/* tvbuff_base64.c

 * Base-64 tvbuff implementation (based on real tvb)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <glib.h>

#include <epan/tvbuff.h>

#include "proto.h"

/* Copy of glib function modified for base64uri */

static const unsigned char mime_base64uri_rank[256] = {

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255, 255,255,63,255,255,

   52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,  0,255,255,

  255,  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, 25,255,255,255,255, 63,

  255, 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, 51,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,

};

 /**

  * Copy of glib function modified for base64uri

  * g_base64uri_decode_step: (skip)

  * @in: (array length=len) (element-type uint8_t): binary input data

  * @len: max length of @in data to decode

  * @out: (out caller-allocates) (array) (element-type uint8_t): output buffer

  * @state: (inout): Saved state between steps, initialize to 0

  * @save: (inout): Saved state between steps, initialize to 0

  *

  * Incrementally decode a sequence of binary data from its Base-64 stringified

  * representation. By calling this function multiple times you can convert

  * data in chunks to avoid having to have the full encoded data in memory.

  *

  * The output buffer must be large enough to fit all the data that will

  * be written to it. Since base64 encodes 3 bytes in 4 chars you need

  * at least: (@len / 4) * 3 + 3 bytes (+ 3 may be needed in case of non-zero

  * state).

  *

  * Returns: The number of bytes of output that was written

  *

  * Since: 2.12

  **/

static size_t

g_base64uri_decode_step(const char* in,

    size_t        len,

    unsigned char* out,

    int* state,

    unsigned* save)

{

    const unsigned char* inptr;

    unsigned char* outptr;

    const unsigned char* inend;

    unsigned char c, rank;

    unsigned char last[2];

    unsigned int v;

    int i;

    g_return_val_if_fail(in != NULL || len == 0, 0);

    g_return_val_if_fail(out != NULL, 0);

    g_return_val_if_fail(state != NULL, 0);

    g_return_val_if_fail(save != NULL, 0);

    if (len == 0)

        return 0;

    inend = (const unsigned char*)in + len;

    outptr = out;

    /* convert 4 base64 bytes to 3 normal bytes */

    v = *save;

    i = *state;

    last[0] = last[1] = 0;

    /* we use the sign in the state to determine if we got a padding character

       in the previous sequence */

    if (i < 0)

    {

        i = -i;

        last[0] = '=';

    }

    inptr = (const unsigned char*)in;

    while (inptr < inend)

    {

        c = *inptr++;

        rank = mime_base64uri_rank[c];

        if (rank != 0xff)

        {

            last[1] = last[0];

            last[0] = c;

            v = (v << 6) | rank;

            i++;

            if (i == 4)

            {

                *outptr++ = v >> 16;

                if (last[1] != '=')

                    *outptr++ = v >> 8;

                if (last[0] != '=')

                    *outptr++ = v;

                i = 0;

            }

        }

    }

    *save = v;

    *state = last[0] == '=' ? -i : i;

    return outptr - out;

}

 /**

  * Copy of glib function modified for base64uri

  * g_base64uri_decode:

  * @text: (not nullable): zero-terminated string with base64 text to decode

  * @out_len: (out): The length of the decoded data is written here

  *

  * Decode a sequence of Base-64 encoded text into binary data.  Note

  * that the returned binary data is not necessarily zero-terminated,

  * so it should not be used as a character string.

  *

  * Returns: (transfer full) (array length=out_len) (element-type uint8_t):

  *               newly allocated buffer containing the binary data

  *               that @text represents. The returned buffer must

  *               be freed with g_free().

  *

  * Since: 2.12

  */

static unsigned char*

g_base64uri_decode(const char* text,

    size_t* out_len)

{

    unsigned char* ret;

    size_t input_length;

    int state = 0;

    unsigned save = 0;

    g_return_val_if_fail(text != NULL, NULL);

    g_return_val_if_fail(out_len != NULL, NULL);

    input_length = strlen(text);

    /* We can use a smaller limit here, since we know the saved state is 0,

       +1 used to avoid calling g_malloc0(0), and hence returning NULL */

    ret = (unsigned char * )g_malloc0((input_length / 4) * 3 + 1);

    *out_len = g_base64uri_decode_step(text, input_length, ret, &state, &save);

    return ret;

}

tvbuff_t *

base64_to_tvb(tvbuff_t *parent, const char *base64)

{

  tvbuff_t *tvb;

  uint8_t *data;

  size_t len;

  data = g_base64_decode(base64, &len);

  tvb = tvb_new_child_real_data(parent, data, (unsigned)len, (unsigned)len);

  tvb_set_free_cb(tvb, g_free);

  return tvb;

}

tvbuff_t*

base64_tvb_to_new_tvb(tvbuff_t* parent, unsigned offset, unsigned length)

{

    tvbuff_t* tvb;

    uint8_t* data, *tmp;

    size_t len;

    /* g_base64_decode only requires NULL termination, not a valid UTF-8

     * or ASCII string (it silently skips over invalid bytes, we don't

     * check that either). So tvb_get_raw_bytes_as_string() would work,

     * but we would need to check the length before allocating the buffer

     * to avoid a memory leak (or push a CLEANUP function on exception).

     *

     * We could also implement our own function that took a length and

     * didn't require NULL termination.

     */

    tmp = tvb_get_string_enc(NULL, parent, offset, length, ENC_ASCII);

    data = g_base64_decode((const char*)tmp, &len);

    wmem_free(NULL, tmp);

    tvb = tvb_new_child_real_data(parent, data, (unsigned)len, (unsigned)len);

    tvb_set_free_cb(tvb, g_free);

    return tvb;

}

tvbuff_t*

base64uri_tvb_to_new_tvb(tvbuff_t* parent, unsigned offset, unsigned length)

{

    tvbuff_t* tvb;

    uint8_t* data, *tmp;

    size_t len = 0;

    tmp = tvb_get_string_enc(NULL, parent, offset, length, ENC_ASCII);

    data = g_base64uri_decode((const char*)tmp, &len);

    wmem_free(NULL, tmp);

    tvb = tvb_new_child_real_data(parent, data, (unsigned)len, (unsigned)len);

    tvb_set_free_cb(tvb, g_free);

    return tvb;

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local Variables:

 * c-basic-offset: 2

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=2 tabstop=8 expandtab:

 * :indentSize=2:tabSize=8:noTabs=true:

 */