Add CHECK_FOR_INTERRUPTS() in scram_SaltedPassword() for the backend

michaelpq · michaelpq · commit 14f2f9eb1a15 · 2023-11-28T08:35:50.000+09:00
scram_SaltedPassword() could take a long time to compute when the number of iterations used is large enough, and this code uses a tight loop to compute a salted password. Note that the same issue exists in libpq when using \password and a large iteration number, but this cannot be interrupted. A CFI in the backend is useful for server-side computations, at least. Backpatch down to 16, where the user-settable GUC scram_iterations has been added. Author: Bowen Shi Reviewed-by: Aleksander Alekseev, Daniel Gustafsson Discussion: https://postgr.es/m/CAM_vCueV6xfr08KczfaCEk5J_qeTZtgqN7+orkNLx=g+phE82Q@mail.gmail.com Backpatch-through: 16
diff --git a/src/common/scram-common.c b/src/common/scram-common.c
@@ -22,6 +22,9 @@
 #include "common/base64.h"
 #include "common/hmac.h"
 #include "common/scram-common.h"
+#ifndef FRONTEND
+#include "miscadmin.h"
+#endif
 #include "port/pg_bswap.h"
 
 /*
@@ -73,6 +76,14 @@ scram_SaltedPassword(const char *password,
 	/* Subsequent iterations */
 	for (i = 2; i <= iterations; i++)
 	{
+#ifndef FRONTEND
+		/*
+		 * Make sure that this is interruptible as scram_iterations could be
+		 * set to a large value.
+		 */
+		CHECK_FOR_INTERRUPTS();
+#endif
+
 		if (pg_hmac_init(hmac_ctx, (uint8 *) password, password_len) < 0 ||
 			pg_hmac_update(hmac_ctx, (uint8 *) Ui_prev, key_length) < 0 ||
 			pg_hmac_final(hmac_ctx, Ui, key_length) < 0)
