/*
 * Copyright (C) 2014-2022 Firejail Authors
 *
 * This file is part of firejail project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include "../include/common.h"
#include "../include/ldd_utils.h"

#include <fcntl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <dirent.h>


static int arg_quiet = 0;
static void copy_libs_for_lib(const char *lib);

typedef struct storage_t {
	struct storage_t *next;
	const char *name;
} Storage;
static Storage *libs = NULL;
static Storage *lib_paths = NULL;

// return 1 if found
static int storage_find(Storage *ptr, const char *name) {
	while (ptr) {
		if (strcmp(ptr->name, name) == 0)
			return 1;
		ptr = ptr->next;
	}

	return 0;
}

static void storage_add(Storage **head, const char *name) {
	if (storage_find(*head, name))
		return;

	Storage *s = malloc(sizeof(Storage));
	if (!s)
		errExit("malloc");
	s->next = *head;
	*head = s;
	s->name = strdup(name);
	if (!s->name)
		errExit("strdup");
}


static void storage_print(Storage *ptr, int fd) {
	while (ptr) {
		dprintf(fd, "%s\n", ptr->name);
		ptr = ptr->next;
	}
}

static bool ptr_ok(const void *ptr, const void *base, const void *end, const char *name) {
	bool r;
	(void) name;

	r = (ptr >= base && ptr < end);
	return r;
}


static void parse_elf(const char *exe) {
	int f;
	f = open(exe, O_RDONLY);
	if (f < 0) {
		if (!arg_quiet)
			fprintf(stderr, "Warning fldd: cannot open %s, skipping...\n", exe);
		return;
	}

	struct stat s;
	char *base = NULL, *end;
	if (fstat(f, &s) == -1)
		goto error_close;
	base = mmap(0, s.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, f, 0);
	if (base == MAP_FAILED)
		goto error_close;

	end = base + s.st_size;

	Elf_Ehdr *ebuf = (Elf_Ehdr *)base;
	if (strncmp((const char *)ebuf->e_ident, ELFMAG, SELFMAG) != 0) {
		if (!arg_quiet)
			fprintf(stderr, "Warning fldd: %s is not an ELF executable or library\n", exe);
		goto close;
	}
//unsigned char elfclass = ebuf->e_ident[EI_CLASS];
//if (elfclass == ELFCLASS32)
//printf("%s 32bit\n", exe);
//else if (elfclass == ELFCLASS64)
//printf("%s 64bit\n", exe);


	Elf_Phdr *pbuf = (Elf_Phdr *)(base + sizeof(*ebuf));
	while (ebuf->e_phnum-- > 0 && ptr_ok(pbuf, base, end, "pbuf")) {
		switch (pbuf->p_type) {
		case PT_INTERP:
			// dynamic loader ld-linux.so
			if (!ptr_ok(base + pbuf->p_offset, base, end, "base + pbuf->p_offset"))
				goto close;

			storage_add(&libs, base + pbuf->p_offset);
			break;
		}
		pbuf++;
	}

	Elf_Shdr *sbuf = (Elf_Shdr *)(base + ebuf->e_shoff);
	if (!ptr_ok(sbuf, base, end, "sbuf"))
		goto close;

	// Find strings section
	char *strbase = NULL;
	int sections = ebuf->e_shnum;
	while (sections-- > 0 && ptr_ok(sbuf, base, end, "sbuf")) {
		if (sbuf->sh_type == SHT_STRTAB) {
			strbase = base + sbuf->sh_offset;
			if (!ptr_ok(strbase, base, end, "strbase"))
				goto close;
			break;
		}
		sbuf++;
	}
	if (strbase == NULL)
		goto error_close;

	// Find dynamic section
	sections = ebuf->e_shnum;
	while (sections-- > 0 && ptr_ok(sbuf, base, end, "sbuf")) {
// TODO: running fldd on large gui programs (fldd /usr/bin/transmission-qt)
// crash on accessing memory location sbuf->sh_type if sbuf->sh_type in the previous section was 0 (SHT_NULL)
// for now we just exit the while loop - this is probably incorrect
// printf("sbuf %p #%s#, sections %d, type %u\n", sbuf, exe, sections, sbuf->sh_type);
		if (!ptr_ok(sbuf, base, end, "sbuf"))
			goto close;

		if (sbuf->sh_type == SHT_NULL)
			break;
		if (sbuf->sh_type == SHT_DYNAMIC) {
			Elf_Dyn *dbuf = (Elf_Dyn *)(base + sbuf->sh_offset);
			if (!ptr_ok(dbuf, base, end, "dbuf"))
				goto close;
			// Find DT_RPATH/DT_RUNPATH tags first
			unsigned long size = sbuf->sh_size;
			while (size >= sizeof(*dbuf) && ptr_ok(dbuf, base, end, "dbuf")) {
				if (dbuf->d_tag == DT_RPATH || dbuf->d_tag ==  DT_RUNPATH) {
					const char *searchpath = strbase + dbuf->d_un.d_ptr;
					if (!ptr_ok(searchpath, base, end, "searchpath"))
						goto close;
					storage_add(&lib_paths, searchpath);
				}
				size -= sizeof(*dbuf);
				dbuf++;
			}
			// Find DT_NEEDED tags
			dbuf = (Elf_Dyn *)(base + sbuf->sh_offset);
			size = sbuf->sh_size;
			while (size >= sizeof(*dbuf) && ptr_ok(dbuf, base, end, "dbuf")) {
				if (dbuf->d_tag == DT_NEEDED) {
					const char *lib = strbase + dbuf->d_un.d_ptr;
					if (!ptr_ok(lib, base, end, "lib"))
						goto close;
					copy_libs_for_lib(lib);
				}
				size -= sizeof(*dbuf);
				dbuf++;
			}
		}
		sbuf++;
	}
	goto close;

 error_close:
	perror("copy libs");
 close:
	if (base)
		munmap(base, s.st_size);

	close(f);
}

static void copy_libs_for_lib(const char *lib) {
	Storage *lib_path;
	for (lib_path = lib_paths; lib_path; lib_path = lib_path->next) {
		char *fname;
		if (asprintf(&fname, "%s/%s", lib_path->name, lib) == -1)
			errExit("asprintf");
		if (access(fname, R_OK) == 0 && is_lib_64(fname)) {
			if (!storage_find(libs, fname)) {
				storage_add(&libs, fname);
				// libs may need other libs
				parse_elf(fname);
			}
			free(fname);
			return;
		}
		free(fname);
	}

	// log a  warning and continue
	if (!arg_quiet)
		fprintf(stderr, "Warning fldd: cannot find %s, skipping...\n", lib);
}

static void lib_paths_init(void) {
	int i;
	for (i = 0; default_lib_paths[i]; i++)
		storage_add(&lib_paths, default_lib_paths[i]);
}


static void walk_directory(const char *dirname) {
	assert(dirname);

	DIR *dir = opendir(dirname);
	if (dir) {
		struct dirent *entry;
		while ((entry = readdir(dir)) != NULL) {
			if (strcmp(entry->d_name, ".") == 0)
				continue;
			if (strcmp(entry->d_name, "..") == 0)
				continue;

			// build full path
			char *path;
			if (asprintf(&path, "%s/%s", dirname, entry->d_name) == -1)
				errExit("asprintf");

			// check regular so library
			char *ptr = strstr(entry->d_name, ".so");
			if (ptr && is_lib_64(path)) {
				if (*(ptr + 3) == '\0' || *(ptr + 3) == '.') {
					parse_elf(path);
					free(path);
					continue;
				}
			}

			// check directory
			// entry->d_type field is supported  in glibc since version 2.19 (Feb 2014)
			// we'll use stat to check for directories using the real path
			// (sometimes the path is a double symlink to a real file and stat would fail)
			char *rpath = realpath(path, NULL);
			if (!rpath) {
				free(path);
				continue;
			}
			free(path);

			struct stat s;
			if (stat(rpath, &s) == -1)
				errExit("stat");
			if (S_ISDIR(s.st_mode))
				walk_directory(rpath);
			free(rpath);
		}
		closedir(dir);
	}
}



static void usage(void) {
	printf("Usage: fldd program_or_directory [file]\n");
	printf("Print a list of libraries used by program or store it in the file.\n");
	printf("Print a list of libraries used by all .so files in a directory or store it in the file.\n");
}

int main(int argc, char **argv) {
#if 0
{
//system("cat /proc/self/status");
int i;
for (i = 0; i < argc; i++)
        printf("*%s* ", argv[i]);
printf("\n");
}
#endif
	if (argc < 2) {
		fprintf(stderr, "Error fldd: invalid arguments\n");
		usage();
		exit(1);
	}


	if (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0) {
		usage();
		return 0;
	}

	warn_dumpable();

	// check program access
	if (access(argv[1], R_OK)) {
		fprintf(stderr, "Error fldd: cannot access %s\n", argv[1]);
		exit(1);
	}

	char *quiet = getenv("FIREJAIL_QUIET");
	if (quiet && strcmp(quiet, "yes") == 0)
		arg_quiet = 1;

	int fd = STDOUT_FILENO;
	// attempt to open the file
	if (argc == 3) {
		fd = open(argv[2], O_CREAT | O_TRUNC | O_WRONLY, 0644);
		if (fd == -1) {
			fprintf(stderr, "Error fldd: invalid arguments\n");
			usage();
			exit(1);
		}
	}

	// initialize local storage
	lib_paths_init();

	// process files
	struct stat s;
	if (stat(argv[1], &s) == -1)
		errExit("stat");
	if (S_ISDIR(s.st_mode))
		walk_directory(argv[1]);
	else {
		if (is_lib_64(argv[1]))
			parse_elf(argv[1]);
		else
			fprintf(stderr, "Warning fldd: %s is not a 64bit program/library\n", argv[1]);
	}


	// print libraries and exit
	storage_print(libs, fd);
	if (argc == 3)
		close(fd);
	return 0;
}
