Fix for bug 209. Required some reworking of the ASN.1 bytestring

decoding code but seems an improvement.

5 files changed, 50 insertions, 47 deletions

diff --git a/src/asn1/asn1_int.h b/src/asn1/asn1_int.h
index 6d254e4db..564f4ecdb 100644
--- a/src/asn1/asn1_int.h
+++ b/src/asn1/asn1_int.h
@@ -23,6 +23,8 @@ enum ASN1_Tag {
 
    CONSTRUCTED      = 0x20,
 
+   PRIVATE          = CONSTRUCTED | CONTEXT_SPECIFIC,
+
    EOC              = 0x00,
    BOOLEAN          = 0x01,
    INTEGER          = 0x02,
diff --git a/src/asn1/asn1_oid.h b/src/asn1/asn1_oid.h
index 85e863907..9d712b256 100644
--- a/src/asn1/asn1_oid.h
+++ b/src/asn1/asn1_oid.h
@@ -27,7 +27,7 @@ class BOTAN_DLL OID : public ASN1_Object
       * Find out whether this OID is empty
       * @return true is no OID value is set
       */
-      bool is_empty() const { return id.size() == 0; }
+      bool empty() const { return id.size() == 0; }
 
       /**
       * Get this OID as list (vector) of its components.
diff --git a/src/asn1/ber_dec.cpp b/src/asn1/ber_dec.cpp
index 25c412600..81b2e34f6 100644
--- a/src/asn1/ber_dec.cpp
+++ b/src/asn1/ber_dec.cpp
@@ -558,41 +558,4 @@ BER_Decoder& BER_Decoder::decode(std::vector<byte>& buffer,
    return (*this);
    }
 
-/*
-* Decode an OPTIONAL string type
-*/
-BER_Decoder& BER_Decoder::decode_optional_string(secure_vector<byte>& out,
-                                                 ASN1_Tag real_type,
-                                                 u16bit type_no)
-   {
-   BER_Object obj = get_next_object();
-
-   ASN1_Tag type_tag = static_cast<ASN1_Tag>(type_no);
-
-   out.clear();
-   push_back(obj);
-
-   if(obj.type_tag == type_tag && obj.class_tag == CONTEXT_SPECIFIC)
-      decode(out, real_type, type_tag, CONTEXT_SPECIFIC);
-
-   return (*this);
-   }
-
-BER_Decoder& BER_Decoder::decode_optional_string(std::vector<byte>& out,
-                                                 ASN1_Tag real_type,
-                                                 u16bit type_no)
-   {
-   BER_Object obj = get_next_object();
-
-   ASN1_Tag type_tag = static_cast<ASN1_Tag>(type_no);
-
-   out.clear();
-   push_back(obj);
-
-   if(obj.type_tag == type_tag && obj.class_tag == CONTEXT_SPECIFIC)
-      decode(out, real_type, type_tag, CONTEXT_SPECIFIC);
-
-   return (*this);
-   }
-
 }
diff --git a/src/asn1/ber_dec.h b/src/asn1/ber_dec.h
index 0d0d0ec72..ebfa91c85 100644
--- a/src/asn1/ber_dec.h
+++ b/src/asn1/ber_dec.h
@@ -123,13 +123,37 @@ class BOTAN_DLL BER_Decoder
          return (*this);
          }
 
-      BER_Decoder& decode_optional_string(std::vector<byte>& out,
+      /*
+      * Decode an OPTIONAL string type
+      */
+      template<typename Alloc>
+      BER_Decoder& decode_optional_string(std::vector<byte, Alloc>& out,
                                           ASN1_Tag real_type,
-                                          u16bit type_no);
+                                          u16bit type_no,
+                                          ASN1_Tag class_tag = CONTEXT_SPECIFIC)
+         {
+         BER_Object obj = get_next_object();
+
+         ASN1_Tag type_tag = static_cast<ASN1_Tag>(type_no);
+
+         if(obj.type_tag == type_tag && obj.class_tag == class_tag)
+            {
+            if((class_tag & CONSTRUCTED) && (class_tag & CONTEXT_SPECIFIC))
+               BER_Decoder(obj.value).decode(out, real_type).verify_end();
+            else
+               {
+               push_back(obj);
+               decode(out, real_type, type_tag, class_tag);
+               }
+            }
+         else
+            {
+            out.clear();
+            push_back(obj);
+            }
 
-      BER_Decoder& decode_optional_string(secure_vector<byte>& out,
-                                          ASN1_Tag real_type,
-                                          u16bit type_no);
+         return (*this);
+         }
 
       BER_Decoder& operator=(const BER_Decoder&) = delete;
 
diff --git a/src/pubkey/ecc_key/ecc_key.cpp b/src/pubkey/ecc_key/ecc_key.cpp
index ead129ec6..2b6deea44 100644
--- a/src/pubkey/ecc_key/ecc_key.cpp
+++ b/src/pubkey/ecc_key/ecc_key.cpp
@@ -113,17 +113,31 @@ EC_PrivateKey::EC_PrivateKey(const AlgorithmIdentifier& alg_id,
    domain_params = EC_Group(alg_id.parameters);
    domain_encoding = EC_DOMPAR_ENC_EXPLICIT;
 
+   OID key_parameters;
+   secure_vector<byte> public_key_bits;
+
    BER_Decoder(key_bits)
       .start_cons(SEQUENCE)
          .decode_and_check<size_t>(1, "Unknown version code for ECC key")
          .decode_octet_string_bigint(private_key)
-      .verify_end()
+         .decode_optional(key_parameters, ASN1_Tag(0), PRIVATE)
+         .decode_optional_string(public_key_bits, BIT_STRING, 1, PRIVATE)
       .end_cons();
 
-   public_key = domain().get_base_point() * private_key;
+   if(!key_parameters.empty() && key_parameters != alg_id.oid)
+      throw Decoding_Error("EC_PrivateKey - inner and outer OIDs did not match");
 
-   BOTAN_ASSERT(public_key.on_the_curve(),
-                "Loaded ECC private key not on the curve");
+   if(public_key_bits.empty())
+      {
+      public_key = domain().get_base_point() * private_key;
+      BOTAN_ASSERT(public_key.on_the_curve(),
+                   "Public key derived from private key was on the curve");
+      }
+   else
+      {
+      public_key = OS2ECP(public_key_bits, domain().get_curve());
+      // OS2ECP verifies that the point is on the curve
+      }
    }
 
 }