Add EVP_PKEY_set1_engine() function.

Add an ENGINE to EVP_PKEY structure which can be used for cryptographic
operations: this will typically be used by an HSM key to redirect calls
to a custom EVP_PKEY_METHOD.
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4503)

crypto/evp/p_lib.c

@@ -188,9 +188,11 @@ static int pkey_set_type(EVP_PKEY *pkey, int type, const char *str, int len)
         if ((type == pkey->save_type) && pkey->ameth)
             return 1;
 #ifndef OPENSSL_NO_ENGINE
-        /* If we have an ENGINE release it */
+        /* If we have ENGINEs release them */
         ENGINE_finish(pkey->engine);
         pkey->engine = NULL;
+        ENGINE_finish(pkey->pmeth_engine);
+        pkey->pmeth_engine = NULL;
 #endif
     }
     if (str)
@@ -224,7 +226,25 @@ int EVP_PKEY_set_type_str(EVP_PKEY *pkey, const char *str, int len)
 {
     return pkey_set_type(pkey, EVP_PKEY_NONE, str, len);
 }
-
+#ifndef OPENSSL_NO_ENGINE
+int EVP_PKEY_set1_engine(EVP_PKEY *pkey, ENGINE *e)
+{
+    if (e != NULL) {
+        if (!ENGINE_init(e)) {
+            EVPerr(EVP_F_EVP_PKEY_SET1_ENGINE, ERR_R_ENGINE_LIB);
+            return 0;
+        }
+        if (ENGINE_get_pkey_meth(e, pkey->type) == NULL) {
+            ENGINE_finish(e);
+            EVPerr(EVP_F_EVP_PKEY_SET1_ENGINE, EVP_R_UNSUPPORTED_ALGORITHM);
+            return 0;
+        }
+    }
+    ENGINE_finish(pkey->pmeth_engine);
+    pkey->pmeth_engine = e;
+    return 1;
+}
+#endif
 int EVP_PKEY_assign(EVP_PKEY *pkey, int type, void *key)
 {
     if (pkey == NULL || !EVP_PKEY_set_type(pkey, type))
@@ -443,6 +463,8 @@ static void EVP_PKEY_free_it(EVP_PKEY *x)
 #ifndef OPENSSL_NO_ENGINE
     ENGINE_finish(x->engine);
     x->engine = NULL;
+    ENGINE_finish(x->pmeth_engine);
+    x->pmeth_engine = NULL;
 #endif
 }
 

crypto/evp/pmeth_lib.c

@@ -106,7 +106,7 @@ static EVP_PKEY_CTX *int_ctx_new(EVP_PKEY *pkey, ENGINE *e, int id)
     }
 #ifndef OPENSSL_NO_ENGINE
     if (e == NULL && pkey != NULL)
-        e = pkey->engine;
+        e = pkey->pmeth_engine != NULL ? pkey->pmeth_engine : pkey->engine;
     /* Try to find an ENGINE which implements this method */
     if (e) {
         if (!ENGINE_init(e)) {

crypto/include/internal/evp_int.h

@@ -369,6 +369,7 @@ struct evp_pkey_st {
     CRYPTO_REF_COUNT references;
     const EVP_PKEY_ASN1_METHOD *ameth;
     ENGINE *engine;
+    ENGINE *pmeth_engine; /* If not NULL public key ENGINE to use */
     union {
         void *ptr;
 # ifndef OPENSSL_NO_RSA

include/openssl/evp.h

@@ -978,6 +978,9 @@ int EVP_PKEY_security_bits(const EVP_PKEY *pkey);
 int EVP_PKEY_size(EVP_PKEY *pkey);
 int EVP_PKEY_set_type(EVP_PKEY *pkey, int type);
 int EVP_PKEY_set_type_str(EVP_PKEY *pkey, const char *str, int len);
+# ifndef OPENSSL_NO_ENGINE
+int EVP_PKEY_set1_engine(EVP_PKEY *pkey, ENGINE *e);
+# endif
 int EVP_PKEY_assign(EVP_PKEY *pkey, int type, void *key);
 void *EVP_PKEY_get0(const EVP_PKEY *pkey);
 const unsigned char *EVP_PKEY_get0_hmac(const EVP_PKEY *pkey, size_t *len);