From 73c2522c7ce821f2c837b58eec7780fb43aa7d4f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bodo=20M=C3=B6ller?= <bodo@openssl.org>
Date: Thu, 30 Nov 2000 00:33:18 +0000
Subject: [PATCH] Handle special cases correctly in exponentation functions.
test_bn still fails in the BN_sqrt test because
small primes appear to turn into zero for no
obvious reason, leading to "div by zero" errors.
---
crypto/bn/bn_exp.c | 31 ++++++++++++++++---------------
crypto/bn/bn_exp2.c | 20 +++++++++++++-------
2 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 51c828259..f7e7ced2c 100644
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -240,11 +240,6 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
ret = BN_one(r);
return ret;
}
- if (BN_is_zero(a))
- {
- ret = BN_zero(r);
- return ret;
- }
BN_CTX_start(ctx);
if ((aa = BN_CTX_get(ctx)) == NULL) goto err;
@@ -256,6 +251,11 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
ts=1;
if (!BN_nnmod(&(val[0]),a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(&(val[0])))
+ {
+ ret = BN_zero(r);
+ goto err;
+ }
window = BN_window_bits_for_exponent_size(bits);
if (window > 1)
@@ -365,11 +365,7 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
ret = BN_one(rr);
return ret;
}
- if (BN_is_zero(a))
- {
- ret = BN_zero(rr);
- return ret;
- }
+
BN_CTX_start(ctx);
d = BN_CTX_get(ctx);
r = BN_CTX_get(ctx);
@@ -396,6 +392,11 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
}
else
aa=a;
+ if (BN_is_zero(aa))
+ {
+ ret = BN_zero(rr);
+ goto err;
+ }
if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */
window = BN_window_bits_for_exponent_size(bits);
@@ -632,11 +633,6 @@ int BN_mod_exp_simple(BIGNUM *r,
ret = BN_one(r);
return ret;
}
- if (BN_is_zero(a))
- {
- ret = BN_one(r);
- return ret;
- }
BN_CTX_start(ctx);
if ((d = BN_CTX_get(ctx)) == NULL) goto err;
@@ -644,6 +640,11 @@ int BN_mod_exp_simple(BIGNUM *r,
BN_init(&(val[0]));
ts=1;
if (!BN_nnmod(&(val[0]),a,m,ctx)) goto err; /* 1 */
+ if (BN_is_zero(&(val[0])))
+ {
+ ret = BN_one(r);
+ return ret;
+ }
window = BN_window_bits_for_exponent_size(bits);
if (window > 1)
diff --git a/crypto/bn/bn_exp2.c b/crypto/bn/bn_exp2.c
index 56f1c959b..4b41dae07 100644
--- a/crypto/bn/bn_exp2.c
+++ b/crypto/bn/bn_exp2.c
@@ -144,11 +144,6 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
ret = BN_one(rr);
return ret;
}
- if (BN_is_zero(a1) || BN_is_zero(a2))
- {
- ret = BN_zero(rr);
- return ret;
- }
bits=(bits1 > bits2)?bits1:bits2;
@@ -173,7 +168,7 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
*/
BN_init(&val1[0]);
ts1=1;
- if (BN_ucmp(a1,m) >= 0)
+ if (a1->neg || BN_ucmp(a1,m) >= 0)
{
if (!BN_mod(&(val1[0]),a1,m,ctx))
goto err;
@@ -181,6 +176,12 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
}
else
a_mod_m = a1;
+ if (BN_is_zero(&(val1[0])))
+ {
+ ret = BN_zero(rr);
+ goto err;
+ }
+
if (!BN_to_montgomery(&(val1[0]),a_mod_m,mont,ctx)) goto err;
if (window1 > 1)
{
@@ -202,7 +203,7 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
*/
BN_init(&val2[0]);
ts2=1;
- if (BN_ucmp(a2,m) >= 0)
+ if (a2->neg || BN_ucmp(a2,m) >= 0)
{
if (!BN_mod(&(val2[0]),a2,m,ctx))
goto err;
@@ -210,6 +211,11 @@ int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
}
else
a_mod_m = a2;
+ if (BN_is_zero(&(val2[0])))
+ {
+ ret = BN_zero(rr);
+ goto err;
+ }
if (!BN_to_montgomery(&(val2[0]),a_mod_m,mont,ctx)) goto err;
if (window2 > 1)
{