Implement provider-side keymgmt_dup function

To avoid mutating key data add OSSL_FUNC_KEYMGMT_DUP function
to the provider API and implement it for all asym-key key
managements.

Use it when copying everything to an empty EVP_PKEY
which is the case with EVP_PKEY_dup().

Fixes #14658

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/14793)

1 files changed, 44 insertions, 0 deletions

diff --git a/crypto/dsa/dsa_backend.c b/crypto/dsa/dsa_backend.c
index f3e54aeb13..856203a200 100644
--- a/crypto/dsa/dsa_backend.c
+++ b/crypto/dsa/dsa_backend.c
@@ -16,6 +16,7 @@
 #include <openssl/core_names.h>
 #include <openssl/err.h>
 #include "crypto/dsa.h"
+#include "dsa_local.h"
 
 /*
  * The intention with the "backend" source file is to offer backend support
@@ -56,6 +57,49 @@ int ossl_dsa_key_fromdata(DSA *dsa, const OSSL_PARAM params[])
     return 0;
 }
 
+static ossl_inline int dsa_bn_dup_check(BIGNUM **out, const BIGNUM *f)
+{
+    if (f != NULL && (*out = BN_dup(f)) == NULL)
+        return 0;
+    return 1;
+}
+
+DSA *ossl_dsa_dup(const DSA *dsa)
+{
+    DSA *dupkey = NULL;
+
+#ifndef FIPS_MODULE
+    /* Do not try to duplicate foreign DSA keys */
+    if (DSA_get_method((DSA *)dsa) != DSA_OpenSSL())
+        return NULL;
+#endif
+
+    if ((dupkey = ossl_dsa_new(dsa->libctx)) == NULL)
+        return NULL;
+
+    if (!ossl_ffc_params_copy(&dupkey->params, &dsa->params))
+        goto err;
+
+    dupkey->flags = dsa->flags;
+
+    if (!dsa_bn_dup_check(&dupkey->pub_key, dsa->pub_key))
+        goto err;
+    if (!dsa_bn_dup_check(&dupkey->priv_key, dsa->priv_key))
+        goto err;
+
+#ifndef FIPS_MODULE
+    if (!CRYPTO_dup_ex_data(CRYPTO_EX_INDEX_DSA,
+                            &dupkey->ex_data, &dsa->ex_data))
+        goto err;
+#endif
+
+    return dupkey;
+
+ err:
+    DSA_free(dupkey);
+    return NULL;
+}
+
 #ifndef FIPS_MODULE
 DSA *ossl_dsa_key_from_pkcs8(const PKCS8_PRIV_KEY_INFO *p8inf,
                              OSSL_LIB_CTX *libctx, const char *propq)