1 files changed, 157 insertions, 0 deletions
diff --git a/src/lib/misc/srp6/srp6.cpp b/src/lib/misc/srp6/srp6.cpp
new file mode 100644
index 000000000..d3f7338bd
--- /dev/null
+++ b/src/lib/misc/srp6/srp6.cpp
@@ -0,0 +1,157 @@
+/*
+* SRP-6a (RFC 5054 compatatible)
+* (C) 2011,2012 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/srp6.h>
+#include <botan/dl_group.h>
+#include <botan/numthry.h>
+#include <botan/lookup.h>
+
+namespace Botan {
+
+namespace {
+
+BigInt hash_seq(const std::string& hash_id,
+                size_t pad_to,
+                const BigInt& in1,
+                const BigInt& in2)
+   {
+   std::unique_ptr<HashFunction> hash_fn(get_hash(hash_id));
+
+   hash_fn->update(BigInt::encode_1363(in1, pad_to));
+   hash_fn->update(BigInt::encode_1363(in2, pad_to));
+
+   return BigInt::decode(hash_fn->final());
+   }
+
+BigInt compute_x(const std::string& hash_id,
+                 const std::string& identifier,
+                 const std::string& password,
+                 const std::vector<byte>& salt)
+   {
+   std::unique_ptr<HashFunction> hash_fn(get_hash(hash_id));
+
+   hash_fn->update(identifier);
+   hash_fn->update(":");
+   hash_fn->update(password);
+
+   secure_vector<byte> inner_h = hash_fn->final();
+
+   hash_fn->update(salt);
+   hash_fn->update(inner_h);
+
+   secure_vector<byte> outer_h = hash_fn->final();
+
+   return BigInt::decode(outer_h);
+   }
+
+}
+
+std::string srp6_group_identifier(const BigInt& N, const BigInt& g)
+   {
+   /*
+   This function assumes that only one 'standard' SRP parameter set has
+   been defined for a particular bitsize. As of this writing that is the case.
+   */
+   try
+      {
+      const std::string group_name = "modp/srp/" + std::to_string(N.bits());
+
+      DL_Group group(group_name);
+
+      if(group.get_p() == N && group.get_g() == g)
+         return group_name;
+
+      throw std::runtime_error("Unknown SRP params");
+      }
+   catch(...)
+      {
+      throw Invalid_Argument("Bad SRP group parameters");
+      }
+   }
+
+std::pair<BigInt, SymmetricKey>
+srp6_client_agree(const std::string& identifier,
+                  const std::string& password,
+                  const std::string& group_id,
+                  const std::string& hash_id,
+                  const std::vector<byte>& salt,
+                  const BigInt& B,
+                  RandomNumberGenerator& rng)
+   {
+   DL_Group group(group_id);
+   const BigInt& g = group.get_g();
+   const BigInt& p = group.get_p();
+
+   const size_t p_bytes = group.get_p().bytes();
+
+   if(B <= 0 || B >= p)
+      throw std::runtime_error("Invalid SRP parameter from server");
+
+   BigInt k = hash_seq(hash_id, p_bytes, p, g);
+
+   BigInt a(rng, 256);
+
+   BigInt A = power_mod(g, a, p);
+
+   BigInt u = hash_seq(hash_id, p_bytes, A, B);
+
+   const BigInt x = compute_x(hash_id, identifier, password, salt);
+
+   BigInt S = power_mod((B - (k * power_mod(g, x, p))) % p, (a + (u * x)), p);
+
+   SymmetricKey Sk(BigInt::encode_1363(S, p_bytes));
+
+   return std::make_pair(A, Sk);
+   }
+
+BigInt generate_srp6_verifier(const std::string& identifier,
+                              const std::string& password,
+                              const std::vector<byte>& salt,
+                              const std::string& group_id,
+                              const std::string& hash_id)
+   {
+   const BigInt x = compute_x(hash_id, identifier, password, salt);
+
+   DL_Group group(group_id);
+   return power_mod(group.get_g(), x, group.get_p());
+   }
+
+BigInt SRP6_Server_Session::step1(const BigInt& v,
+                                  const std::string& group_id,
+                                  const std::string& hash_id,
+                                  RandomNumberGenerator& rng)
+   {
+   DL_Group group(group_id);
+   const BigInt& g = group.get_g();
+   const BigInt& p = group.get_p();
+
+   m_p_bytes = p.bytes();
+   m_v = v;
+   m_b = BigInt(rng, 256);
+   m_p = p;
+   m_hash_id = hash_id;
+
+   const BigInt k = hash_seq(hash_id, m_p_bytes, p, g);
+
+   m_B = (v*k + power_mod(g, m_b, p)) % p;
+
+   return m_B;
+   }
+
+SymmetricKey SRP6_Server_Session::step2(const BigInt& A)
+   {
+   if(A <= 0 || A >= m_p)
+      throw std::runtime_error("Invalid SRP parameter from client");
+
+   const BigInt u = hash_seq(m_hash_id, m_p_bytes, A, m_B);
+
+   const BigInt S = power_mod(A * power_mod(m_v, u, m_p), m_b, m_p);
+
+   return BigInt::encode_1363(S, m_p_bytes);
+   }
+
+}