sandboxing port to linux via landlock

4 files changed, 190 insertions, 39 deletions

diff --git a/Makefile b/Makefile
index 600419d..225031a 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ CFLAGS?=-g -Wall -Wextra -pedantic
 
 all: snac
 
-snac: snac.o main.o data.o http.o httpd.o webfinger.o \
+snac: snac.o main.o sandbox.o data.o http.o httpd.o webfinger.o \
     activitypub.o html.o utils.o format.o upgrade.o mastoapi.o
         $(CC) $(CFLAGS) -L/usr/local/lib *.o -lcurl -lcrypto $(LDFLAGS) -pthread -o $@
 
@@ -36,6 +36,8 @@ uninstall:
 activitypub.o: activitypub.c xs.h xs_json.h xs_curl.h xs_mime.h \
  xs_openssl.h xs_regex.h xs_time.h xs_set.h xs_match.h snac.h \
  http_codes.h
+sandbox.o: sandbox.c xs.h xs_hex.h xs_io.h xs_json.h xs_openssl.h \
+ xs_glob.h xs_set.h xs_time.h xs_regex.h xs_match.h xs_unicode.h snac.h
 data.o: data.c xs.h xs_hex.h xs_io.h xs_json.h xs_openssl.h xs_glob.h \
  xs_set.h xs_time.h xs_regex.h xs_match.h xs_unicode.h xs_random.h snac.h \
  http_codes.h
diff --git a/data.c b/data.c
index 1cd69a5..54099db 100644
--- a/data.c
+++ b/data.c
@@ -115,44 +115,7 @@ int srv_open(const char *basedir, int auto_upgrade)
 #define st_mtim st_mtimespec
 #endif
 
-#ifdef __OpenBSD__
-    if (xs_is_true(xs_dict_get(srv_config, "disable_openbsd_security"))) {
-        srv_debug(1, xs_dup("OpenBSD security disabled by admin"));
-    }
-    else {
-        int smail = !xs_is_true(xs_dict_get(srv_config, "disable_email_notifications"));
-        const char *address = xs_dict_get(srv_config, "address");
-
-        srv_debug(1, xs_fmt("Calling unveil()"));
-        unveil(basedir,                "rwc");
-        unveil("/tmp",                 "rwc");
-        unveil("/etc/resolv.conf",     "r");
-        unveil("/etc/hosts",           "r");
-        unveil("/etc/ssl/openssl.cnf", "r");
-        unveil("/etc/ssl/cert.pem",    "r");
-        unveil("/usr/share/zoneinfo",  "r");
-
-        if (smail)
-            unveil("/usr/sbin/sendmail",   "x");
-
-        if (*address == '/')
-            unveil(address, "rwc");
-
-        unveil(NULL,                   NULL);
-
-        srv_debug(1, xs_fmt("Calling pledge()"));
-
-        xs *p = xs_str_new("stdio rpath wpath cpath flock inet proc dns fattr");
-
-        if (smail)
-            p = xs_str_cat(p, " exec");
-
-        if (*address == '/')
-            p = xs_str_cat(p, " unix");
-
-        pledge(p, NULL);
-    }
-#endif /* __OpenBSD__ */
+    sbox_enter(srv_basedir);
 
     /* read (and drop) emojis.json, possibly creating it */
     xs_free(emojis());
diff --git a/sandbox.c b/sandbox.c
new file mode 100644
index 0000000..f83a947
--- /dev/null
+++ b/sandbox.c
@@ -0,0 +1,184 @@
+#include "xs.h"
+
+#include "snac.h"
+
+#include <unistd.h>
+
+#if defined (__linux__)
+#   define __USE_GNU
+#   include <linux/landlock.h>
+#   include <linux/prctl.h>
+#   include <sys/syscall.h>
+#   include <sys/prctl.h>
+#   include <fcntl.h>
+#   include <arpa/inet.h>
+#endif
+
+void sbox_enter(const char *basedir)
+{
+    if (xs_is_true(xs_dict_get(srv_config, "disable_openbsd_security"))) {
+        srv_log(xs_dup("disable_openbsd_security is deprecated. Use disable_sandbox instead."));
+        return;
+    }
+    if (xs_is_true(xs_dict_get(srv_config, "disable_sandbox"))) {
+        srv_debug(0, xs_dup("Sandbox disabled by admin"));
+        return;
+    }
+
+    const char *address = xs_dict_get(srv_config, "address");
+
+#if defined (__OpenBSD__)
+    int smail = !xs_is_true(xs_dict_get(srv_config, "disable_email_notifications"));
+
+    srv_debug(1, xs_fmt("Calling unveil()"));
+    unveil(basedir,                "rwc");
+    unveil("/tmp",                 "rwc");
+    unveil("/etc/resolv.conf",     "r");
+    unveil("/etc/hosts",           "r");
+    unveil("/etc/ssl/openssl.cnf", "r");
+    unveil("/etc/ssl/cert.pem",    "r");
+    unveil("/usr/share/zoneinfo",  "r");
+
+    if (smail)
+        unveil("/usr/sbin/sendmail",   "x");
+
+    if (*address == '/')
+        unveil(address, "rwc");
+
+    unveil(NULL,                   NULL);
+
+    srv_debug(1, xs_fmt("Calling pledge()"));
+
+    xs *p = xs_str_new("stdio rpath wpath cpath flock inet proc dns fattr");
+
+    if (smail)
+        p = xs_str_cat(p, " exec");
+
+    if (*address == '/')
+        p = xs_str_cat(p, " unix");
+
+    pledge(p, NULL);
+
+    xs_free(p);
+#elif defined (__linux__)
+    int error, ruleset_fd, abi;
+    struct landlock_ruleset_attr      rules = {0};
+    struct landlock_path_beneath_attr path  = {0};
+    struct landlock_net_port_attr     net   = {0};
+
+    rules.handled_access_fs =
+        LANDLOCK_ACCESS_FS_EXECUTE     |
+        LANDLOCK_ACCESS_FS_WRITE_FILE  |
+        LANDLOCK_ACCESS_FS_READ_FILE   |
+        LANDLOCK_ACCESS_FS_REMOVE_DIR  |
+        LANDLOCK_ACCESS_FS_REMOVE_FILE |
+        LANDLOCK_ACCESS_FS_MAKE_CHAR   |
+        LANDLOCK_ACCESS_FS_MAKE_DIR    |
+        LANDLOCK_ACCESS_FS_MAKE_REG    |
+        LANDLOCK_ACCESS_FS_MAKE_SOCK   |
+        LANDLOCK_ACCESS_FS_MAKE_FIFO   |
+        LANDLOCK_ACCESS_FS_MAKE_BLOCK  |
+        LANDLOCK_ACCESS_FS_MAKE_SYM    |
+        LANDLOCK_ACCESS_FS_REFER       |
+        LANDLOCK_ACCESS_FS_TRUNCATE    |
+        LANDLOCK_ACCESS_FS_IOCTL_DEV;
+    rules.handled_access_net =
+        LANDLOCK_ACCESS_NET_BIND_TCP |
+        LANDLOCK_ACCESS_NET_CONNECT_TCP;
+
+    abi = syscall(SYS_landlock_create_ruleset, NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
+    switch (abi) {
+    case -1:
+        srv_debug(0, xs_dup("Kernel without landlock support"));
+        return;
+    case 1:
+        rules.handled_access_fs  &= ~LANDLOCK_ACCESS_FS_REFER;
+        __attribute__((fallthrough));
+    case 2:
+        rules.handled_access_fs  &= ~LANDLOCK_ACCESS_FS_TRUNCATE;
+        __attribute__((fallthrough));
+    case 3:
+        rules.handled_access_net &= ~(LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP);
+        __attribute__((fallthrough));
+    case 4:
+        rules.handled_access_fs  &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
+    }
+    srv_debug(1, xs_fmt("lanlock abi: %d", abi));
+
+    ruleset_fd = syscall(SYS_landlock_create_ruleset, &rules, sizeof(struct landlock_ruleset_attr), 0);
+    if (ruleset_fd == -1) {
+        srv_debug(0, xs_fmt("landlock_create_ruleset failed: %s", strerror(errno)));
+        return;
+    }
+
+#define LL_R LANDLOCK_ACCESS_FS_READ_FILE
+#define LL_X LANDLOCK_ACCESS_FS_EXECUTE
+#define LL_RWC (LL_R | LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_MAKE_REG | LANDLOCK_ACCESS_FS_TRUNCATE)
+#define LL_UNX (LL_R | LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_MAKE_SOCK)
+#define LL_CON LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define LL_BND LANDLOCK_ACCESS_NET_BIND_TCP
+
+#define LANDLOCK_PATH(p, r) do {\
+    path.allowed_access = r;\
+    if (abi < 3)\
+        path.allowed_access &= ~LANDLOCK_ACCESS_FS_TRUNCATE;\
+    path.parent_fd = open(p, O_PATH | O_CLOEXEC);\
+    if (path.parent_fd == -1) {\
+        srv_debug(2, xs_fmt("open %s: %s", p, strerror(errno)));\
+        goto close;\
+    }\
+    error = syscall(SYS_landlock_add_rule, ruleset_fd, LANDLOCK_RULE_PATH_BENEATH, &path, 0); \
+    if (error) {\
+        srv_debug(0, xs_fmt("LANDLOCK_PATH(%s): %s", p, strerror(errno)));\
+        goto close;\
+    }\
+} while (0)
+
+#define LANDLOCK_PORT(p, r) do {\
+    uint16_t _p = p;\
+    net.port = _p;\
+    net.allowed_access = r;\
+    error = syscall(SYS_landlock_add_rule, ruleset_fd, LANDLOCK_RULE_NET_PORT, &net, 0);\
+    if (error) {\
+        srv_debug(0, xs_fmt("LANDLOCK_PORT(%d): %s", _p, strerror(errno)));\
+        goto close;\
+    }\
+} while (0)
+
+    LANDLOCK_PATH(basedir,                LL_RWC);
+    LANDLOCK_PATH("/tmp",                 LL_RWC);
+    LANDLOCK_PATH("/dev/shm",             LL_RWC);
+    LANDLOCK_PATH("/etc/resolv.conf",     LL_R  );
+    LANDLOCK_PATH("/etc/hosts",           LL_R  );
+    LANDLOCK_PATH("/etc/ssl/openssl.cnf", LL_R  );
+    LANDLOCK_PATH("/etc/ssl/cert.pem",    LL_R  );
+    LANDLOCK_PATH("/usr/share/zoneinfo",  LL_R  );
+
+    if (*address == '/')
+        LANDLOCK_PATH(address, LL_UNX);
+
+    if (abi > 3) {
+        if (*address != '/') {
+            LANDLOCK_PORT(
+                (uint16_t)xs_number_get(xs_dict_get(srv_config, "port")), LL_BND);
+        }
+
+        LANDLOCK_PORT(80,  LL_CON);
+        LANDLOCK_PORT(443, LL_CON);
+    }
+    
+    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+        srv_debug(0, xs_fmt("prctl SET_NO_NEW_PRIVS: %s", strerror(errno)));
+        goto close;
+    }
+
+    if (syscall(SYS_landlock_restrict_self, ruleset_fd, 0))
+        srv_debug(0, xs_fmt("landlock_restrict_self: %s", strerror(errno)));
+
+    srv_log(xs_dup("landlocked"));
+
+close:
+    close(ruleset_fd);
+
+#endif
+}
diff --git a/snac.h b/snac.h
index ad2793e..ba84420 100644
--- a/snac.h
+++ b/snac.h
@@ -75,6 +75,8 @@ void snac_log(snac *user, xs_str *str);
 int srv_open(const char *basedir, int auto_upgrade);
 void srv_free(void);
 
+void sbox_enter(const char *basedir);
+
 int user_open(snac *snac, const char *uid);
 void user_free(snac *snac);
 xs_list *user_list(void);