1 files changed, 15 insertions, 14 deletions

diff --git a/src/lib/libcrypto/bn/bn_sqrt.c b/src/lib/libcrypto/bn/bn_sqrt.c
index 8514f23a27..4b9638b6dc 100644
--- a/src/lib/libcrypto/bn/bn_sqrt.c
+++ b/src/lib/libcrypto/bn/bn_sqrt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_sqrt.c,v 1.9 2017/01/29 17:49:22 beck Exp $ */
+/* $OpenBSD: bn_sqrt.c,v 1.10 2022/03/15 15:52:39 tb Exp $ */
 /* Written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * and Bodo Moeller for the OpenSSL project. */
 /* ====================================================================
@@ -351,21 +351,22 @@ BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
                         goto vrfy;
                 }
 
-
-                /* find smallest  i  such that  b^(2^i) = 1 */
-                i = 1;
-                if (!BN_mod_sqr(t, b, p, ctx))
-                        goto end;
-                while (!BN_is_one(t)) {
-                        i++;
-                        if (i == e) {
-                                BNerror(BN_R_NOT_A_SQUARE);
-                                goto end;
+                /* Find the smallest i with 0 < i < e such that b^(2^i) = 1. */
+                for (i = 1; i < e; i++) {
+                        if (i == 1) {
+                                if (!BN_mod_sqr(t, b, p, ctx))
+                                        goto end;
+                        } else {
+                                if (!BN_mod_sqr(t, t, p, ctx))
+                                        goto end;
                         }
-                        if (!BN_mod_mul(t, t, t, p, ctx))
-                                goto end;
+                        if (BN_is_one(t))
+                                break;
+                }
+                if (i >= e) {
+                        BNerror(BN_R_NOT_A_SQUARE);
+                        goto end;
                 }
-
 
                 /* t := y^2^(e - i - 1) */
                 if (!BN_copy(t, y))