Added support code for RSA and EC key encoding (including reconstruction of all publi...

[BearSSL] / src / x509 / encode_rsa_pk8der.c

diff --git a/src/x509/encode_rsa_pk8der.c b/src/x509/encode_rsa_pk8der.c
new file mode 100644 (file)
index 0000000..c053503
--- /dev/null
+++ b/src/x509/encode_rsa_pk8der.c
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_x509.h */
+size_t
+br_encode_rsa_pkcs8_der(void *dest, const br_rsa_private_key *sk,
+       const br_rsa_public_key *pk, const void *d, size_t dlen)
+{
+       /*
+        * ASN.1 format:
+        *
+        *   OneAsymmetricKey ::= SEQUENCE {
+        *     version                   Version,
+        *     privateKeyAlgorithm       PrivateKeyAlgorithmIdentifier,
+        *     privateKey                PrivateKey,
+        *     attributes            [0] Attributes OPTIONAL,
+        *     ...,
+        *     [[2: publicKey        [1] PublicKey OPTIONAL ]],
+        *     ...
+        *   }
+        *
+        * We don't include attributes or public key. The 'version' field
+        * is an INTEGER that we will set to 0 (meaning 'v1', compatible
+        * with previous versions of PKCS#8). The 'privateKeyAlgorithm'
+        * structure is an AlgorithmIdentifier whose OID should be
+        * rsaEncryption, with NULL parameters. The 'privateKey' is an
+        * OCTET STRING, whose value is the "raw DER" encoding of the
+        * key pair.
+        *
+        * Since the private key value comes last, this function really
+        * adds a header, which is mostly fixed (only some lengths have
+        * to be modified.
+        */
+
+       /*
+        * Concatenation of:
+        *  - DER encoding of an INTEGER of value 0 (the 'version' field)
+        *  - DER encoding of a PrivateKeyAlgorithmIdentifier that uses
+        *    the rsaEncryption OID, and NULL parameters
+        *  - An OCTET STRING tag
+        */
+       static const unsigned char PK8_HEAD[] = {
+               0x02, 0x01, 0x00,
+               0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
+               0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00,
+               0x04
+       };
+
+       size_t len_raw, len_seq;
+
+       len_raw = br_encode_rsa_raw_der(NULL, sk, pk, d, dlen);
+       len_seq = (sizeof PK8_HEAD) + len_of_len(len_raw) + len_raw;
+       if (dest == NULL) {
+               return 1 + len_of_len(len_seq) + len_seq;
+       } else {
+               unsigned char *buf;
+               size_t lenlen;
+
+               buf = dest;
+               *buf ++ = 0x30;  /* SEQUENCE tag */
+               lenlen = br_asn1_encode_length(buf, len_seq);
+               buf += lenlen;
+
+               /* version, privateKeyAlgorithm, privateKey tag */
+               memcpy(buf, PK8_HEAD, sizeof PK8_HEAD);
+               buf += sizeof PK8_HEAD;
+
+               /* privateKey */
+               buf += br_asn1_encode_length(buf, len_raw);
+               br_encode_rsa_raw_der(buf, sk, pk, d, dlen);
+
+               return 1 + lenlen + len_seq;
+       }
+}