. int
  390. ed25519_keypair_from_curve25519_keypair(ed25519_keypair_t *out,
  391. int *signbit_out,
  392. const curve25519_keypair_t *inp)
  393. {
  394. const char string[] = "Derive high part of ed25519 key from curve25519 key";
  395. ed25519_public_key_t pubkey_check;
  396. crypto_digest_t *ctx;
  397. uint8_t sha512_output[DIGEST512_LEN];
  398. memcpy(out->seckey.seckey, inp->seckey.secret_key, 32);
  399. ctx = crypto_digest512_new(DIGEST_SHA512);
  400. crypto_digest_add_bytes(ctx, (const char*)out->seckey.seckey, 32);
  401. crypto_digest_add_bytes(ctx, (const char*)string, sizeof(string));
  402. crypto_digest_get_digest(ctx, (char *)sha512_output, sizeof(sha512_output));
  403. crypto_digest_free(ctx);
  404. memcpy(out->seckey.seckey + 32, sha512_output, 32);
  405. ed25519_public_key_generate(&out->pubkey, &out->seckey);
  406. *signbit_out = out->pubkey.pubkey[31] >> 7;
  407. ed25519_public_key_from_curve25519_public_key(&pubkey_check, &inp->pubkey,
  408. *signbit_out);
  409. tor_assert(fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey, 32));
  410. memwipe(&pubkey_check, 0, sizeof(pubkey_check));
  411. memwipe(sha512_output, 0, sizeof(sha512_output));
  412. return 0;
  413. }
  414. /**
  415. * Given a curve25519 public key and sign bit of X coordinate of the ed25519
  416. * public key, generate the corresponding ed25519 public key.
  417. */
  418. int
  419. ed25519_public_key_from_curve25519_public_key(ed25519_public_key_t *pubkey,
  420. const curve25519_public_key_t *pubkey_in,
  421. int signbit)
  422. {
  423. return get_ed_impl()->pubkey_from_curve25519_pubkey(pubkey->pubkey,
  424. pubkey_in->public_key,
  425. signbit);
  426. }
  427. /**
  428. * Given an ed25519 keypair in <b>inp</b>, generate a corresponding
  429. * ed25519 keypair in <b>out</b>, blinded by the corresponding 32-byte input
  430. * in 'param'.
  431. *
  432. * Tor uses key blinding for the "next-generation" hidden services design:
  433. * service descriptors are encrypted with a key derived from the service's
  434. * long-term public key, and then signed with (and stored at a position
  435. * indexed by) a short-term key derived by blinding the long-term keys.
  436. *
  437. * Return 0 if blinding was successful, else return -1. */
  438. int
  439. ed25519_keypair_blind(ed25519_keypair_t *out,
  440. const ed25519_keypair_t *inp,
  441. const uint8_t *param)
  442. {
  443. ed25519_public_key_t pubkey_check;
  444. get_ed_impl()->blind_secret_key(out->seckey.seckey,
  445. inp->seckey.seckey, param);
  446. if (ed25519_public_blind(&pubkey_check, &inp->pubkey, param) < 0) {
  447. return -1;
  448. }
  449. ed25519_public_key_generate(&out->pubkey, &out->seckey);
  450. tor_assert(fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey, 32));
  451. memwipe(&pubkey_check, 0, sizeof(pubkey_check));
  452. return 0;
  453. }
  454. /**
  455. * Given an ed25519 public key in <b>inp</b>, generate a corresponding blinded
  456. * public key in <b>out</b>, blinded with the 32-byte parameter in
  457. * <b>param</b>. Return 0 on sucess, -1 on railure.
  458. */
  459. int
  460. ed25519_public_blind(ed25519_public_key_t *out,
  461. const ed25519_public_key_t *inp,
  462. const uint8_t *param)
  463. {
  464. return get_ed_impl()->blind_public_key(out->pubkey, inp->pubkey, param);
  465. }
  466. /**
  467. * Store seckey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
  468. * Return 0 on success, -1 on failure.
  469. */
  470. int
  471. ed25519_seckey_write_to_file(const ed25519_secret_key_t *seckey,
  472. const char *filename,
  473. const char *tag)
  474. {
  475. return crypto_write_tagged_contents_to_file(filename,
  476. "ed25519v1-secret",
  477. tag,
  478. seckey->seckey,
  479. sizeof(seckey->seckey));
  480. }
  481. /**
  482. * Read seckey unencrypted from <b>filename</b>, storing it into
  483. * <b>seckey_out</b>. Set *<b>tag_out</b> to the tag it was marked with.
  484. * Return 0 on success, -1 on failure.
  485. */
  486. int
  487. ed25519_seckey_read_from_file(ed25519_secret_key_t *seckey_out,
  488. char **tag_out,
  489. const char *filename)
  490. {
  491. ssize_t len;
  492. len = crypto_read_tagged_contents_from_file(filename, "ed25519v1-secret",
  493. tag_out, seckey_out->seckey,
  494. sizeof(seckey_out->seckey));
  495. if (len == sizeof(seckey_out->seckey)) {
  496. return 0;
  497. } else if (len >= 0) {
  498. errno = EINVAL;
  499. }
  500. tor_free(*tag_out);
  501. return -1;
  502. }
  503. /**
  504. * Store pubkey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
  505. * Return 0 on success, -1 on failure.
  506. */
  507. int
  508. ed25519_pubkey_write_to_file(const ed25519_public_key_t *pubkey,
  509. const char *filename,
  510. const char *tag)
  511. {
  512. return crypto_write_tagged_contents_to_file(filename,
  513. "ed25519v1-public",
  514. tag,
  515. pubkey->pubkey,
  516. sizeof(pubkey->pubkey));
  517. }
  518. /**
  519. * Store pubkey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
  520. * Return 0 on success, -1 on failure.
  521. */
  522. int
  523. ed25519_pubkey_read_from_file(ed25519_public_key_t *pubkey_out,
  524. char **tag_out,
  525. const char *filename)
  526. {
  527. ssize_t len;
  528. len = crypto_read_tagged_contents_from_file(filename, "ed25519v1-public",
  529. tag_out, pubkey_out->pubkey,
  530. sizeof(pubkey_out->pubkey));
  531. if (len == sizeof(pubkey_out->pubkey)) {
  532. return 0;
  533. } else if (len >= 0) {
  534. errno = EINVAL;
  535. }
  536. tor_free(*tag_out);
  537. return -1;
  538. }
  539. /** Release all storage held for <b>kp</b>. */
  540. void
  541. ed25519_keypair_free(ed25519_keypair_t *kp)
  542. {
  543. if (! kp)
  544. return;
  545. memwipe(kp, 0, sizeof(*kp));
  546. tor_free(kp);
  547. }
  548. /** Return true iff <b>key1</b> and <b>key2</b> are the same public key. */
  549. int
  550. ed25519_pubkey_eq(const ed25519_public_key_t *key1,
  551. const ed25519_public_key_t *key2)
  552. {
  553. tor_assert(key1);
  554. tor_assert(key2);
  555. return tor_memeq(key1->pubkey, key2->pubkey, ED25519_PUBKEY_LEN);
  556. }
  557. /**
  558. * Set <b>dest</b> to contain the same key as <b>src</b>.
  559. */
  560. void
  561. ed25519_pubkey_copy(ed25519_public_key_t *dest,
  562. const ed25519_public_key_t *src)
  563. {
  564. tor_assert(dest);
  565. tor_assert(src);
  566. memcpy(dest, src, sizeof(ed25519_public_key_t));
  567. }
  568. /** Check whether the given Ed25519 implementation seems to be working.
  569. * If so, return 0; otherwise return -1. */
  570. MOCK_IMPL(STATIC int,
  571. ed25519_impl_spot_check,(void))
  572. {
  573. static const uint8_t alicesk[32] = {
  574. 0xc5,0xaa,0x8d,0xf4,0x3f,0x9f,0x83,0x7b,
  575. 0xed,0xb7,0x44,0x2f,0x31,0xdc,0xb7,0xb1,
  576. 0x66,0xd3,0x85,0x35,0x07,0x6f,0x09,0x4b,
  577. 0x85,0xce,0x3a,0x2e,0x0b,0x44,0x58,0xf7
  578. };
  579. static const uint8_t alicepk[32] = {
  580. 0xfc,0x51,0xcd,0x8e,0x62,0x18,0xa1,0xa3,
  581. 0x8d,0xa4,0x7e,0xd0,0x02,0x30,0xf0,0x58,
  582. 0x08,0x16,0xed,0x13,0xba,0x33,0x03,0xac,
  583. 0x5d,0xeb,0x91,0x15,0x48,0x90,0x80,0x25
  584. };
  585. static const uint8_t alicemsg[2] = { 0xaf, 0x82 };
  586. static const uint8_t alicesig[64] = {
  587. 0x62,0x91,0xd6,0x57,0xde,0xec,0x24,0x02,
  588. 0x48,0x27,0xe6,0x9c,0x3a,0xbe,0x01,0xa3,
  589. 0x0c,0xe5,0x48,0xa2,0x84,0x74,0x3a,0x44,
  590. 0x5e,0x36,0x80,0xd7,0xdb,0x5a,0xc3,0xac,
  591. 0x18,0xff,0x9b,0x53,0x8d,0x16,0xf2,0x90,
  592. 0xae,0x67,0xf7,0x60,0x98,0x4d,0xc6,0x59,
  593. 0x4a,0x7c,0x15,0xe9,0x71,0x6e,0xd2,0x8d,
  594. 0xc0,0x27,0xbe,0xce,0xea,0x1e,0xc4,0x0a
  595. };
  596. const ed25519_impl_t *impl = get_ed_impl();
  597. uint8_t sk[ED25519_SECKEY_LEN];
  598. uint8_t pk[ED25519_PUBKEY_LEN];
  599. uint8_t sig[ED25519_SIG_LEN];
  600. int r = 0;
  601. /* Some implementations (eg: The modified Ed25519-donna) have handy self-test
  602. * code that sanity-checks the internals. If present, use that to screen out
  603. * catastrophic errors like massive compiler failure.
  604. */
  605. if (impl->selftest && impl->selftest() != 0)
  606. goto fail;
  607. /* Validate results versus known answer tests. People really should be
  608. * running "make test" instead of relying on this, but it's better than
  609. * nothing.
  610. *
  611. * Test vectors taken from "EdDSA & Ed25519 - 6. Test Vectors for Ed25519
  612. * (TEST3)" (draft-josefsson-eddsa-ed25519-03).
  613. */
  614. /* Key expansion, public key derivation. */
  615. if (impl->seckey_expand(sk, alicesk) < 0)
  616. goto fail;
  617. if (impl->pubkey(pk, sk) < 0)
  618. goto fail;
  619. if (fast_memneq(pk, alicepk, ED25519_PUBKEY_LEN))
  620. goto fail;
  621. /* Signing, verification. */
  622. if (impl->sign(sig, alicemsg, sizeof(alicemsg), sk, pk) < 0)
  623. return -1;
  624. if (fast_memneq(sig, alicesig, ED25519_SIG_LEN))
  625. return -1;
  626. if (impl->open(sig, alicemsg, sizeof(alicemsg), pk) < 0)
  627. return -1;
  628. /* XXX/yawning: Someone that's more paranoid than I am, can write "Assume
  629. * ref0 is cannonical, and fuzz impl against it" if they want, but I doubt
  630. * that will catch anything that the known answer tests won't.
  631. */
  632. goto end;
  633. // LCOV_EXCL_START -- We can only reach this if our ed25519 implementation is
  634. // broken.
  635. fail:
  636. r = -1;
  637. // LCOV_EXCL_STOP
  638. end:
  639. return r;
  640. }
  641. /** Force the Ed25519 implementation to a given one, without sanity checking
  642. * the output. Used for testing.
  643. */
  644. void
  645. ed25519_set_impl_params(int use_donna)
  646. {
  647. if (use_donna)
  648. ed25519_impl = &impl_donna;
  649. else
  650. ed25519_impl = &impl_ref10;
  651. }
  652. /** Choose whether to use the Ed25519-donna implementation. */
  653. static void
  654. pick_ed25519_impl(void)
  655. {
  656. ed25519_impl = &impl_donna;
  657. if (ed25519_impl_spot_check() == 0)
  658. return;
  659. /* LCOV_EXCL_START
  660. * unreachable unless ed25519_donna is broken */
  661. log_warn(LD_CRYPTO, "The Ed25519-donna implementation seems broken; using "
  662. "the ref10 implementation.");
  663. ed25519_impl = &impl_ref10;
  664. /* LCOV_EXCL_STOP */
  665. }
  666. /* Initialize the Ed25519 implementation. This is neccessary if you're
  667. * going to use them in a multithreaded setting, and not otherwise. */
  668. void
  669. ed25519_init(void)
  670. {
  671. pick_ed25519_impl();
  672. }
  673. /* Return true if <b>point</b> is the identity element of the ed25519 group. */
  674. static int
  675. ed25519_point_is_identity_element(const uint8_t *point)
  676. {
  677. /* The identity element in ed25159 is the point with coordinates (0,1). */
  678. static const uint8_t ed25519_identity[32] = {
  679. 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  680. 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  681. 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  682. 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
  683. tor_assert(sizeof(ed25519_identity) == ED25519_PUBKEY_LEN);
  684. return tor_memeq(point, ed25519_identity, sizeof(ed25519_identity));
  685. }
  686. /** Validate <b>pubkey</b> to ensure that it has no torsion component.
  687. * Return 0 if <b>pubkey</b> is valid, else return -1. */
  688. int
  689. ed25519_validate_pubkey(const ed25519_public_key_t *pubkey)
  690. {
  691. uint8_t result[32] = {9};
  692. /* First check that we were not given the identity element */
  693. if (ed25519_point_is_identity_element(pubkey->pubkey)) {
  694. log_warn(LD_CRYPTO, "ed25519 pubkey is the identity");
  695. return -1;
  696. }
  697. /* For any point on the curve, doing l*point should give the identity element
  698. * (where l is the group order). Do the computation and check that the
  699. * identity element is returned. */
  700. if (get_ed_impl()->ed25519_scalarmult_with_group_order(result,
  701. pubkey->pubkey) < 0) {
  702. log_warn(LD_CRYPTO, "ed25519 group order scalarmult failed");
  703. return -1;
  704. }
  705. if (!ed25519_point_is_identity_element(result)) {
  706. log_warn(LD_CRYPTO, "ed25519 validation failed");
  707. return -1;
  708. }
  709. return 0;
  710. }