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

7 files changed, 17 insertions, 11 deletions

diff --git a/src/lib/x509/key_constraint.cpp b/src/lib/x509/key_constraint.cpp
index dfadedac5..95a59d65f 100644
--- a/src/lib/x509/key_constraint.cpp
+++ b/src/lib/x509/key_constraint.cpp
@@ -93,7 +93,7 @@ void verify_cert_constraints_valid_for_key_type(const Public_Key& pub_key,
 
    if((constraints & permitted) != constraints)
       {
-      throw Exception("Invalid " + name + " constraints " + key_constraints_to_string(constraints));
+      throw Invalid_Argument("Invalid " + name + " constraints " + key_constraints_to_string(constraints));
       }
    }
 
diff --git a/src/lib/x509/key_constraint.h b/src/lib/x509/key_constraint.h
index 3d456f6c4..75f9fb82f 100644
--- a/src/lib/x509/key_constraint.h
+++ b/src/lib/x509/key_constraint.h
@@ -37,7 +37,7 @@ class Public_Key;
 * Check that key constraints are permitted for a specific public key.
 * @param pub_key the public key on which the constraints shall be enforced on
 * @param constraints the constraints that shall be enforced on the key
-* @throw Exception if the given constraints are not permitted for this key
+* @throw Invalid_Argument if the given constraints are not permitted for this key
 */
 BOTAN_PUBLIC_API(2,0) void verify_cert_constraints_valid_for_key_type(const Public_Key& pub_key,
                                                                 Key_Constraints constraints);
diff --git a/src/lib/x509/ocsp.cpp b/src/lib/x509/ocsp.cpp
index 115c4117a..62d814702 100644
--- a/src/lib/x509/ocsp.cpp
+++ b/src/lib/x509/ocsp.cpp
@@ -106,8 +106,11 @@ Response::Response(const uint8_t response_bits[], size_t response_bits_len) :
 
    response_outer.decode(resp_status, ENUMERATED, UNIVERSAL);
 
+   /*
+   * FIXME: properly decode error responses
+   */
    if(resp_status != 0)
-      throw Exception("OCSP response status " + std::to_string(resp_status));
+      throw Decoding_Error("OCSP response status " + std::to_string(resp_status));
 
    if(response_outer.more_items())
       {
diff --git a/src/lib/x509/x509_crl.h b/src/lib/x509/x509_crl.h
index 89925aa04..d52c98e9a 100644
--- a/src/lib/x509/x509_crl.h
+++ b/src/lib/x509/x509_crl.h
@@ -28,12 +28,15 @@ class BOTAN_PUBLIC_API(2,0) X509_CRL final : public X509_Object
    public:
       /**
       * This class represents CRL related errors.
+      *
+      * In a future major release this exception type will be removed and
+      * replaced with Decoding_Error
       */
-      class BOTAN_PUBLIC_API(2,0) X509_CRL_Error final : public Exception
+      class BOTAN_PUBLIC_API(2,0) X509_CRL_Error final : public Decoding_Error
          {
          public:
             explicit X509_CRL_Error(const std::string& error) :
-               Exception("X509_CRL: " + error) {}
+               Decoding_Error("X509_CRL: " + error) {}
          };
 
       /**
diff --git a/src/lib/x509/x509_ext.h b/src/lib/x509/x509_ext.h
index 48a9f338c..11e14e8d6 100644
--- a/src/lib/x509/x509_ext.h
+++ b/src/lib/x509/x509_ext.h
@@ -115,7 +115,7 @@ class BOTAN_PUBLIC_API(2,0) Extensions final : public ASN1_Object
                }
             else
                {
-               throw Exception("Exception::get_extension_object_as dynamic_cast failed");
+               throw Decoding_Error("Exception::get_extension_object_as dynamic_cast failed");
                }
             }
 
diff --git a/src/lib/x509/x509_obj.cpp b/src/lib/x509/x509_obj.cpp
index 49d7fcc60..6c591bde7 100644
--- a/src/lib/x509/x509_obj.cpp
+++ b/src/lib/x509/x509_obj.cpp
@@ -170,7 +170,7 @@ std::string X509_Object::hash_used_for_signature() const
 bool X509_Object::check_signature(const Public_Key* pub_key) const
    {
    if(!pub_key)
-      throw Exception("No key provided for " + PEM_label() + " signature check");
+      throw Invalid_Argument("No key provided for " + PEM_label() + " signature check");
    std::unique_ptr<const Public_Key> key(pub_key);
    return check_signature(*key);
    }
diff --git a/src/lib/x509/x509path.cpp b/src/lib/x509/x509path.cpp
index 8e459e9d2..9fed87f60 100644
--- a/src/lib/x509/x509path.cpp
+++ b/src/lib/x509/x509path.cpp
@@ -452,7 +452,7 @@ PKIX::check_crl_online(const std::vector<std::shared_ptr<const X509_Certificate>
          {
          // Avoid creating a thread for this case
          future_crls.emplace_back(std::async(std::launch::deferred, [&]() -> std::shared_ptr<const X509_CRL> {
-               throw Exception("No CRL distribution point for this certificate");
+               throw Not_Implemented("No CRL distribution point for this certificate");
                }));
          }
       else
@@ -741,7 +741,7 @@ PKIX::build_all_certificate_paths(std::vector<std::vector<std::shared_ptr<const
    if(cert_paths_out.empty())
       {
       if(stats.empty())
-         throw Exception("X509 path building failed for unknown reasons");
+         throw Internal_Error("X509 path building failed for unknown reasons");
       else
          // arbitrarily return the first error
          return stats[0];
@@ -1005,9 +1005,9 @@ Path_Validation_Result::Path_Validation_Result(CertificatePathStatusCodes status
 const X509_Certificate& Path_Validation_Result::trust_root() const
    {
    if(m_cert_path.empty())
-      throw Exception("Path_Validation_Result::trust_root no path set");
+      throw Invalid_State("Path_Validation_Result::trust_root no path set");
    if(result() != Certificate_Status_Code::VERIFIED)
-      throw Exception("Path_Validation_Result::trust_root meaningless with invalid status");
+      throw Invalid_State("Path_Validation_Result::trust_root meaningless with invalid status");
 
    return *m_cert_path[m_cert_path.size()-1];
    }