Make exceptions easier to translate to error codes

Avoid throwing base Botan::Exception type, as it is difficult to
determine what the error is in that case.

Add Exception::error_code and Exception::error_type which allows
(for error code) more information about the error and (for error type)
allows knowing the error type without requiring a sequence of catches.

See GH #1742

8 files changed, 28 insertions, 24 deletions

diff --git a/src/lib/pubkey/blinding.cpp b/src/lib/pubkey/blinding.cpp
index ecd420780..d1f299229 100644
--- a/src/lib/pubkey/blinding.cpp
+++ b/src/lib/pubkey/blinding.cpp
@@ -35,7 +35,7 @@ BigInt Blinder::blinding_nonce() const
 BigInt Blinder::blind(const BigInt& i) const
    {
    if(!m_reducer.initialized())
-      throw Exception("Blinder not initialized, cannot blind");
+      throw Invalid_State("Blinder not initialized, cannot blind");
 
    ++m_counter;
 
@@ -58,7 +58,7 @@ BigInt Blinder::blind(const BigInt& i) const
 BigInt Blinder::unblind(const BigInt& i) const
    {
    if(!m_reducer.initialized())
-      throw Exception("Blinder not initialized, cannot unblind");
+      throw Invalid_State("Blinder not initialized, cannot unblind");
 
    return m_reducer.multiply(i, m_d);
    }
diff --git a/src/lib/pubkey/ec_group/point_gfp.h b/src/lib/pubkey/ec_group/point_gfp.h
index fa447bf87..222b5f474 100644
--- a/src/lib/pubkey/ec_group/point_gfp.h
+++ b/src/lib/pubkey/ec_group/point_gfp.h
@@ -19,23 +19,26 @@ namespace Botan {
 /**
 * Exception thrown if you try to convert a zero point to an affine
 * coordinate
+*
+* In a future major release this exception type will be removed and its
+* usage replaced by Invalid_State
 */
-class BOTAN_PUBLIC_API(2,0) Illegal_Transformation final : public Exception
+class BOTAN_PUBLIC_API(2,0) Illegal_Transformation final : public Invalid_State
    {
    public:
-      explicit Illegal_Transformation(const std::string& err =
-                                      "Requested transformation is not possible") :
-         Exception(err) {}
+      explicit Illegal_Transformation(const std::string& err) : Invalid_State(err) {}
    };
 
 /**
 * Exception thrown if some form of illegal point is decoded
+*
+* In a future major release this exception type will be removed and its
+* usage replaced by Decoding_Error
 */
-class BOTAN_PUBLIC_API(2,0) Illegal_Point final : public Exception
+class BOTAN_PUBLIC_API(2,0) Illegal_Point final : public Decoding_Error
    {
    public:
-      explicit Illegal_Point(const std::string& err = "Malformed ECP point detected") :
-         Exception(err) {}
+      explicit Illegal_Point(const std::string& err) : Decoding_Error(err) {}
    };
 
 /**
diff --git a/src/lib/pubkey/mce/gf2m_small_m.cpp b/src/lib/pubkey/mce/gf2m_small_m.cpp
index 95187c7af..8a2632b10 100644
--- a/src/lib/pubkey/mce/gf2m_small_m.cpp
+++ b/src/lib/pubkey/mce/gf2m_small_m.cpp
@@ -59,7 +59,7 @@ const std::vector<gf2m>& exp_table(size_t deg)
    static std::vector<gf2m> tabs[MAX_EXT_DEG + 1];
 
    if(deg < 2 || deg > MAX_EXT_DEG)
-      throw Exception("GF2m_Field does not support degree " + std::to_string(deg));
+      throw Invalid_Argument("GF2m_Field does not support degree " + std::to_string(deg));
 
    if(tabs[deg].empty())
       tabs[deg] = gf_exp_table(deg, prim_poly[deg]);
@@ -84,7 +84,7 @@ const std::vector<gf2m>& log_table(size_t deg)
    static std::vector<gf2m> tabs[MAX_EXT_DEG + 1];
 
    if(deg < 2 || deg > MAX_EXT_DEG)
-      throw Exception("GF2m_Field does not support degree " + std::to_string(deg));
+      throw Invalid_Argument("GF2m_Field does not support degree " + std::to_string(deg));
 
    if(tabs[deg].empty())
       tabs[deg] = gf_log_table(deg, exp_table(deg));
diff --git a/src/lib/pubkey/mceies/mceies.cpp b/src/lib/pubkey/mceies/mceies.cpp
index 15706d430..875c9dd10 100644
--- a/src/lib/pubkey/mceies/mceies.cpp
+++ b/src/lib/pubkey/mceies/mceies.cpp
@@ -83,7 +83,7 @@ mceies_decrypt(const McEliece_PrivateKey& privkey,
       const size_t nonce_len = aead->default_nonce_length();
 
       if(ct_len < mce_code_bytes + nonce_len + aead->tag_size())
-         throw Exception("Input message too small to be valid");
+         throw Decoding_Error("Input message too small to be valid");
 
       const secure_vector<uint8_t> mce_key = kem_op.decrypt(ct, mce_code_bytes, 64);
 
@@ -102,7 +102,7 @@ mceies_decrypt(const McEliece_PrivateKey& privkey,
       }
    catch(std::exception& e)
       {
-      throw Exception("mce_decrypt failed: " + std::string(e.what()));
+      throw Decoding_Error("mce_decrypt failed: " + std::string(e.what()));
       }
    }
 
diff --git a/src/lib/pubkey/pk_ops_impl.h b/src/lib/pubkey/pk_ops_impl.h
index 1878a7417..6bab2143e 100644
--- a/src/lib/pubkey/pk_ops_impl.h
+++ b/src/lib/pubkey/pk_ops_impl.h
@@ -82,7 +82,7 @@ class Verification_with_EMSA : public Verification
       * @return the message prefix if this signature scheme uses
       * a message prefix, signaled via has_prefix()
       */
-      virtual secure_vector<uint8_t> message_prefix() const { throw Exception( "No prefix" ); }
+      virtual secure_vector<uint8_t> message_prefix() const { throw Invalid_State("No prefix"); }
 
       /**
       * @return boolean specifying if this key type supports message
@@ -146,7 +146,7 @@ class Signature_with_EMSA : public Signature
       * @return the message prefix if this signature scheme uses
       * a message prefix, signaled via has_prefix()
       */
-      virtual secure_vector<uint8_t> message_prefix() const { throw Exception( "No prefix" ); }
+      virtual secure_vector<uint8_t> message_prefix() const { throw Invalid_State("No prefix"); }
 
       std::unique_ptr<EMSA> clone_emsa() const { return std::unique_ptr<EMSA>(m_emsa->clone()); }
 
diff --git a/src/lib/pubkey/pkcs8.cpp b/src/lib/pubkey/pkcs8.cpp
index f6d50256d..d299a98a4 100644
--- a/src/lib/pubkey/pkcs8.cpp
+++ b/src/lib/pubkey/pkcs8.cpp
@@ -105,7 +105,7 @@ secure_vector<uint8_t> PKCS8_decode(
       if(is_encrypted)
          {
          if(OIDS::lookup(pbe_alg_id.get_oid()) != "PBE-PKCS5v20")
-            throw Exception("Unknown PBE type " + pbe_alg_id.get_oid().as_string());
+            throw PKCS8_Exception("Unknown PBE type " + pbe_alg_id.get_oid().as_string());
 #if defined(BOTAN_HAS_PKCS5_PBES2)
          key = pbes2_decrypt(key_data, get_passphrase(), pbe_alg_id.get_parameters());
 #else
@@ -167,10 +167,13 @@ choose_pbe_params(const std::string& pbe_algo, const std::string& key_algo)
       }
 
    SCAN_Name request(pbe_algo);
-   if(request.arg_count() != 2)
-      throw Exception("Unsupported PBE " + pbe_algo);
-   if(request.algo_name() != "PBE-PKCS5v20" && request.algo_name() != "PBES2")
-      throw Exception("Unsupported PBE " + pbe_algo);
+
+   if(request.arg_count() != 2 ||
+      (request.algo_name() != "PBE-PKCS5v20" && request.algo_name() != "PBES2"))
+      {
+      throw Invalid_Argument("Unsupported PBE " + pbe_algo);
+      }
+
    return std::make_pair(request.arg(0), request.arg(1));
    }
 
diff --git a/src/lib/pubkey/xmss/xmss_parameters.cpp b/src/lib/pubkey/xmss/xmss_parameters.cpp
index 288b50fdc..b67e5694e 100644
--- a/src/lib/pubkey/xmss/xmss_parameters.cpp
+++ b/src/lib/pubkey/xmss/xmss_parameters.cpp
@@ -177,8 +177,7 @@ XMSS_Parameters::XMSS_Parameters(xmss_algorithm_t oid)
          m_wots_oid = XMSS_WOTS_Parameters::ots_algorithm_t::WOTSP_SHAKE256_W16;
          break;
       default:
-         throw Unsupported_Argument(
-            "Algorithm id does not match any XMSS algorithm id.");
+         throw Not_Implemented("Algorithm id does not match any known XMSS algorithm id.");
          break;
       }
    }
diff --git a/src/lib/pubkey/xmss/xmss_wots_parameters.cpp b/src/lib/pubkey/xmss/xmss_wots_parameters.cpp
index 7ba3dad58..c2a324475 100644
--- a/src/lib/pubkey/xmss/xmss_wots_parameters.cpp
+++ b/src/lib/pubkey/xmss/xmss_wots_parameters.cpp
@@ -75,8 +75,7 @@ XMSS_WOTS_Parameters::XMSS_WOTS_Parameters(ots_algorithm_t oid)
          m_strength = 512;
          break;
       default:
-         throw Unsupported_Argument(
-            "Algorithm id does not match any XMSS WOTS algorithm id.");
+         throw Not_Implemented("Algorithm id does not match any known XMSS WOTS algorithm id.");
          break;
       }