/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Portions Copyright (c) 1995 by International Business Machines, Inc.
 *
 * International Business Machines, Inc. (hereinafter called IBM) grants
 * permission under its copyrights to use, copy, modify, and distribute this
 * Software with or without fee, provided that the above copyright notice and
 * all paragraphs of this notice appear in all copies, and that the name of IBM
 * not be used in connection with the marketing of any product incorporating
 * the Software or modifications thereof, without specific, written prior
 * permission.
 *
 * To the extent it has a right to do so, IBM grants an immunity from suit
 * under its patents, if any, for the use, sale or manufacture of products to
 * the extent that such products are used for performing Domain Name System
 * dynamic updates in TCP/IP networks by means of the Software.  No immunity is
 * granted for any product per se or for any other function of any product.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", AND IBM DISCLAIMS ALL WARRANTIES,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE.  IN NO EVENT SHALL IBM BE LIABLE FOR ANY SPECIAL,
 * DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE, EVEN
 * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
 */
#include "validator-internal.h"

#define Assert(Cond) if (!(Cond)) abort()

static const char Base64[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char Pad64 = '=';

/*
 * (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
 * The following encoding technique is taken from RFC 1521 by Borenstein
 * and Freed.  It is reproduced here in a slightly edited form for
 * convenience.
 * 
 * A 65-character subset of US-ASCII is used, enabling 6 bits to be
 * represented per printable character. (The extra 65th character, "=",
 * is used to signify a special processing function.)
 * 
 * The encoding process represents 24-bit groups of input bits as output
 * strings of 4 encoded characters. Proceeding from left to right, a
 * 24-bit input group is formed by concatenating 3 8-bit input groups.
 * These 24 bits are then treated as 4 concatenated 6-bit groups, each
 * of which is translated into a single digit in the base64 alphabet.
 * 
 * Each 6-bit group is used as an index into an array of 64 printable
 * characters. The character referenced by the index is placed in the
 * output string.
 * 
 * Table 1: The Base64 Alphabet
 * 
 * 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
 * 
 * Special processing is performed if fewer than 24 bits are available
 * at the end of the data being encoded.  A full encoding quantum is
 * always completed at the end of a quantity.  When fewer than 24 input
 * bits are available in an input group, zero bits are added (on the
 * right) to form an integral number of 6-bit groups.  Padding at the
 * end of the data is performed using the '=' character.
 * 
 * Since all base64 input is an integral number of octets, only the
 * -------------------------------------------------                       
 * following cases can arise:
 * 
 * (1) the final quantum of encoding input is an integral
 * multiple of 24 bits; here, the final unit of encoded
 * output will be an integral multiple of 4 characters
 * with no "=" padding,
 * (2) the final quantum of encoding input is exactly 8 bits;
 * here, the final unit of encoded output will be two
 * characters followed by two "=" padding characters, or
 * (3) the final quantum of encoding input is exactly 16 bits;
 * here, the final unit of encoded output will be three
 * characters followed by one "=" padding character.
 */

int
b64_ntop(u_char const *src, size_t srclength, char *target,
         size_t targsize)
{
    size_t          datalength = 0;
    u_char          input[3];
    u_char          output[4];
    size_t          i;

    while (2U < srclength) {
        input[0] = *src++;
        input[1] = *src++;
        input[2] = *src++;
        srclength -= 3;

        output[0] = input[0] >> 2;
        output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
        output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
        output[3] = input[2] & 0x3f;
        Assert(output[0] < 64);
        Assert(output[1] < 64);
        Assert(output[2] < 64);
        Assert(output[3] < 64);

        if (datalength + 4 > targsize)
            return (-1);
        target[datalength++] = Base64[output[0]];
        target[datalength++] = Base64[output[1]];
        target[datalength++] = Base64[output[2]];
        target[datalength++] = Base64[output[3]];
    }

    /*
     * Now we worry about padding. 
     */
    if (0U != srclength) {
        /*
         * Get what's left. 
         */
        input[0] = input[1] = input[2] = '\0';
        for (i = 0; i < srclength; i++)
            input[i] = *src++;

        output[0] = input[0] >> 2;
        output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
        output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
        Assert(output[0] < 64);
        Assert(output[1] < 64);
        Assert(output[2] < 64);

        if (datalength + 4 > targsize)
            return (-1);
        target[datalength++] = Base64[output[0]];
        target[datalength++] = Base64[output[1]];
        if (srclength == 1U)
            target[datalength++] = Pad64;
        else
            target[datalength++] = Base64[output[2]];
        target[datalength++] = Pad64;
    }
    if (datalength >= targsize)
        return (-1);
    target[datalength] = '\0';  /* Returned value doesn't count \0. */
    return (datalength);
}

/*
 * skips all whitespace anywhere.
 * converts characters, four at a time, starting at (or after)
 * src from base - 64 numbers into three 8 bit bytes in the target area.
 * it returns the number of data bytes stored at the target, or -1 on error.
 */

int
b64_pton(const char *src, u_char *target, size_t targsize)
{
    int             tarindex, state, ch;
    const char      *pos;

    state = 0;
    tarindex = 0;

    while ((ch = *src++) != '\0') {
        if (isspace(ch))        /* Skip whitespace anywhere. */
            continue;

        if (ch == Pad64)
            break;

        pos = strchr(Base64, ch);
        if (pos == 0)           /* A non-base64 character. */
            return (-1);

        switch (state) {
        case 0:
            if (target) {
                if ((size_t) tarindex >= targsize)
                    return (-1);
                target[tarindex] = (pos - Base64) << 2;
            }
            state = 1;
            break;
        case 1:
            if (target) {
                if ((size_t) tarindex + 1 >= targsize)
                    return (-1);
                target[tarindex] |= (pos - Base64) >> 4;
                target[tarindex + 1] = ((pos - Base64) & 0x0f)
                    << 4;
            }
            tarindex++;
            state = 2;
            break;
        case 2:
            if (target) {
                if ((size_t) tarindex + 1 >= targsize)
                    return (-1);
                target[tarindex] |= (pos - Base64) >> 2;
                target[tarindex + 1] = ((pos - Base64) & 0x03)
                    << 6;
            }
            tarindex++;
            state = 3;
            break;
        case 3:
            if (target) {
                if ((size_t) tarindex >= targsize)
                    return (-1);
                target[tarindex] |= (pos - Base64);
            }
            tarindex++;
            state = 0;
            break;
        default:
            abort();
        }
    }

    /*
     * We are done decoding Base-64 chars.  Let's see if we ended
     * on a byte boundary, and/or with erroneous trailing characters.
     */

    if (ch == Pad64) {          /* We got a pad char. */
        ch = *src++;            /* Skip it, get next. */
        switch (state) {
        case 0:                /* Invalid = in first position */
        case 1:                /* Invalid = in second position */
            return (-1);

        case 2:                /* Valid, means one byte of info */
            /*
             * Skip any number of spaces. 
             */
            for ((void) NULL; ch != '\0'; ch = *src++)
                if (!isspace(ch))
                    break;
            /*
             * Make sure there is another trailing = sign. 
             */
            if (ch != Pad64)
                return (-1);
            ch = *src++;        /* Skip the = */
            /*
             * Fall through to "single trailing =" case. 
             */
            /** FALLTHROUGH */

        case 3:                /* Valid, means two bytes of info */
            /*
             * We know this char is an =.  Is there anything but
             * whitespace after it?
             */
            for ((void) NULL; ch != '\0'; ch = *src++)
                if (!isspace(ch))
                    return (-1);

            /*
             * Now make sure for cases 2 and 3 that the "extra"
             * bits that slopped past the last full byte were
             * zeros.  If we don't check them, they become a
             * subliminal channel.
             */
            if (target && target[tarindex] != 0)
                return (-1);
        }
    } else {
        /*
         * We ended by seeing the end of the string.  Make sure we
         * have no partial bytes lying around.
         */
        if (state != 0)
            return (-1);
    }

    return (tarindex);
}
