Adding upstream version 1:9.16.44.upstream/1%9.16.44

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1003 insertions, 0 deletions

diff --git a/lib/isc/win32/file.c b/lib/isc/win32/file.c
new file mode 100644
index 0000000..32f6a19
--- /dev/null
+++ b/lib/isc/win32/file.c
@@ -0,0 +1,1003 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0.  If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#undef rename
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <io.h>
+#include <limits.h>
+#include <process.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/utime.h>
+
+#include <isc/file.h>
+#include <isc/md.h>
+#include <isc/mem.h>
+#include <isc/platform.h>
+#include <isc/print.h>
+#include <isc/random.h>
+#include <isc/result.h>
+#include <isc/stat.h>
+#include <isc/string.h>
+#include <isc/time.h>
+#include <isc/util.h>
+
+#include "errno2result.h"
+
+static const char alphnum[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuv"
+			      "wxyz0123456789";
+
+/*
+ * Emulate UNIX mkstemp, which returns an open FD to the new file
+ *
+ */
+static int
+gettemp(char *path, bool binary, int *doopen) {
+	char *start, *trv;
+	struct stat sbuf;
+	int flags = O_CREAT | O_EXCL | O_RDWR;
+
+	if (binary) {
+		flags |= _O_BINARY;
+	}
+
+	trv = strrchr(path, 'X');
+	trv++;
+	/* extra X's get set to 0's */
+	while (*--trv == 'X') {
+		uint32_t which = isc_random_uniform(sizeof(alphnum) - 1);
+		*trv = alphnum[which];
+	}
+	/*
+	 * check the target directory; if you have six X's and it
+	 * doesn't exist this runs for a *very* long time.
+	 */
+	for (start = trv + 1;; --trv) {
+		if (trv <= path) {
+			break;
+		}
+		if (*trv == '\\') {
+			*trv = '\0';
+			if (stat(path, &sbuf)) {
+				return (0);
+			}
+			if (!S_ISDIR(sbuf.st_mode)) {
+				errno = ENOTDIR;
+				return (0);
+			}
+			*trv = '\\';
+			break;
+		}
+	}
+
+	for (;;) {
+		if (doopen) {
+			if ((*doopen = open(path, flags,
+					    _S_IREAD | _S_IWRITE)) >= 0)
+			{
+				return (1);
+			}
+			if (errno != EEXIST) {
+				return (0);
+			}
+		} else if (stat(path, &sbuf)) {
+			return (errno == ENOENT ? 1 : 0);
+		}
+
+		/* tricky little algorithm for backward compatibility */
+		for (trv = start;;) {
+			if (!*trv) {
+				return (0);
+			}
+			if (*trv == 'z') {
+				*trv++ = 'a';
+			} else {
+				if (isdigit((unsigned char)*trv)) {
+					*trv = 'a';
+				} else {
+					++*trv;
+				}
+				break;
+			}
+		}
+	}
+	/*NOTREACHED*/
+}
+
+static int
+mkstemp(char *path, bool binary) {
+	int fd;
+
+	return (gettemp(path, binary, &fd) ? fd : -1);
+}
+
+/*
+ * XXXDCL As the API for accessing file statistics undoubtedly gets expanded,
+ * it might be good to provide a mechanism that allows for the results
+ * of a previous stat() to be used again without having to do another stat,
+ * such as perl's mechanism of using "_" in place of a file name to indicate
+ * that the results of the last stat should be used.  But then you get into
+ * annoying MP issues.   BTW, Win32 has stat().
+ */
+static isc_result_t
+file_stats(const char *file, struct stat *stats) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(file != NULL);
+	REQUIRE(stats != NULL);
+
+	if (stat(file, stats) != 0) {
+		result = isc__errno2result(errno);
+	}
+
+	return (result);
+}
+
+static isc_result_t
+fd_stats(int fd, struct stat *stats) {
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(stats != NULL);
+
+	if (fstat(fd, stats) != 0) {
+		result = isc__errno2result(errno);
+	}
+
+	return (result);
+}
+
+isc_result_t
+isc_file_getsizefd(int fd, off_t *size) {
+	isc_result_t result;
+	struct stat stats;
+
+	REQUIRE(size != NULL);
+
+	result = fd_stats(fd, &stats);
+
+	if (result == ISC_R_SUCCESS) {
+		*size = stats.st_size;
+	}
+	return (result);
+}
+
+isc_result_t
+isc_file_mode(const char *file, mode_t *modep) {
+	isc_result_t result;
+	struct stat stats;
+
+	REQUIRE(modep != NULL);
+
+	result = file_stats(file, &stats);
+	if (result == ISC_R_SUCCESS) {
+		*modep = (stats.st_mode & 07777);
+	}
+	return (result);
+}
+
+/*
+ * isc_file_safemovefile is needed to be defined here to ensure that
+ * any file with the new name is renamed to a backup name and then the
+ * rename is done. If all goes well then the backup can be deleted,
+ * otherwise it gets renamed back.
+ */
+
+int
+isc_file_safemovefile(const char *oldname, const char *newname) {
+	BOOL filestatus;
+	char buf[512];
+	struct stat sbuf;
+	BOOL exists = FALSE;
+	int tmpfd;
+
+	/*
+	 * Make sure we have something to do
+	 */
+	if (stat(oldname, &sbuf) != 0) {
+		errno = ENOENT;
+		return (-1);
+	}
+
+	/*
+	 * Rename to a backup the new file if it still exists
+	 */
+	if (stat(newname, &sbuf) == 0) {
+		exists = TRUE;
+		strlcpy(buf, newname, sizeof(buf));
+		strlcat(buf, ".XXXXX", sizeof(buf));
+		tmpfd = mkstemp(buf, true);
+		if (tmpfd > 0) {
+			_close(tmpfd);
+		}
+		(void)DeleteFile(buf);
+		_chmod(newname, _S_IREAD | _S_IWRITE);
+
+		filestatus = MoveFile(newname, buf);
+	}
+	/* Now rename the file to the new name
+	 */
+	_chmod(oldname, _S_IREAD | _S_IWRITE);
+
+	filestatus = MoveFile(oldname, newname);
+	if (filestatus == 0) {
+		/*
+		 * Try to rename the backup back to the original name
+		 * if the backup got created
+		 */
+		if (exists == TRUE) {
+			filestatus = MoveFile(buf, newname);
+			if (filestatus == 0) {
+				errno = EACCES;
+			}
+		}
+		return (-1);
+	}
+
+	/*
+	 * Delete the backup file if it got created
+	 */
+	if (exists == TRUE) {
+		(void)DeleteFile(buf);
+	}
+	return (0);
+}
+
+isc_result_t
+isc_file_getmodtime(const char *file, isc_time_t *time) {
+	int fh;
+
+	REQUIRE(file != NULL);
+	REQUIRE(time != NULL);
+
+	if ((fh = open(file, _O_RDONLY | _O_BINARY)) < 0) {
+		return (isc__errno2result(errno));
+	}
+
+	if (!GetFileTime((HANDLE)_get_osfhandle(fh), NULL, NULL,
+			 &time->absolute))
+	{
+		close(fh);
+		errno = EINVAL;
+		return (isc__errno2result(errno));
+	}
+	close(fh);
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_getsize(const char *file, off_t *size) {
+	isc_result_t result;
+	struct stat stats;
+
+	REQUIRE(file != NULL);
+	REQUIRE(size != NULL);
+
+	result = file_stats(file, &stats);
+
+	if (result == ISC_R_SUCCESS) {
+		*size = stats.st_size;
+	}
+
+	return (result);
+}
+
+isc_result_t
+isc_file_settime(const char *file, isc_time_t *time) {
+	int fh;
+
+	REQUIRE(file != NULL && time != NULL);
+
+	if ((fh = open(file, _O_RDWR | _O_BINARY)) < 0) {
+		return (isc__errno2result(errno));
+	}
+
+	/*
+	 * Set the date via the filedate system call and return.  Failing
+	 * this call implies the new file times are not supported by the
+	 * underlying file system.
+	 */
+	if (!SetFileTime((HANDLE)_get_osfhandle(fh), NULL, &time->absolute,
+			 &time->absolute))
+	{
+		close(fh);
+		errno = EINVAL;
+		return (isc__errno2result(errno));
+	}
+
+	close(fh);
+	return (ISC_R_SUCCESS);
+}
+
+#undef TEMPLATE
+#define TEMPLATE "XXXXXXXXXX.tmp" /* 14 characters. */
+
+isc_result_t
+isc_file_mktemplate(const char *path, char *buf, size_t buflen) {
+	return (isc_file_template(path, TEMPLATE, buf, buflen));
+}
+
+isc_result_t
+isc_file_template(const char *path, const char *templet, char *buf,
+		  size_t buflen) {
+	char *s;
+
+	REQUIRE(templet != NULL);
+	REQUIRE(buf != NULL);
+
+	if (path == NULL) {
+		path = "";
+	}
+
+	s = strrchr(templet, '\\');
+	if (s != NULL) {
+		templet = s + 1;
+	}
+
+	s = strrchr(path, '\\');
+
+	if (s != NULL) {
+		size_t prefixlen = s - path + 1;
+		if ((prefixlen + strlen(templet) + 1) > buflen) {
+			return (ISC_R_NOSPACE);
+		}
+
+		/* Copy 'prefixlen' bytes and NUL terminate. */
+		strlcpy(buf, path, ISC_MIN(prefixlen + 1, buflen));
+		strlcat(buf, templet, buflen);
+	} else {
+		if ((strlen(templet) + 1) > buflen) {
+			return (ISC_R_NOSPACE);
+		}
+
+		strlcpy(buf, templet, buflen);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_renameunique(const char *file, char *templet) {
+	int fd;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(file != NULL);
+	REQUIRE(templet != NULL);
+
+	fd = mkstemp(templet, true);
+	if (fd == -1) {
+		result = isc__errno2result(errno);
+	} else {
+		close(fd);
+	}
+
+	if (result == ISC_R_SUCCESS) {
+		int res;
+		res = isc_file_safemovefile(file, templet);
+		if (res != 0) {
+			result = isc__errno2result(errno);
+			(void)unlink(templet);
+		}
+	}
+	return (result);
+}
+
+static isc_result_t
+openuniquemode(char *templet, int mode, bool binary, FILE **fp) {
+	int fd;
+	FILE *f;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(templet != NULL);
+	REQUIRE(fp != NULL && *fp == NULL);
+
+	/*
+	 * Win32 does not have mkstemp. Using emulation above.
+	 */
+	fd = mkstemp(templet, binary);
+
+	if (fd == -1) {
+		result = isc__errno2result(errno);
+	}
+	if (result == ISC_R_SUCCESS) {
+#if 1
+		UNUSED(mode);
+#else  /* if 1 */
+		(void)fchmod(fd, mode);
+#endif /* if 1 */
+		f = fdopen(fd, binary ? "wb+" : "w+");
+		if (f == NULL) {
+			result = isc__errno2result(errno);
+			(void)remove(templet);
+			(void)close(fd);
+		} else {
+			*fp = f;
+		}
+	}
+
+	return (result);
+}
+
+isc_result_t
+isc_file_openuniqueprivate(char *templet, FILE **fp) {
+	int mode = _S_IREAD | _S_IWRITE;
+	return (openuniquemode(templet, mode, false, fp));
+}
+
+isc_result_t
+isc_file_openunique(char *templet, FILE **fp) {
+	int mode = _S_IREAD | _S_IWRITE;
+	return (openuniquemode(templet, mode, false, fp));
+}
+
+isc_result_t
+isc_file_openuniquemode(char *templet, int mode, FILE **fp) {
+	return (openuniquemode(templet, mode, false, fp));
+}
+
+isc_result_t
+isc_file_bopenuniqueprivate(char *templet, FILE **fp) {
+	int mode = _S_IREAD | _S_IWRITE;
+	return (openuniquemode(templet, mode, true, fp));
+}
+
+isc_result_t
+isc_file_bopenunique(char *templet, FILE **fp) {
+	int mode = _S_IREAD | _S_IWRITE;
+	return (openuniquemode(templet, mode, true, fp));
+}
+
+isc_result_t
+isc_file_bopenuniquemode(char *templet, int mode, FILE **fp) {
+	return (openuniquemode(templet, mode, true, fp));
+}
+
+isc_result_t
+isc_file_remove(const char *filename) {
+	int r;
+
+	REQUIRE(filename != NULL);
+
+	r = unlink(filename);
+	if (r == 0) {
+		return (ISC_R_SUCCESS);
+	} else {
+		return (isc__errno2result(errno));
+	}
+}
+
+isc_result_t
+isc_file_rename(const char *oldname, const char *newname) {
+	int r;
+
+	REQUIRE(oldname != NULL);
+	REQUIRE(newname != NULL);
+
+	r = isc_file_safemovefile(oldname, newname);
+	if (r == 0) {
+		return (ISC_R_SUCCESS);
+	} else {
+		return (isc__errno2result(errno));
+	}
+}
+
+bool
+isc_file_exists(const char *pathname) {
+	struct stat stats;
+
+	REQUIRE(pathname != NULL);
+
+	return (file_stats(pathname, &stats) == ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_isplainfile(const char *filename) {
+	/*
+	 * This function returns success if filename is a plain file.
+	 */
+	struct stat filestat;
+	memset(&filestat, 0, sizeof(struct stat));
+
+	if ((stat(filename, &filestat)) == -1) {
+		return (isc__errno2result(errno));
+	}
+
+	if (!S_ISREG(filestat.st_mode)) {
+		return (ISC_R_INVALIDFILE);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_isplainfilefd(int fd) {
+	/*
+	 * This function returns success if filename is a plain file.
+	 */
+	struct stat filestat;
+	memset(&filestat, 0, sizeof(struct stat));
+
+	if ((fstat(fd, &filestat)) == -1) {
+		return (isc__errno2result(errno));
+	}
+
+	if (!S_ISREG(filestat.st_mode)) {
+		return (ISC_R_INVALIDFILE);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_isdirectory(const char *filename) {
+	/*
+	 * This function returns success if filename is a directory.
+	 */
+	struct stat filestat;
+	memset(&filestat, 0, sizeof(struct stat));
+
+	if ((stat(filename, &filestat)) == -1) {
+		return (isc__errno2result(errno));
+	}
+
+	if (!S_ISDIR(filestat.st_mode)) {
+		return (ISC_R_INVALIDFILE);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+bool
+isc_file_isabsolute(const char *filename) {
+	REQUIRE(filename != NULL);
+	/*
+	 * Look for c:\path\... style, c:/path/... or \\computer\shar\path...
+	 * the UNC style file specs
+	 */
+	if ((filename[0] == '\\') && (filename[1] == '\\')) {
+		return (true);
+	}
+	if (isalpha(filename[0]) && filename[1] == ':' && filename[2] == '\\') {
+		return (true);
+	}
+	if (isalpha(filename[0]) && filename[1] == ':' && filename[2] == '/') {
+		return (true);
+	}
+	return (false);
+}
+
+bool
+isc_file_iscurrentdir(const char *filename) {
+	REQUIRE(filename != NULL);
+	return (filename[0] == '.' && filename[1] == '\0');
+}
+
+bool
+isc_file_ischdiridempotent(const char *filename) {
+	REQUIRE(filename != NULL);
+
+	if (isc_file_isabsolute(filename)) {
+		return (true);
+	}
+	if (filename[0] == '\\') {
+		return (true);
+	}
+	if (filename[0] == '/') {
+		return (true);
+	}
+	if (isc_file_iscurrentdir(filename)) {
+		return (true);
+	}
+	return (false);
+}
+
+const char *
+isc_file_basename(const char *filename) {
+	char *s;
+
+	REQUIRE(filename != NULL);
+
+	s = strrchr(filename, '\\');
+	if (s == NULL) {
+		return (filename);
+	}
+	return (s + 1);
+}
+
+isc_result_t
+isc_file_progname(const char *filename, char *progname, size_t namelen) {
+	const char *s;
+	const char *p;
+	size_t len;
+
+	REQUIRE(filename != NULL);
+	REQUIRE(progname != NULL);
+
+	/*
+	 * Strip the path from the name
+	 */
+	s = isc_file_basename(filename);
+	if (s == NULL) {
+		return (ISC_R_NOSPACE);
+	}
+
+	/*
+	 * Strip any and all suffixes
+	 */
+	p = strchr(s, '.');
+	if (p == NULL) {
+		if (namelen <= strlen(s)) {
+			return (ISC_R_NOSPACE);
+		}
+
+		strlcpy(progname, s, namelen);
+		return (ISC_R_SUCCESS);
+	}
+
+	/*
+	 * Copy the result to the buffer
+	 */
+	len = p - s;
+	if (len >= namelen) {
+		return (ISC_R_NOSPACE);
+	}
+
+	/* Copy up to 'len' bytes and NUL terminate. */
+	strlcpy(progname, s, ISC_MIN(len + 1, namelen));
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_absolutepath(const char *filename, char *path, size_t pathlen) {
+	char *ptrname;
+	DWORD retval;
+
+	REQUIRE(filename != NULL);
+	REQUIRE(path != NULL);
+
+	retval = GetFullPathName(filename, (DWORD)pathlen, path, &ptrname);
+
+	/* Something went wrong in getting the path */
+	if (retval == 0) {
+		return (ISC_R_NOTFOUND);
+	}
+	/* Caller needs to provide a larger buffer to contain the string */
+	if (retval >= pathlen) {
+		return (ISC_R_NOSPACE);
+	}
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_truncate(const char *filename, isc_offset_t size) {
+	int fh;
+
+	REQUIRE(filename != NULL && size >= 0);
+
+	if ((fh = open(filename, _O_RDWR | _O_BINARY)) < 0) {
+		return (isc__errno2result(errno));
+	}
+
+	if (_chsize(fh, size) != 0) {
+		close(fh);
+		return (isc__errno2result(errno));
+	}
+	close(fh);
+
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_safecreate(const char *filename, FILE **fp) {
+	isc_result_t result;
+	int flags;
+	struct stat sb;
+	FILE *f;
+	int fd;
+
+	REQUIRE(filename != NULL);
+	REQUIRE(fp != NULL && *fp == NULL);
+
+	result = file_stats(filename, &sb);
+	if (result == ISC_R_SUCCESS) {
+		if ((sb.st_mode & S_IFREG) == 0) {
+			return (ISC_R_INVALIDFILE);
+		}
+		flags = O_WRONLY | O_TRUNC;
+	} else if (result == ISC_R_FILENOTFOUND) {
+		flags = O_WRONLY | O_CREAT | O_EXCL;
+	} else {
+		return (result);
+	}
+
+	fd = open(filename, flags, S_IRUSR | S_IWUSR);
+	if (fd == -1) {
+		return (isc__errno2result(errno));
+	}
+
+	f = fdopen(fd, "w");
+	if (f == NULL) {
+		result = isc__errno2result(errno);
+		close(fd);
+		return (result);
+	}
+
+	*fp = f;
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_splitpath(isc_mem_t *mctx, const char *path, char **dirname,
+		   char const **basename) {
+	char *dir;
+	const char *file, *slash;
+	char *backslash;
+
+	slash = strrchr(path, '/');
+
+	backslash = strrchr(path, '\\');
+	if ((slash != NULL && backslash != NULL && backslash > slash) ||
+	    (slash == NULL && backslash != NULL))
+	{
+		slash = backslash;
+	}
+
+	if (slash == path) {
+		file = ++slash;
+		dir = isc_mem_strdup(mctx, "/");
+	} else if (slash != NULL) {
+		file = ++slash;
+		dir = isc_mem_allocate(mctx, slash - path);
+		strlcpy(dir, path, slash - path);
+	} else {
+		file = path;
+		dir = isc_mem_strdup(mctx, ".");
+	}
+
+	if (dir == NULL) {
+		return (ISC_R_NOMEMORY);
+	}
+
+	if (*file == '\0') {
+		isc_mem_free(mctx, dir);
+		return (ISC_R_INVALIDFILE);
+	}
+
+	*dirname = dir;
+	*basename = file;
+
+	return (ISC_R_SUCCESS);
+}
+
+void *
+isc_file_mmap(void *addr, size_t len, int prot, int flags, int fd,
+	      off_t offset) {
+	void *buf;
+	ssize_t ret;
+	off_t end;
+
+	UNUSED(addr);
+	UNUSED(prot);
+	UNUSED(flags);
+
+	end = lseek(fd, 0, SEEK_END);
+	lseek(fd, offset, SEEK_SET);
+	if (end - offset < (off_t)len) {
+		len = end - offset;
+	}
+
+	buf = malloc(len);
+	if (buf == NULL) {
+		return (NULL);
+	}
+
+	ret = read(fd, buf, (unsigned int)len);
+	if (ret != (ssize_t)len) {
+		free(buf);
+		buf = NULL;
+	}
+
+	return (buf);
+}
+
+int
+isc_file_munmap(void *addr, size_t len) {
+	UNUSED(len);
+	free(addr);
+	return (0);
+}
+
+#define DISALLOW "\\/:ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+static isc_result_t
+digest2hex(unsigned char *digest, unsigned int digestlen, char *hash,
+	   size_t hashlen) {
+	unsigned int i;
+	int ret;
+	for (i = 0; i < digestlen; i++) {
+		size_t left = hashlen - i * 2;
+		ret = snprintf(hash + i * 2, left, "%02x", digest[i]);
+		if (ret < 0 || (size_t)ret >= left) {
+			return (ISC_R_NOSPACE);
+		}
+	}
+	return (ISC_R_SUCCESS);
+}
+
+isc_result_t
+isc_file_sanitize(const char *dir, const char *base, const char *ext,
+		  char *path, size_t length) {
+	char buf[PATH_MAX];
+	unsigned char digest[ISC_MAX_MD_SIZE];
+	unsigned int digestlen;
+	char hash[ISC_MAX_MD_SIZE * 2 + 1];
+	size_t l = 0;
+	isc_result_t err;
+
+	REQUIRE(base != NULL);
+	REQUIRE(path != NULL);
+
+	l = strlen(base) + 1;
+
+	/*
+	 * allow room for a full sha256 hash (64 chars
+	 * plus null terminator)
+	 */
+	if (l < 65) {
+		l = 65;
+	}
+
+	if (dir != NULL) {
+		l += strlen(dir) + 1;
+	}
+	if (ext != NULL) {
+		l += strlen(ext) + 1;
+	}
+
+	if (l > length || l > PATH_MAX) {
+		return (ISC_R_NOSPACE);
+	}
+
+	/* Check whether the full-length SHA256 hash filename exists */
+	err = isc_md(ISC_MD_SHA256, (const unsigned char *)base, strlen(base),
+		     digest, &digestlen);
+	if (err != ISC_R_SUCCESS) {
+		return (err);
+	}
+
+	err = digest2hex(digest, digestlen, hash, sizeof(hash));
+	if (err != ISC_R_SUCCESS) {
+		return (err);
+	}
+
+	snprintf(buf, sizeof(buf), "%s%s%s%s%s", dir != NULL ? dir : "",
+		 dir != NULL ? "/" : "", hash, ext != NULL ? "." : "",
+		 ext != NULL ? ext : "");
+	if (isc_file_exists(buf)) {
+		strlcpy(path, buf, length);
+		return (ISC_R_SUCCESS);
+	}
+
+	/* Check for a truncated SHA256 hash filename */
+	hash[16] = '\0';
+	snprintf(buf, sizeof(buf), "%s%s%s%s%s", dir != NULL ? dir : "",
+		 dir != NULL ? "/" : "", hash, ext != NULL ? "." : "",
+		 ext != NULL ? ext : "");
+	if (isc_file_exists(buf)) {
+		strlcpy(path, buf, length);
+		return (ISC_R_SUCCESS);
+	}
+
+	/*
+	 * If neither hash filename already exists, then we'll use
+	 * the original base name if it has no disallowed characters,
+	 * or the truncated hash name if it does.
+	 */
+	if (strpbrk(base, DISALLOW) != NULL) {
+		strlcpy(path, buf, length);
+		return (ISC_R_SUCCESS);
+	}
+
+	snprintf(buf, sizeof(buf), "%s%s%s%s%s", dir != NULL ? dir : "",
+		 dir != NULL ? "/" : "", base, ext != NULL ? "." : "",
+		 ext != NULL ? ext : "");
+	strlcpy(path, buf, length);
+	return (ISC_R_SUCCESS);
+}
+
+/*
+ * Based on http://blog.aaronballman.com/2011/08/how-to-check-access-rights/
+ */
+bool
+isc_file_isdirwritable(const char *path) {
+	DWORD length = 0;
+	HANDLE hToken = NULL;
+	PSECURITY_DESCRIPTOR security = NULL;
+	bool answer = false;
+
+	if (isc_file_isdirectory(path) != ISC_R_SUCCESS) {
+		return (answer);
+	}
+
+	/*
+	 * Figure out buffer size. GetFileSecurity() should not succeed.
+	 */
+	if (GetFileSecurity(path,
+			    OWNER_SECURITY_INFORMATION |
+				    GROUP_SECURITY_INFORMATION |
+				    DACL_SECURITY_INFORMATION,
+			    NULL, 0, &length))
+	{
+		return (answer);
+	}
+
+	if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+		return (answer);
+	}
+
+	security = malloc(length);
+	if (security == NULL) {
+		return (answer);
+	}
+
+	/*
+	 * GetFileSecurity() should succeed.
+	 */
+	if (!GetFileSecurity(path,
+			     OWNER_SECURITY_INFORMATION |
+				     GROUP_SECURITY_INFORMATION |
+				     DACL_SECURITY_INFORMATION,
+			     security, length, &length))
+	{
+		return (answer);
+	}
+
+	if (OpenProcessToken(GetCurrentProcess(),
+			     TOKEN_IMPERSONATE | TOKEN_QUERY | TOKEN_DUPLICATE |
+				     STANDARD_RIGHTS_READ,
+			     &hToken))
+	{
+		HANDLE hImpersonatedToken = NULL;
+
+		if (DuplicateToken(hToken, SecurityImpersonation,
+				   &hImpersonatedToken))
+		{
+			GENERIC_MAPPING mapping;
+			PRIVILEGE_SET privileges = { 0 };
+			DWORD grantedAccess = 0;
+			DWORD privilegesLength = sizeof(privileges);
+			BOOL result = FALSE;
+			DWORD genericAccessRights = GENERIC_WRITE;
+
+			mapping.GenericRead = FILE_GENERIC_READ;
+			mapping.GenericWrite = FILE_GENERIC_WRITE;
+			mapping.GenericExecute = FILE_GENERIC_EXECUTE;
+			mapping.GenericAll = FILE_ALL_ACCESS;
+
+			MapGenericMask(&genericAccessRights, &mapping);
+			if (AccessCheck(security, hImpersonatedToken,
+					genericAccessRights, &mapping,
+					&privileges, &privilegesLength,
+					&grantedAccess, &result))
+			{
+				answer = result;
+			}
+			CloseHandle(hImpersonatedToken);
+		}
+		CloseHandle(hToken);
+	}
+	free(security);
+	return (answer);
+}