smack: Handling network

- Set Smack ambient to match run label
- Set Smack netlabel host rules

Set Smack ambient to match run label
------------------------------------
Set the Smack networking ambient label to match the
run label of systemd. System services may expect to
communicate with external services over IP. Setting
the ambient label assigns that label to IP packets
that do not include CIPSO headers. This allows systemd
and the services it spawns access to unlabeled IP
packets, and hence external services.

A system may choose to restrict network access to
particular services later in the startup process.
This is easily done by resetting the ambient label
elsewhere.

Set Smack netlabel host rules
-----------------------------
If SMACK_RUN_LABEL is defined set all other hosts to be
single label hosts at the specified label. Set the loopback
address to be a CIPSO host.

If any netlabel host rules are defined in /etc/smack/netlabel.d
install them into the smackfs netlabel interface.

[Patrick Ohly: copied from https://review.tizen.org/git/?p=platform/upstream/systemd.git;a=commit;h=db4f6c9a074644aa2bf]
[Patrick Ohly: adapt to write_string_file() change in "fileio: consolidate write_string_file*()"]
[Patrick Ohly: create write_netlabel_rules() based on the original write_rules() that was removed in "smack: support smack access change-rule"]
[Patrick Ohly: adapted to upstream code review feedback: error logging, string constants]

1 files changed, 98 insertions, 3 deletions

diff --git a/src/core/smack-setup.c b/src/core/smack-setup.c
index 0661ff9ecd..c9374ca0e8 100644
--- a/src/core/smack-setup.c
+++ b/src/core/smack-setup.c
@@ -197,6 +197,75 @@ static int write_cipso2_rules(const char* srcdir) {
         return r;
 }
 
+static int write_netlabel_rules(const char* srcdir) {
+        _cleanup_fclose_ FILE *dst = NULL;
+        _cleanup_closedir_ DIR *dir = NULL;
+        struct dirent *entry;
+        char buf[NAME_MAX];
+        int dfd = -1;
+        int r = 0;
+
+        dst = fopen("/sys/fs/smackfs/netlabel", "we");
+        if (!dst)  {
+                if (errno != ENOENT)
+                        log_warning_errno(errno, "Failed to open /sys/fs/smackfs/netlabel: %m");
+                return -errno; /* negative error */
+        }
+
+        /* write rules to dst from every file in the directory */
+        dir = opendir(srcdir);
+        if (!dir) {
+                if (errno != ENOENT)
+                        log_warning_errno(errno, "Failed to opendir %s: %m", srcdir);
+                return errno; /* positive on purpose */
+        }
+
+        dfd = dirfd(dir);
+        assert(dfd >= 0);
+
+        FOREACH_DIRENT(entry, dir, return 0) {
+                int fd;
+                _cleanup_fclose_ FILE *policy = NULL;
+
+                fd = openat(dfd, entry->d_name, O_RDONLY|O_CLOEXEC);
+                if (fd < 0) {
+                        if (r == 0)
+                                r = -errno;
+                        log_warning_errno(errno, "Failed to open %s: %m", entry->d_name);
+                        continue;
+                }
+
+                policy = fdopen(fd, "re");
+                if (!policy) {
+                        if (r == 0)
+                                r = -errno;
+                        safe_close(fd);
+                        log_error_errno(errno, "Failed to open %s: %m", entry->d_name);
+                        continue;
+                }
+
+                /* load2 write rules in the kernel require a line buffered stream */
+                FOREACH_LINE(buf, policy,
+                             log_error_errno(errno, "Failed to read line from %s: %m",
+                                       entry->d_name)) {
+                        if (!fputs(buf, dst)) {
+                                if (r == 0)
+                                        r = -EINVAL;
+                                log_error_errno(errno, "Failed to write line to /sys/fs/smackfs/netlabel");
+                                break;
+                        }
+                        if (fflush(dst)) {
+                                if (r == 0)
+                                        r = -errno;
+                                log_error_errno(errno, "Failed to flush writes to /sys/fs/smackfs/netlabel: %m");
+                                break;
+                        }
+                }
+        }
+
+       return r;
+}
+
 #endif
 
 int mac_smack_setup(bool *loaded_policy) {
@@ -225,8 +294,18 @@ int mac_smack_setup(bool *loaded_policy) {
 
 #ifdef SMACK_RUN_LABEL
         r = write_string_file("/proc/self/attr/current", SMACK_RUN_LABEL, 0);
-        if (r)
-                log_warning_errno(r, "Failed to set SMACK label \"%s\" on self: %m", SMACK_RUN_LABEL);
+        if (r < 0)
+                log_warning_errno(r, "Failed to set SMACK label \"" SMACK_RUN_LABEL "\" on self: %m");
+        r = write_string_file("/sys/fs/smackfs/ambient", SMACK_RUN_LABEL, 0);
+        if (r < 0)
+                log_warning_errno(r, "Failed to set SMACK ambient label \"" SMACK_RUN_LABEL "\": %m");
+        r = write_string_file("/sys/fs/smackfs/netlabel",
+                              "0.0.0.0/0 " SMACK_RUN_LABEL, 0);
+        if (r < 0)
+                log_warning_errno(r, "Failed to set SMACK netlabel rule \"0.0.0.0/0 " SMACK_RUN_LABEL "\": %m");
+        r = write_string_file("/sys/fs/smackfs/netlabel", "127.0.0.1 -CIPSO", 0);
+        if (r < 0)
+                log_warning_errno(r, "Failed to set SMACK netlabel rule \"127.0.0.1 -CIPSO\": %m");
 #endif
 
         r = write_cipso2_rules("/etc/smack/cipso.d/");
@@ -236,13 +315,29 @@ int mac_smack_setup(bool *loaded_policy) {
                 return 0;
         case ENOENT:
                 log_debug("Smack/CIPSO access rules directory '/etc/smack/cipso.d/' not found");
-                return 0;
+                break;
         case 0:
                 log_info("Successfully loaded Smack/CIPSO policies.");
                 break;
         default:
                 log_warning_errno(r, "Failed to load Smack/CIPSO access rules, ignoring: %m");
+                break;
+        }
+
+        r = write_netlabel_rules("/etc/smack/netlabel.d/");
+        switch(r) {
+        case -ENOENT:
+                log_debug("Smack/CIPSO is not enabled in the kernel.");
                 return 0;
+        case ENOENT:
+                log_debug("Smack network host rules directory '/etc/smack/netlabel.d/' not found");
+                break;
+        case 0:
+                log_info("Successfully loaded Smack network host rules.");
+                break;
+        default:
+                log_warning_errno(r, "Failed to load Smack network host rules: %m, ignoring.");
+                break;
         }
 
         *loaded_policy = true;