1 files changed, 261 insertions, 0 deletions

diff --git a/src/key_derivation.c b/src/key_derivation.c
new file mode 100644
index 0000000..5e3f2c5
--- /dev/null
+++ b/src/key_derivation.c
@@ -0,0 +1,261 @@
+/*
+ *  ľAnytun
+ *
+ *  ľAnytun is a tiny implementation of SATP. Unlike Anytun which is a full
+ *  featured implementation ľAnytun has no support for multiple connections
+ *  or synchronisation. It is a small single threaded implementation intended
+ *  to act as a client on small platforms.
+ *  The secure anycast tunneling protocol (satp) defines a protocol used
+ *  for communication between any combination of unicast and anycast
+ *  tunnel endpoints.  It has less protocol overhead than IPSec in Tunnel
+ *  mode and allows tunneling of every ETHER TYPE protocol (e.g.
+ *  ethernet, ip, arp ...). satp directly includes cryptography and
+ *  message authentication based on the methodes used by SRTP.  It is
+ *  intended to deliver a generic, scaleable and secure solution for
+ *  tunneling and relaying of packets of any protocol.
+ *  
+ *
+ *  Copyright (C) 2007-2008 Christian Pointner <equinox@anytun.org>
+ *
+ *  This file is part of ľAnytun.
+ *
+ *  ľAnytun is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 3 as
+ *  published by the Free Software Foundation.
+ *
+ *  ľAnytun is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with ľAnytun. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "datatypes.h"
+
+#include "key_derivation.h"
+
+#include "log.h"
+
+#include <string.h>
+
+#include <gmp.h>
+
+
+int key_derivation_init(key_derivation_t* kd, const char* type, u_int8_t* key, u_int32_t key_len, u_int8_t* salt, u_int32_t salt_len)
+{
+  if(!kd) 
+    return -1;
+
+  kd->type_ = unknown;
+  if(!strcmp(type, "null"))
+    kd->type_ = null;
+  else if(!strcmp(type, "aes-ctr"))
+    kd->type_ = aes_ctr;
+  else {
+    log_printf(ERR, "unknown key derivation type");
+    return -1;
+  }
+
+  kd->ld_kdr_ = -1;
+  kd->handle_ = 0;
+
+  if(!key) {
+    kd->master_key_.buf_ = NULL;
+    kd->master_key_.length_ = 0;
+  }
+  else {
+    kd->master_key_.buf_ = malloc(key_len);
+    if(!kd->master_key_.buf_)
+      return -2;
+    memcpy(kd->master_key_.buf_, key, key_len);
+    kd->master_key_.length_ = key_len;
+  }
+
+  if(!salt) {
+    kd->master_salt_.buf_ = NULL;
+    kd->master_salt_.length_ = 0;
+  }
+  else {
+    kd->master_salt_.buf_ = malloc(salt_len);
+    if(!kd->master_salt_.buf_) {
+      if(kd->master_key_.buf_)
+        free(kd->master_key_.buf_);
+      return -2;
+    }
+    memcpy(kd->master_salt_.buf_, salt, salt_len);
+    kd->master_salt_.length_ = salt_len;
+  }
+
+  int ret = 0;
+  if(kd->type_ == aes_ctr)
+    ret = key_derivation_aesctr_init(kd, key, key_len, salt, salt_len);
+
+  return ret;
+}
+
+void key_derivation_close(key_derivation_t* kd)
+{
+  if(!kd)
+    return;
+
+  if(kd->type_ == aes_ctr)
+    key_derivation_aesctr_close(kd);
+
+  if(kd->master_key_.buf_)
+    free(kd->master_key_.buf_);
+  if(kd->master_salt_.buf_)
+    free(kd->master_salt_.buf_);
+}
+
+void key_derivation_generate(key_derivation_t* kd, satp_prf_label_t label, seq_nr_t seq_nr, u_int8_t* key, u_int32_t len)
+{
+  if(!kd) 
+    return;
+
+  if(kd->type_ == null)
+    key_derivation_null_generate(key, len);
+  else if(kd->type_ == aes_ctr)
+    key_derivation_aesctr_generate(kd, label, seq_nr, key, len);
+  else {
+    log_printf(ERR, "unknown cipher type");
+    return;
+  }
+}
+
+/* ---------------- NULL Key Derivation ---------------- */
+
+void key_derivation_null_generate(u_int8_t* key, u_int32_t len)
+{
+  memset(key, 0, len);
+}
+
+/* ---------------- AES-Ctr Key Derivation ---------------- */
+
+int key_derivation_aesctr_init(key_derivation_t* kd, u_int8_t* key, u_int32_t key_len, u_int8_t* salt, u_int32_t salt_len)
+{
+  if(!kd)
+    return -1;
+
+  gcry_error_t err = gcry_cipher_open(&kd->handle_, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CTR, 0);
+  if(err) {
+    log_printf(ERR, "failed to open cipher: %s/%s", gcry_strerror(err), gcry_strsource(err));
+    return -1;
+  } 
+
+  err = gcry_cipher_setkey(kd->handle_, kd->master_key_.buf_, kd->master_key_.length_);
+  if(err) {
+    log_printf(ERR, "failed to set cipher key: %s/%s", gcry_strerror(err), gcry_strsource(err));
+    return -1;
+  }
+
+  return 0;
+}
+
+void key_derivation_aesctr_close(key_derivation_t* kd)
+{
+  if(!kd)
+    return;
+
+  if(kd->handle_)
+    gcry_cipher_close(kd->handle_);
+}
+
+buffer_t key_derivation_aesctr_calc_ctr(key_derivation_t* kd, satp_prf_label_t label, seq_nr_t seq_nr)
+{
+  buffer_t result;
+  result.buf_ = NULL;
+  result.length_ = 0;
+
+  if(!kd)
+    return result;
+
+  // see at: http://tools.ietf.org/html/rfc3711#section-4.3
+  // *  Let r = index DIV key_derivation_rate (with DIV as defined above).
+  // *  Let key_id = <label> || r.
+  // *  Let x = key_id XOR master_salt, where key_id and master_salt are
+  //    aligned so that their least significant bits agree (right-
+  //    alignment).
+  //
+
+  mpz_t ctr, key_id, r;
+  mpz_init2(ctr, 128);
+  mpz_init2(key_id, 128);
+  mpz_init2(r, 128);
+
+  int faked_msb = 0;
+  if(!kd->master_salt_.buf_[0])
+    kd->master_salt_.buf_[0] = 1;
+
+  if(kd->ld_kdr_ == -1)
+    mpz_set_ui(r, 0);
+  else {
+    mpz_t seq;
+    mpz_init2(seq, 32);
+    mpz_set_ui(seq, seq_nr);
+
+    mpz_set_ui(r, 1);
+    mpz_mul_2exp(r, r, kd->ld_kdr_);
+
+    mpz_fdiv_q(r, seq, r);
+
+    mpz_clear(seq);
+  }
+/*  TODO: generate key only if index % r == 0, except it is the first time */
+
+  mpz_set_ui(key_id, label);
+  mpz_mul_2exp(key_id, key_id, 48);
+  mpz_add(key_id, key_id, r);
+
+  mpz_import(ctr, kd->master_salt_.length_, 1, 1, 0, 0, kd->master_salt_.buf_);
+
+  mpz_xor(ctr, ctr, key_id);
+  mpz_mul_2exp(ctr, ctr, 16);
+
+  result.buf_ = mpz_export(NULL, (size_t*)&result.length_, 1, 1, 0, 0, ctr);
+  if(faked_msb) {
+    kd->master_salt_.buf_[0] = 0;
+    result.buf_[0] = 0;
+  }
+
+  mpz_clear(ctr);
+  mpz_clear(key_id);
+  mpz_clear(r);
+
+  return result;
+}
+
+void key_derivation_aesctr_generate(key_derivation_t* kd, satp_prf_label_t label, seq_nr_t seq_nr, u_int8_t* key, u_int32_t len)
+{
+  if(!kd || !kd->master_key_.buf_ || !kd->master_salt_.buf_) {
+    log_printf(ERR, "cipher not initialized or no key or salt set");
+    return;
+  }
+
+  gcry_error_t err = gcry_cipher_reset(kd->handle_);
+  if(err) {
+    log_printf(ERR, "failed to reset cipher: %s/%s", gcry_strerror(err), gcry_strsource(err));
+    return;
+  }
+
+  buffer_t ctr = key_derivation_aesctr_calc_ctr(kd, label, seq_nr);
+  if(!ctr.buf_) {
+    log_printf(ERR, "failed to calculate cipher CTR");
+    return;
+  }
+  err = gcry_cipher_setctr(kd->handle_, ctr.buf_, ctr.length_);
+  free(ctr.buf_);
+
+  if(err) {
+    log_printf(ERR, "failed to set cipher CTR: %s/%s", gcry_strerror(err), gcry_strsource(err));
+    return;
+  }
+
+  memset(key, 0, len);
+  err = gcry_cipher_encrypt(kd->handle_, key, len, NULL, 0);
+  if(err) {
+    log_printf(ERR, "failed to generate cipher bitstream: %s/%s", gcry_strerror(err), gcry_strsource(err));
+    return;
+  }
+}