Fix CID-1464802

Improper use of negative value (It just needs to pass zero instead of -1).
Reviewed-by: NTomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: NMatthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/12237)

crypto/dsa/dsa_gen.c

@@ -63,7 +63,7 @@ int DSA_generate_parameters_ex(DSA *dsa, int bits,
             return 0;
     } else {
         if (!dsa_generate_ffc_parameters(dsa, DSA_PARAMGEN_TYPE_FIPS_186_4,
-                                         bits, -1, cb))
+                                         bits, 0, cb))
             return 0;
     }
 

crypto/ffc/ffc_params_generate.c

@@ -504,7 +504,7 @@ int ffc_params_FIPS186_4_gen_verify(OPENSSL_CTX *libctx, FFC_PARAMS *params,
     if (params->mdname != NULL) {
         md = EVP_MD_fetch(libctx, params->mdname, params->mdprops);
     } else {
-        if (N <= 0)
+        if (N == 0)
             N = (L >= 2048 ? SHA256_DIGEST_LENGTH : SHA_DIGEST_LENGTH) * 8;
         md = EVP_MD_fetch(libctx, default_mdname(N), NULL);
     }
@@ -514,7 +514,7 @@ int ffc_params_FIPS186_4_gen_verify(OPENSSL_CTX *libctx, FFC_PARAMS *params,
     if (mdsize <= 0)
         goto err;
 
-    if (N <= 0)
+    if (N == 0)
         N = mdsize * 8;
     qsize = N >> 3;
 
@@ -790,13 +790,13 @@ int ffc_params_FIPS186_2_gen_verify(OPENSSL_CTX *libctx, FFC_PARAMS *params,
     if (params->mdname != NULL) {
         md = EVP_MD_fetch(libctx, params->mdname, params->mdprops);
     } else {
-        if (N <= 0)
+        if (N == 0)
             N = (L >= 2048 ? SHA256_DIGEST_LENGTH : SHA_DIGEST_LENGTH) * 8;
         md = EVP_MD_fetch(libctx, default_mdname(N), NULL);
     }
     if (md == NULL)
         goto err;
-    if (N <= 0)
+    if (N == 0)
         N = EVP_MD_size(md) * 8;
     qsize = N >> 3;