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asn.cpp

// asn.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"
#include "asn.h"

#include <iomanip>
#include <time.h>

NAMESPACE_BEGIN(CryptoPP)
USING_NAMESPACE(std)

unsigned int DERLengthEncode(BufferedTransformation &bt, unsigned int length)
{
        unsigned int i=0;
        if (length <= 0x7f)
        {
                bt.Put(byte(length));
                i++;
        }
        else
        {
                bt.Put(byte(BytePrecision(length) | 0x80));
                i++;
                for (int j=BytePrecision(length); j; --j)
                {
                        bt.Put(byte(length >> (j-1)*8));
                        i++;
                }
        }
        return i;
}

bool BERLengthDecode(BufferedTransformation &bt, unsigned int &length)
{
        byte b;

        if (!bt.Get(b))
                BERDecodeError();

        if (!(b & 0x80))
                length = b;
        else
        {
                unsigned int lengthBytes = b & 0x7f;

                if (lengthBytes == 0)
                        return false;   // indefinite length

                length = 0;
                while (lengthBytes--)
                {
                        if (length >> (8*(sizeof(length)-1)))
                                BERDecodeError();       // length about to overflow

                        if (!bt.Get(b))
                                BERDecodeError();

                        length = (length << 8) | b;
                }
        }
        return true;
}

void DEREncodeNull(BufferedTransformation &out)
{
        out.Put(TAG_NULL);
        out.Put(0);
}

void BERDecodeNull(BufferedTransformation &in)
{
        byte b;
        if (!in.Get(b) || b != TAG_NULL)
                BERDecodeError();
        unsigned int length;
        if (!BERLengthDecode(in, length) || length != 0)
                BERDecodeError();
}

unsigned int DEREncodeOctetString(BufferedTransformation &bt, const byte *str, unsigned int strLen)
{
        bt.Put(OCTET_STRING);
        unsigned int lengthBytes = DERLengthEncode(bt, strLen);
        bt.Put(str, strLen);
        return 1+lengthBytes+strLen;
}

unsigned int DEREncodeOctetString(BufferedTransformation &bt, const SecByteBlock &str)
{
        return DEREncodeOctetString(bt, str.ptr, str.size);
}

unsigned int BERDecodeOctetString(BufferedTransformation &bt, SecByteBlock &str)
{
        byte b;
        if (!bt.Get(b) || b != OCTET_STRING)
                BERDecodeError();

        unsigned int bc;
        if (!BERLengthDecode(bt, bc))
                BERDecodeError();

        str.Resize(bc);
        if (bc != bt.Get(str, bc))
                BERDecodeError();
        return bc;
}

unsigned int BERDecodeOctetString(BufferedTransformation &bt, BufferedTransformation &str)
{
        byte b;
        if (!bt.Get(b) || b != OCTET_STRING)
                BERDecodeError();

        unsigned int bc;
        if (!BERLengthDecode(bt, bc))
                BERDecodeError();

        bt.TransferTo(str, bc);
        return bc;
}

unsigned int DEREncodeTextString(BufferedTransformation &bt, const std::string &str, byte asnTag)
{
        bt.Put(asnTag);
        unsigned int lengthBytes = DERLengthEncode(bt, str.size());
        bt.Put((const byte *)str.data(), str.size());
        return 1+lengthBytes+str.size();
}

unsigned int BERDecodeTextString(BufferedTransformation &bt, std::string &str, byte asnTag)
{
        byte b;
        if (!bt.Get(b) || b != asnTag)
                BERDecodeError();

        unsigned int bc;
        if (!BERLengthDecode(bt, bc))
                BERDecodeError();

        SecByteBlock temp(bc);
        if (bc != bt.Get(temp, bc))
                BERDecodeError();
        str.assign((char *)temp.ptr, bc);
        return bc;
}

unsigned int DEREncodeBitString(BufferedTransformation &bt, const byte *str, unsigned int strLen, unsigned int unusedBits)
{
        bt.Put(BIT_STRING);
        unsigned int lengthBytes = DERLengthEncode(bt, strLen+1);
        bt.Put((byte)unusedBits);
        bt.Put(str, strLen);
        return 1+lengthBytes+strLen;
}

unsigned int BERDecodeBitString(BufferedTransformation &bt, SecByteBlock &str, unsigned int &unusedBits)
{
        byte b;
        if (!bt.Get(b) || b != BIT_STRING)
                BERDecodeError();

        unsigned int bc;
        if (!BERLengthDecode(bt, bc))
                BERDecodeError();

        byte unused;
        if (!bt.Get(unused))
                BERDecodeError();
        unusedBits = unused;
        str.Resize(bc-1);
        if ((bc-1) != bt.Get(str, bc-1))
                BERDecodeError();
        return bc-1;
}

void OID::EncodeValue(BufferedTransformation &bt, unsigned long v)
{
        for (unsigned int i=RoundUpToMultipleOf(STDMAX(7U,BitPrecision(v)), 7)-7; i != 0; i-=7)
                bt.Put(0x80 | ((v >> i) & 0x7f));
        bt.Put(v & 0x7f);
}

unsigned int OID::DecodeValue(BufferedTransformation &bt, unsigned long &v)
{
        byte b;
        unsigned int i=0;
        v = 0;
        while (true)
        {
                if (!bt.Get(b))
                        BERDecodeError();
                i++;
                v <<= 7;
                v += b & 0x7f;
                if (!(b & 0x80))
                        return i;
        }
}

void OID::DEREncode(BufferedTransformation &bt) const
{
        assert(m_values.size() >= 2);
        ByteQueue temp;
        temp.Put(byte(m_values[0] * 40 + m_values[1]));
        for (unsigned int i=2; i<m_values.size(); i++)
                EncodeValue(temp, m_values[i]);
        bt.Put(OBJECT_IDENTIFIER);
        DERLengthEncode(bt, temp.CurrentSize());
        temp.TransferTo(bt);
}

void OID::BERDecode(BufferedTransformation &bt)
{
        byte b;
        if (!bt.Get(b) || b != OBJECT_IDENTIFIER)
                BERDecodeError();

        unsigned int length;
        if (!BERLengthDecode(bt, length) || length < 1)
                BERDecodeError();

        if (!bt.Get(b))
                BERDecodeError();
        
        length--;
        m_values.resize(2);
        m_values[0] = b / 40;
        m_values[1] = b % 40;

        while (length > 0)
        {
                unsigned long v;
                unsigned int valueLen = DecodeValue(bt, v);
                if (valueLen > length)
                        BERDecodeError();
                m_values.push_back(v);
                length -= valueLen;
        }
}

void OID::BERDecodeAndCheck(BufferedTransformation &bt) const
{
        OID oid(bt);
        if (*this != oid)
                BERDecodeError();
}

BERGeneralDecoder::BERGeneralDecoder(BufferedTransformation &inQueue, byte asnTag)
        : m_inQueue(inQueue), m_finished(false)
{
        byte b;
        if (!m_inQueue.Get(b) || b != asnTag)
                BERDecodeError();

        m_definiteLength = BERLengthDecode(m_inQueue, m_length);
}

BERGeneralDecoder::BERGeneralDecoder(BERGeneralDecoder &inQueue, byte asnTag)
        : m_inQueue(inQueue), m_finished(false)
{
        byte b;
        if (!m_inQueue.Get(b) || b != asnTag)
                BERDecodeError();

        m_definiteLength = BERLengthDecode(m_inQueue, m_length);
        if (!m_definiteLength && !(asnTag | CONSTRUCTED))
                BERDecodeError();       // cannot be primitive have indefinite length
}

BERGeneralDecoder::~BERGeneralDecoder()
{
        try     // avoid throwing in constructor
        {
                if (!m_finished)
                        MessageEnd();
        }
        catch (...)
        {
        }
}

bool BERGeneralDecoder::EndReached() const
{
        if (m_definiteLength)
                return m_length == 0;
        else
        {       // check end-of-content octets
                word16 i;
                return (m_inQueue.PeekWord16(i)==2 && i==0);
        }
}

byte BERGeneralDecoder::PeekByte() const
{
        byte b;
        if (!Peek(b))
                BERDecodeError();
        return b;
}

void BERGeneralDecoder::CheckByte(byte check)
{
        byte b;
        if (!Get(b) || b != check)
                BERDecodeError();
}

void BERGeneralDecoder::MessageEnd(int)
{
        m_finished = true;
        if (m_definiteLength)
        {
                if (m_length != 0)
                        BERDecodeError();
        }
        else
        {       // remove end-of-content octets
                word16 i;
                if (m_inQueue.GetWord16(i) != 2 || i != 0)
                        BERDecodeError();
        }
}

unsigned long BERGeneralDecoder::TransferTo(BufferedTransformation &target, unsigned long transferMax)
{
        return ReduceLength(m_inQueue.TransferTo(target, m_definiteLength ? STDMIN(transferMax, (unsigned long)m_length) : transferMax));
}

unsigned long BERGeneralDecoder::CopyTo(BufferedTransformation &target, unsigned long copyMax) const
{
        return m_inQueue.CopyTo(target, m_definiteLength ? STDMIN(copyMax, (unsigned long)m_length) : copyMax);
}

unsigned int BERGeneralDecoder::ReduceLength(unsigned int delta)
{
        if (m_definiteLength)
        {
                if (m_length < delta)
                        BERDecodeError();
                m_length -= delta;
        }
        return delta;
}

DERGeneralEncoder::DERGeneralEncoder(BufferedTransformation &outQueue, byte asnTag)
        : m_outQueue(outQueue), m_asnTag(asnTag), m_finished(false)
{
}

DERGeneralEncoder::DERGeneralEncoder(DERGeneralEncoder &outQueue, byte asnTag)
        : m_outQueue(outQueue), m_asnTag(asnTag), m_finished(false)
{
}

DERGeneralEncoder::~DERGeneralEncoder()
{
        try     // avoid throwing in constructor
        {
                if (!m_finished)
                        MessageEnd();
        }
        catch (...)
        {
        }
}

void DERGeneralEncoder::MessageEnd(int)
{
        m_finished = true;
        unsigned int length = (unsigned int)CurrentSize();
        m_outQueue.Put(m_asnTag);
        DERLengthEncode(m_outQueue, length);
        TransferTo(m_outQueue);
}

NAMESPACE_END

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