/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or 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.
 */

/* $Id: base32.c,v 1.8 2020/09/14 08:40:44 florian Exp $ */

/*! \file */

#include <isc/base32.h>
#include <isc/buffer.h>
#include <isc/region.h>
#include <string.h>
#include <isc/util.h>

#define RETERR(x) do { \
        isc_result_t _r = (x); \
        if (_r != ISC_R_SUCCESS) \
                return (_r); \
        } while (0)

/*@}*/

static const char base32hex[] =
        "0123456789ABCDEFGHIJKLMNOPQRSTUV=0123456789abcdefghijklmnopqrstuv";

static isc_result_t
base32_totext(isc_region_t *source, int wordlength, const char *wordbreak,
              isc_buffer_t *target, const char base[], char pad)
{
        char buf[9];
        unsigned int loops = 0;

        if (wordlength >= 0 && wordlength < 8)
                wordlength = 8;

        memset(buf, 0, sizeof(buf));
        while (source->length > 0) {
                buf[0] = base[((source->base[0]>>3)&0x1f)];     /* 5 + */
                if (source->length == 1) {
                        buf[1] = base[(source->base[0]<<2)&0x1c];
                        buf[2] = buf[3] = buf[4] = pad;
                        buf[5] = buf[6] = buf[7] = pad;
                        RETERR(isc_str_tobuffer(buf, target));
                        break;
                }
                buf[1] = base[((source->base[0]<<2)&0x1c)|      /* 3 = 8 */
                              ((source->base[1]>>6)&0x03)];     /* 2 + */
                buf[2] = base[((source->base[1]>>1)&0x1f)];     /* 5 + */
                if (source->length == 2) {
                        buf[3] = base[(source->base[1]<<4)&0x10];
                        buf[4] = buf[5] = buf[6] = buf[7] = pad;
                        RETERR(isc_str_tobuffer(buf, target));
                        break;
                }
                buf[3] = base[((source->base[1]<<4)&0x10)|      /* 1 = 8 */
                              ((source->base[2]>>4)&0x0f)];     /* 4 + */
                if (source->length == 3) {
                        buf[4] = base[(source->base[2]<<1)&0x1e];
                        buf[5] = buf[6] = buf[7] = pad;
                        RETERR(isc_str_tobuffer(buf, target));
                        break;
                }
                buf[4] = base[((source->base[2]<<1)&0x1e)|      /* 4 = 8 */
                              ((source->base[3]>>7)&0x01)];     /* 1 + */
                buf[5] = base[((source->base[3]>>2)&0x1f)];     /* 5 + */
                if (source->length == 4) {
                        buf[6] = base[(source->base[3]<<3)&0x18];
                        buf[7] = pad;
                        RETERR(isc_str_tobuffer(buf, target));
                        break;
                }
                buf[6] = base[((source->base[3]<<3)&0x18)|      /* 2 = 8 */
                              ((source->base[4]>>5)&0x07)];     /* 3 + */
                buf[7] = base[source->base[4]&0x1f];            /* 5 = 8 */
                RETERR(isc_str_tobuffer(buf, target));
                isc_region_consume(source, 5);

                loops++;
                if (source->length != 0 && wordlength >= 0 &&
                    (int)((loops + 1) * 8) >= wordlength)
                {
                        loops = 0;
                        RETERR(isc_str_tobuffer(wordbreak, target));
                }
        }
        if (source->length > 0)
                isc_region_consume(source, source->length);
        return (ISC_R_SUCCESS);
}

isc_result_t
isc_base32hexnp_totext(isc_region_t *source, int wordlength,
                     const char *wordbreak, isc_buffer_t *target)
{
        return (base32_totext(source, wordlength, wordbreak, target,
                              base32hex, 0));
}

/*%
 * State of a base32 decoding process in progress.
 */
typedef struct {
        int length;             /*%< Desired length of binary data or -1 */
        isc_buffer_t *target;   /*%< Buffer for resulting binary data */
        int digits;             /*%< Number of buffered base32 digits */
        int seen_end;   /*%< True if "=" end marker seen */
        int val[8];
        const char *base;       /*%< Which encoding we are using */
        int seen_32;            /*%< Number of significant bytes if non zero */
        int pad;        /*%< Expect padding */
} base32_decode_ctx_t;

static inline void
base32_decode_init(base32_decode_ctx_t *ctx, int length, const char base[],
                   int pad, isc_buffer_t *target)
{
        ctx->digits = 0;
        ctx->seen_end = 0;
        ctx->seen_32 = 0;
        ctx->length = length;
        ctx->target = target;
        ctx->base = base;
        ctx->pad = pad;
}

static inline isc_result_t
base32_decode_char(base32_decode_ctx_t *ctx, int c) {
        const char *s;
        unsigned int last;

        if (ctx->seen_end)
                return (ISC_R_BADBASE32);
        if ((s = strchr(ctx->base, c)) == NULL)
                return (ISC_R_BADBASE32);
        last = (unsigned int)(s - ctx->base);

        /*
         * Handle lower case.
         */
        if (last > 32)
                last -= 33;

        /*
         * Check that padding is contiguous.
         */
        if (last != 32 && ctx->seen_32 != 0)
                return (ISC_R_BADBASE32);

        /*
         * If padding is not permitted flag padding as a error.
         */
        if (last == 32 && !ctx->pad)
                return (ISC_R_BADBASE32);

        /*
         * Check that padding starts at the right place and that
         * bits that should be zero are.
         * Record how many significant bytes in answer (seen_32).
         */
        if (last == 32 && ctx->seen_32 == 0)
                switch (ctx->digits) {
                case 0:
                case 1:
                        return (ISC_R_BADBASE32);
                case 2:
                        if ((ctx->val[1]&0x03) != 0)
                                return (ISC_R_BADBASE32);
                        ctx->seen_32 = 1;
                        break;
                case 3:
                        return (ISC_R_BADBASE32);
                case 4:
                        if ((ctx->val[3]&0x0f) != 0)
                                return (ISC_R_BADBASE32);
                        ctx->seen_32 = 3;
                        break;
                case 5:
                        if ((ctx->val[4]&0x01) != 0)
                                return (ISC_R_BADBASE32);
                        ctx->seen_32 = 3;
                        break;
                case 6:
                        return (ISC_R_BADBASE32);
                case 7:
                        if ((ctx->val[6]&0x07) != 0)
                                return (ISC_R_BADBASE32);
                        ctx->seen_32 = 4;
                        break;
                }

        /*
         * Zero fill pad values.
         */
        ctx->val[ctx->digits++] = (last == 32) ? 0 : last;

        if (ctx->digits == 8) {
                int n = 5;
                unsigned char buf[5];

                if (ctx->seen_32 != 0) {
                        ctx->seen_end = 1;
                        n = ctx->seen_32;
                }
                buf[0] = (ctx->val[0]<<3)|(ctx->val[1]>>2);
                buf[1] = (ctx->val[1]<<6)|(ctx->val[2]<<1)|(ctx->val[3]>>4);
                buf[2] = (ctx->val[3]<<4)|(ctx->val[4]>>1);
                buf[3] = (ctx->val[4]<<7)|(ctx->val[5]<<2)|(ctx->val[6]>>3);
                buf[4] = (ctx->val[6]<<5)|(ctx->val[7]);
                RETERR(isc_mem_tobuffer(ctx->target, buf, n));
                if (ctx->length >= 0) {
                        if (n > ctx->length)
                                return (ISC_R_BADBASE32);
                        else
                                ctx->length -= n;
                }
                ctx->digits = 0;
        }
        return (ISC_R_SUCCESS);
}

static inline isc_result_t
base32_decode_finish(base32_decode_ctx_t *ctx) {

        if (ctx->length > 0)
                return (ISC_R_UNEXPECTEDEND);
        /*
         * Add missing padding if required.
         */
        if (!ctx->pad && ctx->digits != 0) {
                ctx->pad = 1;
                do {
                        RETERR(base32_decode_char(ctx, '='));
                } while (ctx->digits != 0);
        }
        if (ctx->digits != 0)
                return (ISC_R_BADBASE32);
        return (ISC_R_SUCCESS);
}

static isc_result_t
base32_decoderegion(isc_region_t *source, const char base[],
                    int pad, isc_buffer_t *target)
{
        base32_decode_ctx_t ctx;

        base32_decode_init(&ctx, -1, base, pad, target);
        while (source->length != 0) {
                int c = *source->base;
                RETERR(base32_decode_char(&ctx, c));
                isc_region_consume(source, 1);
        }
        RETERR(base32_decode_finish(&ctx));
        return (ISC_R_SUCCESS);
}

isc_result_t
isc_base32hexnp_decoderegion(isc_region_t *source, isc_buffer_t *target) {
        return (base32_decoderegion(source, base32hex, 0, target));
}