/*
 * Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * This is a decoder that's completely internal to the 'file:' store
 * implementation.  Only code in file_store.c know about this one.  Because
 * of this close relationship, we can cut certain corners, such as making
 * assumptions about the "provider context", which is currently simply the
 * provider context that the file_store.c code operates within.
 *
 * All this does is to read DER from the input if it can, and passes it on
 * to the data callback as an object abstraction, leaving it to the callback
 * to figure out what it actually is.
 *
 * This MUST be made the last decoder in a chain, leaving it to other more
 * specialized decoders to recognise and process their stuff first.
 */

#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
#include <openssl/core_object.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>
#include <openssl/err.h>
#include <openssl/asn1err.h>
#include <openssl/params.h>
#include "internal/asn1.h"
#include "prov/bio.h"
#include "file_store_local.h"

/*
 * newctx and freectx are not strictly necessary.  However, the method creator,
 * ossl_decoder_from_dispatch(), demands that they exist, so we make sure to
 * oblige.
 */

static OSSL_FUNC_decoder_newctx_fn der2obj_newctx;
static OSSL_FUNC_decoder_freectx_fn der2obj_freectx;

static void *der2obj_newctx(void *provctx)
{
    return provctx;
}

static void der2obj_freectx(void *vctx)
{
}

static OSSL_FUNC_decoder_gettable_params_fn der2obj_gettable_params;
static OSSL_FUNC_decoder_get_params_fn der2obj_get_params;
static OSSL_FUNC_decoder_decode_fn der2obj_decode;

static const OSSL_PARAM *der2obj_gettable_params(void *provctx)
{
    static const OSSL_PARAM gettables[] = {
        { OSSL_DECODER_PARAM_INPUT_TYPE, OSSL_PARAM_UTF8_PTR, NULL, 0, 0 },
        OSSL_PARAM_END,
    };

    return gettables;
}

static int der2obj_get_params(OSSL_PARAM params[])
{
    OSSL_PARAM *p;

    p = OSSL_PARAM_locate(params, OSSL_DECODER_PARAM_INPUT_TYPE);
    if (p != NULL && !OSSL_PARAM_set_utf8_ptr(p, "DER"))
        return 0;

    return 1;
}

static int der2obj_decode(void *provctx, OSSL_CORE_BIO *cin, int selection,
                          OSSL_CALLBACK *data_cb, void *data_cbarg,
                          OSSL_PASSPHRASE_CALLBACK *pw_cb, void *pw_cbarg)
{
    /*
     * We're called from file_store.c, so we know that OSSL_CORE_BIO is a
     * BIO in this case.
     */
    BIO *in = (BIO *)cin;
    BUF_MEM *mem = NULL;
    int err, ok;

    ERR_set_mark();
    ok = (asn1_d2i_read_bio(in, &mem) >= 0);
    /*
     * Prune low-level ASN.1 parse errors from error queue, assuming that
     * this is called by decoder_process() in a loop trying several formats.
     */
    err = ERR_peek_last_error();
    if (ERR_GET_LIB(err) == ERR_LIB_ASN1
            && (ERR_GET_REASON(err) == ASN1_R_HEADER_TOO_LONG
                || ERR_GET_REASON(err) == ERR_R_NESTED_ASN1_ERROR))
        ERR_pop_to_mark();
    else
        ERR_clear_last_mark();
    if (ok) {
        OSSL_PARAM params[3];
        int object_type = OSSL_OBJECT_UNKNOWN;

        params[0] =
            OSSL_PARAM_construct_int(OSSL_OBJECT_PARAM_TYPE, &object_type);
        params[1] =
            OSSL_PARAM_construct_octet_string(OSSL_OBJECT_PARAM_DATA,
                                              mem->data, mem->length);
        params[2] = OSSL_PARAM_construct_end();

        ok = data_cb(params, data_cbarg);
        OPENSSL_free(mem->data);
        OPENSSL_free(mem);
    }
    return ok;
}

static const OSSL_DISPATCH der_to_obj_decoder_functions[] = {
    { OSSL_FUNC_DECODER_NEWCTX, (void (*)(void))der2obj_newctx },
    { OSSL_FUNC_DECODER_FREECTX, (void (*)(void))der2obj_freectx },
    { OSSL_FUNC_DECODER_GETTABLE_PARAMS,
      (void (*)(void))der2obj_gettable_params },
    { OSSL_FUNC_DECODER_GET_PARAMS, (void (*)(void))der2obj_get_params },
    { OSSL_FUNC_DECODER_DECODE, (void (*)(void))der2obj_decode },
    { 0, NULL }
};

const OSSL_ALGORITHM ossl_der_to_obj_algorithm =
    { "obj", NULL, der_to_obj_decoder_functions };