From 7a707064d7d212cd4f2fbb7e90720cb3893686d1 Mon Sep 17 00:00:00 2001
From: Erwin Nindl <nine@wirdorange.org>
Date: Tue, 11 Dec 2007 12:24:54 +0000
Subject: fixes in mpi class, keyderivation iv generation

---
 keyDerivation.cpp |  5 ++---
 mpi.cpp           | 31 ++++++++++++++++++++++++-------
 mpi.h             |  4 +++-
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/keyDerivation.cpp b/keyDerivation.cpp
index b068c0c..3c25ae3 100644
--- a/keyDerivation.cpp
+++ b/keyDerivation.cpp
@@ -101,7 +101,7 @@ void KeyDerivation::generate(satp_prf_label label, seq_nr_t seq_nr, Buffer& key,
   gcry_error_t err;
 
   Mpi r;
-  Mpi key_id;
+  Mpi key_id(128);
   Mpi iv(128);
 
   // see at: http://tools.ietf.org/html/rfc3711#section-4.3
@@ -118,7 +118,7 @@ void KeyDerivation::generate(satp_prf_label label, seq_nr_t seq_nr, Buffer& key,
     // FIXXME: kdr can be greater than 2^32 (= 2^48)
     r = static_cast<long unsigned int>(seq_nr / ( 0x01 << ld_kdr_ ));
 
-  r.rShift(8);
+  r = r.mul2exp(8);
   key_id = r + Mpi(static_cast<long unsigned int>(label));
 
   Mpi salt = Mpi(salt_.getBuf(), salt_.getLength());
@@ -127,7 +127,6 @@ void KeyDerivation::generate(satp_prf_label label, seq_nr_t seq_nr, Buffer& key,
   err = gcry_cipher_reset( cipher_ );
   if( err ) 
     cLog.msg(Log::PRIO_ERR) << "KeyDerivation::generate: Failed to reset cipher: " << gpg_strerror( err );
-
   
   err = gcry_cipher_setiv( cipher_ , iv.getBuf().getBuf(), iv.getBuf().getLength());
   if( err )
diff --git a/mpi.cpp b/mpi.cpp
index 510a17f..c22e503 100644
--- a/mpi.cpp
+++ b/mpi.cpp
@@ -55,6 +55,7 @@ Mpi::Mpi(const u_int8_t * src, u_int32_t len)
 {
   gcry_mpi_scan( &val_, GCRYMPI_FMT_STD, src, len, NULL );
 }
+
 void Mpi::operator=(const Mpi &src)
 {
   val_ = gcry_mpi_copy(src.val_);
@@ -72,18 +73,27 @@ Mpi Mpi::operator+(const Mpi &b) const
   return res;
 }
 
-Mpi Mpi::operator^(const Mpi &b) const
+Mpi Mpi::operator*(const unsigned long int n) const
 {
-  u_int32_t len = 0;
+  Mpi res;
+  gcry_mpi_mul_ui(res.val_, val_, n);
+  return res;
+}
 
-  Mpi res(gcry_mpi_get_nbits(val_));
+Mpi Mpi::operator^(const Mpi &b) const
+{
+  u_int32_t a_len=0, b_len=0;
+  Mpi res;
 
-  if(gcry_mpi_get_nbits(val_) != gcry_mpi_get_nbits(b.val_))
-    throw std::length_error("mpi::operator^ const");
+  a_len = gcry_mpi_get_nbits(val_);
+  b_len = gcry_mpi_get_nbits(b.val_);
 
-  len = gcry_mpi_get_nbits(val_);
+  if(a_len>=b_len)
+    res = Mpi(*this);
+  else
+    res = Mpi(b);
 
-  for(u_int32_t i=0; i<len; i++) {
+  for(u_int32_t i=0; i<a_len && i<b_len; i++) {
     if(gcry_mpi_test_bit(val_, i) ^ gcry_mpi_test_bit(b.val_, i))
       gcry_mpi_set_bit(res.val_, i);
   }
@@ -95,6 +105,13 @@ void Mpi::rShift(u_int8_t n)
   gcry_mpi_rshift(val_, val_, n);
 }
 
+Mpi Mpi::mul2exp(u_int32_t e) const
+{
+  Mpi res;
+  gcry_mpi_mul_2exp( res.val_, val_, e );
+  return res;
+}
+
 Buffer Mpi::getBuf() const
 {
   u_int32_t len = 0, written = 0;
diff --git a/mpi.h b/mpi.h
index c8a9907..1be758e 100644
--- a/mpi.h
+++ b/mpi.h
@@ -49,8 +49,10 @@ public:
   void operator=(long unsigned int);
   Mpi operator+(const Mpi &b) const;
   Mpi operator^(const Mpi &b) const;
+  Mpi operator*(const unsigned long int n) const;
 
-  void rShift(u_int8_t n);
+  void rShift(u_int8_t n);            // LSB on the right side!
+  Mpi mul2exp(u_int32_t e) const;     // value * 2^e
   Buffer getBuf() const;
   u_int32_t getLen() const;
  
-- 
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