Add evp_keymgmt_export_to_provider(), for key transfer between providers

This function is used to transport private key materia from whatever
is already attached to the EVP_PKEY to the new provider, using key
data export and import functionality.

If a legacy lower level key has been assigned to the EVP_PKEY, we use
its data to create a provider side key, and thereby have a bridge
between old style public key types and the EVP_PKEY on providers.

If successful, this function returns a reference to the appropriate
provider side data for the key.

This can be used by any operation that wants to use this key.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9312)

4 files changed, 206 insertions, 2 deletions

diff --git a/crypto/evp/build.info b/crypto/evp/build.info
index d889897b18..c650c28882 100644
--- a/crypto/evp/build.info
+++ b/crypto/evp/build.info
@@ -1,6 +1,6 @@
 LIBS=../../libcrypto
-$COMMON=digest.c evp_enc.c evp_lib.c evp_fetch.c cmeth_lib.c keymgmt_meth.c \
-        evp_utils.c
+$COMMON=digest.c evp_enc.c evp_lib.c evp_fetch.c cmeth_lib.c evp_utils.c \
+        keymgmt_meth.c keymgmt_lib.c
 SOURCE[../../libcrypto]=$COMMON\
         encode.c evp_key.c evp_cnf.c \
         e_des.c e_bf.c e_idea.c e_des3.c e_camellia.c\
diff --git a/crypto/evp/keymgmt_lib.c b/crypto/evp/keymgmt_lib.c
new file mode 100644
index 0000000000..76c4a30a1c
--- /dev/null
+++ b/crypto/evp/keymgmt_lib.c
@@ -0,0 +1,188 @@
+/*
+ * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include "internal/cryptlib.h"
+#include "internal/nelem.h"
+#include "internal/evp_int.h"
+#include "internal/asn1_int.h"
+#include "internal/provider.h"
+#include "evp_locl.h"
+
+static OSSL_PARAM *paramdefs_to_params(const OSSL_PARAM *paramdefs)
+{
+    size_t cnt;
+    const OSSL_PARAM *p;
+    OSSL_PARAM *params, *q;
+
+    for (cnt = 1, p = paramdefs; p->key != NULL; p++, cnt++)
+        continue;
+
+    params = OPENSSL_zalloc(cnt * sizeof(*params));
+
+    for (p = paramdefs, q = params; ; p++, q++) {
+        *q = *p;
+        if (p->key == NULL)
+            break;
+
+        q->data = NULL;          /* In case the provider used it */
+        q->return_size = 0;
+    }
+
+    return params;
+}
+
+typedef union align_block_un {
+    OSSL_UNION_ALIGN;
+} ALIGN_BLOCK;
+
+#define ALIGN_SIZE  sizeof(ALIGN_BLOCK)
+
+static void *allocate_params_space(OSSL_PARAM *params)
+{
+    unsigned char *data = NULL;
+    size_t space;
+    OSSL_PARAM *p;
+
+    for (space = 0, p = params; p->key != NULL; p++)
+        space += ((p->return_size + ALIGN_SIZE - 1) / ALIGN_SIZE) * ALIGN_SIZE;
+
+    data = OPENSSL_zalloc(space);
+
+    for (space = 0, p = params; p->key != NULL; p++) {
+        p->data = data + space;
+        space += ((p->return_size + ALIGN_SIZE - 1) / ALIGN_SIZE) * ALIGN_SIZE;
+    }
+
+    return data;
+}
+
+void *evp_keymgmt_export_to_provider(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt)
+{
+    void *provkey = NULL;
+    size_t i, j;
+
+    /*
+     * If there is an underlying legacy key and it has changed, invalidate
+     * the cache of provider keys.
+     */
+    if (pk->pkey.ptr != NULL) {
+        /*
+         * If there is no dirty counter, this key can't be used with
+         * providers.
+         */
+        if (pk->ameth->dirty_cnt == NULL)
+            return NULL;
+
+        if (pk->ameth->dirty_cnt(pk) != pk->dirty_cnt_copy)
+            for (i = 0;
+                 i < OSSL_NELEM(pk->pkeys) && pk->pkeys[i].keymgmt != NULL;
+                 i++) {
+                pk->pkeys[i].keymgmt->freekey(pk->pkeys[i].provkey);
+                pk->pkeys[i].keymgmt = NULL;
+                pk->pkeys[i].provkey = NULL;
+            }
+    }
+
+    /*
+     * See if we have exported to this provider already.
+     * If we have, return immediately.
+     */
+    for (i = 0;
+         i < OSSL_NELEM(pk->pkeys) && pk->pkeys[i].keymgmt != NULL;
+         i++) {
+        if (keymgmt == pk->pkeys[i].keymgmt)
+            return pk->pkeys[i].provkey;
+    }
+
+    if (pk->pkey.ptr != NULL) {
+        /* There is a legacy key, try to export that one to the provider */
+
+        /* If the legacy key doesn't have an export function, give up */
+        if (pk->ameth->export_to == NULL)
+            return NULL;
+
+        /* Otherwise, simply use it */
+        provkey = pk->ameth->export_to(pk, keymgmt);
+
+        /* Synchronize the dirty count, but only if we exported successfully */
+        if (provkey != NULL)
+            pk->dirty_cnt_copy = pk->ameth->dirty_cnt(pk);
+
+    } else {
+        /*
+         * Here, there is no legacy key, so we look at the already cached
+         * provider keys, and import from the first that supports it
+         * (i.e. use its export function), and export the imported data to
+         * the new provider.
+         */
+
+        /*
+         * If the given keymgmt doesn't have an import function, give up
+         */
+        if (keymgmt->importkey == NULL)
+            return NULL;
+
+        for (j = 0; j < i && pk->pkeys[j].keymgmt != NULL; j++) {
+            if (pk->pkeys[j].keymgmt->exportkey != NULL) {
+                const OSSL_PARAM *paramdefs = NULL;
+                OSSL_PARAM *params = NULL;
+                void *data = NULL;
+                void *provctx =
+                    ossl_provider_ctx(EVP_KEYMGMT_provider(keymgmt));
+
+                paramdefs = pk->pkeys[j].keymgmt->exportkey_types();
+                /*
+                 * All params have 'data' set to NULL.  In that case,
+                 * the exportkey call should just fill in 'return_size'
+                 * in all applicable params.
+                 */
+                params = paramdefs_to_params(paramdefs);
+                /* Get 'return_size' filled */
+                pk->pkeys[j].keymgmt->exportkey(pk->pkeys[j].provkey, params);
+
+                /*
+                 * Allocate space and assign 'data' to point into the
+                 * data block
+                 */
+                data = allocate_params_space(params);
+
+                /*
+                 * Call the exportkey function a second time, to get
+                 * the data filled
+                 */
+                pk->pkeys[j].keymgmt->exportkey(pk->pkeys[j].provkey, params);
+
+                /*
+                 * We should have all the data at this point, so import
+                 * into the new provider and hope to get a key back.
+                 */
+                provkey = keymgmt->importkey(provctx, params);
+                OPENSSL_free(params);
+                OPENSSL_free(data);
+
+                if (provkey != NULL)
+                    break;
+            }
+        }
+    }
+
+    /*
+     * TODO(3.0) Right now, we assume we have ample space.  We will
+     * have to think about a cache aging scheme, though, if |i| indexes
+     * outside the array.
+     */
+    j = ossl_assert(i < OSSL_NELEM(pk->pkeys));
+
+    if (provkey != NULL) {
+        EVP_KEYMGMT_up_ref(keymgmt);
+        pk->pkeys[i].keymgmt = keymgmt;
+        pk->pkeys[i].provkey = provkey;
+    }
+    return provkey;
+}
diff --git a/crypto/include/internal/asn1_int.h b/crypto/include/internal/asn1_int.h
index 1f62063b08..674fa704a1 100644
--- a/crypto/include/internal/asn1_int.h
+++ b/crypto/include/internal/asn1_int.h
@@ -63,6 +63,14 @@ struct evp_pkey_asn1_method_st {
     int (*set_pub_key) (EVP_PKEY *pk, const unsigned char *pub, size_t len);
     int (*get_priv_key) (const EVP_PKEY *pk, unsigned char *priv, size_t *len);
     int (*get_pub_key) (const EVP_PKEY *pk, unsigned char *pub, size_t *len);
+
+    /*
+     * TODO: Make sure these functions are defined for key types that are
+     * implemented in providers.
+     */
+    /* Exports to providers */
+    size_t (*dirty_cnt) (const EVP_PKEY *pk);
+    void *(*export_to) (const EVP_PKEY *pk, EVP_KEYMGMT *keymgmt);
 } /* EVP_PKEY_ASN1_METHOD */ ;
 
 DEFINE_STACK_OF_CONST(EVP_PKEY_ASN1_METHOD)
diff --git a/crypto/include/internal/evp_int.h b/crypto/include/internal/evp_int.h
index 359d561342..ff9b6e545b 100644
--- a/crypto/include/internal/evp_int.h
+++ b/crypto/include/internal/evp_int.h
@@ -545,6 +545,11 @@ struct evp_pkey_st {
         EVP_KEYMGMT *keymgmt;
         void *provkey;
     } pkeys[10];
+    /*
+     * If there is a legacy key assigned to this structure, we keep
+     * a copy of that key's dirty count.
+     */
+    size_t dirty_cnt_copy;
 } /* EVP_PKEY */ ;
 
 
@@ -555,6 +560,9 @@ void openssl_add_all_kdfs_int(void);
 void evp_cleanup_int(void);
 void evp_app_cleanup_int(void);
 
+void *evp_keymgmt_export_to_provider(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt);
+
+
 /* Pulling defines out of C source files */
 
 #define EVP_RC4_KEY_SIZE 16