Adding upstream version 2:4.17.12+dfsg.upstream/2%4.17.12+dfsgupstream

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

1 files changed, 662 insertions, 0 deletions

diff --git a/source4/ntvfs/posix/pvfs_sys.c b/source4/ntvfs/posix/pvfs_sys.c
new file mode 100644
index 0000000..f567046
--- /dev/null
+++ b/source4/ntvfs/posix/pvfs_sys.c
@@ -0,0 +1,662 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   POSIX NTVFS backend - pvfs_sys wrappers
+
+   Copyright (C) Andrew Tridgell 2010
+   Copyright (C) Andrew Bartlett 2010
+
+   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 3 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, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "vfs_posix.h"
+#include "../lib/util/unix_privs.h"
+
+/*
+  these wrapper functions must only be called when the appropriate ACL
+  has already been checked. The wrappers will override a EACCES result
+  by gaining root privileges if the 'pvfs:perm override' is set on the
+  share (it is enabled by default)
+
+  Careful use of O_NOFOLLOW and O_DIRECTORY is used to prevent
+  security attacks via symlinks
+ */
+
+
+struct pvfs_sys_ctx {
+	struct pvfs_state *pvfs;
+	void *privs;
+	const char *old_wd;
+	struct stat st_orig;
+};
+
+
+/*
+  we create PVFS_NOFOLLOW and PVFS_DIRECTORY as aliases for O_NOFOLLOW
+  and O_DIRECTORY on systems that have them. On systems that don't
+  have O_NOFOLLOW we are less safe, but the root override code is off
+  by default.
+ */
+#ifdef O_NOFOLLOW
+#define PVFS_NOFOLLOW O_NOFOLLOW
+#else
+#define PVFS_NOFOLLOW 0
+#endif
+#ifdef O_DIRECTORY
+#define PVFS_DIRECTORY O_DIRECTORY
+#else
+#define PVFS_DIRECTORY 0
+#endif
+
+/*
+  return to original directory when context is destroyed
+ */
+static int pvfs_sys_pushdir_destructor(struct pvfs_sys_ctx *ctx)
+{
+	struct stat st;
+
+	if (ctx->old_wd == NULL) {
+		return 0;
+	}
+
+	if (chdir(ctx->old_wd) != 0) {
+		smb_panic("Failed to restore working directory");
+	}
+	if (stat(".", &st) != 0) {
+		smb_panic("Failed to stat working directory");
+	}
+	if (st.st_ino != ctx->st_orig.st_ino ||
+	    st.st_dev != ctx->st_orig.st_dev) {
+		smb_panic("Working directory changed during call");
+	}
+
+	return 0;
+}
+
+
+/*
+  chdir() to the directory part of a pathname, but disallow any
+  component with a symlink
+
+  Note that we can't use O_NOFOLLOW on the whole path as that only
+  prevents links in the final component of the path
+ */
+static int pvfs_sys_chdir_nosymlink(struct pvfs_sys_ctx *ctx, const char *pathname)
+{
+	char *p, *path;
+	size_t base_len = strlen(ctx->pvfs->base_directory);
+
+	/* don't check for symlinks in the base directory of the share */
+	if (strncmp(ctx->pvfs->base_directory, pathname, base_len) == 0 &&
+	    pathname[base_len] == '/') {
+		if (chdir(ctx->pvfs->base_directory) != 0) {
+			return -1;
+		}
+		pathname += base_len + 1;
+	}
+
+	path = talloc_strdup(ctx, pathname);
+	if (path == NULL) {
+		return -1;
+	}
+	while ((p = strchr(path, '/'))) {
+		int fd;
+		struct stat st1, st2;
+		*p = 0;
+		fd = open(path, PVFS_NOFOLLOW | PVFS_DIRECTORY | O_RDONLY);
+		if (fd == -1) {
+			return -1;
+		}
+		if (chdir(path) != 0) {
+			close(fd);
+			return -1;
+		}
+		if (stat(".", &st1) != 0 ||
+		    fstat(fd, &st2) != 0) {
+			close(fd);
+			return -1;
+		}
+		close(fd);
+		if (st1.st_ino != st2.st_ino ||
+		    st1.st_dev != st2.st_dev) {
+			DEBUG(0,(__location__ ": Inode changed during chdir in '%s' - symlink attack?",
+				 pathname));
+			return -1;
+		}
+		path = p + 1;
+	}
+
+	return 0;
+}
+
+
+/*
+  become root, and change directory to the directory component of a
+  path. Return a talloc context which when freed will move us back
+  to the original directory, and return us to the original uid
+
+  change the pathname argument to contain just the base component of
+  the path
+
+  return NULL on error, which could include an attempt to subvert
+  security using symlink tricks
+ */
+static struct pvfs_sys_ctx *pvfs_sys_pushdir(struct pvfs_state *pvfs,
+					     const char **pathname)
+{
+	struct pvfs_sys_ctx *ctx;
+	char *cwd, *p, *dirname;
+	int ret;
+
+	ctx = talloc_zero(pvfs, struct pvfs_sys_ctx);
+	if (ctx == NULL) {
+		return NULL;
+	}
+	ctx->pvfs = pvfs;
+	ctx->privs = root_privileges();
+	if (ctx->privs == NULL) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	talloc_steal(ctx, ctx->privs);
+
+	if (!pathname) {
+		/* no pathname needed */
+		return ctx;
+	}
+
+	p = strrchr(*pathname, '/');
+	if (p == NULL) {
+		/* we don't need to change directory */
+		return ctx;
+	}
+
+	/* we keep the old st around, so we can tell that
+	   we have come back to the right directory */
+	if (stat(".", &ctx->st_orig) != 0) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	cwd = get_current_dir_name();
+	if (cwd == NULL) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	ctx->old_wd = talloc_strdup(ctx, cwd);
+	free(cwd);
+
+	if (ctx->old_wd == NULL) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	dirname = talloc_strndup(ctx, *pathname, (p - *pathname));
+	if (dirname == NULL) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	ret = pvfs_sys_chdir_nosymlink(ctx, *pathname);
+	if (ret == -1) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	talloc_set_destructor(ctx, pvfs_sys_pushdir_destructor);
+
+	/* return the basename as the filename that should be operated on */
+	(*pathname) = talloc_strdup(ctx, p+1);
+	if (! *pathname) {
+		talloc_free(ctx);
+		return NULL;
+	}
+
+	return ctx;
+}
+
+
+/*
+  chown a file that we created with a root privileges override
+ */
+static int pvfs_sys_fchown(struct pvfs_state *pvfs, struct pvfs_sys_ctx *ctx, int fd)
+{
+	return fchown(fd, root_privileges_original_uid(ctx->privs), -1);
+}
+
+/*
+  chown a directory that we created with a root privileges override
+ */
+static int pvfs_sys_chown(struct pvfs_state *pvfs, struct pvfs_sys_ctx *ctx, const char *name)
+{
+	/* to avoid symlink hacks, we need to use fchown() on a directory fd */
+	int ret, fd;
+	fd = open(name, PVFS_DIRECTORY | PVFS_NOFOLLOW | O_RDONLY);
+	if (fd == -1) {
+		return -1;
+	}
+	ret = pvfs_sys_fchown(pvfs, ctx, fd);
+	close(fd);
+	return ret;
+}
+
+
+/*
+  wrap open for system override
+*/
+int pvfs_sys_open(struct pvfs_state *pvfs, const char *filename, int flags, mode_t mode, bool allow_override)
+{
+	int fd, ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+	int retries = 5;
+
+	orig_errno = errno;
+
+	fd = open(filename, flags, mode);
+	if (fd != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return fd;
+	}
+
+	saved_errno = errno;
+	ctx = pvfs_sys_pushdir(pvfs, &filename);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	/* don't allow permission overrides to follow links */
+	flags |= PVFS_NOFOLLOW;
+
+	/*
+	   if O_CREAT was specified and O_EXCL was not specified
+	   then initially do the open without O_CREAT, as in that case
+	   we know that we did not create the file, so we don't have
+	   to fchown it
+	 */
+	if ((flags & O_CREAT) && !(flags & O_EXCL)) {
+	try_again:
+		fd = open(filename, flags & ~O_CREAT, mode);
+		/* if this open succeeded, or if it failed
+		   with anything other than ENOENT, then we return the
+		   open result, with the original errno */
+		if (fd == -1 && errno != ENOENT) {
+			talloc_free(ctx);
+			errno = saved_errno;
+			return -1;
+		}
+		if (fd != -1) {
+			/* the file already existed and we opened it */
+			talloc_free(ctx);
+			errno = orig_errno;
+			return fd;
+		}
+
+		fd = open(filename, flags | O_EXCL, mode);
+		if (fd == -1 && errno != EEXIST) {
+			talloc_free(ctx);
+			errno = saved_errno;
+			return -1;
+		}
+		if (fd != -1) {
+			/* we created the file, we need to set the
+			   right ownership on it */
+			ret = pvfs_sys_fchown(pvfs, ctx, fd);
+			if (ret == -1) {
+				close(fd);
+				unlink(filename);
+				talloc_free(ctx);
+				errno = saved_errno;
+				return -1;
+			}
+			talloc_free(ctx);
+			errno = orig_errno;
+			return fd;
+		}
+
+		/* the file got created between the two times
+		   we tried to open it! Try again */
+		if (retries-- > 0) {
+			goto try_again;
+		}
+
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	fd = open(filename, flags, mode);
+	if (fd == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	/* if we have created a file then fchown it */
+	if (flags & O_CREAT) {
+		ret = pvfs_sys_fchown(pvfs, ctx, fd);
+		if (ret == -1) {
+			close(fd);
+			unlink(filename);
+			talloc_free(ctx);
+			errno = saved_errno;
+			return -1;
+		}
+	}
+
+	talloc_free(ctx);
+	return fd;
+}
+
+
+/*
+  wrap unlink for system override
+*/
+int pvfs_sys_unlink(struct pvfs_state *pvfs, const char *filename, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = unlink(filename);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	ctx = pvfs_sys_pushdir(pvfs, &filename);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = unlink(filename);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}
+
+
+static bool contains_symlink(const char *path)
+{
+	int fd = open(path, PVFS_NOFOLLOW | O_RDONLY);
+	int posix_errno = errno;
+	if (fd != -1) {
+		close(fd);
+		return false;
+	}
+
+#if defined(ENOTSUP) && defined(OSF1)
+	/* handle special Tru64 errno */
+	if (errno == ENOTSUP) {
+		posix_errno = ELOOP;
+	}
+#endif /* ENOTSUP */
+
+#ifdef EFTYPE
+	/* fix broken NetBSD errno */
+	if (errno == EFTYPE) {
+		posix_errno = ELOOP;
+	}
+#endif /* EFTYPE */
+
+	/* fix broken FreeBSD errno */
+	if (errno == EMLINK) {
+		posix_errno = ELOOP;
+	}
+
+	return (posix_errno == ELOOP);
+}
+
+/*
+  wrap rename for system override
+*/
+int pvfs_sys_rename(struct pvfs_state *pvfs, const char *name1, const char *name2, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = rename(name1, name2);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	ctx = pvfs_sys_pushdir(pvfs, &name1);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	/* we need the destination as an absolute path */
+	if (name2[0] != '/') {
+		name2 = talloc_asprintf(ctx, "%s/%s", ctx->old_wd, name2);
+		if (name2 == NULL) {
+			talloc_free(ctx);
+			errno = saved_errno;
+			return -1;
+		}
+	}
+
+	/* make sure the destination isn't a symlink beforehand */
+	if (contains_symlink(name2)) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = rename(name1, name2);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	/* make sure the destination isn't a symlink afterwards */
+	if (contains_symlink(name2)) {
+		DEBUG(0,(__location__ ": Possible symlink attack in rename to '%s' - unlinking\n", name2));
+		unlink(name2);
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}
+
+
+/*
+  wrap mkdir for system override
+*/
+int pvfs_sys_mkdir(struct pvfs_state *pvfs, const char *dirname, mode_t mode, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = mkdir(dirname, mode);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+	ctx = pvfs_sys_pushdir(pvfs, &dirname);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = mkdir(dirname, mode);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = pvfs_sys_chown(pvfs, ctx, dirname);
+	if (ret == -1) {
+		rmdir(dirname);
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}
+
+
+/*
+  wrap rmdir for system override
+*/
+int pvfs_sys_rmdir(struct pvfs_state *pvfs, const char *dirname, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = rmdir(dirname);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	ctx = pvfs_sys_pushdir(pvfs, &dirname);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = rmdir(dirname);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}
+
+/*
+  wrap fchmod for system override
+*/
+int pvfs_sys_fchmod(struct pvfs_state *pvfs, int fd, mode_t mode, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = fchmod(fd, mode);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	ctx = pvfs_sys_pushdir(pvfs, NULL);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = fchmod(fd, mode);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}
+
+
+/*
+  wrap chmod for system override
+*/
+int pvfs_sys_chmod(struct pvfs_state *pvfs, const char *filename, mode_t mode, bool allow_override)
+{
+	int ret;
+	struct pvfs_sys_ctx *ctx;
+	int saved_errno, orig_errno;
+
+	orig_errno = errno;
+
+	ret = chmod(filename, mode);
+	if (ret != -1 ||
+	    !allow_override ||
+	    errno != EACCES) {
+		return ret;
+	}
+
+	saved_errno = errno;
+
+	ctx = pvfs_sys_pushdir(pvfs, &filename);
+	if (ctx == NULL) {
+		errno = saved_errno;
+		return -1;
+	}
+
+	ret = chmod(filename, mode);
+	if (ret == -1) {
+		talloc_free(ctx);
+		errno = saved_errno;
+		return -1;
+	}
+
+	talloc_free(ctx);
+	errno = orig_errno;
+	return ret;
+}