/*
	R_ENCODE.C - RFC 1113 encoding and decoding routines

	Based in a similar form to the PGP RFC 1113 coding routines.
*/

#include "rsaeuro.h"

/* RFC 1113 encoding:

	 Value Encoding  Value Encoding  Value Encoding  Value Encoding
			 0 A            17 R            34 i            51 z
			 1 B            18 S            35 j            52 0
			 2 C            19 T            36 k            53 1
			 3 D            20 U            37 l            54 2
			 4 E            21 V            38 m            55 3
			 5 F            22 W            39 n            56 4
			 6 G            23 X            40 o            57 5
			 7 H            24 Y            41 p            58 6
			 8 I            25 Z            42 q            59 7
			 9 J            26 a            43 r            60 8
			10 K            27 b            44 s            61 9
			11 L            28 c            45 t            62 +
			12 M            29 d            46 u            63 /
			13 N            30 e            47 v
			14 O            31 f            48 w         (pad) =
			15 P            32 g            49 x
			16 Q            33 h            50 y
*/

/*
	PEM routines.
	This converts a binary file into printable ASCII characters, in a
	radix-64 form mostly compatible with the PEM RFC 1113 format.
	This makes it easier to send encrypted files over a 7-bit channel.
*/

/* ENC is the basic 1 character encoding function to make a char printing */

#define ENC(c) ((int)bintoasc[((c) & 077)])
#define PAD             '='

/* Index this array by a 6 bit value to get the character corresponding
	 to that value. */

static unsigned char bintoasc[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ\
abcdefghijklmnopqrstuvwxyz0123456789+/";

/* Index this array by a 7 bit value to get the 6-bit binary field
	 corresponding to that value.  Any illegal characters return high bit set. */

static unsigned char asctobin[] =
{
	0200,0200,0200,0200,0200,0200,0200,0200,
	0200,0200,0200,0200,0200,0200,0200,0200,
	0200,0200,0200,0200,0200,0200,0200,0200,
	0200,0200,0200,0200,0200,0200,0200,0200,
	0200,0200,0200,0200,0200,0200,0200,0200,
	0200,0200,0200,0076,0200,0200,0200,0077,
	0064,0065,0066,0067,0070,0071,0072,0073,
	0074,0075,0200,0200,0200,0200,0200,0200,
	0200,0000,0001,0002,0003,0004,0005,0006,
	0007,0010,0011,0012,0013,0014,0015,0016,
	0017,0020,0021,0022,0023,0024,0025,0026,
	0027,0030,0031,0200,0200,0200,0200,0200,
	0200,0032,0033,0034,0035,0036,0037,0040,
	0041,0042,0043,0044,0045,0046,0047,0050,
	0051,0052,0053,0054,0055,0056,0057,0060,
	0061,0062,0063,0200,0200,0200,0200,0200
};

static void encode PROTO_LIST((unsigned char [4], unsigned char [3], int ));

/* This will always returns 0.  It is an int function for future compatibility,
	 done to provide compatibility with RSAREF(tm). */

int R_EncodePEMBlock(encodedBlock, encodedBlockLen, block, blockLen)
unsigned char *encodedBlock;    /* encoded block */
unsigned int *encodedBlockLen;  /* length of encoded block */
unsigned char *block;           /* block */
unsigned int blockLen;          /* length of block */
{
	unsigned int i, lastLen;

	if(blockLen < 1) {
		*encodedBlockLen = 0;
		return (ID_OK);
	}

	*encodedBlockLen = 0;

        /* Bug Fixed By SK 02/09/95 */
    for (i = 0, lastLen = blockLen; i < blockLen; i += 3) {
        encode(&encodedBlock[4*i/3], &block[i], (lastLen >= 3 ? 3 : lastLen));
        lastLen -= 3;
		*encodedBlockLen += 4;
	}

	return(ID_OK);
}

int R_DecodePEMBlock (outbuf, outlength, inbuf, inlength)
unsigned char *outbuf;          /* block */
unsigned int *outlength;        /* length of block */
unsigned char *inbuf;           /* encoded block */
unsigned int inlength;          /* length of encoded block */
{
	unsigned char *bp;
	int     length;
	unsigned int c1,c2,c3,c4;
	register int j;

	if(inlength % 4)
		return (RE_ENCODING);

	if(inlength < 1) {
		*outlength = 0;
		return (ID_OK);
	}

	length = 0;
	bp = (unsigned char *)inbuf;

	/* FOUR input characters go into each THREE output charcters */

	while(inlength > 0) {
		if(*bp&0x80 || (c1=asctobin[*bp])&0x80)
			return(RE_ENCODING);
		++bp;
		if(*bp&0x80 || (c2=asctobin[*bp])&0x80)
			return(RE_ENCODING);
		if(*++bp == PAD){
			c3 = c4 = 0;
			length += 1;
			if(*++bp != PAD)
				return(RE_ENCODING);
		}
		else if(*bp&0x80 || (c3=asctobin[*bp])&0x80)
				return(RE_ENCODING);
		else
        {
			if(*++bp == PAD)
            {
				c4 = 0;
				length += 2;
			}
			else if (*bp&0x80 || (c4=asctobin[*bp])&0x80)
				return(RE_ENCODING);
			else
				length += 3;
		}
		++bp;
		j = (c1 << 2) | (c2 >> 4);
		*outbuf++=j;
		j = (c2 << 4) | (c3 >> 2);
		*outbuf++=j;
		j = (c3 << 6) | c4;
		*outbuf++=j;
		inlength -= 4;
	}

	*outlength = length;
	return(ID_OK);   /* normal return */

}

/*
	Output one group of up to 3 bytes, pointed at by p, to buffer at f.
	If fewer than 3 are present, the 1 or two extras must be zeros.
*/

static void encode(f, p, count)
unsigned char *f;               /* output buffer */
unsigned char *p;               /* input buffer */
int count;                      /* count */
{
	int c1, c2, c3, c4;

	c1 = *p >> 2;
	c2 = ((*p << 4) & 060) | ((p[1] >> 4) & 017);
	c3 = ((p[1] << 2) & 074) | ((p[2] >> 6) & 03);
	c4 = p[2] & 077;
	*f++ = ENC(c1);
	*f++ = ENC(c2);
	if (count == 1)
	{
		*f++ = PAD;
		*f++ = PAD;
	}else{
		*f++ = ENC(c3);
		if(count == 2) *f++ = PAD;
		else *f++ = ENC(c4);
	}
}