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).

1 files changed, 12 insertions, 0 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);