Don't error with -1 for BIGNUM exp operations

The man pages say that BIGNUM arithmetic operations fail with a 0 return.
However some functions were returning -1 on error. In master and 1.1.0 they
already return 0, so this brings 1.0.2 in line.

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/4682)

diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 35facd213a253db05a1a7209e8d0fa70e6874c7b..c4b63e44ba369ab8c34aa3d34fd8c076586f5ea5 100644 (file)
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -149,7 +149,7 @@ int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
             || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-        return -1;
+        return 0;
     }
 
     BN_CTX_start(ctx);
@@ -285,7 +285,7 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
             || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-        return -1;
+        return 0;
     }
 
     bits = BN_num_bits(p);
@@ -1228,7 +1228,7 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
             || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-        return -1;
+        return 0;
     }
 
     bn_check_top(p);
@@ -1361,7 +1361,7 @@ int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
             || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_SIMPLE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-        return -1;
+        return 0;
     }
 
     bits = BN_num_bits(p);