base64.c

/*
cencoder.c - c source to a base64 encoding algorithm implementation

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/

/*
  Modified by Eugene Crosser to fit pam_pcsc_cr project, 2013
*/

#include <string.h>
#include <base64.h>
/*
cencode.h - c header for a base64 encoding algorithm

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/

/*
  Modified by Eugene Crosser to fit pam_pcsc_cr project, 2013
*/

typedef enum
{
	step_A, step_B, step_C
} base64_encodestep;

typedef struct
{
	base64_encodestep step;
	char result;
	int stepcount;
} base64_encodestate;

/*
cdecode.h - c header for a base64 decoding algorithm

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/

typedef enum
{
	step_a, step_b, step_c, step_d
} base64_decodestep;

typedef struct
{
	base64_decodestep step;
	char plainchar;
} base64_decodestate;

static void base64_init_encodestate(base64_encodestate* state_in)
{
	state_in->step = step_A;
	state_in->result = 0;
	state_in->stepcount = 0;
}

static char base64_encode_value(char value_in)
{
	static const char* encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	if (value_in > 63) return '=';
	return encoding[(int)value_in];
}

static int base64_encode_block(const unsigned char* plaintext_in, int length_in, char* code_out, base64_encodestate* state_in)
{
	const unsigned char* plainchar = plaintext_in;
	const unsigned char* const plaintextend = plaintext_in + length_in;
	char* codechar = code_out;
	char result;
	char fragment;
	
	result = state_in->result;
	
	switch (state_in->step)
	{
		while (1)
		{
	case step_A:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_A;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result = (fragment & 0x0fc) >> 2;
			*codechar++ = base64_encode_value(result);
			result = (fragment & 0x003) << 4;
			/* fallthrough */
	case step_B:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_B;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result |= (fragment & 0x0f0) >> 4;
			*codechar++ = base64_encode_value(result);
			result = (fragment & 0x00f) << 2;
			/* fallthrough */
	case step_C:
			if (plainchar == plaintextend)
			{
				state_in->result = result;
				state_in->step = step_C;
				return codechar - code_out;
			}
			fragment = *plainchar++;
			result |= (fragment & 0x0c0) >> 6;
			*codechar++ = base64_encode_value(result);
			result  = (fragment & 0x03f) >> 0;
			*codechar++ = base64_encode_value(result);
			
			++(state_in->stepcount);
		}
	}
	/* control should not reach here */
	return codechar - code_out;
}

static int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
{
	char* codechar = code_out;
	
	switch (state_in->step)
	{
	case step_B:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		*codechar++ = '=';
		break;
	case step_C:
		*codechar++ = base64_encode_value(state_in->result);
		*codechar++ = '=';
		break;
	case step_A:
		break;
	}
	
	return codechar - code_out;
}

/*
cdecoder.c - c source to a base64 decoding algorithm implementation

This is part of the libb64 project, and has been placed in the public domain.
For details, see http://sourceforge.net/projects/libb64
*/

static int base64_decode_value(char value_in)
{
	static const char decoding[] = {62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51};
	static const char decoding_size = sizeof(decoding);
	value_in -= 43;
	if (value_in < 0 || value_in >= decoding_size) return -1;
	return decoding[(int)value_in];
}

static void base64_init_decodestate(base64_decodestate* state_in)
{
	state_in->step = step_a;
	state_in->plainchar = 0;
}

static int base64_decode_block(const char* code_in, const int length_in, unsigned char* plaintext_out, base64_decodestate* state_in)
{
	const char* codechar = code_in;
	unsigned char* plainchar = plaintext_out;
	char fragment;
	
	*plainchar = state_in->plainchar;
	
	switch (state_in->step)
	{
		while (1)
		{
	case step_a:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_a;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar    = (fragment & 0x03f) << 2;
			/* fallthrough */
	case step_b:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_b;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++ |= (fragment & 0x030) >> 4;
			*plainchar    = (fragment & 0x00f) << 4;
			/* fallthrough */
	case step_c:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_c;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++ |= (fragment & 0x03c) >> 2;
			*plainchar    = (fragment & 0x003) << 6;
			/* fallthrough */
	case step_d:
			do {
				if (codechar == code_in+length_in)
				{
					state_in->step = step_d;
					state_in->plainchar = *plainchar;
					return plainchar - plaintext_out;
				}
				fragment = (char)base64_decode_value(*codechar++);
			} while (fragment < 0);
			*plainchar++   |= (fragment & 0x03f);
		}
	}
	/* control should not reach here */
	return plainchar - plaintext_out;
}

int b64_encode(const unsigned char *src, const int ssize,
		char *const b64, int *const bsize)
{
	base64_encodestate s;
	int cnt1, cnt2;
	char *c = b64;

	if (*bsize < ((ssize-1)/3+1)*4+1) return 1;
	base64_init_encodestate(&s);
	cnt1 = base64_encode_block(src, ssize, c, &s);
	c += cnt1;
	cnt2 = base64_encode_blockend(c, &s);
	c += cnt2;
	*c = 0;
	*bsize = cnt1 + cnt2;
	return 0;
}

int b64_decode(const char *b64, unsigned char *const dst, int *const dsize)
{
	base64_decodestate s;
	int cnt;
	int bsize = strlen(b64);

	if (*dsize < (bsize*3/4)) return 1;
	base64_init_decodestate(&s);
	cnt = base64_decode_block(b64, bsize, dst, &s);
	*dsize = cnt;
	return 0;
}