Improve the performance of EVP_PKCS82PKEY_ex

We can easily find out the keytype which should significantly improve
the performance of this function because we don't have to try every loaded
decoder.

Partial fix for #20399

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #20412)

crypto/evp/evp_pkey.c

@@ -15,6 +15,7 @@
 #include <openssl/encoder.h>
 #include <openssl/decoder.h>
 #include "internal/provider.h"
+#include "internal/sizes.h"
 #include "crypto/asn1.h"
 #include "crypto/evp.h"
 #include "crypto/x509.h"
@@ -73,6 +74,13 @@ EVP_PKEY *EVP_PKCS82PKEY_ex(const PKCS8_PRIV_KEY_INFO *p8, OSSL_LIB_CTX *libctx,
     int selection;
     size_t len;
     OSSL_DECODER_CTX *dctx = NULL;
+    const ASN1_OBJECT *algoid = NULL;
+    char keytype[OSSL_MAX_NAME_SIZE];
+
+    if (p8 == NULL
+            || !PKCS8_pkey_get0(&algoid, NULL, NULL, NULL, p8)
+            || !OBJ_obj2txt(keytype, sizeof(keytype), algoid, 0))
+        return NULL;
 
     if ((encoded_len = i2d_PKCS8_PRIV_KEY_INFO(p8, &encoded_data)) <= 0
             || encoded_data == NULL)
@@ -82,7 +90,20 @@ EVP_PKEY *EVP_PKCS82PKEY_ex(const PKCS8_PRIV_KEY_INFO *p8, OSSL_LIB_CTX *libctx,
     len = encoded_len;
     selection = EVP_PKEY_KEYPAIR | EVP_PKEY_KEY_PARAMETERS;
     dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, "DER", "PrivateKeyInfo",
-                                         NULL, selection, libctx, propq);
+                                         keytype, selection, libctx, propq);
+
+    if (dctx != NULL && OSSL_DECODER_CTX_get_num_decoders(dctx) == 0) {
+        OSSL_DECODER_CTX_free(dctx);
+
+        /*
+         * This could happen if OBJ_obj2txt() returned a text OID and the
+         * decoder has not got that OID as an alias. We fall back to a NULL
+         * keytype
+         */
+        dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, "DER", "PrivateKeyInfo",
+                                             NULL, selection, libctx, propq);
+    }
+
     if (dctx == NULL
         || !OSSL_DECODER_from_data(dctx, &p8_data, &len))
         /* try legacy */