tmpfiles, man: Add xattr support to tmpfiles

This patch makes it possible to set extended attributes on files created
by tmpfiles. This can be especially used to set SMACK security labels on
volatile files and directories.

It is done by adding new line of type "t". Such line should contain
attributes in Argument field, using following format:

name=value

All other fields are ignored.

If value contains spaces, then it must be surrounded by quotation marks.
User can also put quotation mark in value by escaping it with backslash.

Example:
D /var/run/cups - - - -
t /var/run/cups - - - - security.SMACK64=printing

1 files changed, 129 insertions, 10 deletions

diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index d60c57793b..d40bd96f1b 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -39,6 +39,7 @@
 #include <glob.h>
 #include <fnmatch.h>
 #include <sys/capability.h>
+#include <sys/xattr.h>
 
 #include "log.h"
 #include "util.h"
@@ -71,6 +72,7 @@ typedef enum ItemType {
         CREATE_CHAR_DEVICE = 'c',
         CREATE_BLOCK_DEVICE = 'b',
         COPY_FILES = 'C',
+        SET_XATTR = 't',
 
         /* These ones take globs */
         WRITE_FILE = 'w',
@@ -88,6 +90,7 @@ typedef struct Item {
 
         char *path;
         char *argument;
+        char **xattrs;
         uid_t uid;
         gid_t gid;
         mode_t mode;
@@ -487,6 +490,67 @@ static int item_set_perms(Item *i, const char *path) {
         return label_fix(path, false, false);
 }
 
+static int get_xattrs_from_arg(Item *i) {
+        char *xattr;
+        const char *p;
+        int r;
+
+        assert(i);
+
+        if (!i->argument) {
+                log_error("%s: Argument can't be empty!", i->path);
+                return -EBADMSG;
+        }
+        p = i->argument;
+
+        while ((r = unquote_first_word(&p, &xattr, false)) > 0) {
+                _cleanup_free_ char *tmp = NULL, *name = NULL, *value = NULL;
+                r = split_pair(xattr, "=", &name, &value);
+                if (r < 0) {
+                        log_warning("Illegal xattr found: \"%s\" - ignoring.", xattr);
+                        free(xattr);
+                        continue;
+                }
+                free(xattr);
+                if (streq(name, "") || streq(value, "")) {
+                        log_warning("Malformed xattr found: \"%s=%s\" - ignoring.", name, value);
+                        continue;
+                }
+                tmp = unquote(value, "\"");
+                if (!tmp)
+                        return log_oom();
+                free(value);
+                value = cunescape(tmp);
+                if (!value)
+                        return log_oom();
+                if (strv_consume_pair(&i->xattrs, name, value) < 0)
+                        return log_oom();
+                name = value = NULL;
+        }
+
+        return r;
+}
+
+static int item_set_xattrs(Item *i, const char *path) {
+        char **name, **value;
+
+        assert(i);
+        assert(path);
+
+        if (strv_isempty(i->xattrs))
+                return 0;
+
+        STRV_FOREACH_PAIR(name, value, i->xattrs) {
+                int n;
+                n = strlen(*value);
+                if (lsetxattr(path, *name, *value, n, 0) < 0) {
+                        log_error("Setting extended attribute %s=%s on %s failed: %m", *name, *value, path);
+                        return -errno;
+                }
+        }
+        return 0;
+}
+
 static int write_one_file(Item *i, const char *path) {
         _cleanup_close_ int fd = -1;
         int flags, r = 0;
@@ -544,6 +608,10 @@ static int write_one_file(Item *i, const char *path) {
         if (r < 0)
                 return r;
 
+        r = item_set_xattrs(i, i->path);
+        if (r < 0)
+                return r;
+
         return 0;
 }
 
@@ -716,6 +784,10 @@ static int create_item(Item *i) {
                 if (r < 0)
                         return r;
 
+                r = item_set_xattrs(i, i->path);
+                if (r < 0)
+                        return r;
+
                 break;
 
         case CREATE_FIFO:
@@ -756,6 +828,10 @@ static int create_item(Item *i) {
                 if (r < 0)
                         return r;
 
+                r = item_set_xattrs(i, i->path);
+                if (r < 0)
+                        return r;
+
                 break;
 
         case CREATE_SYMLINK:
@@ -787,6 +863,10 @@ static int create_item(Item *i) {
                         }
                 }
 
+                r = item_set_xattrs(i, i->path);
+                if (r < 0)
+                       return r;
+
                 break;
 
         case CREATE_BLOCK_DEVICE:
@@ -847,6 +927,10 @@ static int create_item(Item *i) {
                 if (r < 0)
                         return r;
 
+                r = item_set_xattrs(i, i->path);
+                if (r < 0)
+                        return r;
+
                 break;
         }
 
@@ -863,7 +947,12 @@ static int create_item(Item *i) {
                 r = glob_item(i, item_set_perms_recursive);
                 if (r < 0)
                         return r;
+                break;
 
+        case SET_XATTR:
+                r = item_set_xattrs(i, i->path);
+                if (r < 0)
+                        return r;
                 break;
         }
 
@@ -893,6 +982,7 @@ static int remove_item_instance(Item *i, const char *instance) {
         case RECURSIVE_RELABEL_PATH:
         case WRITE_FILE:
         case COPY_FILES:
+        case SET_XATTR:
                 break;
 
         case REMOVE_PATH:
@@ -936,6 +1026,7 @@ static int remove_item(Item *i) {
         case RECURSIVE_RELABEL_PATH:
         case WRITE_FILE:
         case COPY_FILES:
+        case SET_XATTR:
                 break;
 
         case REMOVE_PATH:
@@ -1059,6 +1150,7 @@ static void item_free(Item *i) {
 
         free(i->path);
         free(i->argument);
+        strv_free(i->xattrs);
         free(i);
 }
 
@@ -1257,6 +1349,16 @@ static int parse_line(const char *fname, unsigned line, const char *buffer) {
                 break;
         }
 
+        case SET_XATTR:
+                if (!i->argument) {
+                        log_error("[%s:%u] Set extended attribute requires argument.", fname, line);
+                        return -EBADMSG;
+                }
+                r = get_xattrs_from_arg(i);
+                if (r < 0)
+                        return r;
+                break;
+
         default:
                 log_error("[%s:%u] Unknown command type '%c'.", fname, line, type);
                 return -EBADMSG;
@@ -1350,18 +1452,35 @@ static int parse_line(const char *fname, unsigned line, const char *buffer) {
 
         existing = hashmap_get(h, i->path);
         if (existing) {
-
-                /* Two identical items are fine */
-                if (!item_equal(existing, i))
-                        log_warning("Two or more conflicting lines for %s configured, ignoring.", i->path);
-
-                return 0;
+                if (i->type == SET_XATTR) {
+                        r = strv_extend_strv(&existing->xattrs, i->xattrs);
+                        if (r < 0)
+                                return log_oom();
+                        return 0;
+                } else if (existing->type == SET_XATTR) {
+                        r = strv_extend_strv(&i->xattrs, existing->xattrs);
+                        if (r < 0)
+                                return log_oom();
+                        r = hashmap_replace(h, i->path, i);
+                        if (r < 0) {
+                                log_error("Failed to replace item for %s.", i->path);
+                                return r;
+                        }
+                        item_free(existing);
+                } else {
+                        /* Two identical items are fine */
+                        if (!item_equal(existing, i))
+                                log_warning("Two or more conflicting lines for %s configured, ignoring.", i->path);
+                        return 0;
+                }
+        } else {
+                r = hashmap_put(h, i->path, i);
+                if (r < 0) {
+                        log_error("Failed to insert item %s: %s", i->path, strerror(-r));
+                        return r;
+                }
         }
 
-        r = hashmap_put(h, i->path, i);
-        if (r < 0)
-                return log_error_errno(r, "Failed to insert item %s: %m", i->path);
-
         i = NULL; /* avoid cleanup */
 
         return 0;