crypto: Support export akcipher to pkcs8

crypto: support export RSA private keys with PKCS#8 standard.
So that users can upload this private key to linux kernel.

Signed-off-by: lei he <helei.sig11@bytedance.com>
Message-Id: <20221008085030.70212-4-helei.sig11@bytedance.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

crypto/akcipher.c

@@ -22,6 +22,8 @@
 #include "qemu/osdep.h"
 #include "crypto/akcipher.h"
 #include "akcipherpriv.h"
+#include "der.h"
+#include "rsakey.h"
 
 #if defined(CONFIG_GCRYPT)
 #include "akcipher-gcrypt.c.inc"
@@ -106,3 +108,19 @@ void qcrypto_akcipher_free(QCryptoAkCipher *akcipher)
 
     drv->free(akcipher);
 }
+
+int qcrypto_akcipher_export_p8info(const QCryptoAkCipherOptions *opts,
+                                   uint8_t *key, size_t keylen,
+                                   uint8_t **dst, size_t *dst_len,
+                                   Error **errp)
+{
+    switch (opts->alg) {
+    case QCRYPTO_AKCIPHER_ALG_RSA:
+        qcrypto_akcipher_rsakey_export_p8info(key, keylen, dst, dst_len);
+        return 0;
+
+    default:
+        error_setg(errp, "Unsupported algorithm: %u", opts->alg);
+        return -1;
+    }
+}

crypto/rsakey.c

@@ -19,6 +19,8 @@
  *
  */
 
+#include "qemu/osdep.h"
+#include "der.h"
 #include "rsakey.h"
 
 void qcrypto_akcipher_rsakey_free(QCryptoAkCipherRSAKey *rsa_key)
@@ -37,6 +39,46 @@ void qcrypto_akcipher_rsakey_free(QCryptoAkCipherRSAKey *rsa_key)
     g_free(rsa_key);
 }
 
+/**
+ * PKCS#8 private key info for RSA
+ *
+ * PrivateKeyInfo ::= SEQUENCE {
+ * version         INTEGER,
+ * privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
+ * privateKey      OCTET STRING,
+ * attributes      [0] IMPLICIT Attributes OPTIONAL
+ * }
+ */
+void qcrypto_akcipher_rsakey_export_p8info(const uint8_t *key,
+                                           size_t keylen,
+                                           uint8_t **dst,
+                                           size_t *dlen)
+{
+    QCryptoEncodeContext *ctx = qcrypto_der_encode_ctx_new();
+    uint8_t version = 0;
+
+    qcrypto_der_encode_seq_begin(ctx);
+
+    /* version */
+    qcrypto_der_encode_int(ctx, &version, sizeof(version));
+
+    /* algorithm identifier */
+    qcrypto_der_encode_seq_begin(ctx);
+    qcrypto_der_encode_oid(ctx, (uint8_t *)QCRYPTO_OID_rsaEncryption,
+                           sizeof(QCRYPTO_OID_rsaEncryption) - 1);
+    qcrypto_der_encode_null(ctx);
+    qcrypto_der_encode_seq_end(ctx);
+
+    /* RSA private key */
+    qcrypto_der_encode_octet_str(ctx, key, keylen);
+
+    qcrypto_der_encode_seq_end(ctx);
+
+    *dlen = qcrypto_der_encode_ctx_buffer_len(ctx);
+    *dst = g_malloc(*dlen);
+    qcrypto_der_encode_ctx_flush_and_free(ctx, *dst);
+}
+
 #if defined(CONFIG_NETTLE) && defined(CONFIG_HOGWEED)
 #include "rsakey-nettle.c.inc"
 #else

crypto/rsakey.h

@@ -22,7 +22,6 @@
 #ifndef QCRYPTO_RSAKEY_H
 #define QCRYPTO_RSAKEY_H
 
-#include "qemu/osdep.h"
 #include "qemu/host-utils.h"
 #include "crypto/akcipher.h"
 
@@ -84,6 +83,16 @@ QCryptoAkCipherRSAKey *qcrypto_akcipher_rsakey_parse(
     QCryptoAkCipherKeyType type,
     const uint8_t *key, size_t keylen, Error **errp);
 
+/**
+ * qcrypto_akcipher_rsakey_export_as_p8info:
+ *
+ * Export RSA private key to PKCS#8 private key info.
+ */
+void qcrypto_akcipher_rsakey_export_p8info(const uint8_t *key,
+                                           size_t keylen,
+                                           uint8_t **dst,
+                                           size_t *dlen);
+
 void qcrypto_akcipher_rsakey_free(QCryptoAkCipherRSAKey *key);
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoAkCipherRSAKey,

include/crypto/akcipher.h

@@ -153,6 +153,27 @@ int qcrypto_akcipher_max_dgst_len(QCryptoAkCipher *akcipher);
  */
 void qcrypto_akcipher_free(QCryptoAkCipher *akcipher);
 
+/**
+ * qcrypto_akcipher_export_p8info:
+ * @opts: the options of the akcipher to be exported.
+ * @key: the original key of the akcipher to be exported.
+ * @keylen: length of the 'key'
+ * @dst: output parameter, if export succeed, *dst is set to the
+ * PKCS#8 encoded private key, caller MUST free this key with
+ * g_free after use.
+ * @dst_len: output parameter, indicates the length of PKCS#8 encoded
+ * key.
+ *
+ * Export the akcipher into DER encoded pkcs#8 private key info, expects
+ * |key| stores a valid asymmetric PRIVATE key.
+ *
+ * Returns: 0 for succeed, otherwise -1 is returned.
+ */
+int qcrypto_akcipher_export_p8info(const QCryptoAkCipherOptions *opts,
+                                   uint8_t *key, size_t keylen,
+                                   uint8_t **dst, size_t *dst_len,
+                                   Error **errp);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoAkCipher, qcrypto_akcipher_free)
 
 #endif /* QCRYPTO_AKCIPHER_H */