Add HOTP (RFC 4226) and TOTP (RFC 6238)

5 files changed, 242 insertions, 0 deletions

diff --git a/src/lib/misc/hotp/hotp.cpp b/src/lib/misc/hotp/hotp.cpp
new file mode 100644
index 000000000..f07c11c9f
--- /dev/null
+++ b/src/lib/misc/hotp/hotp.cpp
@@ -0,0 +1,62 @@
+/*
+* HOTP
+* (C) 2017 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/hotp.h>
+
+namespace Botan {
+
+HOTP::HOTP(const SymmetricKey& key, const std::string& hash_algo, size_t digits)
+   {
+   if(digits == 6)
+      m_digit_mod = 1000000;
+   else if(digits == 7)
+      m_digit_mod = 10000000;
+   else if(digits == 8)
+      m_digit_mod = 100000000;
+   else
+      throw Invalid_Argument("Invalid HOTP digits");
+
+   /*
+   RFC 4228 only supports SHA-1 but TOTP allows SHA-256 and SHA-512
+   and some HOTP libs support one or both as extensions
+   */
+   if(hash_algo == "SHA-1")
+      m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-1)");
+   else if(hash_algo == "SHA-256")
+      m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
+   else if(hash_algo == "SHA-512")
+      m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-512)");
+   else
+      throw Invalid_Argument("Unsupported HOTP hash function");
+
+   m_mac->set_key(key);
+   }
+
+uint32_t HOTP::generate_hotp(uint64_t counter)
+   {
+   uint8_t counter8[8] = { 0 };
+   store_be(counter, counter8);
+   m_mac->update(counter8, sizeof(counter8));
+   const secure_vector<uint8_t> mac = m_mac->final();
+
+   const size_t offset = mac[mac.size()-1] & 0x0F;
+   const uint32_t code = load_be<uint32_t>(mac.data() + offset, 0) & 0x7FFFFFFF;
+   return code % m_digit_mod;
+   }
+
+std::pair<bool,uint64_t> HOTP::verify_hotp(uint32_t otp, uint64_t starting_counter, size_t resync_range)
+   {
+   for(size_t i = 0; i <= resync_range; ++i)
+      {
+      if(generate_hotp(starting_counter + i) == otp)
+         return std::make_pair(true, starting_counter + i + 1);
+      }
+   return std::make_pair(false, starting_counter);
+   }
+
+}
+
diff --git a/src/lib/misc/hotp/hotp.h b/src/lib/misc/hotp/hotp.h
new file mode 100644
index 000000000..cc222e5c0
--- /dev/null
+++ b/src/lib/misc/hotp/hotp.h
@@ -0,0 +1,52 @@
+/*
+* HOTP
+* (C) 2017 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_HOTP_H__
+#define BOTAN_HOTP_H__
+
+#include <botan/mac.h>
+
+namespace Botan {
+
+/**
+* HOTP one time passwords (RFC 4226)
+*/
+class BOTAN_DLL HOTP
+   {
+   public:
+      /**
+      * @param key the secret key shared between client and server
+      * @param hash_algo the hash algorithm to use, should be SHA-1 or SHA-256
+      * @param digits the number of digits in the OTP (must be 6, 7, or 8)
+      */
+      HOTP(const SymmetricKey& key, const std::string& hash_algo = "SHA-1", size_t digits = 6);
+
+      /**
+      * Generate the HOTP for a particular counter value
+      * @warning if the counter value is repeated the OTP ceases to be one-time
+      */
+      uint32_t generate_hotp(uint64_t counter);
+
+      /**
+      * Check an OTP value using a starting counter and a resync range
+      * @param otp the client provided OTP
+      * @param starting_counter the server's guess as to the current counter state
+      * @param resync_range if 0 then only HOTP(starting_counter) is accepted
+      * If larger than 0, up to resync_range values after HOTP are also checked.
+      * @return (valid,next_counter). If the OTP does not validate, always
+      * returns (false,starting_counter). Otherwise returns (true,next_counter)
+      * where next_counter is at most starting_counter + resync_range + 1
+      */
+      std::pair<bool,uint64_t> verify_hotp(uint32_t otp, uint64_t starting_counter, size_t resync_range = 0);
+   private:
+      std::unique_ptr<MessageAuthenticationCode> m_mac;
+      uint32_t m_digit_mod;
+   };
+
+}
+
+#endif
diff --git a/src/lib/misc/hotp/info.txt b/src/lib/misc/hotp/info.txt
new file mode 100644
index 000000000..ad74686c3
--- /dev/null
+++ b/src/lib/misc/hotp/info.txt
@@ -0,0 +1,9 @@
+<defines>
+HOTP -> 20170513
+TOTP -> 20170519
+</defines>
+
+<requires>
+hmac
+utils
+</requires>
diff --git a/src/lib/misc/hotp/totp.cpp b/src/lib/misc/hotp/totp.cpp
new file mode 100644
index 000000000..c3203c32a
--- /dev/null
+++ b/src/lib/misc/hotp/totp.cpp
@@ -0,0 +1,63 @@
+/*
+* TOTP
+* (C) 2017 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/totp.h>
+#include <botan/calendar.h>
+
+namespace Botan {
+
+TOTP::TOTP(const SymmetricKey& key, const std::string& hash_algo,
+           size_t digits, size_t time_step)
+   : m_hotp(key, hash_algo, digits)
+   , m_time_step(time_step)
+   , m_unix_epoch(calendar_point(1970, 1, 1, 0, 0, 0).to_std_timepoint())
+   {
+   /*
+   * Technically any time step except 0 is valid, but 30 is typical
+   * and over 5 minutes seems unlikely.
+   */
+   if(m_time_step == 0 || m_time_step > 300)
+      throw Invalid_Argument("Invalid TOTP time step");
+   }
+
+uint32_t TOTP::generate_totp(std::chrono::system_clock::time_point current_time)
+   {
+   const uint64_t unix_time =
+      std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
+   return this->generate_totp(unix_time);
+   }
+
+uint32_t TOTP::generate_totp(uint64_t unix_time)
+   {
+   return m_hotp.generate_hotp(unix_time / m_time_step);
+   }
+
+bool TOTP::verify_totp(uint32_t otp, std::chrono::system_clock::time_point current_time,
+                       size_t clock_drift_accepted)
+   {
+   const uint64_t unix_time =
+      std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
+   return verify_totp(otp, unix_time, clock_drift_accepted);
+   }
+
+bool TOTP::verify_totp(uint32_t otp, uint64_t unix_time,
+                       size_t clock_drift_accepted)
+   {
+   uint64_t t = unix_time / m_time_step;
+
+   for(size_t i = 0; i <= clock_drift_accepted; ++i)
+      {
+      if(m_hotp.generate_hotp(t-i) == otp)
+         {
+         return true;
+         }
+      }
+
+   return false;
+   }
+
+}
diff --git a/src/lib/misc/hotp/totp.h b/src/lib/misc/hotp/totp.h
new file mode 100644
index 000000000..767c7cc5a
--- /dev/null
+++ b/src/lib/misc/hotp/totp.h
@@ -0,0 +1,56 @@
+/*
+* (C) 2017 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_TOTP_H__
+#define BOTAN_TOTP_H__
+
+#include <botan/hotp.h>
+#include <chrono>
+
+namespace Botan {
+
+/**
+* TOTP (time based) one time passwords (RFC 6238)
+*/
+class BOTAN_DLL TOTP
+   {
+   public:
+      /**
+      * @param key the secret key shared between client and server
+      * @param hash_algo the hash algorithm to use, should be SHA-1, SHA-256 or SHA-512
+      * @param digits the number of digits in the OTP (must be 6, 7, or 8)
+      * @param time_step granularity of OTP in seconds
+      */
+      TOTP(const SymmetricKey& key, const std::string& hash_algo = "SHA-1",
+           size_t digits = 6, size_t time_step = 30);
+
+      /**
+      * Convert the provided time_point to a Unix timestamp and call generate_totp
+      */
+      uint32_t generate_totp(std::chrono::system_clock::time_point time_point);
+
+      /**
+      * Generate the OTP cooresponding the the provided "Unix timestamp" (ie
+      * number of seconds since midnight Jan 1, 1970)
+      */
+      uint32_t generate_totp(uint64_t unix_time);
+
+      bool verify_totp(uint32_t otp,
+                       std::chrono::system_clock::time_point time,
+                       size_t clock_drift_accepted = 0);
+
+      bool verify_totp(uint32_t otp, uint64_t unix_time,
+                       size_t clock_drift_accepted = 0);
+
+   private:
+      HOTP m_hotp;
+      size_t m_time_step;
+      std::chrono::system_clock::time_point m_unix_epoch;
+   };
+
+}
+
+#endif