/*
 *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
 *
 *  Licensed under the Apache License, Version 2.0 (the License); you may
 *  not use this file except in compliance with the License.
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <assert.h>
#include <gmssl/base64.h>
#include <gmssl/error.h>

static unsigned char conv_ascii2bin(unsigned char a);
#define conv_bin2ascii(a)       (data_bin2ascii[(a)&0x3f])


/*-
 * 64 char lines
 * pad input with 0
 * left over chars are set to =
 * 1 byte  => xx==
 * 2 bytes => xxx=
 * 3 bytes => xxxx
 */
#define BIN_PER_LINE    (64/4*3)
#define CHUNKS_PER_LINE (64/4)
#define CHAR_PER_LINE   (64+1)

static const unsigned char data_bin2ascii[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ\
abcdefghijklmnopqrstuvwxyz0123456789+/";

/*-
 * 0xF0 is a EOLN
 * 0xF1 is ignore but next needs to be 0xF0 (for \r\n processing).
 * 0xF2 is EOF
 * 0xE0 is ignore at start of line.
 * 0xFF is error
 */

#define B64_EOLN                0xF0
#define B64_CR                  0xF1
#define B64_EOF                 0xF2
#define B64_WS                  0xE0
#define B64_ERROR               0xFF
#define B64_NOT_BASE64(a)       (((a)|0x13) == 0xF3)
#define B64_BASE64(a)           (!B64_NOT_BASE64(a))

static const unsigned char data_ascii2bin[128] = {
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    0xFF, 0xE0, 0xF0, 0xFF, 0xFF, 0xF1, 0xFF, 0xFF,
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    0xE0, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0xF2, 0xFF, 0x3F,
    0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B,
    0x3C, 0x3D, 0xFF, 0xFF, 0xFF, 0x00, 0xFF, 0xFF,
    0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
    0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
    0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
    0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20,
    0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
    0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30,
    0x31, 0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
};

static unsigned char conv_ascii2bin(unsigned char a)
{
    if (a & 0x80)
        return B64_ERROR;
    return data_ascii2bin[a];
}


int base64_ctx_num(BASE64_CTX *ctx)
{
    return ctx->num;
}

void base64_encode_init(BASE64_CTX *ctx)
{
    ctx->length = 48;
    ctx->num = 0;
    ctx->line_num = 0;
}

int base64_encode_update(BASE64_CTX *ctx, const uint8_t *in, int inl, uint8_t *out, int *outl)
{
    int i, j;
    size_t total = 0;

    *outl = 0;
    if (inl <= 0)
        return 0;
    assert(ctx->length <= (int)sizeof(ctx->enc_data));
    if (ctx->length - ctx->num > inl) {
        memcpy(&(ctx->enc_data[ctx->num]), in, inl);
        ctx->num += inl;
        return 1;
    }
    if (ctx->num != 0) {
        i = ctx->length - ctx->num;
        memcpy(&(ctx->enc_data[ctx->num]), in, i);
        in += i;
        inl -= i;
        j = base64_encode_block(out, ctx->enc_data, ctx->length);
        ctx->num = 0;
        out += j;
        *(out++) = '\n';
        *out = '\0';
        total = j + 1;
    }
    while (inl >= ctx->length && total <= INT_MAX) {
        j = base64_encode_block(out, in, ctx->length);
        in += ctx->length;
        inl -= ctx->length;
        out += j;
        *(out++) = '\n';
        *out = '\0';
        total += j + 1;
    }
    if (total > INT_MAX) {
        /* Too much output data! */
        *outl = 0;
        return 0;
    }
    if (inl != 0)
        memcpy(&(ctx->enc_data[0]), in, inl);
    ctx->num = inl;
    *outl = (int)total;

    return 1;
}

void base64_encode_finish(BASE64_CTX *ctx, uint8_t *out, int *outl)
{
    unsigned int ret = 0;

    if (ctx->num != 0) {
        ret = base64_encode_block(out, ctx->enc_data, ctx->num);
        out[ret++] = '\n';
        out[ret] = '\0';
        ctx->num = 0;
    }
    *outl = ret;
}

int base64_encode_block(unsigned char *t, const unsigned char *f, int dlen)
{
    int i, ret = 0;
    unsigned long l;

    for (i = dlen; i > 0; i -= 3) {
        if (i >= 3) {
            l = (((unsigned long)f[0]) << 16L) |
                (((unsigned long)f[1]) << 8L) | f[2];
            *(t++) = conv_bin2ascii(l >> 18L);
            *(t++) = conv_bin2ascii(l >> 12L);
            *(t++) = conv_bin2ascii(l >> 6L);
            *(t++) = conv_bin2ascii(l);
        } else {
            l = ((unsigned long)f[0]) << 16L;
            if (i == 2)
                l |= ((unsigned long)f[1] << 8L);

            *(t++) = conv_bin2ascii(l >> 18L);
            *(t++) = conv_bin2ascii(l >> 12L);
            *(t++) = (i == 1) ? '=' : conv_bin2ascii(l >> 6L);
            *(t++) = '=';
        }
        ret += 4;
        f += 3;
    }

    *t = '\0';
    return (ret);
}

void base64_decode_init(BASE64_CTX *ctx)
{
    /* Only ctx->num is used during decoding. */
    ctx->num = 0;
    ctx->length = 0;
    ctx->line_num = 0;
    ctx->expect_nl = 0;
}

/*-
 * -1 for error
 *  0 for last line
 *  1 for full line
 *
 * Note: even though base64_decode_update attempts to detect and report end of
 * content, the context doesn't currently remember it and will accept more data
 * in the next call. Therefore, the caller is responsible for checking and
 * rejecting a 0 return value in the middle of content.
 *
 * Note: even though base64_decode_update has historically tried to detect end of
 * content based on line length, this has never worked properly. Therefore,
 * we now return 0 when one of the following is true:
 *   - Padding or B64_EOF was detected and the last block is complete.
 *   - Input has zero-length.
 * -1 is returned if:
 *   - Invalid characters are detected.
 *   - There is extra trailing padding, or data after padding.
 *   - B64_EOF is detected after an incomplete base64 block.
 */
int base64_decode_update_ex(BASE64_CTX *ctx, const uint8_t *in, int inl, uint8_t *out, int *outl, size_t maxout)
{
    int seof = 0, eof = 0, rv = -1, ret = 0, i, v, tmp, n, decoded_len, block_len, output_len;
    unsigned char *d;
    unsigned char block[BIN_PER_LINE];
    unsigned char *p;

    n = ctx->num;
    d = ctx->enc_data;

    if (n > 0 && d[n - 1] == '=') {
        eof++;
        if (n > 1 && d[n - 2] == '=')
            eof++;
    }

     /* Legacy behaviour: an empty input chunk signals end of input. */
    if (inl == 0) {
        rv = 0;
        goto end;
    }

    for (i = 0; i < inl; i++) {
        tmp = *(in++);
        v = conv_ascii2bin(tmp);
        if (v == B64_ERROR) {
            rv = -1;
		error_print();
            goto end;
        }

        if (tmp == '=') {
            eof++;
        } else if (eof > 0 && B64_BASE64(v)) {
            /* More data after padding. */
            rv = -1;
		error_print();
            goto end;
        }

        if (eof > 2) {
            rv = -1;
		error_print();
            goto end;
        }

        if (v == B64_EOF) {
            seof = 1;
            goto tail;
        }

        /* Only save valid base64 characters. */
        if (B64_BASE64(v)) {
            if (n >= 64) {
                /*
                 * We increment n once per loop, and empty the buffer as soon as
                 * we reach 64 characters, so this can only happen if someone's
                 * manually messed with the ctx. Refuse to write any more data.
                 */
                rv = -1;
		error_print();
                goto end;
            }
            assert(n < (int)sizeof(ctx->enc_data));
            d[n++] = tmp;
        }

        if (n == 64) {
            block_len = n / 4 * 3;
            output_len = block_len - eof;
            if (eof > block_len
                || (size_t)ret > maxout
                || (size_t)output_len > maxout - (size_t)ret) {
		error_print();
                rv = -1;
                goto end;
            }
            p = eof ? block : out;
            decoded_len = base64_decode_block(p, d, n);
            n = 0;
            if (decoded_len < 0 || eof > decoded_len) {
                rv = -1;
                goto end;
            }
            if (eof && output_len > 0) {
                memcpy(out, block, output_len);
            }
            ret += output_len;
            out += output_len;
        }
    }

    /*
     * Legacy behaviour: if the current line is a full base64-block (i.e., has
     * 0 mod 4 base64 characters), it is processed immediately. We keep this
     * behaviour as applications may not be calling base64_decode_final properly.
     */
tail:
    if (n > 0) {
        if ((n & 3) == 0) {
            block_len = n / 4 * 3;
            output_len = block_len - eof;
            if (eof > block_len
                || (size_t)ret > maxout
                || (size_t)output_len > maxout - (size_t)ret) {
		error_print();
                rv = -1;
                goto end;
            }
            p = eof ? block : out;
            decoded_len = base64_decode_block(p, d, n);
            n = 0;
            if (decoded_len < 0 || eof > decoded_len) {
		error_print();
                rv = -1;
                goto end;
            }
            if (eof && output_len > 0) {
                memcpy(out, block, output_len);
            }
            ret += output_len;
            out += output_len;
        } else if (seof) {
            /* EOF in the middle of a base64 block. */
		error_print();
            rv = -1;
            goto end;
        }
    }

    rv = seof || (n == 0 && eof) ? 0 : 1;
end:
    /* Legacy behaviour. This should probably rather be zeroed on error. */
    *outl = ret;
    ctx->num = n;
    return (rv);
}

int base64_decode_update(BASE64_CTX *ctx, const uint8_t *in, int inl, uint8_t *out, int *outl)
{
    return base64_decode_update_ex(ctx, in, inl, out, outl, (size_t)-1);
}

int base64_decode_block(unsigned char *t, const unsigned char *f, int n)
{
    int i, ret = 0, a, b, c, d;
    unsigned long l;

    /* trim white space from the start of the line. */
    while ((conv_ascii2bin(*f) == B64_WS) && (n > 0)) {
        f++;
        n--;
    }

    /*
     * strip off stuff at the end of the line ascii2bin values B64_WS,
     * B64_EOLN, B64_EOLN and B64_EOF
     */
    while ((n > 3) && (B64_NOT_BASE64(conv_ascii2bin(f[n - 1]))))
        n--;

    if (n % 4 != 0)
        return (-1);

    for (i = 0; i < n; i += 4) {
        a = conv_ascii2bin(*(f++));
        b = conv_ascii2bin(*(f++));
        c = conv_ascii2bin(*(f++));
        d = conv_ascii2bin(*(f++));
        if ((a & 0x80) || (b & 0x80) || (c & 0x80) || (d & 0x80))
            return (-1);
        l = ((((unsigned long)a) << 18L) |
             (((unsigned long)b) << 12L) |
             (((unsigned long)c) << 6L) | (((unsigned long)d)));
        *(t++) = (unsigned char)(l >> 16L) & 0xff;
        *(t++) = (unsigned char)(l >> 8L) & 0xff;
        *(t++) = (unsigned char)(l) & 0xff;
        ret += 3;
    }
    return (ret);
}

int base64_decode_finish_ex(BASE64_CTX *ctx, uint8_t *out, int *outl, size_t maxout)
{
    int i;

    *outl = 0;
    if (ctx->num != 0) {
        if ((ctx->num & 3) != 0
            || (size_t)(ctx->num / 4 * 3) > maxout) {
		error_print();
            return (-1);
        }
        i = base64_decode_block(out, ctx->enc_data, ctx->num);
        if (i < 0) {
		error_print();
            return (-1);
        }
        ctx->num = 0;
        *outl = i;
        return (1);
    } else
        return (1);
}

int base64_decode_finish(BASE64_CTX *ctx, uint8_t *out, int *outl)
{
    return base64_decode_finish_ex(ctx, out, outl, (size_t)-1);
}
