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

2 files changed, 7 insertions, 7 deletions

diff --git a/src/lib/misc/fpe_fe1/fpe_fe1.cpp b/src/lib/misc/fpe_fe1/fpe_fe1.cpp
index 680967ea9..3bd01ce34 100644
--- a/src/lib/misc/fpe_fe1/fpe_fe1.cpp
+++ b/src/lib/misc/fpe_fe1/fpe_fe1.cpp
@@ -50,7 +50,7 @@ void factor(BigInt n, BigInt& a, BigInt& b)
    a *= n;
 
    if(a <= 1 || b <= 1)
-      throw Exception("Could not factor n for use in FPE");
+      throw Internal_Error("Could not factor n for use in FPE");
    }
 
 }
@@ -69,7 +69,7 @@ FPE_FE1::FPE_FE1(const BigInt& n,
    m_n_bytes = BigInt::encode(n);
 
    if(m_n_bytes.size() > MAX_N_BYTES)
-      throw Exception("N is too large for FPE encryption");
+      throw Invalid_Argument("N is too large for FPE encryption");
 
    factor(n, m_a, m_b);
 
diff --git a/src/lib/misc/srp6/srp6.cpp b/src/lib/misc/srp6/srp6.cpp
index cb7e3c600..0ec4fd2bb 100644
--- a/src/lib/misc/srp6/srp6.cpp
+++ b/src/lib/misc/srp6/srp6.cpp
@@ -64,13 +64,13 @@ std::string srp6_group_identifier(const BigInt& N, const BigInt& g)
 
       if(group.get_p() == N && group.get_g() == g)
          return group_name;
-
-      throw Exception("Unknown SRP params");
       }
    catch(...)
       {
-      throw Invalid_Argument("Bad SRP group parameters");
       }
+
+   // If we didn't return, the group was unknown or did not match
+   throw Invalid_Argument("Invalid or unknown SRP group parameters");
    }
 
 std::pair<BigInt, SymmetricKey>
@@ -91,7 +91,7 @@ srp6_client_agree(const std::string& identifier,
    const size_t p_bytes = group.p_bytes();
 
    if(B <= 0 || B >= p)
-      throw Exception("Invalid SRP parameter from server");
+      throw Decoding_Error("Invalid SRP parameter from server");
 
    const BigInt k = hash_seq(hash_id, p_bytes, p, g);
 
@@ -150,7 +150,7 @@ BigInt SRP6_Server_Session::step1(const BigInt& v,
 SymmetricKey SRP6_Server_Session::step2(const BigInt& A)
    {
    if(A <= 0 || A >= m_p)
-      throw Exception("Invalid SRP parameter from client");
+      throw Decoding_Error("Invalid SRP parameter from client");
 
    const BigInt u = hash_seq(m_hash_id, m_p_bytes, A, m_B);