1 files changed, 95 insertions, 0 deletions
diff --git a/botan/src/engine/openssl/ossl_elg.cpp b/botan/src/engine/openssl/ossl_elg.cpp
new file mode 100644
index 0000000..aefda9a
--- /dev/null
+++ b/botan/src/engine/openssl/ossl_elg.cpp
@@ -0,0 +1,95 @@
+/*
+* OpenSSL Engine
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/eng_ossl.h>
+#include <botan/bn_wrap.h>
+#include <openssl/opensslv.h>
+
+#if OPENSSL_VERSION_NUMBER < 0x0090700F
+  #error Your OpenSSL install is too old, upgrade to 0.9.7 or later
+#endif
+
+namespace Botan {
+
+#if defined(BOTAN_HAS_ELGAMAL)
+
+namespace {
+
+/*
+* OpenSSL ElGamal Operation
+*/
+class OpenSSL_ELG_Op : public ELG_Operation
+   {
+   public:
+      SecureVector<byte> encrypt(const byte[], u32bit, const BigInt&) const;
+      BigInt decrypt(const BigInt&, const BigInt&) const;
+
+      ELG_Operation* clone() const { return new OpenSSL_ELG_Op(*this); }
+      OpenSSL_ELG_Op(const DL_Group& group, const BigInt& y1,
+                     const BigInt& x1) :
+         x(x1), y(y1), g(group.get_g()), p(group.get_p()) {}
+   private:
+      OSSL_BN x, y, g, p;
+      OSSL_BN_CTX ctx;
+   };
+
+/*
+* OpenSSL ElGamal Encrypt Operation
+*/
+SecureVector<byte> OpenSSL_ELG_Op::encrypt(const byte in[], u32bit length,
+                                           const BigInt& k_bn) const
+   {
+   OSSL_BN i(in, length);
+
+   if(BN_cmp(i.value, p.value) >= 0)
+      throw Invalid_Argument("OpenSSL_ELG_Op: Input is too large");
+
+   OSSL_BN a, b, k(k_bn);
+
+   BN_mod_exp(a.value, g.value, k.value, p.value, ctx.value);
+   BN_mod_exp(b.value, y.value, k.value, p.value, ctx.value);
+   BN_mod_mul(b.value, b.value, i.value, p.value, ctx.value);
+
+   const u32bit p_bytes = p.bytes();
+   SecureVector<byte> output(2*p_bytes);
+   a.encode(output, p_bytes);
+   b.encode(output + p_bytes, p_bytes);
+   return output;
+   }
+
+/*
+* OpenSSL ElGamal Decrypt Operation
+*/
+BigInt OpenSSL_ELG_Op::decrypt(const BigInt& a_bn, const BigInt& b_bn) const
+   {
+   if(BN_is_zero(x.value))
+      throw Internal_Error("OpenSSL_ELG_Op::decrypt: No private key");
+
+   OSSL_BN a(a_bn), b(b_bn), t;
+
+   if(BN_cmp(a.value, p.value) >= 0 || BN_cmp(b.value, p.value) >= 0)
+      throw Invalid_Argument("OpenSSL_ELG_Op: Invalid message");
+
+   BN_mod_exp(t.value, a.value, x.value, p.value, ctx.value);
+   BN_mod_inverse(a.value, t.value, p.value, ctx.value);
+   BN_mod_mul(a.value, a.value, b.value, p.value, ctx.value);
+   return a.to_bigint();
+   }
+
+}
+
+/*
+* Acquire an ElGamal op
+*/
+ELG_Operation* OpenSSL_Engine::elg_op(const DL_Group& group, const BigInt& y,
+                                      const BigInt& x) const
+   {
+   return new OpenSSL_ELG_Op(group, y, x);
+   }
+#endif
+
+}