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/*************************************************
* BER Decoding Source File *
* (C) 1999-2005 The Botan Project *
*************************************************/
#include <botan/asn1.h>
#include <botan/parsing.h>
namespace Botan {
/*************************************************
* BER Decoding Exceptions *
*************************************************/
BER_Decoding_Error::BER_Decoding_Error(const std::string& str) :
Decoding_Error("BER: " + str) {}
BER_Bad_Tag::BER_Bad_Tag(const std::string& str, ASN1_Tag tag) :
BER_Decoding_Error(str + ": " + to_string(tag)) {}
BER_Bad_Tag::BER_Bad_Tag(const std::string& str,
ASN1_Tag tag1, ASN1_Tag tag2) :
BER_Decoding_Error(str + ": " + to_string(tag1) + "/" + to_string(tag2)) {}
namespace {
/*************************************************
* Check an object's type and size *
*************************************************/
void check_object(const BER_Object& obj,
ASN1_Tag type_tag, ASN1_Tag class_tag,
u32bit length = 0, bool check_length = false)
{
if(obj.type_tag != type_tag || obj.class_tag != class_tag)
throw BER_Decoding_Error("Tag mismatch when decoding");
if(check_length && obj.value.size() != length)
throw BER_Decoding_Error("Incorrect size for type");
}
}
namespace BER {
/*************************************************
* Decode a BER encoded NULL *
*************************************************/
void decode_null(BER_Decoder& decoder)
{
BER_Object obj = decoder.get_next_object();
check_object(obj, NULL_TAG, UNIVERSAL, 0, true);
}
/*************************************************
* Decode a BER encoded BOOLEAN *
*************************************************/
void decode(BER_Decoder& decoder, bool& out)
{
decode(decoder, out, BOOLEAN, UNIVERSAL);
}
/*************************************************
* Decode a small BER encoded INTEGER *
*************************************************/
void decode(BER_Decoder& decoder, u32bit& out)
{
decode(decoder, out, INTEGER, UNIVERSAL);
}
/*************************************************
* Decode a BER encoded INTEGER *
*************************************************/
void decode(BER_Decoder& decoder, BigInt& out)
{
decode(decoder, out, INTEGER, UNIVERSAL);
}
/*************************************************
* BER decode a BIT STRING or OCTET STRING *
*************************************************/
void decode(BER_Decoder& decoder, MemoryRegion<byte>& out, ASN1_Tag real_type)
{
decode(decoder, out, real_type, real_type, UNIVERSAL);
}
/*************************************************
* Decode a BER encoded BOOLEAN *
*************************************************/
void decode(BER_Decoder& decoder, bool& out,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BER_Object obj = decoder.get_next_object();
check_object(obj, type_tag, class_tag, 1, true);
out = (obj.value[0]) ? true : false;
}
/*************************************************
* Decode a small BER encoded INTEGER *
*************************************************/
void decode(BER_Decoder& decoder, u32bit& out,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BigInt integer;
decode(decoder, integer, type_tag, class_tag);
out = integer.to_u32bit();
}
/*************************************************
* Decode a BER encoded INTEGER *
*************************************************/
void decode(BER_Decoder& decoder, BigInt& out,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BER_Object obj = decoder.get_next_object();
check_object(obj, type_tag, class_tag);
out = 0;
if(obj.value.is_empty())
return;
const bool negative = (obj.value[0] & 0x80) ? true : false;
if(negative)
{
for(u32bit j = obj.value.size(); j > 0; j--)
if(obj.value[j-1]--)
break;
for(u32bit j = 0; j != obj.value.size(); j++)
obj.value[j] = ~obj.value[j];
}
out = BigInt(obj.value, obj.value.size());
if(negative)
out.flip_sign();
}
/*************************************************
* BER decode a BIT STRING or OCTET STRING *
*************************************************/
void decode(BER_Decoder& decoder, MemoryRegion<byte>& buffer,
ASN1_Tag real_type, ASN1_Tag type_tag, ASN1_Tag class_tag)
{
if(real_type != OCTET_STRING && real_type != BIT_STRING)
throw BER_Bad_Tag("Bad tag for {BIT,OCTET} STRING", real_type);
BER_Object obj = decoder.get_next_object();
check_object(obj, type_tag, class_tag);
if(real_type == OCTET_STRING)
buffer = obj.value;
else
{
if(obj.value[0] >= 8)
throw BER_Decoding_Error("Bad number of unused bits in BIT STRING");
buffer.set(obj.value + 1, obj.value.size() - 1);
}
}
/*************************************************
* Decode and return a BER encoded SEQUENCE *
*************************************************/
BER_Decoder get_subsequence(BER_Decoder& decoder)
{
return get_subsequence(decoder, SEQUENCE, CONSTRUCTED);
}
/*************************************************
* Decode and return a BER encoded SET *
*************************************************/
BER_Decoder get_subset(BER_Decoder& decoder)
{
return get_subset(decoder, SET, CONSTRUCTED);
}
/*************************************************
* Decode and return a BER encoded SEQUENCE *
*************************************************/
BER_Decoder get_subsequence(BER_Decoder& decoder,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BER_Object obj = decoder.get_next_object();
check_object(obj, type_tag, ASN1_Tag(class_tag | CONSTRUCTED));
return BER_Decoder(obj.value, obj.value.size());
}
/*************************************************
* Decode and return a BER encoded SET *
*************************************************/
BER_Decoder get_subset(BER_Decoder& decoder,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BER_Object obj = decoder.get_next_object();
check_object(obj, type_tag, ASN1_Tag(class_tag | CONSTRUCTED));
return BER_Decoder(obj.value, obj.value.size());
}
/*************************************************
* Convert a BER object into a string object *
*************************************************/
std::string to_string(const BER_Object& obj)
{
std::string str((const char*)obj.value.begin(), obj.value.size());
return str;
}
/*************************************************
* Decode an OPTIONAL string type *
*************************************************/
bool decode_optional_string(BER_Decoder& in, MemoryRegion<byte>& out,
ASN1_Tag real_type,
ASN1_Tag type_tag, ASN1_Tag class_tag)
{
BER_Object obj = in.get_next_object();
if(obj.type_tag == type_tag && obj.class_tag == class_tag)
{
if(class_tag & CONSTRUCTED)
{
BER_Decoder stored_value(obj.value);
BER::decode(stored_value, out, real_type);
stored_value.verify_end();
}
else
{
in.push_back(obj);
BER::decode(in, out, real_type, type_tag, class_tag);
}
return true;
}
else
{
out.clear();
in.push_back(obj);
return false;
}
}
/*************************************************
* Do heuristic tests for BER data *
*************************************************/
bool maybe_BER(DataSource& source)
{
byte first_byte;
if(!source.peek_byte(first_byte))
throw Stream_IO_Error("BER::maybe_BER: Source was empty");
if(first_byte == (SEQUENCE | CONSTRUCTED))
return true;
return false;
}
}
}
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