Allow signature using `Raw(hashname)`

This confirms the message is exactly the size of the expected hash,
and also causes RFC 6979 nonces to be generated using the specified
hash. See also https://github.com/riboseinc/rnp/issues/367

3 files changed, 38 insertions, 7 deletions

diff --git a/src/lib/pk_pad/emsa.cpp b/src/lib/pk_pad/emsa.cpp
index 074af273a..0fd35ef43 100644
--- a/src/lib/pk_pad/emsa.cpp
+++ b/src/lib/pk_pad/emsa.cpp
@@ -134,9 +134,18 @@ EMSA* get_emsa(const std::string& algo_spec)
 #endif
 
 #if defined(BOTAN_HAS_EMSA_RAW)
-   if(req.algo_name() == "Raw" && req.arg_count() == 0)
+   if(req.algo_name() == "Raw")
       {
-      return new EMSA_Raw;
+      if(req.arg_count() == 0)
+         {
+         return new EMSA_Raw;
+         }
+      else
+         {
+         auto hash = HashFunction::create(req.arg(0));
+         if(hash)
+            return new EMSA_Raw(hash->output_length());
+         }
       }
 #endif
 
diff --git a/src/lib/pk_pad/emsa_raw/emsa_raw.cpp b/src/lib/pk_pad/emsa_raw/emsa_raw.cpp
index d15012a0d..bae7b2d04 100644
--- a/src/lib/pk_pad/emsa_raw/emsa_raw.cpp
+++ b/src/lib/pk_pad/emsa_raw/emsa_raw.cpp
@@ -22,6 +22,12 @@ void EMSA_Raw::update(const uint8_t input[], size_t length)
 */
 secure_vector<uint8_t> EMSA_Raw::raw_data()
    {
+   if(m_expected_size && m_message.size() != m_expected_size)
+      throw Invalid_Argument("EMSA_Raw was configured to use a " +
+                             std::to_string(m_expected_size) +
+                             " byte hash but instead was used for a " +
+                             std::to_string(m_message.size()) + " hash");
+
    secure_vector<uint8_t> output;
    std::swap(m_message, output);
    return output;
@@ -30,10 +36,17 @@ secure_vector<uint8_t> EMSA_Raw::raw_data()
 /*
 * EMSA-Raw Encode Operation
 */
-secure_vector<uint8_t> EMSA_Raw::encoding_of(const secure_vector<uint8_t>& msg,
-                                         size_t,
-                                         RandomNumberGenerator&)
+secure_vector<uint8_t>
+EMSA_Raw::encoding_of(const secure_vector<uint8_t>& msg,
+                      size_t,
+                      RandomNumberGenerator&)
    {
+   if(m_expected_size && msg.size() != m_expected_size)
+      throw Invalid_Argument("EMSA_Raw was configured to use a " +
+                             std::to_string(m_expected_size) +
+                             " byte hash but instead was used for a " +
+                             std::to_string(msg.size()) + " hash");
+
    return msg;
    }
 
@@ -44,6 +57,9 @@ bool EMSA_Raw::verify(const secure_vector<uint8_t>& coded,
                       const secure_vector<uint8_t>& raw,
                       size_t)
    {
+   if(m_expected_size && raw.size() != m_expected_size)
+      return false;
+
    if(coded.size() == raw.size())
       return (coded == raw);
 
diff --git a/src/lib/pk_pad/emsa_raw/emsa_raw.h b/src/lib/pk_pad/emsa_raw/emsa_raw.h
index 288969257..598b9b97c 100644
--- a/src/lib/pk_pad/emsa_raw/emsa_raw.h
+++ b/src/lib/pk_pad/emsa_raw/emsa_raw.h
@@ -21,15 +21,21 @@ class BOTAN_DLL EMSA_Raw final : public EMSA
    public:
       EMSA* clone() override { return new EMSA_Raw(); }
 
+      explicit EMSA_Raw(size_t expected_hash_size = 0) :
+         m_expected_size(expected_hash_size) {}
+
    private:
       void update(const uint8_t[], size_t) override;
       secure_vector<uint8_t> raw_data() override;
 
       secure_vector<uint8_t> encoding_of(const secure_vector<uint8_t>&, size_t,
-                                     RandomNumberGenerator&) override;
-      bool verify(const secure_vector<uint8_t>&, const secure_vector<uint8_t>&,
+                                         RandomNumberGenerator&) override;
+
+      bool verify(const secure_vector<uint8_t>&,
+                  const secure_vector<uint8_t>&,
                   size_t) override;
 
+      const size_t m_expected_size;
       secure_vector<uint8_t> m_message;
    };