Misc SCRAM code cleanups.
* Move computation of SaltedPassword to a separate function from scram_ClientOrServerKey(). This saves a lot of cycles in libpq, by computing SaltedPassword only once per authentication. (Computing SaltedPassword is expensive by design.) * Split scram_ClientOrServerKey() into two functions. Improves readability, by making the calling code less verbose. * Rename "server proof" to "server signature", to better match the nomenclature used in RFC 5802. * Rename SCRAM_SALT_LEN to SCRAM_DEFAULT_SALT_LEN, to make it more clear that the salt can be of any length, and the constant only specifies how long a salt we use when we generate a new verifier. Also rename SCRAM_ITERATIONS_DEFAULT to SCRAM_DEFAULT_ITERATIONS, for consistency. These things caught my eye while working on other upcoming changes.
This commit is contained in:
Heikki Linnakangas
parent
b9a3ef55b2
commit
d981074c24
@ -396,7 +396,8 @@ scram_build_verifier(const char *username, const char *password,
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{
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char *prep_password = NULL;
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pg_saslprep_rc rc;
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char saltbuf[SCRAM_SALT_LEN];
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char saltbuf[SCRAM_DEFAULT_SALT_LEN];
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uint8 salted_password[SCRAM_KEY_LEN];
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uint8 keybuf[SCRAM_KEY_LEN];
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char *encoded_salt;
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char *encoded_storedkey;
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@ -414,10 +415,10 @@ scram_build_verifier(const char *username, const char *password,
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password = (const char *) prep_password;
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if (iterations <= 0)
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iterations = SCRAM_ITERATIONS_DEFAULT;
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iterations = SCRAM_DEFAULT_ITERATIONS;
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/* Generate salt, and encode it in base64 */
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if (!pg_backend_random(saltbuf, SCRAM_SALT_LEN))
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if (!pg_backend_random(saltbuf, SCRAM_DEFAULT_SALT_LEN))
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{
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ereport(LOG,
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(errcode(ERRCODE_INTERNAL_ERROR),
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@ -425,13 +426,14 @@ scram_build_verifier(const char *username, const char *password,
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return NULL;
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}
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encoded_salt = palloc(pg_b64_enc_len(SCRAM_SALT_LEN) + 1);
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encoded_len = pg_b64_encode(saltbuf, SCRAM_SALT_LEN, encoded_salt);
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encoded_salt = palloc(pg_b64_enc_len(SCRAM_DEFAULT_SALT_LEN) + 1);
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encoded_len = pg_b64_encode(saltbuf, SCRAM_DEFAULT_SALT_LEN, encoded_salt);
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encoded_salt[encoded_len] = '\0';
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/* Calculate StoredKey, and encode it in base64 */
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scram_ClientOrServerKey(password, saltbuf, SCRAM_SALT_LEN,
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iterations, SCRAM_CLIENT_KEY_NAME, keybuf);
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scram_SaltedPassword(password, saltbuf, SCRAM_DEFAULT_SALT_LEN,
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iterations, salted_password);
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scram_ClientKey(salted_password, keybuf);
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scram_H(keybuf, SCRAM_KEY_LEN, keybuf); /* StoredKey */
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encoded_storedkey = palloc(pg_b64_enc_len(SCRAM_KEY_LEN) + 1);
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@ -440,8 +442,7 @@ scram_build_verifier(const char *username, const char *password,
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encoded_storedkey[encoded_len] = '\0';
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/* And same for ServerKey */
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scram_ClientOrServerKey(password, saltbuf, SCRAM_SALT_LEN, iterations,
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SCRAM_SERVER_KEY_NAME, keybuf);
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scram_ServerKey(salted_password, keybuf);
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encoded_serverkey = palloc(pg_b64_enc_len(SCRAM_KEY_LEN) + 1);
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encoded_len = pg_b64_encode((const char *) keybuf, SCRAM_KEY_LEN,
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@ -473,6 +474,7 @@ scram_verify_plain_password(const char *username, const char *password,
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char *salt;
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int saltlen;
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int iterations;
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uint8 salted_password[SCRAM_KEY_LEN];
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uint8 stored_key[SCRAM_KEY_LEN];
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uint8 server_key[SCRAM_KEY_LEN];
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uint8 computed_key[SCRAM_KEY_LEN];
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@ -502,9 +504,9 @@ scram_verify_plain_password(const char *username, const char *password,
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if (rc == SASLPREP_SUCCESS)
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password = prep_password;
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/* Compute Server key based on the user-supplied plaintext password */
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scram_ClientOrServerKey(password, salt, saltlen, iterations,
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SCRAM_SERVER_KEY_NAME, computed_key);
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/* Compute Server Key based on the user-supplied plaintext password */
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scram_SaltedPassword(password, salt, saltlen, iterations, salted_password);
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scram_ServerKey(salted_password, computed_key);
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if (prep_password)
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pfree(prep_password);
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@ -630,12 +632,12 @@ mock_scram_verifier(const char *username, int *iterations, char **salt,
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/* Generate deterministic salt */
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raw_salt = scram_MockSalt(username);
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encoded_salt = (char *) palloc(pg_b64_enc_len(SCRAM_SALT_LEN) + 1);
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encoded_len = pg_b64_encode(raw_salt, SCRAM_SALT_LEN, encoded_salt);
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encoded_salt = (char *) palloc(pg_b64_enc_len(SCRAM_DEFAULT_SALT_LEN) + 1);
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encoded_len = pg_b64_encode(raw_salt, SCRAM_DEFAULT_SALT_LEN, encoded_salt);
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encoded_salt[encoded_len] = '\0';
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*salt = encoded_salt;
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*iterations = SCRAM_ITERATIONS_DEFAULT;
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*iterations = SCRAM_DEFAULT_ITERATIONS;
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/* StoredKey and ServerKey are not used in a doomed authentication */
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memset(stored_key, 0, SCRAM_KEY_LEN);
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@ -1179,7 +1181,7 @@ build_server_final_message(scram_state *state)
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/*
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* Determinisitcally generate salt for mock authentication, using a SHA256
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* hash based on the username and a cluster-level secret key. Returns a
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* pointer to a static buffer of size SCRAM_SALT_LEN.
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* pointer to a static buffer of size SCRAM_DEFAULT_SALT_LEN.
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*/
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static char *
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scram_MockSalt(const char *username)
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@ -1194,7 +1196,7 @@ scram_MockSalt(const char *username)
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* not larger the SHA256 digest length. If the salt is smaller, the caller
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* will just ignore the extra data))
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*/
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StaticAssertStmt(PG_SHA256_DIGEST_LENGTH >= SCRAM_SALT_LEN,
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StaticAssertStmt(PG_SHA256_DIGEST_LENGTH >= SCRAM_DEFAULT_SALT_LEN,
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"salt length greater than SHA256 digest length");
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pg_sha256_init(&ctx);
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@ -98,14 +98,16 @@ scram_HMAC_final(uint8 *result, scram_HMAC_ctx *ctx)
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}
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/*
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* Iterate hash calculation of HMAC entry using given salt.
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* scram_Hi() is essentially PBKDF2 (see RFC2898) with HMAC() as the
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* pseudorandom function.
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* Calculate SaltedPassword.
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*
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* The password should already be normalized by SASLprep.
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*/
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static void
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scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *result)
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void
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scram_SaltedPassword(const char *password,
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const char *salt, int saltlen, int iterations,
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uint8 *result)
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{
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int str_len = strlen(str);
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int password_len = strlen(password);
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uint32 one = htonl(1);
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int i,
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j;
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@ -113,8 +115,14 @@ scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *
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uint8 Ui_prev[SCRAM_KEY_LEN];
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scram_HMAC_ctx hmac_ctx;
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/*
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* Iterate hash calculation of HMAC entry using given salt. This is
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* essentially PBKDF2 (see RFC2898) with HMAC() as the pseudorandom
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* function.
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*/
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/* First iteration */
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scram_HMAC_init(&hmac_ctx, (uint8 *) str, str_len);
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scram_HMAC_init(&hmac_ctx, (uint8 *) password, password_len);
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scram_HMAC_update(&hmac_ctx, salt, saltlen);
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scram_HMAC_update(&hmac_ctx, (char *) &one, sizeof(uint32));
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scram_HMAC_final(Ui_prev, &hmac_ctx);
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@ -123,7 +131,7 @@ scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *
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/* Subsequent iterations */
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for (i = 2; i <= iterations; i++)
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{
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scram_HMAC_init(&hmac_ctx, (uint8 *) str, str_len);
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scram_HMAC_init(&hmac_ctx, (uint8 *) password, password_len);
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scram_HMAC_update(&hmac_ctx, (const char *) Ui_prev, SCRAM_KEY_LEN);
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scram_HMAC_final(Ui, &hmac_ctx);
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for (j = 0; j < SCRAM_KEY_LEN; j++)
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@ -148,20 +156,27 @@ scram_H(const uint8 *input, int len, uint8 *result)
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}
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/*
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* Calculate ClientKey or ServerKey.
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*
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* The password should already be normalized by SASLprep.
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* Calculate ClientKey.
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*/
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void
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scram_ClientOrServerKey(const char *password,
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const char *salt, int saltlen, int iterations,
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const char *keystr, uint8 *result)
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scram_ClientKey(const uint8 *salted_password, uint8 *result)
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{
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uint8 keybuf[SCRAM_KEY_LEN];
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scram_HMAC_ctx ctx;
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scram_Hi(password, salt, saltlen, iterations, keybuf);
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scram_HMAC_init(&ctx, keybuf, SCRAM_KEY_LEN);
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scram_HMAC_update(&ctx, keystr, strlen(keystr));
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scram_HMAC_init(&ctx, salted_password, SCRAM_KEY_LEN);
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scram_HMAC_update(&ctx, "Client Key", strlen("Client Key"));
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scram_HMAC_final(result, &ctx);
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}
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/*
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* Calculate ServerKey.
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*/
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void
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scram_ServerKey(const uint8 *salted_password, uint8 *result)
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{
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scram_HMAC_ctx ctx;
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scram_HMAC_init(&ctx, salted_password, SCRAM_KEY_LEN);
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scram_HMAC_update(&ctx, "Server Key", strlen("Server Key"));
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scram_HMAC_final(result, &ctx);
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}
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@ -29,14 +29,10 @@
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#define SCRAM_RAW_NONCE_LEN 10
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/* length of salt when generating new verifiers */
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#define SCRAM_SALT_LEN 10
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#define SCRAM_DEFAULT_SALT_LEN 10
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/* default number of iterations when generating verifier */
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#define SCRAM_ITERATIONS_DEFAULT 4096
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/* Base name of keys used for proof generation */
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#define SCRAM_SERVER_KEY_NAME "Server Key"
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#define SCRAM_CLIENT_KEY_NAME "Client Key"
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#define SCRAM_DEFAULT_ITERATIONS 4096
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/*
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* Context data for HMAC used in SCRAM authentication.
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@ -51,9 +47,10 @@ extern void scram_HMAC_init(scram_HMAC_ctx *ctx, const uint8 *key, int keylen);
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extern void scram_HMAC_update(scram_HMAC_ctx *ctx, const char *str, int slen);
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extern void scram_HMAC_final(uint8 *result, scram_HMAC_ctx *ctx);
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extern void scram_SaltedPassword(const char *password, const char *salt,
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int saltlen, int iterations, uint8 *result);
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extern void scram_H(const uint8 *str, int len, uint8 *result);
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extern void scram_ClientOrServerKey(const char *password, const char *salt,
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int saltlen, int iterations,
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const char *keystr, uint8 *result);
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extern void scram_ClientKey(const uint8 *salted_password, uint8 *result);
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extern void scram_ServerKey(const uint8 *salted_password, uint8 *result);
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#endif /* SCRAM_COMMON_H */
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@ -46,6 +46,7 @@ typedef struct
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char *password;
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/* We construct these */
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uint8 SaltedPassword[SCRAM_KEY_LEN];
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char *client_nonce;
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char *client_first_message_bare;
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char *client_final_message_without_proof;
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@ -59,7 +60,7 @@ typedef struct
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/* These come from the server-final message */
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char *server_final_message;
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char ServerProof[SCRAM_KEY_LEN];
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char ServerSignature[SCRAM_KEY_LEN];
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} fe_scram_state;
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static bool read_server_first_message(fe_scram_state *state, char *input,
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@ -70,7 +71,7 @@ static char *build_client_first_message(fe_scram_state *state,
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PQExpBuffer errormessage);
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static char *build_client_final_message(fe_scram_state *state,
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PQExpBuffer errormessage);
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static bool verify_server_proof(fe_scram_state *state);
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static bool verify_server_signature(fe_scram_state *state);
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static void calculate_client_proof(fe_scram_state *state,
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const char *client_final_message_without_proof,
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uint8 *result);
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@ -216,12 +217,12 @@ pg_fe_scram_exchange(void *opaq, char *input, int inputlen,
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goto error;
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/*
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* Verify server proof, to make sure we're talking to the genuine
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* server. XXX: A fake server could simply not require
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* Verify server signature, to make sure we're talking to the
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* genuine server. XXX: A fake server could simply not require
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* authentication, though. There is currently no option in libpq
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* to reject a connection, if SCRAM authentication did not happen.
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*/
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if (verify_server_proof(state))
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if (verify_server_signature(state))
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*success = true;
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else
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{
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@ -486,12 +487,11 @@ read_server_first_message(fe_scram_state *state, char *input,
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* Read the final exchange message coming from the server.
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*/
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static bool
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read_server_final_message(fe_scram_state *state,
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char *input,
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read_server_final_message(fe_scram_state *state, char *input,
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PQExpBuffer errormessage)
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{
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char *encoded_server_proof;
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int server_proof_len;
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char *encoded_server_signature;
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int server_signature_len;
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state->server_final_message = strdup(input);
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if (!state->server_final_message)
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@ -513,8 +513,8 @@ read_server_final_message(fe_scram_state *state,
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}
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/* Parse the message. */
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encoded_server_proof = read_attr_value(&input, 'v', errormessage);
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if (encoded_server_proof == NULL)
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encoded_server_signature = read_attr_value(&input, 'v', errormessage);
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if (encoded_server_signature == NULL)
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{
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/* read_attr_value() has generated an error message */
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return false;
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@ -524,13 +524,13 @@ read_server_final_message(fe_scram_state *state,
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printfPQExpBuffer(errormessage,
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libpq_gettext("malformed SCRAM message (garbage at end of server-final-message)\n"));
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server_proof_len = pg_b64_decode(encoded_server_proof,
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strlen(encoded_server_proof),
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state->ServerProof);
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if (server_proof_len != SCRAM_KEY_LEN)
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server_signature_len = pg_b64_decode(encoded_server_signature,
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strlen(encoded_server_signature),
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state->ServerSignature);
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if (server_signature_len != SCRAM_KEY_LEN)
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{
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printfPQExpBuffer(errormessage,
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libpq_gettext("malformed SCRAM message (invalid server proof)\n"));
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libpq_gettext("malformed SCRAM message (invalid server signature)\n"));
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return false;
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}
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@ -552,8 +552,14 @@ calculate_client_proof(fe_scram_state *state,
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int i;
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scram_HMAC_ctx ctx;
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scram_ClientOrServerKey(state->password, state->salt, state->saltlen,
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state->iterations, SCRAM_CLIENT_KEY_NAME, ClientKey);
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/*
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* Calculate SaltedPassword, and store it in 'state' so that we can reuse
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* it later in verify_server_signature.
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*/
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scram_SaltedPassword(state->password, state->salt, state->saltlen,
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state->iterations, state->SaltedPassword);
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scram_ClientKey(state->SaltedPassword, ClientKey);
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scram_H(ClientKey, SCRAM_KEY_LEN, StoredKey);
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scram_HMAC_init(&ctx, StoredKey, SCRAM_KEY_LEN);
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@ -575,19 +581,17 @@ calculate_client_proof(fe_scram_state *state,
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}
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/*
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* Validate the server proof, received as part of the final exchange message
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* received from the server.
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* Validate the server signature, received as part of the final exchange
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* message received from the server.
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*/
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static bool
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verify_server_proof(fe_scram_state *state)
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verify_server_signature(fe_scram_state *state)
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{
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uint8 ServerSignature[SCRAM_KEY_LEN];
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uint8 expected_ServerSignature[SCRAM_KEY_LEN];
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uint8 ServerKey[SCRAM_KEY_LEN];
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scram_HMAC_ctx ctx;
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scram_ClientOrServerKey(state->password, state->salt, state->saltlen,
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state->iterations, SCRAM_SERVER_KEY_NAME,
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ServerKey);
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scram_ServerKey(state->SaltedPassword, ServerKey);
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/* calculate ServerSignature */
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scram_HMAC_init(&ctx, ServerKey, SCRAM_KEY_LEN);
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@ -602,9 +606,9 @@ verify_server_proof(fe_scram_state *state)
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scram_HMAC_update(&ctx,
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state->client_final_message_without_proof,
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strlen(state->client_final_message_without_proof));
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scram_HMAC_final(ServerSignature, &ctx);
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scram_HMAC_final(expected_ServerSignature, &ctx);
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if (memcmp(ServerSignature, state->ServerProof, SCRAM_KEY_LEN) != 0)
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if (memcmp(expected_ServerSignature, state->ServerSignature, SCRAM_KEY_LEN) != 0)
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return false;
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return true;
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