3 files changed, 184 insertions, 0 deletions
diff --git a/src/lib/pk_pad/eme_oaep/info.txt b/src/lib/pk_pad/eme_oaep/info.txt
new file mode 100644
index 000000000..7a9360633
--- /dev/null
+++ b/src/lib/pk_pad/eme_oaep/info.txt
@@ -0,0 +1,8 @@
+define EME_OAEP 20140118
+
+load_on auto
+
+<requires>
+hash
+mgf1
+</requires>
diff --git a/src/lib/pk_pad/eme_oaep/oaep.cpp b/src/lib/pk_pad/eme_oaep/oaep.cpp
new file mode 100644
index 000000000..6186ba1e9
--- /dev/null
+++ b/src/lib/pk_pad/eme_oaep/oaep.cpp
@@ -0,0 +1,134 @@
+/*
+* OAEP
+* (C) 1999-2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/oaep.h>
+#include <botan/mgf1.h>
+#include <botan/mem_ops.h>
+#include <memory>
+
+namespace Botan {
+
+/*
+* OAEP Pad Operation
+*/
+secure_vector<byte> OAEP::pad(const byte in[], size_t in_length,
+                             size_t key_length,
+                             RandomNumberGenerator& rng) const
+   {
+   key_length /= 8;
+
+   if(key_length < in_length + 2*m_Phash.size() + 1)
+      throw Invalid_Argument("OAEP: Input is too large");
+
+   secure_vector<byte> out(key_length);
+
+   rng.randomize(&out[0], m_Phash.size());
+
+   buffer_insert(out, m_Phash.size(), &m_Phash[0], m_Phash.size());
+   out[out.size() - in_length - 1] = 0x01;
+   buffer_insert(out, out.size() - in_length, in, in_length);
+
+   mgf1_mask(*m_hash,
+             &out[0], m_Phash.size(),
+             &out[m_Phash.size()], out.size() - m_Phash.size());
+
+   mgf1_mask(*m_hash,
+             &out[m_Phash.size()], out.size() - m_Phash.size(),
+             &out[0], m_Phash.size());
+
+   return out;
+   }
+
+/*
+* OAEP Unpad Operation
+*/
+secure_vector<byte> OAEP::unpad(const byte in[], size_t in_length,
+                               size_t key_length) const
+   {
+   /*
+   Must be careful about error messages here; if an attacker can
+   distinguish them, it is easy to use the differences as an oracle to
+   find the secret key, as described in "A Chosen Ciphertext Attack on
+   RSA Optimal Asymmetric Encryption Padding (OAEP) as Standardized in
+   PKCS #1 v2.0", James Manger, Crypto 2001
+
+   Also have to be careful about timing attacks! Pointed out by Falko
+   Strenzke.
+   */
+
+   key_length /= 8;
+
+   // Invalid input: truncate to zero length input, causing later
+   // checks to fail
+   if(in_length > key_length)
+      in_length = 0;
+
+   secure_vector<byte> input(key_length);
+   buffer_insert(input, key_length - in_length, in, in_length);
+
+   mgf1_mask(*m_hash,
+             &input[m_Phash.size()], input.size() - m_Phash.size(),
+             &input[0], m_Phash.size());
+
+   mgf1_mask(*m_hash,
+             &input[0], m_Phash.size(),
+             &input[m_Phash.size()], input.size() - m_Phash.size());
+
+   bool waiting_for_delim = true;
+   bool bad_input = false;
+   size_t delim_idx = 2 * m_Phash.size();
+
+   /*
+   * GCC 4.5 on x86-64 compiles this in a way that is still vunerable
+   * to timing analysis. Other compilers, or GCC on other platforms,
+   * may or may not.
+   */
+   for(size_t i = delim_idx; i < input.size(); ++i)
+      {
+      const bool zero_p = !input[i];
+      const bool one_p = input[i] == 0x01;
+
+      const bool add_1 = waiting_for_delim && zero_p;
+
+      bad_input |= waiting_for_delim && !(zero_p || one_p);
+
+      delim_idx += add_1;
+
+      waiting_for_delim &= zero_p;
+      }
+
+   // If we never saw any non-zero byte, then it's not valid input
+   bad_input |= waiting_for_delim;
+
+   bad_input |= !same_mem(&input[m_Phash.size()], &m_Phash[0], m_Phash.size());
+
+   if(bad_input)
+      throw Decoding_Error("Invalid OAEP encoding");
+
+   return secure_vector<byte>(&input[delim_idx + 1], &input[input.size()]);
+   }
+
+/*
+* Return the max input size for a given key size
+*/
+size_t OAEP::maximum_input_size(size_t keybits) const
+   {
+   if(keybits / 8 > 2*m_Phash.size() + 1)
+      return ((keybits / 8) - 2*m_Phash.size() - 1);
+   else
+      return 0;
+   }
+
+/*
+* OAEP Constructor
+*/
+OAEP::OAEP(HashFunction* hash, const std::string& P) : m_hash(hash)
+   {
+   m_Phash = m_hash->process(P);
+   }
+
+}
diff --git a/src/lib/pk_pad/eme_oaep/oaep.h b/src/lib/pk_pad/eme_oaep/oaep.h
new file mode 100644
index 000000000..250759821
--- /dev/null
+++ b/src/lib/pk_pad/eme_oaep/oaep.h
@@ -0,0 +1,42 @@
+/*
+* OAEP
+* (C) 1999-2007 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_OAEP_H__
+#define BOTAN_OAEP_H__
+
+#include <botan/eme.h>
+#include <botan/kdf.h>
+#include <botan/hash.h>
+#include <memory>
+
+namespace Botan {
+
+/**
+* OAEP (called EME1 in IEEE 1363 and in earlier versions of the library)
+*/
+class BOTAN_DLL OAEP : public EME
+   {
+   public:
+      size_t maximum_input_size(size_t) const;
+
+      /**
+      * @param hash object to use for hashing (takes ownership)
+      * @param P an optional label. Normally empty.
+      */
+      OAEP(HashFunction* hash, const std::string& P = "");
+   private:
+      secure_vector<byte> pad(const byte[], size_t, size_t,
+                             RandomNumberGenerator&) const;
+      secure_vector<byte> unpad(const byte[], size_t, size_t) const;
+
+      secure_vector<byte> m_Phash;
+      std::unique_ptr<HashFunction> m_hash;
+   };
+
+}
+
+#endif