Function PrehashPassword

pg_documentdb/src/commands/users.c:1298–1352

* This method is mostly copied from pg_be_scram_build_secret in PG. The only substantial change * is that we use a default salt length of 28 as opposed to 16 used by PG. This is to ensure * compatiblity with drivers that expect a salt length of 28. */

 * compatiblity with drivers that expect a salt length of 28.
 */
static char *
PrehashPassword(const char *password)
{
	char *prep_password;
	pg_saslprep_rc rc;
	char_uint8_compat saltbuf[SCRAM_MAX_SALT_LEN];
	char *result;
	const char *errstr = NULL;

	/*
	 * Validate that the default salt length is not greater than the max salt length allowed
	 */
	if (ScramDefaultSaltLen > SCRAM_MAX_SALT_LEN)
	{
		ereport(ERROR, (errcode(ERRCODE_DOCUMENTDB_BADVALUE),
						errmsg("Salt length value is invalid.")));
	}

	/*
	 * Normalize the password with SASLprep.  If that doesn't work, because
	 * the password isn't valid UTF-8 or contains prohibited characters, just
	 * proceed with the original password.  (See comments at top of file.)
	 */
	rc = pg_saslprep(password, &prep_password);
	if (rc == SASLPREP_SUCCESS)
	{
		password = (const char *) prep_password;
	}

	/* Generate random salt */
	if (!pg_strong_random(saltbuf, ScramDefaultSaltLen))
	{
		ereport(ERROR,
				(errcode(ERRCODE_INTERNAL_ERROR),
				 errmsg("Could not generate random salt.")));
	}

	#if PG_VERSION_NUM >= 160000  /* PostgreSQL 16.0 or higher */
	result = scram_build_secret(PG_SHA256, SCRAM_SHA_256_KEY_LEN,
								saltbuf, ScramDefaultSaltLen,
								scram_sha_256_iterations, password,
								&errstr);
	#else
	result = scram_build_secret(saltbuf, ScramDefaultSaltLen,
								SCRAM_DEFAULT_ITERATIONS, password,
								&errstr);
	#endif

	if (prep_password)
	{
		pfree(prep_password);
	}

	return result;
}


/*