1 files changed, 92 insertions, 0 deletions
diff --git a/src/lib/kdf/prf_x942/prf_x942.cpp b/src/lib/kdf/prf_x942/prf_x942.cpp
new file mode 100644
index 000000000..149be163f
--- /dev/null
+++ b/src/lib/kdf/prf_x942/prf_x942.cpp
@@ -0,0 +1,92 @@
+/*
+* X9.42 PRF
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/prf_x942.h>
+#include <botan/der_enc.h>
+#include <botan/oids.h>
+#include <botan/sha160.h>
+#include <botan/loadstor.h>
+#include <algorithm>
+#include <memory>
+
+namespace Botan {
+
+namespace {
+
+/*
+* Encode an integer as an OCTET STRING
+*/
+std::vector<byte> encode_x942_int(u32bit n)
+   {
+   byte n_buf[4] = { 0 };
+   store_be(n, n_buf);
+   return DER_Encoder().encode(n_buf, 4, OCTET_STRING).get_contents_unlocked();
+   }
+
+}
+
+/*
+* X9.42 PRF
+*/
+secure_vector<byte> X942_PRF::derive(size_t key_len,
+                                    const byte secret[], size_t secret_len,
+                                    const byte salt[], size_t salt_len) const
+   {
+   SHA_160 hash;
+   const OID kek_algo(key_wrap_oid);
+
+   secure_vector<byte> key;
+   u32bit counter = 1;
+
+   while(key.size() != key_len && counter)
+      {
+      hash.update(secret, secret_len);
+
+      hash.update(
+         DER_Encoder().start_cons(SEQUENCE)
+
+            .start_cons(SEQUENCE)
+               .encode(kek_algo)
+               .raw_bytes(encode_x942_int(counter))
+            .end_cons()
+
+            .encode_if(salt_len != 0,
+               DER_Encoder()
+                  .start_explicit(0)
+                     .encode(salt, salt_len, OCTET_STRING)
+                  .end_explicit()
+               )
+
+            .start_explicit(2)
+               .raw_bytes(encode_x942_int(static_cast<u32bit>(8 * key_len)))
+            .end_explicit()
+
+         .end_cons().get_contents()
+         );
+
+      secure_vector<byte> digest = hash.final();
+      const size_t needed = std::min(digest.size(), key_len - key.size());
+      key += std::make_pair(&digest[0], needed);
+
+      ++counter;
+      }
+
+   return key;
+   }
+
+/*
+* X9.42 Constructor
+*/
+X942_PRF::X942_PRF(const std::string& oid)
+   {
+   if(OIDS::have_oid(oid))
+      key_wrap_oid = OIDS::lookup(oid).as_string();
+   else
+      key_wrap_oid = oid;
+   }
+
+}