Add (back) OpenPGP-S2K

It was removed somewhere along the line in 1.11, with the logic
that it is a funky PGP-specific scheme and (quoting the commit
that removed it) "not really useful outside of a full PGP implementation".

This assumed that the PGP implementation would be in Botan itself, but
PGP is implemented in https://github.com/evpo/EncryptPad/ (which is
a PGP implementation using 1.10), and RNP (https://github.com/riboseinc/rnp)
would like to use it also.

This work was sponsored by Ribose Inc (@riboseinc).

6 files changed, 245 insertions, 2 deletions

diff --git a/src/lib/pbkdf/pbkdf.cpp b/src/lib/pbkdf/pbkdf.cpp
index a60c93d5c..40610998b 100644
--- a/src/lib/pbkdf/pbkdf.cpp
+++ b/src/lib/pbkdf/pbkdf.cpp
@@ -16,6 +16,10 @@
 #include <botan/pbkdf2.h>
 #endif
 
+#if defined(BOTAN_HAS_PGP_S2K)
+#include <botan/pgp_s2k.h>
+#endif
+
 namespace Botan {
 
 std::unique_ptr<PBKDF> PBKDF::create(const std::string& algo_spec,
@@ -50,6 +54,14 @@ std::unique_ptr<PBKDF> PBKDF::create(const std::string& algo_spec,
       }
 #endif
 
+#if defined(BOTAN_HAS_PGP_S2K)
+   if(req.algo_name() == "OpenPGP-S2K" && req.arg_count() == 1)
+      {
+      if(auto hash = HashFunction::create(req.arg(0)))
+         return std::unique_ptr<PBKDF>(new OpenPGP_S2K(hash.release()));
+      }
+#endif
+
    BOTAN_UNUSED(req);
    BOTAN_UNUSED(provider);
 
diff --git a/src/lib/pbkdf/pgp_s2k/info.txt b/src/lib/pbkdf/pgp_s2k/info.txt
new file mode 100644
index 000000000..5aabc0919
--- /dev/null
+++ b/src/lib/pbkdf/pgp_s2k/info.txt
@@ -0,0 +1,7 @@
+<defines>
+PGP_S2K -> 20170527
+</defines>
+
+<requires>
+hash
+</requires>
diff --git a/src/lib/pbkdf/pgp_s2k/pgp_s2k.cpp b/src/lib/pbkdf/pgp_s2k/pgp_s2k.cpp
new file mode 100644
index 000000000..d8b5d770e
--- /dev/null
+++ b/src/lib/pbkdf/pgp_s2k/pgp_s2k.cpp
@@ -0,0 +1,90 @@
+/*
+* OpenPGP S2K
+* (C) 1999-2007,2017 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/pgp_s2k.h>
+
+namespace Botan {
+
+//static
+uint8_t OpenPGP_S2K::encode_count(size_t desired_iterations)
+   {
+   /*
+   Only 256 different iterations are actually representable in OpenPGP format ...
+   */
+   for(size_t c = 0; c < 256; ++c)
+      {
+      size_t decoded_iter = OpenPGP_S2K::decode_count(c);
+      if(decoded_iter >= desired_iterations)
+         return c;
+      }
+   }
+
+//static
+size_t OpenPGP_S2K::decode_count(uint8_t iter)
+   {
+   // See RFC 4880 section 3.7.1.3
+   return (16 + (iter & 0x0F)) << ((iter >> 4) + 6);
+   }
+
+size_t OpenPGP_S2K::pbkdf(uint8_t output_buf[], size_t output_len,
+                          const std::string& passphrase,
+                          const uint8_t salt[], size_t salt_len,
+                          size_t iterations,
+                          std::chrono::milliseconds msec) const
+   {
+   if(iterations == 0 && msec.count() > 0) // FIXME
+      throw Not_Implemented("OpenPGP_S2K does not implemented timed KDF");
+
+   secure_vector<uint8_t> input_buf(salt_len + passphrase.size());
+   if(salt_len > 0)
+      {
+      copy_mem(&input_buf[0], salt, salt_len);
+      }
+   if(passphrase.empty() == false)
+      {
+      copy_mem(&input_buf[salt_len],
+               reinterpret_cast<const uint8_t*>(passphrase.data()),
+               passphrase.size());
+      }
+
+   /*
+   The input is always fully processed even if iterations is very small
+   */
+   const size_t to_hash = std::max(iterations, input_buf.size());
+
+   secure_vector<uint8_t> hash_buf(m_hash->output_length());
+
+   size_t pass = 0;
+   size_t generated = 0;
+
+   while(generated != output_len)
+      {
+      const size_t output_this_pass =
+         std::min(hash_buf.size(), output_len - generated);
+
+      // Preload some number of zero bytes (empty first iteration)
+      std::vector<uint8_t> zero_padding(pass);
+      m_hash->update(zero_padding);
+
+      size_t left = to_hash;
+      while(left > 0)
+         {
+         const size_t input_to_take = std::min(left, input_buf.size());
+         m_hash->update(input_buf.data(), input_to_take);
+         left -= input_to_take;
+         }
+
+      m_hash->final(hash_buf.data());
+      copy_mem(output_buf + generated, hash_buf.data(), output_this_pass);
+      generated += output_this_pass;
+      ++pass;
+      }
+
+   return iterations;
+   }
+
+}
diff --git a/src/lib/pbkdf/pgp_s2k/pgp_s2k.h b/src/lib/pbkdf/pgp_s2k/pgp_s2k.h
new file mode 100644
index 000000000..3d85ba306
--- /dev/null
+++ b/src/lib/pbkdf/pgp_s2k/pgp_s2k.h
@@ -0,0 +1,67 @@
+/*
+* OpenPGP PBKDF
+* (C) 1999-2007,2017 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_OPENPGP_S2K_H__
+#define BOTAN_OPENPGP_S2K_H__
+
+#include <botan/pbkdf.h>
+#include <botan/hash.h>
+
+namespace Botan {
+
+/**
+* OpenPGP's S2K
+*
+* See RFC 4880 sections 3.7.1.1, 3.7.1.2, and 3.7.1.3
+* If the salt is empty and iterations == 1, "simple" S2K is used
+* If the salt is non-empty and iterations == 1, "salted" S2K is used
+* If the salt is non-empty and iterations > 1, "iterated" S2K is used
+*
+* If iterations == 0 and msec.count() > 0, "iterated" S2K is assumed,
+* and the number of iterations performed is returned.
+*
+* Note that unlike PBKDF2, OpenPGP S2K's "iterations" are defined as
+* the number of bytes hashed.
+*/
+class BOTAN_DLL OpenPGP_S2K final : public PBKDF
+   {
+   public:
+      /**
+      * @param hash_in the hash function to use
+      */
+      explicit OpenPGP_S2K(HashFunction* hash) : m_hash(hash) {}
+
+      std::string name() const override
+         {
+         return "OpenPGP-S2K(" + m_hash->name() + ")";
+         }
+
+      PBKDF* clone() const
+         {
+         return new OpenPGP_S2K(m_hash->clone());
+         }
+
+      size_t pbkdf(uint8_t output_buf[], size_t output_len,
+                   const std::string& passphrase,
+                   const uint8_t salt[], size_t salt_len,
+                   size_t iterations,
+                   std::chrono::milliseconds msec) const override;
+
+      /**
+      * RFC 4880 encodes the iteration count to a single-byte value
+      */
+      static uint8_t encode_count(size_t iterations);
+
+      static size_t decode_count(uint8_t encoded_iter);
+
+   private:
+      std::unique_ptr<HashFunction> m_hash;
+   };
+
+}
+
+#endif
diff --git a/src/tests/data/pbkdf/pgp_s2k.vec b/src/tests/data/pbkdf/pgp_s2k.vec
new file mode 100644
index 000000000..21bac5343
--- /dev/null
+++ b/src/tests/data/pbkdf/pgp_s2k.vec
@@ -0,0 +1,67 @@
+[OpenPGP-S2K(SHA-160)]
+# Generated using Golang x/crypto/openpgp/s2k
+
+Salt =
+Iterations = 1
+Passphrase = hello
+Output = AAF4C61D
+
+Salt = 01020304
+Iterations = 1
+Passphrase = hello
+Output = 10295AC1
+
+Salt = 01020304
+Iterations = 1
+Passphrase = bar
+Output = BD8AAC6B9EA9CAE04EAE6A91C6133B58B5D9A61C14F355516ED9370456
+
+Salt = 04030201
+Iterations = 31
+Passphrase = bar
+Output = 2AF5A99B54F093789FD657F19BD245AF7604D0F6AE06F66602A46A08AE
+
+Salt = 2AE6E5831A717917
+Iterations = 65536
+Passphrase = ilikepie
+Output = A32F874A4CF95DFAD8359302B395455C
+
+Salt = 0102030405060708
+Iterations = 1
+Passphrase = passphrase
+Output = eec8929a31187dd3a9a7ce5a97d96a67706382bbef70fe3b2a3aeeaf176bce252c117970a51fd8b770a69f8ecb199505395bd7b0c0760d6a38ac82900b23fe3b
+
+Salt = 0102030405060708
+Iterations = 65536
+Passphrase = passphrase
+Output = 24ce08a4a31de2208acdc15347def7a63492d38a0c08f80533a746279d91cb25e1b6b740b09e20a4884ca1944d506eb200753761066e8d4b24957c2593388457
+
+Salt = 0102030405060708
+Iterations = 10000000
+Passphrase = passphrase
+Output = 09efbd3599e2453c6cf1749a7ed169514a12d1a721549468c6d0ef6737fa3e27ab6d100f9839694fc70c484a42b00ef87463d07e2aafb92033843a4bd5f37971
+
+[OpenPGP-S2K(SHA-384)]
+# Generated using Golang x/crypto/openpgp/s2k
+
+Salt = 0102030405060708
+Iterations = 1
+Passphrase = passphrase
+Output = ea024c2de8af9a3edfbac9422f7b17e17c3165147b43f4edd58b55af9a412d07e0631f431a7e0028fbb145d9d5e059a888f1a7526cd338b1b6082a8681b446fa
+
+Salt = 0102030405060708
+Iterations = 18
+Passphrase = passphrase
+Output = ea024c2de8af9a3edfbac9422f7b17e17c3165147b43f4edd58b55af9a412d07e0631f431a7e0028fbb145d9d5e059a888f1a7526cd338b1b6082a8681b446fa
+
+Salt = 0102030405060708
+Iterations = 19
+Passphrase = passphrase
+Output = 491aa377a1a9526d53b118587a03f85f5dc64568f3aabaad66aafc923397fb74d7017a6a4812bff2d9beddcbc6a0dbd3b96a3f9a69b637d68670acd48d4dfa4e
+
+Salt = 0102030405060708
+Iterations = 1000000
+Passphrase = passphrase
+Output = af4986488f4e53ac4f7991a0bb8de15441ba1070481fe63b126ff3de2e1072f568dd3d6c5887d008925d27649494ae6f4860e141d5eeabe4f93745ca9cb8e08c
+
+
diff --git a/src/tests/test_pbkdf.cpp b/src/tests/test_pbkdf.cpp
index bd2fd8f89..32144bd9b 100644
--- a/src/tests/test_pbkdf.cpp
+++ b/src/tests/test_pbkdf.cpp
@@ -18,15 +18,15 @@ namespace {
 class PBKDF_KAT_Tests : public Text_Based_Test
    {
    public:
-      PBKDF_KAT_Tests() : Text_Based_Test("pbkdf", "OutputLen,Iterations,Salt,Passphrase,Output") {}
+      PBKDF_KAT_Tests() : Text_Based_Test("pbkdf", "Iterations,Salt,Passphrase,Output", "OutputLen") {}
 
       Test::Result run_one_test(const std::string& pbkdf_name, const VarMap& vars) override
          {
-         const size_t outlen = get_req_sz(vars, "OutputLen");
          const size_t iterations = get_req_sz(vars, "Iterations");
          const std::vector<uint8_t> salt = get_req_bin(vars, "Salt");
          const std::string passphrase = get_req_str(vars, "Passphrase");
          const std::vector<uint8_t> expected = get_req_bin(vars, "Output");
+         const size_t outlen = get_opt_sz(vars, "OutputLen", expected.size());
 
          Test::Result result(pbkdf_name);
          std::unique_ptr<Botan::PBKDF> pbkdf(Botan::PBKDF::create(pbkdf_name));