asn.cpp

来自「各种加密算法的集合」· C++ 代码 · 共 108 行

#include "pch.h" 
#include "asn.h" 
#include "misc.h" 
 
NAMESPACE_BEGIN(CryptoPP) 
 
unsigned int DERLengthEncode(unsigned int length, byte *output) 
{ 
	unsigned int i=0; 
	if (length <= 0x7f) 
	{ 
		output[i++] = byte(length); 
	} 
	else 
	{ 
		output[i++] = byte(BytePrecision(length) | 0x80); 
		for (int j=BytePrecision(length); j; --j) 
		{ 
			output[i++] = byte (length >> (j-1)*8); 
		} 
	} 
	return i; 
} 
 
unsigned int DERLengthEncode(unsigned int length, BufferedTransformation &bt) 
{ 
	byte buf[10];   // should be more than enough 
	unsigned int i = DERLengthEncode(length, buf); 
	assert(i <= 10); 
	bt.Put(buf, 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 (bt.MaxRetrieveable() < lengthBytes) 
			BERDecodeError(); 
 
		bt.Get(b); 
		while (!b && lengthBytes>1) 
		{ 
			bt.Get(b); 
			lengthBytes--; 
		} 
 
		switch (lengthBytes) 
		{ 
		case 0: 
			return false;   // indefinite length 
		case 1: 
			length = b; 
			break; 
		case 2: 
			length = b << 8; 
			length |= (bt.Get(b), b); 
			break; 
		default: 
			BERDecodeError(); 
		} 
	} 
	return true; 
} 
 
BERSequenceDecoder::BERSequenceDecoder(BufferedTransformation &inQueue) 
	: inQueue(inQueue) 
{ 
	byte b; 
	if (!inQueue.Get(b) || b != (SEQUENCE | CONSTRUCTED)) 
		BERDecodeError(); 
 
	definiteLength = BERLengthDecode(inQueue, length); 
} 
 
BERSequenceDecoder::~BERSequenceDecoder() 
{ 
	if (!definiteLength) 
	{   // remove end-of-content octects 
		word16 i; 
		if (!inQueue.GetShort(i) || (i!=0)) 
			BERDecodeError(); 
	} 
} 
 
DERSequenceEncoder::DERSequenceEncoder(BufferedTransformation &outQueue) 
	: outQueue(outQueue) 
{ 
} 
 
DERSequenceEncoder::~DERSequenceEncoder() 
{ 
	unsigned int length = (unsigned int)CurrentSize(); 
	outQueue.Put(SEQUENCE | CONSTRUCTED); 
	DERLengthEncode(length, outQueue); 
	TransferTo(outQueue); 
} 
 
NAMESPACE_END