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authorLennart Poettering <lennart@poettering.net>2016-07-26 17:23:28 +0200
committerLennart Poettering <lennart@poettering.net>2016-08-04 16:27:07 +0200
commit992e8f224b91cacc3d6589bea7882c7ab9c0911b (patch)
tree7b1869a11a353488ba9c9857f57086e4dc7e046b /src/basic
parenteb18df724ba541ac1c7fd5c77d9244fa6bc5cabf (diff)
util-lib: rework /tmp and /var/tmp handling code
Beef up the existing var_tmp() call, rename it to var_tmp_dir() and add a matching tmp_dir() call (the former looks for the place for /var/tmp, the latter for /tmp). Both calls check $TMPDIR, $TEMP, $TMP, following the algorithm Python3 uses. All dirs are validated before use. secure_getenv() is used in order to limite exposure in suid binaries. This also ports a couple of users over to these new APIs. The var_tmp() return parameter is changed from an allocated buffer the caller will own to a const string either pointing into environ[], or into a static const buffer. Given that environ[] is mostly considered constant (and this is exposed in the very well-known getenv() call), this should be OK behaviour and allows us to avoid memory allocations in most cases. Note that $TMPDIR and friends override both /var/tmp and /tmp usage if set.
Diffstat (limited to 'src/basic')
-rw-r--r--src/basic/fileio.c17
-rw-r--r--src/basic/fs-util.c98
-rw-r--r--src/basic/fs-util.h3
3 files changed, 94 insertions, 24 deletions
diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index f183de4999..6114bf3315 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -1161,8 +1161,8 @@ int tempfn_random_child(const char *p, const char *extra, char **ret) {
char *t, *x;
uint64_t u;
unsigned i;
+ int r;
- assert(p);
assert(ret);
/* Turns this:
@@ -1171,6 +1171,12 @@ int tempfn_random_child(const char *p, const char *extra, char **ret) {
* /foo/bar/waldo/.#<extra>3c2b6219aa75d7d0
*/
+ if (!p) {
+ r = tmp_dir(&p);
+ if (r < 0)
+ return r;
+ }
+
if (!extra)
extra = "";
@@ -1257,10 +1263,13 @@ int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space)
int open_tmpfile_unlinkable(const char *directory, int flags) {
char *p;
- int fd;
+ int fd, r;
- if (!directory)
- directory = "/tmp";
+ if (!directory) {
+ r = tmp_dir(&directory);
+ if (r < 0)
+ return r;
+ }
/* Returns an unlinked temporary file that cannot be linked into the file system anymore */
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index f0c6f3265e..ce87257bc1 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -496,34 +496,94 @@ int get_files_in_directory(const char *path, char ***list) {
return n;
}
-int var_tmp(char **ret) {
- const char *tmp_dir = NULL;
- const char *env_tmp_dir = NULL;
- char *c = NULL;
- int r;
+static int getenv_tmp_dir(const char **ret_path) {
+ const char *n;
+ int r, ret = 0;
- assert(ret);
+ assert(ret_path);
- env_tmp_dir = getenv("TMPDIR");
- if (env_tmp_dir != NULL) {
- r = is_dir(env_tmp_dir, true);
- if (r < 0 && r != -ENOENT)
- return r;
- if (r > 0)
- tmp_dir = env_tmp_dir;
+ /* We use the same order of environment variables python uses in tempfile.gettempdir():
+ * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
+ FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
+ const char *e;
+
+ e = secure_getenv(n);
+ if (!e)
+ continue;
+ if (!path_is_absolute(e)) {
+ r = -ENOTDIR;
+ goto next;
+ }
+ if (!path_is_safe(e)) {
+ r = -EPERM;
+ goto next;
+ }
+
+ r = is_dir(e, true);
+ if (r < 0)
+ goto next;
+ if (r == 0) {
+ r = -ENOTDIR;
+ goto next;
+ }
+
+ *ret_path = e;
+ return 1;
+
+ next:
+ /* Remember first error, to make this more debuggable */
+ if (ret >= 0)
+ ret = r;
}
- if (!tmp_dir)
- tmp_dir = "/var/tmp";
+ if (ret < 0)
+ return ret;
- c = strdup(tmp_dir);
- if (!c)
- return -ENOMEM;
- *ret = c;
+ *ret_path = NULL;
+ return ret;
+}
+static int tmp_dir_internal(const char *def, const char **ret) {
+ const char *e;
+ int r, k;
+
+ assert(def);
+ assert(ret);
+
+ r = getenv_tmp_dir(&e);
+ if (r > 0) {
+ *ret = e;
+ return 0;
+ }
+
+ k = is_dir(def, true);
+ if (k == 0)
+ k = -ENOTDIR;
+ if (k < 0)
+ return r < 0 ? r : k;
+
+ *ret = def;
return 0;
}
+int var_tmp_dir(const char **ret) {
+
+ /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
+ * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
+ * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
+ * making it a variable that overrides all temporary file storage locations. */
+
+ return tmp_dir_internal("/var/tmp", ret);
+}
+
+int tmp_dir(const char **ret) {
+
+ /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
+ * backed by an in-memory file system: /tmp. */
+
+ return tmp_dir_internal("/tmp", ret);
+}
+
int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
int r;
diff --git a/src/basic/fs-util.h b/src/basic/fs-util.h
index 075e5942b1..2c3b9a1c74 100644
--- a/src/basic/fs-util.h
+++ b/src/basic/fs-util.h
@@ -61,7 +61,8 @@ int mkfifo_atomic(const char *path, mode_t mode);
int get_files_in_directory(const char *path, char ***list);
-int var_tmp(char **ret);
+int tmp_dir(const char **ret);
+int var_tmp_dir(const char **ret);
#define INOTIFY_EVENT_MAX (sizeof(struct inotify_event) + NAME_MAX + 1)