Fix a ** 0 mod 1 = 0 for real this time.

[openssl.git] / crypto / bn / bn_exp.c

diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 50cf3231b07b71c1b8de04c27b789d7ca00a0dcd..98db765f3829af0a5c1bb7fd4dfaaecd7b1fc66f 100644 (file)
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -282,9 +282,14 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
     }
 
     bits = BN_num_bits(p);
-
     if (bits == 0) {
-        ret = BN_one(r);
+        /* x**0 mod 1 is still zero. */
+        if (BN_is_one(m)) {
+            ret = 1;
+            BN_zero(r);
+        } else {
+            ret = BN_one(r);
+        }
         return ret;
     }
 
@@ -418,7 +423,13 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
     }
     bits = BN_num_bits(p);
     if (bits == 0) {
-        ret = BN_one(rr);
+        /* x**0 mod 1 is still zero. */
+        if (BN_is_one(m)) {
+            ret = 1;
+            BN_zero(rr);
+        } else {
+            ret = BN_one(rr);
+        }
         return ret;
     }
 
@@ -671,7 +682,13 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
 
     bits = BN_num_bits(p);
     if (bits == 0) {
-        ret = BN_one(rr);
+        /* x**0 mod 1 is still zero. */
+        if (BN_is_one(m)) {
+            ret = 1;
+            BN_zero(rr);
+        } else {
+            ret = BN_one(rr);
+        }
         return ret;
     }
 
@@ -1182,8 +1199,9 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
         if (BN_is_one(m)) {
             ret = 1;
             BN_zero(rr);
-        } else
+        } else {
             ret = BN_one(rr);
+        }
         return ret;
     }
     if (a == 0) {
@@ -1297,9 +1315,14 @@ int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
     }
 
     bits = BN_num_bits(p);
-
-    if (bits == 0) {
-        ret = BN_one(r);
+   if (bits == 0) {
+        /* x**0 mod 1 is still zero. */
+        if (BN_is_one(m)) {
+            ret = 1;
+            BN_zero(r);
+        } else {
+            ret = BN_one(r);
+        }
         return ret;
     }