sortix--sortix/sysinstall/fileops.c

/*
 * Copyright (c) 2015, 2016, 2017 Jonas 'Sortie' Termansen.
 *
 * Permission to use, copy, modify, and 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * fileops.c
 * File operation utility functions.
 */

#include <sys/stat.h>
#include <sys/types.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <ioleast.h>
#include <libgen.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "fileops.h"

char* join_paths(const char* a, const char* b)
{
	size_t a_len = strlen(a);
	bool has_slash = (a_len && a[a_len-1] == '/') || b[0] == '/';
	char* result;
	if ( (has_slash && asprintf(&result, "%s%s", a, b) < 0) ||
	     (!has_slash && asprintf(&result, "%s/%s", a, b) < 0) )
		return NULL;
	return result;
}

int mkdir_p(const char* path, mode_t mode)
{
	int saved_errno = errno;
	if ( !mkdir(path, mode) )
		return 0;
	if ( errno == ENOENT )
	{
		char* prev = strdup(path);
		if ( !prev )
			return -1;
		int status =  mkdir_p(dirname(prev), mode | 0500);
		free(prev);
		if ( status < 0 )
			return -1;
		errno = saved_errno;
		if ( !mkdir(path, mode) )
			return 0;
	}
	if ( errno == EEXIST )
		return errno = saved_errno, 0;
	return -1;
}

int access_or_die(const char* path, int mode)
{
	if ( access(path, mode) < 0 )
	{
		if ( errno == EACCES ||
		     errno == ENOENT ||
             errno == ELOOP ||
             errno == ENAMETOOLONG ||
             errno == ENOTDIR )
			return -1;
		warn("%s", path);
		_exit(2);
	}
	return 0;
}

void mkdir_or_chmod_or_die(const char* path, mode_t mode)
{
	if ( mkdir(path, mode) == 0 )
		return;
	if ( errno == EEXIST )
	{
		if ( chmod(path, mode) == 0 )
			return;
		err(2, "chmod: %s", path);
	}
	err(2, "mkdir: %s", path);
}

void write_random_seed(const char* path)
{
	int fd = open(path, O_WRONLY | O_CREAT | O_NOFOLLOW, 0600);
	if ( fd < 0 )
	{
		warn("%s", path);
		_exit(2);
	}
	if ( fchown(fd, 0, 0) < 0 )
	{
		warn("chown: %s", path);
		_exit(2);
	}
	if ( fchmod(fd, 0600) < 0 )
	{
		warn("chmod: %s", path);
		_exit(2);
	}
	// Write out randomness, but mix in some fresh kernel randomness in case the
	// randomness used to seed arc4random didn't have enough entropy, there may
	// be more now.
	unsigned char buf[256];
	arc4random_buf(buf, sizeof(buf));
	unsigned char newbuf[256];
	getentropy(newbuf, sizeof(newbuf));
	size_t done = writeall(fd, buf, sizeof(buf));
	explicit_bzero(buf, sizeof(buf));
	for ( size_t i = 0; i < 256; i++ )
		buf[i] ^= newbuf[i];
	if ( done < sizeof(buf) )
	{
		warn("write: %s", path);
		_exit(2);
	}
	if ( ftruncate(fd, sizeof(buf)) < 0  )
	{
		warn("truncate: %s", path);
		_exit(2);
	}
	close(fd);
}

char* read_string_file(const char* path)
{
	FILE* fp = fopen(path, "r");
	if ( !fp )
		return NULL;
	struct stat st;
	if ( fstat(fileno(fp), &st) < 0 )
	{
		fclose(fp);
		return NULL;
	}
	size_t content_length;
	if ( __builtin_add_overflow(1, st.st_size, &content_length) )
	{
		fclose(fp);
		errno = EOVERFLOW;
		return NULL;
	}
	char* content = malloc(content_length);
	if ( !content )
	{
		fclose(fp);
		return NULL;
	}
	size_t amount = fread(content, 1, content_length - 1, fp);
	if ( ferror(fp) )
	{
		fclose(fp);
		free(content);
		return NULL;
	}
	fclose(fp);
	if ( 0 < amount && content[amount - 1] == '\n' )
		content[amount - 1] = '\0';
	else
		content[amount] = '\0';
	return content;
}