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commit    07cb7bc1c7a88299e6bce281320397f07ca045c2
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Mon Nov 27 23:35:56 2023 +0000
First released in: 17.0, 16.2

    Add CHECK_FOR_INTERRUPTS() in scram_SaltedPassword() for the backend
    
    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


 src/common/scram-common.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/common/scram-common.c b/src/common/scram-common.c
index ef997ef6849..6448564a08c 100644
--- 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)


[parent: bc22bd257551]