opt-in: skip blacklisted files in private-etc - #5010, #5230

5 files changed, 13 insertions, 2 deletions

diff --git a/etc/firejail.config b/etc/firejail.config
index e8bf45751..26125e4b6 100644
--- a/etc/firejail.config
+++ b/etc/firejail.config
@@ -78,6 +78,9 @@
 # Enable or disable overlayfs features, default enabled.
 # overlayfs yes
 
+# Hide blacklisted files in /etc directory, default disabled.
+# etc-no-blacklisted no
+
 # Set the limit for file copy in several --private-* options. The size is set
 # in megabytes. By default we allow up to 500MB.
 # Note: the files are copied in RAM.
diff --git a/src/firejail/checkcfg.c b/src/firejail/checkcfg.c
index 62b8c4dc4..590543217 100644
--- a/src/firejail/checkcfg.c
+++ b/src/firejail/checkcfg.c
@@ -51,6 +51,7 @@ int checkcfg(int val) {
                         cfg_val[i] = 1; // most of them are enabled by default
                 cfg_val[CFG_RESTRICTED_NETWORK] = 0; // disabled by default
                 cfg_val[CFG_FORCE_NONEWPRIVS] = 0;
+                cfg_val[CFG_ETC_NO_BLACKLISTED] = 0;
                 cfg_val[CFG_PRIVATE_BIN_NO_LOCAL] = 0;
                 cfg_val[CFG_FIREJAIL_PROMPT] = 0;
                 cfg_val[CFG_DISABLE_MNT] = 0;
@@ -115,6 +116,7 @@ int checkcfg(int val) {
                         PARSE_YESNO(CFG_TRACELOG, "tracelog")
                         PARSE_YESNO(CFG_XEPHYR_WINDOW_TITLE, "xephyr-window-title")
                         PARSE_YESNO(CFG_OVERLAYFS, "overlayfs")
+                        PARSE_YESNO(CFG_ETC_NO_BLACKLISTED, "etc-no-blacklisted")
                         PARSE_YESNO(CFG_PRIVATE_BIN, "private-bin")
                         PARSE_YESNO(CFG_PRIVATE_BIN_NO_LOCAL, "private-bin-no-local")
                         PARSE_YESNO(CFG_PRIVATE_CACHE, "private-cache")
diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index 4fe3a5974..cf5c5b2fa 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -811,6 +811,7 @@ enum {
         CFG_FORCE_NONEWPRIVS,
         CFG_XEPHYR_WINDOW_TITLE,
         CFG_OVERLAYFS,
+        CFG_ETC_NO_BLACKLISTED,
         CFG_PRIVATE_BIN,
         CFG_PRIVATE_BIN_NO_LOCAL,
         CFG_PRIVATE_CACHE,
diff --git a/src/firejail/fs.c b/src/firejail/fs.c
index b44eb65ee..3066c50ed 100644
--- a/src/firejail/fs.c
+++ b/src/firejail/fs.c
@@ -162,7 +162,7 @@ static void disable_file(OPERATION op, const char *filename) {
                                 fs_logger2("blacklist-nolog", fname);
 
                         // files in /etc will be reprocessed during /etc rebuild
-                        if (strncmp(fname, "/etc/", 5) == 0) {
+                        if (checkcfg(CFG_ETC_NO_BLACKLISTED) && strncmp(fname, "/etc/", 5) == 0) {
                                 ProfileEntry *prf = malloc(sizeof(ProfileEntry));
                                 if (!prf)
                                         errExit("malloc");
diff --git a/src/firejail/fs_etc.c b/src/firejail/fs_etc.c
index 77fa00d6b..e58537e49 100644
--- a/src/firejail/fs_etc.c
+++ b/src/firejail/fs_etc.c
@@ -264,8 +264,13 @@ void fs_private_dir_list(const char *private_dir, const char *private_run_dir, c
 
 void fs_rebuild_etc(void) {
         int have_dhcp = 1;
-        if (cfg.dns1 == NULL && !any_dhcp())
+        if (cfg.dns1 == NULL && !any_dhcp()) {
+                // this function has the effect that updates to files using rename(2) don't propagate into the sandbox
+                // avoid this in the default setting, in order to not break /etc/resolv.conf (issue #5010)
+                if (!checkcfg(CFG_ETC_NO_BLACKLISTED))
+                        return;
                 have_dhcp = 0;
+        }
 
         if (arg_debug)
                 printf("rebuilding /etc directory\n");