Add a couple of new helper functions to BER_Decoder:

decode_and_check takes an expected value; if the decoded value does
not match, a Decoding_Error with a specified string is thrown. Useful
for checking embedded version codes.

decode_octet_string_bigint is for decoding INTEGER values that are
stored as OCTET STRINGs. Totally obnoxious and useless, but common
especially in the ECC standards.

2 files changed, 30 insertions, 3 deletions

diff --git a/src/asn1/ber_dec.cpp b/src/asn1/ber_dec.cpp
index 66a27dd4e..ea0334202 100644
--- a/src/asn1/ber_dec.cpp
+++ b/src/asn1/ber_dec.cpp
@@ -355,6 +355,14 @@ BER_Decoder& BER_Decoder::decode(BigInt& out)
    return decode(out, INTEGER, UNIVERSAL);
    }
 
+BER_Decoder& BER_Decoder::decode_octet_string_bigint(BigInt& out)
+   {
+   SecureVector<byte> out_vec;
+   decode(out_vec, OCTET_STRING);
+   out = BigInt::decode(&out_vec[0], out_vec.size());
+   return (*this);
+   }
+
 /*
 * Decode a BER encoded BOOLEAN
 */
diff --git a/src/asn1/ber_dec.h b/src/asn1/ber_dec.h
index 2e38af301..3658aeba4 100644
--- a/src/asn1/ber_dec.h
+++ b/src/asn1/ber_dec.h
@@ -1,6 +1,6 @@
 /*
 * BER Decoder
-* (C) 1999-2008 Jack Lloyd
+* (C) 1999-2010 Jack Lloyd
 *
 * Distributed under the terms of the Botan license
 */
@@ -46,11 +46,30 @@ class BOTAN_DLL BER_Decoder
 
       BER_Decoder& decode(class ASN1_Object&);
 
+      BER_Decoder& decode_octet_string_bigint(class BigInt&);
+
+      template<typename T>
+         BER_Decoder& decode_optional(T& out,
+                                      ASN1_Tag type_tag,
+                                      ASN1_Tag class_tag,
+                                      const T& default_value = T());
+
       template<typename T>
-      BER_Decoder& decode_optional(T&, ASN1_Tag, ASN1_Tag, const T& = T());
+         BER_Decoder& decode_list(std::vector<T>& out,
+                                  bool clear_out = true);
 
       template<typename T>
-      BER_Decoder& decode_list(std::vector<T>&, bool = true);
+         BER_Decoder& decode_and_check(const T& expected,
+                                       const std::string& error_msg)
+         {
+         T actual;
+         decode(actual);
+
+         if(actual != expected)
+            throw Decoding_Error(error_msg);
+
+         return (*this);
+         }
 
       BER_Decoder& decode_optional_string(MemoryRegion<byte>&,
                                           ASN1_Tag, u16bit);