Function PQencryptPasswordConn

src/interfaces/libpq/fe-auth.c:1198–1292

* PQencryptPasswordConn -- exported routine to encrypt a password * * This is intended to be used by client applications that wish to send * commands like ALTER USER joe PASSWORD 'pwd'. The password need not * be sent in cleartext if it is encrypted on the client side. This is * good because it ensures the cleartext password won't end up in logs, * pg_stat displays, etc. We export the fun

 * returns NULL.
 */
char *
PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
					  const char *algorithm)
{
#define MAX_ALGORITHM_NAME_LEN 50
	char		algobuf[MAX_ALGORITHM_NAME_LEN + 1];
	char	   *crypt_pwd = NULL;

	if (!conn)
		return NULL;

	resetPQExpBuffer(&conn->errorMessage);

	/* If no algorithm was given, ask the server. */
	if (algorithm == NULL)
	{
		PGresult   *res;
		char	   *val;

		res = PQexec(conn, "show password_encryption");
		if (res == NULL)
		{
			/* PQexec() should've set conn->errorMessage already */
			return NULL;
		}
		if (PQresultStatus(res) != PGRES_TUPLES_OK)
		{
			/* PQexec() should've set conn->errorMessage already */
			PQclear(res);
			return NULL;
		}
		if (PQntuples(res) != 1 || PQnfields(res) != 1)
		{
			PQclear(res);
			appendPQExpBufferStr(&conn->errorMessage,
								 libpq_gettext("unexpected shape of result set returned for SHOW\n"));
			return NULL;
		}
		val = PQgetvalue(res, 0, 0);

		if (strlen(val) > MAX_ALGORITHM_NAME_LEN)
		{
			PQclear(res);
			appendPQExpBufferStr(&conn->errorMessage,
								 libpq_gettext("password_encryption value too long\n"));
			return NULL;
		}
		strcpy(algobuf, val);
		PQclear(res);

		algorithm = algobuf;
	}

	/*
	 * Also accept "on" and "off" as aliases for "md5", because
	 * password_encryption was a boolean before PostgreSQL 10.  We refuse to
	 * send the password in plaintext even if it was "off".
	 */