/*
 * spdxtool-fuzzer.c
 * SPDX SBOM serializer fuzzing harness
 *
 * SPDX-License-Identifier: pkgconf
 *
 * Copyright (c) 2026 pkgconf authors (see AUTHORS).
 *
 * 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.
 *
 * This software is provided 'as is' and without any warranty, express or
 * implied.  In no event shall the authors be liable for any damages arising
 * from the use of this software.
 */

#include <libpkgconf/stdinc.h>
#include <libpkgconf/libpkgconf.h>

#include "util.h"
#include "generate.h"

#include "alloc-inject.h"

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);

/* Bound the allocation site selected for fault injection.  Exhaustively
 * replaying every allocation for every libFuzzer input makes this relatively
 * expensive solve-and-serialize target prohibitively slow. */
#define ALLOC_FAIL_MAX 4096

/* the fuzzer input is split on NUL bytes into up to this many .pc files, named
 * a.pc, b.pc, ... so that Requires/Conflicts/Provides between them resolve, and
 * the resulting graph is serialized to an SPDX SBOM.
 */
#define UNIVERSE_MAX 4
#define SOLVE_MAXDEPTH 10

static const char universe_names[UNIVERSE_MAX] = { 'a', 'b', 'c', 'd' };

static unsigned long
allocation_failure_for_input(const uint8_t *data, size_t size)
{
	uint32_t hash = UINT32_C(2166136261);

	for (size_t i = 0; i < size; i++)
	{
		hash ^= data[i];
		hash *= UINT32_C(16777619);
	}

	return (unsigned long)(hash % ALLOC_FAIL_MAX) + 1;
}

static const char *
environ_lookup_handler(const pkgconf_client_t *client, const char *key)
{
	(void) client;
	(void) key;

	return NULL;
}

static int
write_all(int fd, const uint8_t *data, size_t size)
{
	while (size > 0)
	{
		ssize_t n = write(fd, data, size);

		if (n < 0)
		{
			if (errno == EINTR)
				continue;
			return -1;
		}

		data += n;
		size -= n;
	}

	return 0;
}

static void
write_pkg(const char *dir, char name, const uint8_t *data, size_t size)
{
	char path[PKGCONF_ITEM_SIZE];
	int fd;

	snprintf(path, sizeof path, "%s/%c.pc", dir, name);

	fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0600);
	if (fd < 0)
		return;

	write_all(fd, data, size);
	close(fd);
}

static void
write_universe(const char *dir, const uint8_t *data, size_t size)
{
	size_t start = 0, idx = 0;

	for (size_t i = 0; i < size && idx < UNIVERSE_MAX; i++)
	{
		if (data[i] == 0x00)
		{
			write_pkg(dir, universe_names[idx++], data + start, i - start);
			start = i + 1;
		}
	}

	if (idx < UNIVERSE_MAX)
		write_pkg(dir, universe_names[idx], data + start, size - start);
}

static void
cleanup_universe(const char *dir)
{
	char path[PKGCONF_ITEM_SIZE];

	for (size_t i = 0; i < UNIVERSE_MAX; i++)
	{
		snprintf(path, sizeof path, "%s/%c.pc", dir, universe_names[i]);
		unlink(path);
	}

	rmdir(dir);
}

/*
 * Solve a freshly-written universe rooted at "a", then drive the real spdxtool
 * SBOM serialization pipeline (cli/spdxtool/generate.c) over the result.
 */
static void
run_spdx(const pkgconf_cross_personality_t *pers, const char *dir, FILE *out)
{
	pkgconf_client_t *client = pkgconf_client_new(NULL, NULL, pers, NULL, environ_lookup_handler);
	if (client == NULL)
		return;

	pkgconf_client_set_flags(client, PKGCONF_PKG_PKGF_SEARCH_PRIVATE);
	pkgconf_path_add(dir, &client->dir_list, false);

	/* the serializers read these back via the client's global tuples */
	spdxtool_util_set_uri_root(client, "https://example.com/test");
	spdxtool_util_set_uri_separator_colon(client, false);
	spdxtool_util_set_spdx_license(client, "CC0-1.0");
	spdxtool_util_set_spdx_version(client, "3.0.1");

	pkgconf_pkg_t world = {
		.id = "virtual:world",
		.realname = "virtual world package",
		.flags = PKGCONF_PKG_PROPF_STATIC | PKGCONF_PKG_PROPF_VIRTUAL,
	};
	pkgconf_list_t pkgq = PKGCONF_LIST_INITIALIZER;

	pkgconf_queue_push(&pkgq, "a");

	if (pkgconf_queue_solve(client, &pkgq, &world, SOLVE_MAXDEPTH))
		/* fixed timestamp keeps the harness deterministic */
		spdxtool_generate(client, &world, out, SOLVE_MAXDEPTH,
			"2020-01-01T00:00:00Z", "_:creationinfo_1", "Default");

	pkgconf_solution_free(client, &world);
	pkgconf_queue_free(&pkgq);
	pkgconf_client_free(client);
}

int
LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
{
	if (size == 0)
		return 0;

	char dir[] = "/tmp/pkgconf-fuzz-spdx-XXXXXX";
	if (mkdtemp(dir) == NULL)
		return 0;

	write_universe(dir, data, size);

	/* discard the serialized output; opened outside the injection loop so the
	 * allocations behind it are never the fault-injection target.
	 */
	FILE *out = fopen("/dev/null", "w");
	if (out == NULL)
	{
		cleanup_universe(dir);
		return 0;
	}

	pkgconf_cross_personality_t *pers = pkgconf_cross_personality_default();

	/* baseline run with all allocations succeeding */
	run_spdx(pers, dir, out);

	/* Exercise one deterministic allocation failure per input.  Mutations vary
	 * the selected site, while keeping the per-input cost constant. */
	alloc_inject_arm(allocation_failure_for_input(data, size));
	run_spdx(pers, dir, out);
	alloc_inject_disarm();

	pkgconf_cross_personality_deinit(pers);
	fclose(out);
	cleanup_universe(dir);

	return 0;
}
