Add some helpers for start_cons

Nothing in the library uses start_cons anymore but it is left
exposed for applications which need to encode something unusual.

9 files changed, 49 insertions, 23 deletions

diff --git a/src/lib/asn1/ber_dec.h b/src/lib/asn1/ber_dec.h
index 3784c929d..3a485470a 100644
--- a/src/lib/asn1/ber_dec.h
+++ b/src/lib/asn1/ber_dec.h
@@ -106,14 +106,26 @@ class BOTAN_PUBLIC_API(2,0) BER_Decoder final
       */
       BER_Decoder& discard_remaining();
 
-      /**
-      * Start decoding a constructed data (sequence or set)
-      */
-      BER_Decoder start_cons(ASN1_Type type_tag, ASN1_Class class_tag = ASN1_Class::UNIVERSAL);
+      BER_Decoder start_cons(ASN1_Type type_tag, ASN1_Class class_tag);
 
       BER_Decoder start_sequence()
          {
-         return start_cons(ASN1_Type::SEQUENCE);
+         return start_cons(ASN1_Type::SEQUENCE, ASN1_Class::UNIVERSAL);
+         }
+
+      BER_Decoder start_set()
+         {
+         return start_cons(ASN1_Type::SET, ASN1_Class::UNIVERSAL);
+         }
+
+      BER_Decoder start_context_specific(uint32_t tag)
+         {
+         return start_cons(ASN1_Type(tag), ASN1_Class::CONTEXT_SPECIFIC);
+         }
+
+      BER_Decoder start_explicit_context_specific(uint32_t tag)
+         {
+         return start_cons(ASN1_Type(tag), ASN1_Class::EXPLICIT_CONTEXT_SPECIFIC);
          }
 
       /**
diff --git a/src/lib/asn1/der_enc.h b/src/lib/asn1/der_enc.h
index e8ac2bf4f..ba49ea421 100644
--- a/src/lib/asn1/der_enc.h
+++ b/src/lib/asn1/der_enc.h
@@ -61,12 +61,26 @@ class BOTAN_PUBLIC_API(2,0) DER_Encoder final
       BOTAN_DEPRECATED("Use DER_Encoder(vector) instead")
       std::vector<uint8_t> get_contents_unlocked();
 
-      DER_Encoder& start_cons(ASN1_Type type_tag,
-                              ASN1_Class class_tag = ASN1_Class::UNIVERSAL);
+      DER_Encoder& start_cons(ASN1_Type type_tag, ASN1_Class class_tag);
 
       DER_Encoder& start_sequence()
          {
-         return start_cons(ASN1_Type::SEQUENCE);
+         return start_cons(ASN1_Type::SEQUENCE, ASN1_Class::UNIVERSAL);
+         }
+
+      DER_Encoder& start_set()
+         {
+         return start_cons(ASN1_Type::SET, ASN1_Class::UNIVERSAL);
+         }
+
+      DER_Encoder& start_context_specific(uint32_t tag)
+         {
+         return start_cons(ASN1_Type(tag), ASN1_Class::CONTEXT_SPECIFIC);
+         }
+
+      DER_Encoder& start_explicit_context_specific(uint32_t tag)
+         {
+         return start_cons(ASN1_Type(tag), ASN1_Class::EXPLICIT_CONTEXT_SPECIFIC);
          }
 
       DER_Encoder& end_cons();
diff --git a/src/lib/pk_pad/emsa_pssr/pssr.cpp b/src/lib/pk_pad/emsa_pssr/pssr.cpp
index 2920e81db..cf7312900 100644
--- a/src/lib/pk_pad/emsa_pssr/pssr.cpp
+++ b/src/lib/pk_pad/emsa_pssr/pssr.cpp
@@ -208,10 +208,10 @@ AlgorithmIdentifier PSSR::config_for_x509(const Private_Key& key,
    std::vector<uint8_t> parameters;
    DER_Encoder(parameters)
       .start_sequence()
-      .start_cons(ASN1_Type(0), ASN1_Class::CONTEXT_SPECIFIC).encode(hash_id).end_cons()
-      .start_cons(ASN1_Type(1), ASN1_Class::CONTEXT_SPECIFIC).encode(mgf_id).end_cons()
-      .start_cons(ASN1_Type(2), ASN1_Class::CONTEXT_SPECIFIC).encode(m_salt_size).end_cons()
-      .start_cons(ASN1_Type(3), ASN1_Class::CONTEXT_SPECIFIC).encode(size_t(1)).end_cons() // trailer field
+      .start_context_specific(0).encode(hash_id).end_cons()
+      .start_context_specific(1).encode(mgf_id).end_cons()
+      .start_context_specific(2).encode(m_salt_size).end_cons()
+      .start_context_specific(3).encode(size_t(1)).end_cons() // trailer field
       .end_cons();
 
    // hardcoded as RSA is the only valid algorithm for EMSA4 at the moment
diff --git a/src/lib/prov/openssl/openssl_ec.cpp b/src/lib/prov/openssl/openssl_ec.cpp
index 5229952dc..4f04618f3 100644
--- a/src/lib/prov/openssl/openssl_ec.cpp
+++ b/src/lib/prov/openssl/openssl_ec.cpp
@@ -51,11 +51,11 @@ secure_vector<uint8_t> PKCS8_for_openssl(const EC_PrivateKey& ec)
      .start_sequence()
         .encode(static_cast<size_t>(1))
         .encode(BigInt::encode_1363(priv_key, priv_key.bytes()), ASN1_Type::OCTET_STRING)
-      .start_cons(ASN1_Type(0), ASN1_Class::EXPLICIT_CONTEXT_SPECIFIC)
-      .raw_bytes(ec.domain().DER_encode(EC_Group_Encoding::NamedCurve))
+      .start_explicit_context_specific(0)
+        .raw_bytes(ec.domain().DER_encode(EC_Group_Encoding::NamedCurve))
       .end_cons()
-      .start_cons(ASN1_Type(1), ASN1_Class::EXPLICIT_CONTEXT_SPECIFIC)
-      .encode(pub_key.encode(PointGFp::UNCOMPRESSED), ASN1_Type::BIT_STRING)
+      .start_explicit_context_specific(1)
+        .encode(pub_key.encode(PointGFp::UNCOMPRESSED), ASN1_Type::BIT_STRING)
       .end_cons()
       .end_cons()
       .get_contents();
diff --git a/src/lib/pubkey/ecc_key/ecc_key.cpp b/src/lib/pubkey/ecc_key/ecc_key.cpp
index 559c42dad..94d6b4202 100644
--- a/src/lib/pubkey/ecc_key/ecc_key.cpp
+++ b/src/lib/pubkey/ecc_key/ecc_key.cpp
@@ -146,7 +146,7 @@ secure_vector<uint8_t> EC_PrivateKey::private_key_bits() const
       .start_sequence()
          .encode(static_cast<size_t>(1))
          .encode(BigInt::encode_1363(m_private_key, m_private_key.bytes()), ASN1_Type::OCTET_STRING)
-         .start_cons(ASN1_Type(1), ASN1_Class::EXPLICIT_CONTEXT_SPECIFIC)
+         .start_explicit_context_specific(1)
             .encode(m_public_key.encode(PointGFp::Compression_Type::UNCOMPRESSED), ASN1_Type::BIT_STRING)
          .end_cons()
       .end_cons()
diff --git a/src/lib/x509/ocsp.cpp b/src/lib/x509/ocsp.cpp
index 1155c7a42..d229aa188 100644
--- a/src/lib/x509/ocsp.cpp
+++ b/src/lib/x509/ocsp.cpp
@@ -115,7 +115,7 @@ Response::Response(const uint8_t response_bits[], size_t response_bits_len) :
    if(response_outer.more_items())
       {
       BER_Decoder response_bytes =
-         response_outer.start_cons(ASN1_Type(0), ASN1_Class::CONTEXT_SPECIFIC).start_sequence();
+         response_outer.start_context_specific(0).start_sequence();
 
       response_bytes.decode_and_check(OID("1.3.6.1.5.5.7.48.1.1"),
                                       "Unknown response type in OCSP response");
diff --git a/src/lib/x509/x509_attribute.cpp b/src/lib/x509/x509_attribute.cpp
index 52ea23b14..b92ee00e0 100644
--- a/src/lib/x509/x509_attribute.cpp
+++ b/src/lib/x509/x509_attribute.cpp
@@ -36,7 +36,7 @@ void Attribute::encode_into(DER_Encoder& codec) const
    {
    codec.start_sequence()
       .encode(m_oid)
-      .start_cons(ASN1_Type::SET)
+      .start_set()
          .raw_bytes(m_parameters)
       .end_cons()
    .end_cons();
@@ -49,7 +49,7 @@ void Attribute::decode_from(BER_Decoder& codec)
    {
    codec.start_sequence()
       .decode(m_oid)
-      .start_cons(ASN1_Type::SET)
+      .start_set()
          .raw_bytes(m_parameters)
       .end_cons()
    .end_cons();
diff --git a/src/lib/x509/x509_dn.cpp b/src/lib/x509/x509_dn.cpp
index 4c1b1e9e2..1747a12dc 100644
--- a/src/lib/x509/x509_dn.cpp
+++ b/src/lib/x509/x509_dn.cpp
@@ -262,7 +262,7 @@ void X509_DN::encode_into(DER_Encoder& der) const
       {
       for(const auto& dn : m_rdn)
          {
-         der.start_cons(ASN1_Type::SET)
+         der.start_set()
             .start_sequence()
             .encode(dn.first)
             .encode(dn.second)
@@ -291,7 +291,7 @@ void X509_DN::decode_from(BER_Decoder& source)
 
    while(sequence.more_items())
       {
-      BER_Decoder rdn = sequence.start_cons(ASN1_Type::SET);
+      BER_Decoder rdn = sequence.start_set();
 
       while(rdn.more_items())
          {
diff --git a/src/lib/x509/x509_ext.cpp b/src/lib/x509/x509_ext.cpp
index c5713e3b6..b90eef523 100644
--- a/src/lib/x509/x509_ext.cpp
+++ b/src/lib/x509/x509_ext.cpp
@@ -840,7 +840,7 @@ void CRL_Distribution_Points::Distribution_Point::encode_into(class DER_Encoder&
 void CRL_Distribution_Points::Distribution_Point::decode_from(class BER_Decoder& ber)
    {
    ber.start_sequence()
-      .start_cons(ASN1_Type(0), ASN1_Class::CONTEXT_SPECIFIC)
+      .start_context_specific(0)
         .decode_optional_implicit(m_point, ASN1_Type(0),
                                   ASN1_Class::CONTEXT_SPECIFIC | ASN1_Class::CONSTRUCTED,
                                   ASN1_Type::SEQUENCE, ASN1_Class::CONSTRUCTED)