modular arithmetics

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

diff --git a/crypto/bn/bn_recp.c b/crypto/bn/bn_recp.c
index a175e1c5f2fcdef12cd8f74d9cd49a5fa414481f..0700a0f06375265589911333ae2935ab11a3a0eb 100644 (file)
--- a/crypto/bn/bn_recp.c
+++ b/crypto/bn/bn_recp.c
@@ -167,7 +167,8 @@ int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m,
 
        if (i != recp->shift)
                recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),
-                       i,ctx);
+                       i,ctx); /* BN_reciprocal returns i, or -1 for an error */
+       if (recp->shift == -1) goto err;
 
        if (!BN_rshift(a,m,j)) goto err;
        if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;
@@ -203,6 +204,7 @@ err:
  * We actually calculate with an extra word of precision, so
  * we can do faster division if the remainder is not required.
  */
+/* r := 2^len / m */
 int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
        {
        int ret= -1;