// SPDX-License-Identifier: GPL-2.0-only
/*
 * vpd_decode.c
 *
 * Google VPD decoding routines.
 *
 * Copyright 2017 Google Inc.
 */

#include "vpd_decode.h"

static int vpd_decode_len(const u32 max_len, const u8 *in,
                          u32 *length, u32 *decoded_len)
{
        u8 more;
        int i = 0;

        if (!length || !decoded_len)
                return VPD_FAIL;

        *length = 0;
        do {
                if (i >= max_len)
                        return VPD_FAIL;

                more = in[i] & 0x80;
                *length <<= 7;
                *length |= in[i] & 0x7f;
                ++i;
        } while (more);

        *decoded_len = i;
        return VPD_OK;
}

static int vpd_decode_entry(const u32 max_len, const u8 *input_buf,
                            u32 *_consumed, const u8 **entry, u32 *entry_len)
{
        u32 decoded_len;
        u32 consumed = *_consumed;

        if (vpd_decode_len(max_len - consumed, &input_buf[consumed],
                           entry_len, &decoded_len) != VPD_OK)
                return VPD_FAIL;
        if (max_len - consumed < decoded_len)
                return VPD_FAIL;

        consumed += decoded_len;
        *entry = input_buf + consumed;

        /* entry_len is untrusted data and must be checked again. */
        if (max_len - consumed < *entry_len)
                return VPD_FAIL;

        consumed += *entry_len;
        *_consumed = consumed;
        return VPD_OK;
}

int vpd_decode_string(const u32 max_len, const u8 *input_buf, u32 *consumed,
                      vpd_decode_callback callback, void *callback_arg)
{
        int type;
        u32 key_len;
        u32 value_len;
        const u8 *key;
        const u8 *value;

        /* type */
        if (*consumed >= max_len)
                return VPD_FAIL;

        type = input_buf[*consumed];

        switch (type) {
        case VPD_TYPE_INFO:
        case VPD_TYPE_STRING:
                (*consumed)++;

                if (vpd_decode_entry(max_len, input_buf, consumed, &key,
                                     &key_len) != VPD_OK)
                        return VPD_FAIL;

                if (vpd_decode_entry(max_len, input_buf, consumed, &value,
                                     &value_len) != VPD_OK)
                        return VPD_FAIL;

                if (type == VPD_TYPE_STRING)
                        return callback(key, key_len, value, value_len,
                                        callback_arg);
                break;

        default:
                return VPD_FAIL;
        }

        return VPD_OK;
}