Factor the actual setup step for the blinding into a helper

ok jsing

1 files changed, 43 insertions, 30 deletions

diff --git a/src/lib/libcrypto/bn/bn_blind.c b/src/lib/libcrypto/bn/bn_blind.c
index e530bdfb27..edc1a9d1ab 100644
--- a/src/lib/libcrypto/bn/bn_blind.c
+++ b/src/lib/libcrypto/bn/bn_blind.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_blind.c,v 1.33 2023/08/08 13:59:04 tb Exp $ */
+/* $OpenBSD: bn_blind.c,v 1.34 2023/08/08 14:40:56 tb Exp $ */
 /* ====================================================================
  * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
  *
@@ -179,6 +179,45 @@ BN_BLINDING_free(BN_BLINDING *r)
 }
 
 static int
+BN_BLINDING_setup(BN_BLINDING *ret, BN_CTX *ctx)
+{
+        int retry_counter = 32;
+
+        /*
+         * XXX - remove this loop. If we happen to find a non-invertible A,
+         * we have basically factored mod = (p-1)(q-1)...
+         */
+        do {
+                if (!BN_rand_range(ret->A, ret->mod))
+                        return 0;
+                if (BN_mod_inverse_ct(ret->Ai, ret->A, ret->mod, ctx) == NULL) {
+                        /* this should almost never happen for good RSA keys */
+                        unsigned long error = ERR_peek_last_error();
+                        if (ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
+                                if (retry_counter-- == 0) {
+                                        BNerror(BN_R_TOO_MANY_ITERATIONS);
+                                        return 0;
+                                }
+                                ERR_clear_error();
+                        } else
+                                return 0;
+                } else
+                        break;
+        } while (1);
+
+        if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
+                if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod,
+                    ctx, ret->m_ctx))
+                        return 0;
+        } else {
+                if (!BN_mod_exp_ct(ret->A, ret->A, ret->e, ret->mod, ctx))
+                        return 0;
+        }
+
+        return 1;
+}
+
+static int
 BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
 {
         int ret = 0;
@@ -187,8 +226,7 @@ BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
                 b->counter = 0;
 
         if (++b->counter == BN_BLINDING_COUNTER) {
-                /* re-create blinding parameters */
-                if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
+                if (!BN_BLINDING_setup(b, ctx))
                         goto err;
         } else {
                 if (!BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
@@ -258,7 +296,6 @@ BN_BLINDING_create_param(BN_BLINDING *b, const BIGNUM *e, BIGNUM *m, BN_CTX *ctx
         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx), BN_MONT_CTX *m_ctx)
 {
         BN_BLINDING *ret = NULL;
-        int retry_counter = 32;
 
         if ((ret = b) == NULL)
                 ret = BN_BLINDING_new(e, m);
@@ -270,32 +307,8 @@ BN_BLINDING_create_param(BN_BLINDING *b, const BIGNUM *e, BIGNUM *m, BN_CTX *ctx
         if (m_ctx != NULL)
                 ret->m_ctx = m_ctx;
 
-        do {
-                if (!BN_rand_range(ret->A, ret->mod))
-                        goto err;
-                if (BN_mod_inverse_ct(ret->Ai, ret->A, ret->mod, ctx) == NULL) {
-                        /* this should almost never happen for good RSA keys */
-                        unsigned long error = ERR_peek_last_error();
-                        if (ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
-                                if (retry_counter-- == 0) {
-                                        BNerror(BN_R_TOO_MANY_ITERATIONS);
-                                        goto err;
-                                }
-                                ERR_clear_error();
-                        } else
-                                goto err;
-                } else
-                        break;
-        } while (1);
-
-        if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
-                if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod,
-                    ctx, ret->m_ctx))
-                        goto err;
-        } else {
-                if (!BN_mod_exp_ct(ret->A, ret->A, ret->e, ret->mod, ctx))
-                        goto err;
-        }
+        if (!BN_BLINDING_setup(ret, ctx))
+                goto err;
 
         return ret;