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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * auth-scram.c
4 : : * Server-side implementation of the SASL SCRAM-SHA-256 mechanism.
5 : : *
6 : : * See the following RFCs for more details:
7 : : * - RFC 5802: https://tools.ietf.org/html/rfc5802
8 : : * - RFC 5803: https://tools.ietf.org/html/rfc5803
9 : : * - RFC 7677: https://tools.ietf.org/html/rfc7677
10 : : *
11 : : * Here are some differences:
12 : : *
13 : : * - Username from the authentication exchange is not used. The client
14 : : * should send an empty string as the username.
15 : : *
16 : : * - If the password isn't valid UTF-8, or contains characters prohibited
17 : : * by the SASLprep profile, we skip the SASLprep pre-processing and use
18 : : * the raw bytes in calculating the hash.
19 : : *
20 : : * - If channel binding is used, the channel binding type is always
21 : : * "tls-server-end-point". The spec says the default is "tls-unique"
22 : : * (RFC 5802, section 6.1. Default Channel Binding), but there are some
23 : : * problems with that. Firstly, not all SSL libraries provide an API to
24 : : * get the TLS Finished message, required to use "tls-unique". Secondly,
25 : : * "tls-unique" is not specified for TLS v1.3, and as of this writing,
26 : : * it's not clear if there will be a replacement. We could support both
27 : : * "tls-server-end-point" and "tls-unique", but for our use case,
28 : : * "tls-unique" doesn't really have any advantages. The main advantage
29 : : * of "tls-unique" would be that it works even if the server doesn't
30 : : * have a certificate, but PostgreSQL requires a server certificate
31 : : * whenever SSL is used, anyway.
32 : : *
33 : : *
34 : : * The password stored in pg_authid consists of the iteration count, salt,
35 : : * StoredKey and ServerKey.
36 : : *
37 : : * SASLprep usage
38 : : * --------------
39 : : *
40 : : * One notable difference to the SCRAM specification is that while the
41 : : * specification dictates that the password is in UTF-8, and prohibits
42 : : * certain characters, we are more lenient. If the password isn't a valid
43 : : * UTF-8 string, or contains prohibited characters, the raw bytes are used
44 : : * to calculate the hash instead, without SASLprep processing. This is
45 : : * because PostgreSQL supports other encodings too, and the encoding being
46 : : * used during authentication is undefined (client_encoding isn't set until
47 : : * after authentication). In effect, we try to interpret the password as
48 : : * UTF-8 and apply SASLprep processing, but if it looks invalid, we assume
49 : : * that it's in some other encoding.
50 : : *
51 : : * In the worst case, we misinterpret a password that's in a different
52 : : * encoding as being Unicode, because it happens to consists entirely of
53 : : * valid UTF-8 bytes, and we apply Unicode normalization to it. As long
54 : : * as we do that consistently, that will not lead to failed logins.
55 : : * Fortunately, the UTF-8 byte sequences that are ignored by SASLprep
56 : : * don't correspond to any commonly used characters in any of the other
57 : : * supported encodings, so it should not lead to any significant loss in
58 : : * entropy, even if the normalization is incorrectly applied to a
59 : : * non-UTF-8 password.
60 : : *
61 : : * Error handling
62 : : * --------------
63 : : *
64 : : * Don't reveal user information to an unauthenticated client. We don't
65 : : * want an attacker to be able to probe whether a particular username is
66 : : * valid. In SCRAM, the server has to read the salt and iteration count
67 : : * from the user's stored secret, and send it to the client. To avoid
68 : : * revealing whether a user exists, when the client tries to authenticate
69 : : * with a username that doesn't exist, or doesn't have a valid SCRAM
70 : : * secret in pg_authid, we create a fake salt and iteration count
71 : : * on-the-fly, and proceed with the authentication with that. In the end,
72 : : * we'll reject the attempt, as if an incorrect password was given. When
73 : : * we are performing a "mock" authentication, the 'doomed' flag in
74 : : * scram_state is set.
75 : : *
76 : : * In the error messages, avoid printing strings from the client, unless
77 : : * you check that they are pure ASCII. We don't want an unauthenticated
78 : : * attacker to be able to spam the logs with characters that are not valid
79 : : * to the encoding being used, whatever that is. We cannot avoid that in
80 : : * general, after logging in, but let's do what we can here.
81 : : *
82 : : *
83 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
84 : : * Portions Copyright (c) 1994, Regents of the University of California
85 : : *
86 : : * src/backend/libpq/auth-scram.c
87 : : *
88 : : *-------------------------------------------------------------------------
89 : : */
90 : : #include "postgres.h"
91 : :
92 : : #include <unistd.h>
93 : :
94 : : #include "access/xlog.h"
95 : : #include "catalog/pg_control.h"
96 : : #include "common/base64.h"
97 : : #include "common/hmac.h"
98 : : #include "common/saslprep.h"
99 : : #include "common/scram-common.h"
100 : : #include "common/sha2.h"
101 : : #include "libpq/crypt.h"
102 : : #include "libpq/sasl.h"
103 : : #include "libpq/scram.h"
104 : : #include "miscadmin.h"
105 : :
106 : : static void scram_get_mechanisms(Port *port, StringInfo buf);
107 : : static void *scram_init(Port *port, const char *selected_mech,
108 : : const char *shadow_pass);
109 : : static int scram_exchange(void *opaq, const char *input, int inputlen,
110 : : char **output, int *outputlen,
111 : : const char **logdetail);
112 : :
113 : : /* Mechanism declaration */
114 : : const pg_be_sasl_mech pg_be_scram_mech = {
115 : : scram_get_mechanisms,
116 : : scram_init,
117 : : scram_exchange,
118 : :
119 : : PG_MAX_SASL_MESSAGE_LENGTH
120 : : };
121 : :
122 : : /*
123 : : * Status data for a SCRAM authentication exchange. This should be kept
124 : : * internal to this file.
125 : : */
126 : : typedef enum
127 : : {
128 : : SCRAM_AUTH_INIT,
129 : : SCRAM_AUTH_SALT_SENT,
130 : : SCRAM_AUTH_FINISHED,
131 : : } scram_state_enum;
132 : :
133 : : typedef struct
134 : : {
135 : : scram_state_enum state;
136 : :
137 : : Port *port;
138 : : bool channel_binding_in_use;
139 : :
140 : : /* State data depending on the hash type */
141 : : pg_cryptohash_type hash_type;
142 : : int key_length;
143 : :
144 : : int iterations;
145 : : char *salt; /* base64-encoded */
146 : : uint8 ClientKey[SCRAM_MAX_KEY_LEN];
147 : : uint8 StoredKey[SCRAM_MAX_KEY_LEN];
148 : : uint8 ServerKey[SCRAM_MAX_KEY_LEN];
149 : :
150 : : /* Fields of the first message from client */
151 : : char cbind_flag;
152 : : char *client_first_message_bare;
153 : : char *client_username;
154 : : char *client_nonce;
155 : :
156 : : /* Fields from the last message from client */
157 : : char *client_final_message_without_proof;
158 : : char *client_final_nonce;
159 : : uint8 ClientProof[SCRAM_MAX_KEY_LEN];
160 : :
161 : : /* Fields generated in the server */
162 : : char *server_first_message;
163 : : char *server_nonce;
164 : :
165 : : /*
166 : : * If something goes wrong during the authentication, or we are performing
167 : : * a "mock" authentication (see comments at top of file), the 'doomed'
168 : : * flag is set. A reason for the failure, for the server log, is put in
169 : : * 'logdetail'.
170 : : */
171 : : bool doomed;
172 : : char *logdetail;
173 : : } scram_state;
174 : :
175 : : static void read_client_first_message(scram_state *state, const char *input);
176 : : static void read_client_final_message(scram_state *state, const char *input);
177 : : static char *build_server_first_message(scram_state *state);
178 : : static char *build_server_final_message(scram_state *state);
179 : : static bool verify_client_proof(scram_state *state);
180 : : static bool verify_final_nonce(scram_state *state);
181 : : static void mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
182 : : int *iterations, int *key_length, char **salt,
183 : : uint8 *stored_key, uint8 *server_key);
184 : : static bool is_scram_printable(char *p);
185 : : static char *sanitize_char(char c);
186 : : static char *sanitize_str(const char *s);
187 : : static uint8 *scram_mock_salt(const char *username,
188 : : pg_cryptohash_type hash_type,
189 : : int key_length);
190 : :
191 : : /*
192 : : * The number of iterations to use when generating new secrets.
193 : : */
194 : : int scram_sha_256_iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
195 : :
196 : : /*
197 : : * Get a list of SASL mechanisms that this module supports.
198 : : *
199 : : * For the convenience of building the FE/BE packet that lists the
200 : : * mechanisms, the names are appended to the given StringInfo buffer,
201 : : * separated by '\0' bytes.
202 : : */
203 : : static void
204 : 0 : scram_get_mechanisms(Port *port, StringInfo buf)
205 : : {
206 : : /*
207 : : * Advertise the mechanisms in decreasing order of importance. So the
208 : : * channel-binding variants go first, if they are supported. Channel
209 : : * binding is only supported with SSL.
210 : : */
211 : : #ifdef USE_SSL
212 [ # # ]: 0 : if (port->ssl_in_use)
213 : : {
214 : 0 : appendStringInfoString(buf, SCRAM_SHA_256_PLUS_NAME);
215 : 0 : appendStringInfoChar(buf, '\0');
216 : 0 : }
217 : : #endif
218 : 0 : appendStringInfoString(buf, SCRAM_SHA_256_NAME);
219 : 0 : appendStringInfoChar(buf, '\0');
220 : 0 : }
221 : :
222 : : /*
223 : : * Initialize a new SCRAM authentication exchange status tracker. This
224 : : * needs to be called before doing any exchange. It will be filled later
225 : : * after the beginning of the exchange with authentication information.
226 : : *
227 : : * 'selected_mech' identifies the SASL mechanism that the client selected.
228 : : * It should be one of the mechanisms that we support, as returned by
229 : : * scram_get_mechanisms().
230 : : *
231 : : * 'shadow_pass' is the role's stored secret, from pg_authid.rolpassword.
232 : : * The username was provided by the client in the startup message, and is
233 : : * available in port->user_name. If 'shadow_pass' is NULL, we still perform
234 : : * an authentication exchange, but it will fail, as if an incorrect password
235 : : * was given.
236 : : */
237 : : static void *
238 : 0 : scram_init(Port *port, const char *selected_mech, const char *shadow_pass)
239 : : {
240 : 0 : scram_state *state;
241 : 0 : bool got_secret;
242 : :
243 : 0 : state = palloc0_object(scram_state);
244 : 0 : state->port = port;
245 : 0 : state->state = SCRAM_AUTH_INIT;
246 : :
247 : : /*
248 : : * Parse the selected mechanism.
249 : : *
250 : : * Note that if we don't support channel binding, or if we're not using
251 : : * SSL at all, we would not have advertised the PLUS variant in the first
252 : : * place. If the client nevertheless tries to select it, it's a protocol
253 : : * violation like selecting any other SASL mechanism we don't support.
254 : : */
255 : : #ifdef USE_SSL
256 [ # # # # ]: 0 : if (strcmp(selected_mech, SCRAM_SHA_256_PLUS_NAME) == 0 && port->ssl_in_use)
257 : 0 : state->channel_binding_in_use = true;
258 : : else
259 : : #endif
260 [ # # ]: 0 : if (strcmp(selected_mech, SCRAM_SHA_256_NAME) == 0)
261 : 0 : state->channel_binding_in_use = false;
262 : : else
263 [ # # # # ]: 0 : ereport(ERROR,
264 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
265 : : errmsg("client selected an invalid SASL authentication mechanism")));
266 : :
267 : : /*
268 : : * Parse the stored secret.
269 : : */
270 [ # # ]: 0 : if (shadow_pass)
271 : : {
272 : 0 : int password_type = get_password_type(shadow_pass);
273 : :
274 [ # # ]: 0 : if (password_type == PASSWORD_TYPE_SCRAM_SHA_256)
275 : : {
276 [ # # # # ]: 0 : if (parse_scram_secret(shadow_pass, &state->iterations,
277 : 0 : &state->hash_type, &state->key_length,
278 : 0 : &state->salt,
279 : 0 : state->StoredKey,
280 : 0 : state->ServerKey))
281 : 0 : got_secret = true;
282 : : else
283 : : {
284 : : /*
285 : : * The password looked like a SCRAM secret, but could not be
286 : : * parsed.
287 : : */
288 [ # # # # ]: 0 : ereport(LOG,
289 : : (errmsg("invalid SCRAM secret for user \"%s\"",
290 : : state->port->user_name)));
291 : 0 : got_secret = false;
292 : : }
293 : 0 : }
294 : : else
295 : : {
296 : : /*
297 : : * The user doesn't have SCRAM secret. (You cannot do SCRAM
298 : : * authentication with an MD5 hash.)
299 : : */
300 : 0 : state->logdetail = psprintf(_("User \"%s\" does not have a valid SCRAM secret."),
301 : 0 : state->port->user_name);
302 : 0 : got_secret = false;
303 : : }
304 : 0 : }
305 : : else
306 : : {
307 : : /*
308 : : * The caller requested us to perform a dummy authentication. This is
309 : : * considered normal, since the caller requested it, so don't set log
310 : : * detail.
311 : : */
312 : 0 : got_secret = false;
313 : : }
314 : :
315 : : /*
316 : : * If the user did not have a valid SCRAM secret, we still go through the
317 : : * motions with a mock one, and fail as if the client supplied an
318 : : * incorrect password. This is to avoid revealing information to an
319 : : * attacker.
320 : : */
321 [ # # ]: 0 : if (!got_secret)
322 : : {
323 : 0 : mock_scram_secret(state->port->user_name, &state->hash_type,
324 : 0 : &state->iterations, &state->key_length,
325 : 0 : &state->salt,
326 : 0 : state->StoredKey, state->ServerKey);
327 : 0 : state->doomed = true;
328 : 0 : }
329 : :
330 : 0 : return state;
331 : 0 : }
332 : :
333 : : /*
334 : : * Continue a SCRAM authentication exchange.
335 : : *
336 : : * 'input' is the SCRAM payload sent by the client. On the first call,
337 : : * 'input' contains the "Initial Client Response" that the client sent as
338 : : * part of the SASLInitialResponse message, or NULL if no Initial Client
339 : : * Response was given. (The SASL specification distinguishes between an
340 : : * empty response and non-existing one.) On subsequent calls, 'input'
341 : : * cannot be NULL. For convenience in this function, the caller must
342 : : * ensure that there is a null terminator at input[inputlen].
343 : : *
344 : : * The next message to send to client is saved in 'output', for a length
345 : : * of 'outputlen'. In the case of an error, optionally store a palloc'd
346 : : * string at *logdetail that will be sent to the postmaster log (but not
347 : : * the client).
348 : : */
349 : : static int
350 : 0 : scram_exchange(void *opaq, const char *input, int inputlen,
351 : : char **output, int *outputlen, const char **logdetail)
352 : : {
353 : 0 : scram_state *state = (scram_state *) opaq;
354 : 0 : int result;
355 : :
356 : 0 : *output = NULL;
357 : :
358 : : /*
359 : : * If the client didn't include an "Initial Client Response" in the
360 : : * SASLInitialResponse message, send an empty challenge, to which the
361 : : * client will respond with the same data that usually comes in the
362 : : * Initial Client Response.
363 : : */
364 [ # # ]: 0 : if (input == NULL)
365 : : {
366 [ # # ]: 0 : Assert(state->state == SCRAM_AUTH_INIT);
367 : :
368 : 0 : *output = pstrdup("");
369 : 0 : *outputlen = 0;
370 : 0 : return PG_SASL_EXCHANGE_CONTINUE;
371 : : }
372 : :
373 : : /*
374 : : * Check that the input length agrees with the string length of the input.
375 : : * We can ignore inputlen after this.
376 : : */
377 [ # # ]: 0 : if (inputlen == 0)
378 [ # # # # ]: 0 : ereport(ERROR,
379 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
380 : : errmsg("malformed SCRAM message"),
381 : : errdetail("The message is empty.")));
382 [ # # ]: 0 : if (inputlen != strlen(input))
383 [ # # # # ]: 0 : ereport(ERROR,
384 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
385 : : errmsg("malformed SCRAM message"),
386 : : errdetail("Message length does not match input length.")));
387 : :
388 [ # # # ]: 0 : switch (state->state)
389 : : {
390 : : case SCRAM_AUTH_INIT:
391 : :
392 : : /*
393 : : * Initialization phase. Receive the first message from client
394 : : * and be sure that it parsed correctly. Then send the challenge
395 : : * to the client.
396 : : */
397 : 0 : read_client_first_message(state, input);
398 : :
399 : : /* prepare message to send challenge */
400 : 0 : *output = build_server_first_message(state);
401 : :
402 : 0 : state->state = SCRAM_AUTH_SALT_SENT;
403 : 0 : result = PG_SASL_EXCHANGE_CONTINUE;
404 : 0 : break;
405 : :
406 : : case SCRAM_AUTH_SALT_SENT:
407 : :
408 : : /*
409 : : * Final phase for the server. Receive the response to the
410 : : * challenge previously sent, verify, and let the client know that
411 : : * everything went well (or not).
412 : : */
413 : 0 : read_client_final_message(state, input);
414 : :
415 [ # # ]: 0 : if (!verify_final_nonce(state))
416 [ # # # # ]: 0 : ereport(ERROR,
417 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
418 : : errmsg("invalid SCRAM response"),
419 : : errdetail("Nonce does not match.")));
420 : :
421 : : /*
422 : : * Now check the final nonce and the client proof.
423 : : *
424 : : * If we performed a "mock" authentication that we knew would fail
425 : : * from the get go, this is where we fail.
426 : : *
427 : : * The SCRAM specification includes an error code,
428 : : * "invalid-proof", for authentication failure, but it also allows
429 : : * erroring out in an application-specific way. We choose to do
430 : : * the latter, so that the error message for invalid password is
431 : : * the same for all authentication methods. The caller will call
432 : : * ereport(), when we return PG_SASL_EXCHANGE_FAILURE with no
433 : : * output.
434 : : *
435 : : * NB: the order of these checks is intentional. We calculate the
436 : : * client proof even in a mock authentication, even though it's
437 : : * bound to fail, to thwart timing attacks to determine if a role
438 : : * with the given name exists or not.
439 : : */
440 [ # # # # ]: 0 : if (!verify_client_proof(state) || state->doomed)
441 : : {
442 : 0 : result = PG_SASL_EXCHANGE_FAILURE;
443 : 0 : break;
444 : : }
445 : :
446 : : /* Build final message for client */
447 : 0 : *output = build_server_final_message(state);
448 : :
449 : : /* Success! */
450 : 0 : result = PG_SASL_EXCHANGE_SUCCESS;
451 : 0 : state->state = SCRAM_AUTH_FINISHED;
452 : 0 : break;
453 : :
454 : : default:
455 [ # # # # ]: 0 : elog(ERROR, "invalid SCRAM exchange state");
456 : 0 : result = PG_SASL_EXCHANGE_FAILURE;
457 : 0 : }
458 : :
459 [ # # # # : 0 : if (result == PG_SASL_EXCHANGE_FAILURE && state->logdetail && logdetail)
# # ]
460 : 0 : *logdetail = state->logdetail;
461 : :
462 [ # # ]: 0 : if (*output)
463 : 0 : *outputlen = strlen(*output);
464 : :
465 [ # # # # ]: 0 : if (result == PG_SASL_EXCHANGE_SUCCESS && state->state == SCRAM_AUTH_FINISHED)
466 : : {
467 : 0 : memcpy(MyProcPort->scram_ClientKey, state->ClientKey, sizeof(MyProcPort->scram_ClientKey));
468 : 0 : memcpy(MyProcPort->scram_ServerKey, state->ServerKey, sizeof(MyProcPort->scram_ServerKey));
469 : 0 : MyProcPort->has_scram_keys = true;
470 : 0 : }
471 : :
472 : 0 : return result;
473 : 0 : }
474 : :
475 : : /*
476 : : * Construct a SCRAM secret, for storing in pg_authid.rolpassword.
477 : : *
478 : : * The result is palloc'd, so caller is responsible for freeing it.
479 : : */
480 : : char *
481 : 9 : pg_be_scram_build_secret(const char *password)
482 : : {
483 : 9 : char *prep_password;
484 : 9 : pg_saslprep_rc rc;
485 : 9 : uint8 saltbuf[SCRAM_DEFAULT_SALT_LEN];
486 : 9 : char *result;
487 : 9 : const char *errstr = NULL;
488 : :
489 : : /*
490 : : * Normalize the password with SASLprep. If that doesn't work, because
491 : : * the password isn't valid UTF-8 or contains prohibited characters, just
492 : : * proceed with the original password. (See comments at top of file.)
493 : : */
494 : 9 : rc = pg_saslprep(password, &prep_password);
495 [ - + ]: 9 : if (rc == SASLPREP_SUCCESS)
496 : 9 : password = (const char *) prep_password;
497 : :
498 : : /* Generate random salt */
499 [ + - ]: 9 : if (!pg_strong_random(saltbuf, SCRAM_DEFAULT_SALT_LEN))
500 [ # # # # ]: 0 : ereport(ERROR,
501 : : (errcode(ERRCODE_INTERNAL_ERROR),
502 : : errmsg("could not generate random salt")));
503 : :
504 : 9 : result = scram_build_secret(PG_SHA256, SCRAM_SHA_256_KEY_LEN,
505 : 9 : saltbuf, SCRAM_DEFAULT_SALT_LEN,
506 : 9 : scram_sha_256_iterations, password,
507 : : &errstr);
508 : :
509 [ - + ]: 9 : if (prep_password)
510 : 9 : pfree(prep_password);
511 : :
512 : 18 : return result;
513 : 9 : }
514 : :
515 : : /*
516 : : * Verify a plaintext password against a SCRAM secret. This is used when
517 : : * performing plaintext password authentication for a user that has a SCRAM
518 : : * secret stored in pg_authid.
519 : : */
520 : : bool
521 : 5 : scram_verify_plain_password(const char *username, const char *password,
522 : : const char *secret)
523 : : {
524 : 5 : char *encoded_salt;
525 : 5 : uint8 *salt;
526 : 5 : int saltlen;
527 : 5 : int iterations;
528 : 5 : int key_length = 0;
529 : 5 : pg_cryptohash_type hash_type;
530 : 5 : uint8 salted_password[SCRAM_MAX_KEY_LEN];
531 : 5 : uint8 stored_key[SCRAM_MAX_KEY_LEN];
532 : 5 : uint8 server_key[SCRAM_MAX_KEY_LEN];
533 : 5 : uint8 computed_key[SCRAM_MAX_KEY_LEN];
534 : 5 : char *prep_password;
535 : 5 : pg_saslprep_rc rc;
536 : 5 : const char *errstr = NULL;
537 : :
538 [ + - + - ]: 10 : if (!parse_scram_secret(secret, &iterations, &hash_type, &key_length,
539 : 5 : &encoded_salt, stored_key, server_key))
540 : : {
541 : : /*
542 : : * The password looked like a SCRAM secret, but could not be parsed.
543 : : */
544 [ # # # # ]: 0 : ereport(LOG,
545 : : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
546 : 0 : return false;
547 : : }
548 : :
549 : 5 : saltlen = pg_b64_dec_len(strlen(encoded_salt));
550 : 5 : salt = palloc(saltlen);
551 : 10 : saltlen = pg_b64_decode(encoded_salt, strlen(encoded_salt), salt,
552 : 5 : saltlen);
553 [ + - ]: 5 : if (saltlen < 0)
554 : : {
555 [ # # # # ]: 0 : ereport(LOG,
556 : : (errmsg("invalid SCRAM secret for user \"%s\"", username)));
557 : 0 : return false;
558 : : }
559 : :
560 : : /* Normalize the password */
561 : 5 : rc = pg_saslprep(password, &prep_password);
562 [ - + ]: 5 : if (rc == SASLPREP_SUCCESS)
563 : 5 : password = prep_password;
564 : :
565 : : /* Compute Server Key based on the user-supplied plaintext password */
566 : 10 : if (scram_SaltedPassword(password, hash_type, key_length,
567 : 5 : salt, saltlen, iterations,
568 [ + - + - ]: 10 : salted_password, &errstr) < 0 ||
569 : 10 : scram_ServerKey(salted_password, hash_type, key_length,
570 : 10 : computed_key, &errstr) < 0)
571 : : {
572 [ # # # # ]: 0 : elog(ERROR, "could not compute server key: %s", errstr);
573 : 0 : }
574 : :
575 [ - + ]: 5 : if (prep_password)
576 : 5 : pfree(prep_password);
577 : :
578 : : /*
579 : : * Compare the secret's Server Key with the one computed from the
580 : : * user-supplied password.
581 : : */
582 : 5 : return memcmp(computed_key, server_key, key_length) == 0;
583 : 5 : }
584 : :
585 : :
586 : : /*
587 : : * Parse and validate format of given SCRAM secret.
588 : : *
589 : : * On success, the iteration count, salt, stored key, and server key are
590 : : * extracted from the secret, and returned to the caller. For 'stored_key'
591 : : * and 'server_key', the caller must pass pre-allocated buffers of size
592 : : * SCRAM_MAX_KEY_LEN. Salt is returned as a base64-encoded, null-terminated
593 : : * string. The buffer for the salt is palloc'd by this function.
594 : : *
595 : : * Returns true if the SCRAM secret has been parsed, and false otherwise.
596 : : */
597 : : bool
598 : 49 : parse_scram_secret(const char *secret, int *iterations,
599 : : pg_cryptohash_type *hash_type, int *key_length,
600 : : char **salt, uint8 *stored_key, uint8 *server_key)
601 : : {
602 : 49 : char *v;
603 : 49 : char *p;
604 : 49 : char *scheme_str;
605 : 49 : char *salt_str;
606 : 49 : char *iterations_str;
607 : 49 : char *storedkey_str;
608 : 49 : char *serverkey_str;
609 : 49 : int decoded_len;
610 : 49 : uint8 *decoded_salt_buf;
611 : 49 : uint8 *decoded_stored_buf;
612 : 49 : uint8 *decoded_server_buf;
613 : :
614 : : /*
615 : : * The secret is of form:
616 : : *
617 : : * SCRAM-SHA-256$<iterations>:<salt>$<storedkey>:<serverkey>
618 : : */
619 : 49 : v = pstrdup(secret);
620 : 49 : scheme_str = strsep(&v, "$");
621 [ + + ]: 49 : if (v == NULL)
622 : 18 : goto invalid_secret;
623 : 31 : iterations_str = strsep(&v, ":");
624 [ + + ]: 31 : if (v == NULL)
625 : 2 : goto invalid_secret;
626 : 29 : salt_str = strsep(&v, "$");
627 [ + - ]: 29 : if (v == NULL)
628 : 0 : goto invalid_secret;
629 : 29 : storedkey_str = strsep(&v, ":");
630 [ + - ]: 29 : if (v == NULL)
631 : 0 : goto invalid_secret;
632 : 29 : serverkey_str = v;
633 : :
634 : : /* Parse the fields */
635 [ - + ]: 29 : if (strcmp(scheme_str, "SCRAM-SHA-256") != 0)
636 : 0 : goto invalid_secret;
637 : 29 : *hash_type = PG_SHA256;
638 : 29 : *key_length = SCRAM_SHA_256_KEY_LEN;
639 : :
640 : 29 : errno = 0;
641 : 29 : *iterations = strtol(iterations_str, &p, 10);
642 [ + - - + ]: 29 : if (*p || errno != 0)
643 : 0 : goto invalid_secret;
644 : :
645 : : /*
646 : : * Verify that the salt is in Base64-encoded format, by decoding it,
647 : : * although we return the encoded version to the caller.
648 : : */
649 : 29 : decoded_len = pg_b64_dec_len(strlen(salt_str));
650 : 29 : decoded_salt_buf = palloc(decoded_len);
651 : 58 : decoded_len = pg_b64_decode(salt_str, strlen(salt_str),
652 : 29 : decoded_salt_buf, decoded_len);
653 [ + - ]: 29 : if (decoded_len < 0)
654 : 0 : goto invalid_secret;
655 : 29 : *salt = pstrdup(salt_str);
656 : :
657 : : /*
658 : : * Decode StoredKey and ServerKey.
659 : : */
660 : 29 : decoded_len = pg_b64_dec_len(strlen(storedkey_str));
661 : 29 : decoded_stored_buf = palloc(decoded_len);
662 : 58 : decoded_len = pg_b64_decode(storedkey_str, strlen(storedkey_str),
663 : 29 : decoded_stored_buf, decoded_len);
664 [ + + ]: 29 : if (decoded_len != *key_length)
665 : 2 : goto invalid_secret;
666 : 27 : memcpy(stored_key, decoded_stored_buf, *key_length);
667 : :
668 : 27 : decoded_len = pg_b64_dec_len(strlen(serverkey_str));
669 : 27 : decoded_server_buf = palloc(decoded_len);
670 : 54 : decoded_len = pg_b64_decode(serverkey_str, strlen(serverkey_str),
671 : 27 : decoded_server_buf, decoded_len);
672 [ + + ]: 27 : if (decoded_len != *key_length)
673 : 2 : goto invalid_secret;
674 : 25 : memcpy(server_key, decoded_server_buf, *key_length);
675 : :
676 : 25 : return true;
677 : :
678 : : invalid_secret:
679 : 24 : *salt = NULL;
680 : 24 : return false;
681 : 49 : }
682 : :
683 : : /*
684 : : * Generate plausible SCRAM secret parameters for mock authentication.
685 : : *
686 : : * In a normal authentication, these are extracted from the secret
687 : : * stored in the server. This function generates values that look
688 : : * realistic, for when there is no stored secret, using SCRAM-SHA-256.
689 : : *
690 : : * Like in parse_scram_secret(), for 'stored_key' and 'server_key', the
691 : : * caller must pass pre-allocated buffers of size SCRAM_MAX_KEY_LEN, and
692 : : * the buffer for the salt is palloc'd by this function.
693 : : */
694 : : static void
695 : 0 : mock_scram_secret(const char *username, pg_cryptohash_type *hash_type,
696 : : int *iterations, int *key_length, char **salt,
697 : : uint8 *stored_key, uint8 *server_key)
698 : : {
699 : 0 : uint8 *raw_salt;
700 : 0 : char *encoded_salt;
701 : 0 : int encoded_len;
702 : :
703 : : /* Enforce the use of SHA-256, which would be realistic enough */
704 : 0 : *hash_type = PG_SHA256;
705 : 0 : *key_length = SCRAM_SHA_256_KEY_LEN;
706 : :
707 : : /*
708 : : * Generate deterministic salt.
709 : : *
710 : : * Note that we cannot reveal any information to an attacker here so the
711 : : * error messages need to remain generic. This should never fail anyway
712 : : * as the salt generated for mock authentication uses the cluster's nonce
713 : : * value.
714 : : */
715 : 0 : raw_salt = scram_mock_salt(username, *hash_type, *key_length);
716 [ # # ]: 0 : if (raw_salt == NULL)
717 [ # # # # ]: 0 : elog(ERROR, "could not encode salt");
718 : :
719 : 0 : encoded_len = pg_b64_enc_len(SCRAM_DEFAULT_SALT_LEN);
720 : : /* don't forget the zero-terminator */
721 : 0 : encoded_salt = (char *) palloc(encoded_len + 1);
722 : 0 : encoded_len = pg_b64_encode(raw_salt, SCRAM_DEFAULT_SALT_LEN, encoded_salt,
723 : 0 : encoded_len);
724 : :
725 [ # # ]: 0 : if (encoded_len < 0)
726 [ # # # # ]: 0 : elog(ERROR, "could not encode salt");
727 : 0 : encoded_salt[encoded_len] = '\0';
728 : :
729 : 0 : *salt = encoded_salt;
730 : 0 : *iterations = SCRAM_SHA_256_DEFAULT_ITERATIONS;
731 : :
732 : : /* StoredKey and ServerKey are not used in a doomed authentication */
733 : 0 : memset(stored_key, 0, SCRAM_MAX_KEY_LEN);
734 : 0 : memset(server_key, 0, SCRAM_MAX_KEY_LEN);
735 : 0 : }
736 : :
737 : : /*
738 : : * Read the value in a given SCRAM exchange message for given attribute.
739 : : */
740 : : static char *
741 : 0 : read_attr_value(char **input, char attr)
742 : : {
743 : 0 : char *begin = *input;
744 : 0 : char *end;
745 : :
746 [ # # ]: 0 : if (*begin != attr)
747 [ # # # # ]: 0 : ereport(ERROR,
748 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
749 : : errmsg("malformed SCRAM message"),
750 : : errdetail("Expected attribute \"%c\" but found \"%s\".",
751 : : attr, sanitize_char(*begin))));
752 : 0 : begin++;
753 : :
754 [ # # ]: 0 : if (*begin != '=')
755 [ # # # # ]: 0 : ereport(ERROR,
756 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
757 : : errmsg("malformed SCRAM message"),
758 : : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
759 : 0 : begin++;
760 : :
761 : 0 : end = begin;
762 [ # # # # ]: 0 : while (*end && *end != ',')
763 : 0 : end++;
764 : :
765 [ # # ]: 0 : if (*end)
766 : : {
767 : 0 : *end = '\0';
768 : 0 : *input = end + 1;
769 : 0 : }
770 : : else
771 : 0 : *input = end;
772 : :
773 : 0 : return begin;
774 : 0 : }
775 : :
776 : : static bool
777 : 0 : is_scram_printable(char *p)
778 : : {
779 : : /*------
780 : : * Printable characters, as defined by SCRAM spec: (RFC 5802)
781 : : *
782 : : * printable = %x21-2B / %x2D-7E
783 : : * ;; Printable ASCII except ",".
784 : : * ;; Note that any "printable" is also
785 : : * ;; a valid "value".
786 : : *------
787 : : */
788 [ # # ]: 0 : for (; *p; p++)
789 : : {
790 [ # # # # : 0 : if (*p < 0x21 || *p > 0x7E || *p == 0x2C /* comma */ )
# # ]
791 : 0 : return false;
792 : 0 : }
793 : 0 : return true;
794 : 0 : }
795 : :
796 : : /*
797 : : * Convert an arbitrary byte to printable form. For error messages.
798 : : *
799 : : * If it's a printable ASCII character, print it as a single character.
800 : : * otherwise, print it in hex.
801 : : *
802 : : * The returned pointer points to a static buffer.
803 : : */
804 : : static char *
805 : 0 : sanitize_char(char c)
806 : : {
807 : : static char buf[5];
808 : :
809 [ # # # # ]: 0 : if (c >= 0x21 && c <= 0x7E)
810 : 0 : snprintf(buf, sizeof(buf), "'%c'", c);
811 : : else
812 : 0 : snprintf(buf, sizeof(buf), "0x%02x", (unsigned char) c);
813 : 0 : return buf;
814 : : }
815 : :
816 : : /*
817 : : * Convert an arbitrary string to printable form, for error messages.
818 : : *
819 : : * Anything that's not a printable ASCII character is replaced with
820 : : * '?', and the string is truncated at 30 characters.
821 : : *
822 : : * The returned pointer points to a static buffer.
823 : : */
824 : : static char *
825 : 0 : sanitize_str(const char *s)
826 : : {
827 : : static char buf[30 + 1];
828 : 0 : int i;
829 : :
830 [ # # ]: 0 : for (i = 0; i < sizeof(buf) - 1; i++)
831 : : {
832 : 0 : char c = s[i];
833 : :
834 [ # # ]: 0 : if (c == '\0')
835 : 0 : break;
836 : :
837 [ # # # # ]: 0 : if (c >= 0x21 && c <= 0x7E)
838 : 0 : buf[i] = c;
839 : : else
840 : 0 : buf[i] = '?';
841 [ # # # ]: 0 : }
842 : 0 : buf[i] = '\0';
843 : 0 : return buf;
844 : 0 : }
845 : :
846 : : /*
847 : : * Read the next attribute and value in a SCRAM exchange message.
848 : : *
849 : : * The attribute character is set in *attr_p, the attribute value is the
850 : : * return value.
851 : : */
852 : : static char *
853 : 0 : read_any_attr(char **input, char *attr_p)
854 : : {
855 : 0 : char *begin = *input;
856 : 0 : char *end;
857 : 0 : char attr = *begin;
858 : :
859 [ # # ]: 0 : if (attr == '\0')
860 [ # # # # ]: 0 : ereport(ERROR,
861 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
862 : : errmsg("malformed SCRAM message"),
863 : : errdetail("Attribute expected, but found end of string.")));
864 : :
865 : : /*------
866 : : * attr-val = ALPHA "=" value
867 : : * ;; Generic syntax of any attribute sent
868 : : * ;; by server or client
869 : : *------
870 : : */
871 [ # # # # ]: 0 : if (!((attr >= 'A' && attr <= 'Z') ||
872 [ # # ]: 0 : (attr >= 'a' && attr <= 'z')))
873 [ # # # # ]: 0 : ereport(ERROR,
874 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
875 : : errmsg("malformed SCRAM message"),
876 : : errdetail("Attribute expected, but found invalid character \"%s\".",
877 : : sanitize_char(attr))));
878 [ # # ]: 0 : if (attr_p)
879 : 0 : *attr_p = attr;
880 : 0 : begin++;
881 : :
882 [ # # ]: 0 : if (*begin != '=')
883 [ # # # # ]: 0 : ereport(ERROR,
884 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
885 : : errmsg("malformed SCRAM message"),
886 : : errdetail("Expected character \"=\" for attribute \"%c\".", attr)));
887 : 0 : begin++;
888 : :
889 : 0 : end = begin;
890 [ # # # # ]: 0 : while (*end && *end != ',')
891 : 0 : end++;
892 : :
893 [ # # ]: 0 : if (*end)
894 : : {
895 : 0 : *end = '\0';
896 : 0 : *input = end + 1;
897 : 0 : }
898 : : else
899 : 0 : *input = end;
900 : :
901 : 0 : return begin;
902 : 0 : }
903 : :
904 : : /*
905 : : * Read and parse the first message from client in the context of a SCRAM
906 : : * authentication exchange message.
907 : : *
908 : : * At this stage, any errors will be reported directly with ereport(ERROR).
909 : : */
910 : : static void
911 : 0 : read_client_first_message(scram_state *state, const char *input)
912 : : {
913 : 0 : char *p = pstrdup(input);
914 : 0 : char *channel_binding_type;
915 : :
916 : :
917 : : /*------
918 : : * The syntax for the client-first-message is: (RFC 5802)
919 : : *
920 : : * saslname = 1*(value-safe-char / "=2C" / "=3D")
921 : : * ;; Conforms to <value>.
922 : : *
923 : : * authzid = "a=" saslname
924 : : * ;; Protocol specific.
925 : : *
926 : : * cb-name = 1*(ALPHA / DIGIT / "." / "-")
927 : : * ;; See RFC 5056, Section 7.
928 : : * ;; E.g., "tls-server-end-point" or
929 : : * ;; "tls-unique".
930 : : *
931 : : * gs2-cbind-flag = ("p=" cb-name) / "n" / "y"
932 : : * ;; "n" -> client doesn't support channel binding.
933 : : * ;; "y" -> client does support channel binding
934 : : * ;; but thinks the server does not.
935 : : * ;; "p" -> client requires channel binding.
936 : : * ;; The selected channel binding follows "p=".
937 : : *
938 : : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
939 : : * ;; GS2 header for SCRAM
940 : : * ;; (the actual GS2 header includes an optional
941 : : * ;; flag to indicate that the GSS mechanism is not
942 : : * ;; "standard", but since SCRAM is "standard", we
943 : : * ;; don't include that flag).
944 : : *
945 : : * username = "n=" saslname
946 : : * ;; Usernames are prepared using SASLprep.
947 : : *
948 : : * reserved-mext = "m=" 1*(value-char)
949 : : * ;; Reserved for signaling mandatory extensions.
950 : : * ;; The exact syntax will be defined in
951 : : * ;; the future.
952 : : *
953 : : * nonce = "r=" c-nonce [s-nonce]
954 : : * ;; Second part provided by server.
955 : : *
956 : : * c-nonce = printable
957 : : *
958 : : * client-first-message-bare =
959 : : * [reserved-mext ","]
960 : : * username "," nonce ["," extensions]
961 : : *
962 : : * client-first-message =
963 : : * gs2-header client-first-message-bare
964 : : *
965 : : * For example:
966 : : * n,,n=user,r=fyko+d2lbbFgONRv9qkxdawL
967 : : *
968 : : * The "n,," in the beginning means that the client doesn't support
969 : : * channel binding, and no authzid is given. "n=user" is the username.
970 : : * However, in PostgreSQL the username is sent in the startup packet, and
971 : : * the username in the SCRAM exchange is ignored. libpq always sends it
972 : : * as an empty string. The last part, "r=fyko+d2lbbFgONRv9qkxdawL" is
973 : : * the client nonce.
974 : : *------
975 : : */
976 : :
977 : : /*
978 : : * Read gs2-cbind-flag. (For details see also RFC 5802 Section 6 "Channel
979 : : * Binding".)
980 : : */
981 : 0 : state->cbind_flag = *p;
982 [ # # # # ]: 0 : switch (*p)
983 : : {
984 : : case 'n':
985 : :
986 : : /*
987 : : * The client does not support channel binding or has simply
988 : : * decided to not use it. In that case just let it go.
989 : : */
990 [ # # ]: 0 : if (state->channel_binding_in_use)
991 [ # # # # ]: 0 : ereport(ERROR,
992 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
993 : : errmsg("malformed SCRAM message"),
994 : : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
995 : :
996 : 0 : p++;
997 [ # # ]: 0 : if (*p != ',')
998 [ # # # # ]: 0 : ereport(ERROR,
999 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1000 : : errmsg("malformed SCRAM message"),
1001 : : errdetail("Comma expected, but found character \"%s\".",
1002 : : sanitize_char(*p))));
1003 : 0 : p++;
1004 : 0 : break;
1005 : : case 'y':
1006 : :
1007 : : /*
1008 : : * The client supports channel binding and thinks that the server
1009 : : * does not. In this case, the server must fail authentication if
1010 : : * it supports channel binding.
1011 : : */
1012 [ # # ]: 0 : if (state->channel_binding_in_use)
1013 [ # # # # ]: 0 : ereport(ERROR,
1014 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1015 : : errmsg("malformed SCRAM message"),
1016 : : errdetail("The client selected SCRAM-SHA-256-PLUS, but the SCRAM message does not include channel binding data.")));
1017 : :
1018 : : #ifdef USE_SSL
1019 [ # # ]: 0 : if (state->port->ssl_in_use)
1020 [ # # # # ]: 0 : ereport(ERROR,
1021 : : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1022 : : errmsg("SCRAM channel binding negotiation error"),
1023 : : errdetail("The client supports SCRAM channel binding but thinks the server does not. "
1024 : : "However, this server does support channel binding.")));
1025 : : #endif
1026 : 0 : p++;
1027 [ # # ]: 0 : if (*p != ',')
1028 [ # # # # ]: 0 : ereport(ERROR,
1029 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1030 : : errmsg("malformed SCRAM message"),
1031 : : errdetail("Comma expected, but found character \"%s\".",
1032 : : sanitize_char(*p))));
1033 : 0 : p++;
1034 : 0 : break;
1035 : : case 'p':
1036 : :
1037 : : /*
1038 : : * The client requires channel binding. Channel binding type
1039 : : * follows, e.g., "p=tls-server-end-point".
1040 : : */
1041 [ # # ]: 0 : if (!state->channel_binding_in_use)
1042 [ # # # # ]: 0 : ereport(ERROR,
1043 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1044 : : errmsg("malformed SCRAM message"),
1045 : : errdetail("The client selected SCRAM-SHA-256 without channel binding, but the SCRAM message includes channel binding data.")));
1046 : :
1047 : 0 : channel_binding_type = read_attr_value(&p, 'p');
1048 : :
1049 : : /*
1050 : : * The only channel binding type we support is
1051 : : * tls-server-end-point.
1052 : : */
1053 [ # # ]: 0 : if (strcmp(channel_binding_type, "tls-server-end-point") != 0)
1054 [ # # # # ]: 0 : ereport(ERROR,
1055 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1056 : : errmsg("unsupported SCRAM channel-binding type \"%s\"",
1057 : : sanitize_str(channel_binding_type))));
1058 : 0 : break;
1059 : : default:
1060 [ # # # # ]: 0 : ereport(ERROR,
1061 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1062 : : errmsg("malformed SCRAM message"),
1063 : : errdetail("Unexpected channel-binding flag \"%s\".",
1064 : : sanitize_char(*p))));
1065 : 0 : }
1066 : :
1067 : : /*
1068 : : * Forbid optional authzid (authorization identity). We don't support it.
1069 : : */
1070 [ # # ]: 0 : if (*p == 'a')
1071 [ # # # # ]: 0 : ereport(ERROR,
1072 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1073 : : errmsg("client uses authorization identity, but it is not supported")));
1074 [ # # ]: 0 : if (*p != ',')
1075 [ # # # # ]: 0 : ereport(ERROR,
1076 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1077 : : errmsg("malformed SCRAM message"),
1078 : : errdetail("Unexpected attribute \"%s\" in client-first-message.",
1079 : : sanitize_char(*p))));
1080 : 0 : p++;
1081 : :
1082 : 0 : state->client_first_message_bare = pstrdup(p);
1083 : :
1084 : : /*
1085 : : * Any mandatory extensions would go here. We don't support any.
1086 : : *
1087 : : * RFC 5802 specifies error code "e=extensions-not-supported" for this,
1088 : : * but it can only be sent in the server-final message. We prefer to fail
1089 : : * immediately (which the RFC also allows).
1090 : : */
1091 [ # # ]: 0 : if (*p == 'm')
1092 [ # # # # ]: 0 : ereport(ERROR,
1093 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1094 : : errmsg("client requires an unsupported SCRAM extension")));
1095 : :
1096 : : /*
1097 : : * Read username. Note: this is ignored. We use the username from the
1098 : : * startup message instead, still it is kept around if provided as it
1099 : : * proves to be useful for debugging purposes.
1100 : : */
1101 : 0 : state->client_username = read_attr_value(&p, 'n');
1102 : :
1103 : : /* read nonce and check that it is made of only printable characters */
1104 : 0 : state->client_nonce = read_attr_value(&p, 'r');
1105 [ # # ]: 0 : if (!is_scram_printable(state->client_nonce))
1106 [ # # # # ]: 0 : ereport(ERROR,
1107 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1108 : : errmsg("non-printable characters in SCRAM nonce")));
1109 : :
1110 : : /*
1111 : : * There can be any number of optional extensions after this. We don't
1112 : : * support any extensions, so ignore them.
1113 : : */
1114 [ # # ]: 0 : while (*p != '\0')
1115 : 0 : read_any_attr(&p, NULL);
1116 : :
1117 : : /* success! */
1118 : 0 : }
1119 : :
1120 : : /*
1121 : : * Verify the final nonce contained in the last message received from
1122 : : * client in an exchange.
1123 : : */
1124 : : static bool
1125 : 0 : verify_final_nonce(scram_state *state)
1126 : : {
1127 : 0 : int client_nonce_len = strlen(state->client_nonce);
1128 : 0 : int server_nonce_len = strlen(state->server_nonce);
1129 : 0 : int final_nonce_len = strlen(state->client_final_nonce);
1130 : :
1131 [ # # ]: 0 : if (final_nonce_len != client_nonce_len + server_nonce_len)
1132 : 0 : return false;
1133 [ # # ]: 0 : if (memcmp(state->client_final_nonce, state->client_nonce, client_nonce_len) != 0)
1134 : 0 : return false;
1135 [ # # ]: 0 : if (memcmp(state->client_final_nonce + client_nonce_len, state->server_nonce, server_nonce_len) != 0)
1136 : 0 : return false;
1137 : :
1138 : 0 : return true;
1139 : 0 : }
1140 : :
1141 : : /*
1142 : : * Verify the client proof contained in the last message received from
1143 : : * client in an exchange. Returns true if the verification is a success,
1144 : : * or false for a failure.
1145 : : */
1146 : : static bool
1147 : 0 : verify_client_proof(scram_state *state)
1148 : : {
1149 : 0 : uint8 ClientSignature[SCRAM_MAX_KEY_LEN];
1150 : 0 : uint8 client_StoredKey[SCRAM_MAX_KEY_LEN];
1151 : 0 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1152 : 0 : int i;
1153 : 0 : const char *errstr = NULL;
1154 : :
1155 : : /*
1156 : : * Calculate ClientSignature. Note that we don't log directly a failure
1157 : : * here even when processing the calculations as this could involve a mock
1158 : : * authentication.
1159 : : */
1160 [ # # ]: 0 : if (pg_hmac_init(ctx, state->StoredKey, state->key_length) < 0 ||
1161 : 0 : pg_hmac_update(ctx,
1162 : 0 : (uint8 *) state->client_first_message_bare,
1163 : 0 : strlen(state->client_first_message_bare)) < 0 ||
1164 : 0 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1165 : 0 : pg_hmac_update(ctx,
1166 : 0 : (uint8 *) state->server_first_message,
1167 : 0 : strlen(state->server_first_message)) < 0 ||
1168 : 0 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1169 : 0 : pg_hmac_update(ctx,
1170 : 0 : (uint8 *) state->client_final_message_without_proof,
1171 : 0 : strlen(state->client_final_message_without_proof)) < 0 ||
1172 : 0 : pg_hmac_final(ctx, ClientSignature, state->key_length) < 0)
1173 : : {
1174 [ # # # # ]: 0 : elog(ERROR, "could not calculate client signature: %s",
1175 : : pg_hmac_error(ctx));
1176 : 0 : }
1177 : :
1178 : 0 : pg_hmac_free(ctx);
1179 : :
1180 : : /* Extract the ClientKey that the client calculated from the proof */
1181 [ # # ]: 0 : for (i = 0; i < state->key_length; i++)
1182 : 0 : state->ClientKey[i] = state->ClientProof[i] ^ ClientSignature[i];
1183 : :
1184 : : /* Hash it one more time, and compare with StoredKey */
1185 : 0 : if (scram_H(state->ClientKey, state->hash_type, state->key_length,
1186 [ # # # # ]: 0 : client_StoredKey, &errstr) < 0)
1187 [ # # # # ]: 0 : elog(ERROR, "could not hash stored key: %s", errstr);
1188 : :
1189 [ # # ]: 0 : if (memcmp(client_StoredKey, state->StoredKey, state->key_length) != 0)
1190 : 0 : return false;
1191 : :
1192 : 0 : return true;
1193 : 0 : }
1194 : :
1195 : : /*
1196 : : * Build the first server-side message sent to the client in a SCRAM
1197 : : * communication exchange.
1198 : : */
1199 : : static char *
1200 : 0 : build_server_first_message(scram_state *state)
1201 : : {
1202 : : /*------
1203 : : * The syntax for the server-first-message is: (RFC 5802)
1204 : : *
1205 : : * server-first-message =
1206 : : * [reserved-mext ","] nonce "," salt ","
1207 : : * iteration-count ["," extensions]
1208 : : *
1209 : : * nonce = "r=" c-nonce [s-nonce]
1210 : : * ;; Second part provided by server.
1211 : : *
1212 : : * c-nonce = printable
1213 : : *
1214 : : * s-nonce = printable
1215 : : *
1216 : : * salt = "s=" base64
1217 : : *
1218 : : * iteration-count = "i=" posit-number
1219 : : * ;; A positive number.
1220 : : *
1221 : : * Example:
1222 : : *
1223 : : * r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,s=QSXCR+Q6sek8bf92,i=4096
1224 : : *------
1225 : : */
1226 : :
1227 : : /*
1228 : : * Per the spec, the nonce may consist of any printable ASCII characters.
1229 : : * For convenience, however, we don't use the whole range available,
1230 : : * rather, we generate some random bytes, and base64 encode them.
1231 : : */
1232 : 0 : uint8 raw_nonce[SCRAM_RAW_NONCE_LEN];
1233 : 0 : int encoded_len;
1234 : :
1235 [ # # ]: 0 : if (!pg_strong_random(raw_nonce, SCRAM_RAW_NONCE_LEN))
1236 [ # # # # ]: 0 : ereport(ERROR,
1237 : : (errcode(ERRCODE_INTERNAL_ERROR),
1238 : : errmsg("could not generate random nonce")));
1239 : :
1240 : 0 : encoded_len = pg_b64_enc_len(SCRAM_RAW_NONCE_LEN);
1241 : : /* don't forget the zero-terminator */
1242 : 0 : state->server_nonce = palloc(encoded_len + 1);
1243 : 0 : encoded_len = pg_b64_encode(raw_nonce, SCRAM_RAW_NONCE_LEN,
1244 : 0 : state->server_nonce, encoded_len);
1245 [ # # ]: 0 : if (encoded_len < 0)
1246 [ # # # # ]: 0 : ereport(ERROR,
1247 : : (errcode(ERRCODE_INTERNAL_ERROR),
1248 : : errmsg("could not encode random nonce")));
1249 : 0 : state->server_nonce[encoded_len] = '\0';
1250 : :
1251 : 0 : state->server_first_message =
1252 : 0 : psprintf("r=%s%s,s=%s,i=%d",
1253 : 0 : state->client_nonce, state->server_nonce,
1254 : 0 : state->salt, state->iterations);
1255 : :
1256 : 0 : return pstrdup(state->server_first_message);
1257 : 0 : }
1258 : :
1259 : :
1260 : : /*
1261 : : * Read and parse the final message received from client.
1262 : : */
1263 : : static void
1264 : 0 : read_client_final_message(scram_state *state, const char *input)
1265 : : {
1266 : 0 : char attr;
1267 : 0 : char *channel_binding;
1268 : 0 : char *value;
1269 : 0 : char *begin,
1270 : : *proof;
1271 : 0 : char *p;
1272 : 0 : uint8 *client_proof;
1273 : 0 : int client_proof_len;
1274 : :
1275 : 0 : begin = p = pstrdup(input);
1276 : :
1277 : : /*------
1278 : : * The syntax for the server-first-message is: (RFC 5802)
1279 : : *
1280 : : * gs2-header = gs2-cbind-flag "," [ authzid ] ","
1281 : : * ;; GS2 header for SCRAM
1282 : : * ;; (the actual GS2 header includes an optional
1283 : : * ;; flag to indicate that the GSS mechanism is not
1284 : : * ;; "standard", but since SCRAM is "standard", we
1285 : : * ;; don't include that flag).
1286 : : *
1287 : : * cbind-input = gs2-header [ cbind-data ]
1288 : : * ;; cbind-data MUST be present for
1289 : : * ;; gs2-cbind-flag of "p" and MUST be absent
1290 : : * ;; for "y" or "n".
1291 : : *
1292 : : * channel-binding = "c=" base64
1293 : : * ;; base64 encoding of cbind-input.
1294 : : *
1295 : : * proof = "p=" base64
1296 : : *
1297 : : * client-final-message-without-proof =
1298 : : * channel-binding "," nonce [","
1299 : : * extensions]
1300 : : *
1301 : : * client-final-message =
1302 : : * client-final-message-without-proof "," proof
1303 : : *------
1304 : : */
1305 : :
1306 : : /*
1307 : : * Read channel binding. This repeats the channel-binding flags and is
1308 : : * then followed by the actual binding data depending on the type.
1309 : : */
1310 : 0 : channel_binding = read_attr_value(&p, 'c');
1311 [ # # ]: 0 : if (state->channel_binding_in_use)
1312 : : {
1313 : : #ifdef USE_SSL
1314 : 0 : const char *cbind_data = NULL;
1315 : 0 : size_t cbind_data_len = 0;
1316 : 0 : size_t cbind_header_len;
1317 : 0 : char *cbind_input;
1318 : 0 : size_t cbind_input_len;
1319 : 0 : char *b64_message;
1320 : 0 : int b64_message_len;
1321 : :
1322 [ # # ]: 0 : Assert(state->cbind_flag == 'p');
1323 : :
1324 : : /* Fetch hash data of server's SSL certificate */
1325 : 0 : cbind_data = be_tls_get_certificate_hash(state->port,
1326 : : &cbind_data_len);
1327 : :
1328 : : /* should not happen */
1329 [ # # ]: 0 : if (cbind_data == NULL || cbind_data_len == 0)
1330 [ # # # # ]: 0 : elog(ERROR, "could not get server certificate hash");
1331 : :
1332 : 0 : cbind_header_len = strlen("p=tls-server-end-point,,"); /* p=type,, */
1333 : 0 : cbind_input_len = cbind_header_len + cbind_data_len;
1334 : 0 : cbind_input = palloc(cbind_input_len);
1335 : 0 : snprintf(cbind_input, cbind_input_len, "p=tls-server-end-point,,");
1336 : 0 : memcpy(cbind_input + cbind_header_len, cbind_data, cbind_data_len);
1337 : :
1338 : 0 : b64_message_len = pg_b64_enc_len(cbind_input_len);
1339 : : /* don't forget the zero-terminator */
1340 : 0 : b64_message = palloc(b64_message_len + 1);
1341 : 0 : b64_message_len = pg_b64_encode((uint8 *) cbind_input, cbind_input_len,
1342 : 0 : b64_message, b64_message_len);
1343 [ # # ]: 0 : if (b64_message_len < 0)
1344 [ # # # # ]: 0 : elog(ERROR, "could not encode channel binding data");
1345 : 0 : b64_message[b64_message_len] = '\0';
1346 : :
1347 : : /*
1348 : : * Compare the value sent by the client with the value expected by the
1349 : : * server.
1350 : : */
1351 [ # # ]: 0 : if (strcmp(channel_binding, b64_message) != 0)
1352 [ # # # # ]: 0 : ereport(ERROR,
1353 : : (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
1354 : : errmsg("SCRAM channel binding check failed")));
1355 : : #else
1356 : : /* shouldn't happen, because we checked this earlier already */
1357 : : elog(ERROR, "channel binding not supported by this build");
1358 : : #endif
1359 : 0 : }
1360 : : else
1361 : : {
1362 : : /*
1363 : : * If we are not using channel binding, the binding data is expected
1364 : : * to always be "biws", which is "n,," base64-encoded, or "eSws",
1365 : : * which is "y,,". We also have to check whether the flag is the same
1366 : : * one that the client originally sent.
1367 : : */
1368 [ # # # # ]: 0 : if (!(strcmp(channel_binding, "biws") == 0 && state->cbind_flag == 'n') &&
1369 [ # # ]: 0 : !(strcmp(channel_binding, "eSws") == 0 && state->cbind_flag == 'y'))
1370 [ # # # # ]: 0 : ereport(ERROR,
1371 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1372 : : errmsg("unexpected SCRAM channel-binding attribute in client-final-message")));
1373 : : }
1374 : :
1375 : 0 : state->client_final_nonce = read_attr_value(&p, 'r');
1376 : :
1377 : : /* ignore optional extensions, read until we find "p" attribute */
1378 : 0 : do
1379 : : {
1380 : 0 : proof = p - 1;
1381 : 0 : value = read_any_attr(&p, &attr);
1382 [ # # ]: 0 : } while (attr != 'p');
1383 : :
1384 : 0 : client_proof_len = pg_b64_dec_len(strlen(value));
1385 : 0 : client_proof = palloc(client_proof_len);
1386 : 0 : if (pg_b64_decode(value, strlen(value), client_proof,
1387 [ # # # # ]: 0 : client_proof_len) != state->key_length)
1388 [ # # # # ]: 0 : ereport(ERROR,
1389 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1390 : : errmsg("malformed SCRAM message"),
1391 : : errdetail("Malformed proof in client-final-message.")));
1392 : 0 : memcpy(state->ClientProof, client_proof, state->key_length);
1393 : 0 : pfree(client_proof);
1394 : :
1395 [ # # ]: 0 : if (*p != '\0')
1396 [ # # # # ]: 0 : ereport(ERROR,
1397 : : (errcode(ERRCODE_PROTOCOL_VIOLATION),
1398 : : errmsg("malformed SCRAM message"),
1399 : : errdetail("Garbage found at the end of client-final-message.")));
1400 : :
1401 : 0 : state->client_final_message_without_proof = palloc(proof - begin + 1);
1402 : 0 : memcpy(state->client_final_message_without_proof, input, proof - begin);
1403 : 0 : state->client_final_message_without_proof[proof - begin] = '\0';
1404 : 0 : }
1405 : :
1406 : : /*
1407 : : * Build the final server-side message of an exchange.
1408 : : */
1409 : : static char *
1410 : 0 : build_server_final_message(scram_state *state)
1411 : : {
1412 : 0 : uint8 ServerSignature[SCRAM_MAX_KEY_LEN];
1413 : 0 : char *server_signature_base64;
1414 : 0 : int siglen;
1415 : 0 : pg_hmac_ctx *ctx = pg_hmac_create(state->hash_type);
1416 : :
1417 : : /* calculate ServerSignature */
1418 [ # # ]: 0 : if (pg_hmac_init(ctx, state->ServerKey, state->key_length) < 0 ||
1419 : 0 : pg_hmac_update(ctx,
1420 : 0 : (uint8 *) state->client_first_message_bare,
1421 : 0 : strlen(state->client_first_message_bare)) < 0 ||
1422 : 0 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1423 : 0 : pg_hmac_update(ctx,
1424 : 0 : (uint8 *) state->server_first_message,
1425 : 0 : strlen(state->server_first_message)) < 0 ||
1426 : 0 : pg_hmac_update(ctx, (uint8 *) ",", 1) < 0 ||
1427 : 0 : pg_hmac_update(ctx,
1428 : 0 : (uint8 *) state->client_final_message_without_proof,
1429 : 0 : strlen(state->client_final_message_without_proof)) < 0 ||
1430 : 0 : pg_hmac_final(ctx, ServerSignature, state->key_length) < 0)
1431 : : {
1432 [ # # # # ]: 0 : elog(ERROR, "could not calculate server signature: %s",
1433 : : pg_hmac_error(ctx));
1434 : 0 : }
1435 : :
1436 : 0 : pg_hmac_free(ctx);
1437 : :
1438 : 0 : siglen = pg_b64_enc_len(state->key_length);
1439 : : /* don't forget the zero-terminator */
1440 : 0 : server_signature_base64 = palloc(siglen + 1);
1441 : 0 : siglen = pg_b64_encode(ServerSignature,
1442 : 0 : state->key_length, server_signature_base64,
1443 : 0 : siglen);
1444 [ # # ]: 0 : if (siglen < 0)
1445 [ # # # # ]: 0 : elog(ERROR, "could not encode server signature");
1446 : 0 : server_signature_base64[siglen] = '\0';
1447 : :
1448 : : /*------
1449 : : * The syntax for the server-final-message is: (RFC 5802)
1450 : : *
1451 : : * verifier = "v=" base64
1452 : : * ;; base-64 encoded ServerSignature.
1453 : : *
1454 : : * server-final-message = (server-error / verifier)
1455 : : * ["," extensions]
1456 : : *
1457 : : *------
1458 : : */
1459 : 0 : return psprintf("v=%s", server_signature_base64);
1460 : 0 : }
1461 : :
1462 : :
1463 : : /*
1464 : : * Deterministically generate salt for mock authentication, using a SHA256
1465 : : * hash based on the username and a cluster-level secret key. Returns a
1466 : : * pointer to a static buffer of size SCRAM_DEFAULT_SALT_LEN, or NULL.
1467 : : */
1468 : : static uint8 *
1469 : 0 : scram_mock_salt(const char *username, pg_cryptohash_type hash_type,
1470 : : int key_length)
1471 : : {
1472 : 0 : pg_cryptohash_ctx *ctx;
1473 : : static uint8 sha_digest[SCRAM_MAX_KEY_LEN];
1474 : 0 : char *mock_auth_nonce = GetMockAuthenticationNonce();
1475 : :
1476 : : /*
1477 : : * Generate salt using a SHA256 hash of the username and the cluster's
1478 : : * mock authentication nonce. (This works as long as the salt length is
1479 : : * not larger than the SHA256 digest length. If the salt is smaller, the
1480 : : * caller will just ignore the extra data.)
1481 : : */
1482 : : StaticAssertDecl(PG_SHA256_DIGEST_LENGTH >= SCRAM_DEFAULT_SALT_LEN,
1483 : : "salt length greater than SHA256 digest length");
1484 : :
1485 : : /*
1486 : : * This may be worth refreshing if support for more hash methods is\
1487 : : * added.
1488 : : */
1489 [ # # ]: 0 : Assert(hash_type == PG_SHA256);
1490 : :
1491 : 0 : ctx = pg_cryptohash_create(hash_type);
1492 [ # # ]: 0 : if (pg_cryptohash_init(ctx) < 0 ||
1493 [ # # ]: 0 : pg_cryptohash_update(ctx, (uint8 *) username, strlen(username)) < 0 ||
1494 [ # # # # ]: 0 : pg_cryptohash_update(ctx, (uint8 *) mock_auth_nonce, MOCK_AUTH_NONCE_LEN) < 0 ||
1495 : 0 : pg_cryptohash_final(ctx, sha_digest, key_length) < 0)
1496 : : {
1497 : 0 : pg_cryptohash_free(ctx);
1498 : 0 : return NULL;
1499 : : }
1500 : 0 : pg_cryptohash_free(ctx);
1501 : :
1502 : 0 : return sha_digest;
1503 : 0 : }
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