seccomp: add support for seccomp notify

add support for seccomp notify and add a basic support for emulating
mknod and mknodat.  The handler implementation is likely going to
change, for now it is just a PoC to show how it would work.

Requires: containers/crun#438
Requires: libseccomp-2.5

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

.cirrus.yml

@@ -68,7 +68,7 @@ fedora_packaging_task:
         memory: 4
 
     script:
-        - dnf install -y make glib2-devel git gcc rpm-build golang
+        - dnf install -y make glib2-devel git gcc rpm-build golang libseccomp-devel
         - cd $CIRRUS_WORKING_DIR
         - make
         - make -f .rpmbuild/Makefile

Makefile

@@ -6,7 +6,8 @@ GO ?= go
 PROJECT := github.com/containers/conmon
 PKG_CONFIG ?= pkg-config
 HEADERS := $(wildcard src/*.h)
-OBJS := src/conmon.o src/cmsg.o src/ctr_logging.o src/utils.o src/cli.o src/globals.o src/cgroup.o src/conn_sock.o src/oom.o src/ctrl.o src/ctr_stdio.o src/parent_pipe_fd.o src/ctr_exit.o src/runtime_args.o src/close_fds.o
+
+OBJS := src/conmon.o src/cmsg.o src/ctr_logging.o src/utils.o src/cli.o src/globals.o src/cgroup.o src/conn_sock.o src/oom.o src/ctrl.o src/ctr_stdio.o src/parent_pipe_fd.o src/ctr_exit.o src/runtime_args.o src/close_fds.o src/seccomp_notify.o
 
 MAKEFILE_PATH := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
 
@@ -45,6 +46,11 @@ else ifeq ($(shell $(PKG_CONFIG) --exists libsystemd && echo "0" || echo "1"), 0
 	override CFLAGS += $(shell $(PKG_CONFIG) --cflags libsystemd) -D USE_JOURNALD=0
 endif
 
+ifeq ($(shell $(PKG_CONFIG) --exists libseccomp && echo "0" || echo "1"), 0)
+	override LIBS += $(shell $(PKG_CONFIG) --libs libseccomp) -ldl
+	override CFLAGS += $(shell $(PKG_CONFIG) --cflags libseccomp)
+endif
+
 # Update nix/nixpkgs.json its latest stable commit
 .PHONY: nixpkgs
 nixpkgs:

contrib/spec/conmon.spec.in

@@ -22,6 +22,7 @@ ExclusiveArch: aarch64 %{arm} ppc64le s390x x86_64
 BuildRequires: gcc
 BuildRequires: glib2-devel
 BuildRequires: glibc-devel
+BuildRequires: libseccomp-devel
 BuildRequires: git
 # If go_compiler is not set to 1, there is no virtual provide. Use golang instead.
 BuildRequires: golang

meson.build

@@ -34,6 +34,7 @@ add_project_arguments('-Os', '-Wall', '-Werror',
                       language : 'c')
 
 glib = dependency('glib-2.0')
+libdl = cc.find_library('dl')
 
 executable('conmon',
            ['src/conmon.c',
@@ -67,8 +68,10 @@ executable('conmon',
             'src/runtime_args.c',
             'src/runtime_args.h',
             'src/utils.c',
-            'src/utils.h'],
-           dependencies : [glib],
+            'src/utils.h',
+            'src/seccomp_notify.c',
+            'src/seccomp_notify.h'],
+           dependencies : [glib, libdl],
            install : true,
            install_dir : join_paths(get_option('libexecdir'), 'podman'),
 )

nix/default.nix

@@ -13,6 +13,7 @@ let
         autogen = (static pkg.autogen);
         e2fsprogs = (static pkg.e2fsprogs);
         libuv = (static pkg.libuv);
+        libseccomp = (static pkg.libseccomp);
         glib = (static pkg.glib).overrideAttrs(x: {
           outputs = [ "bin" "out" "dev" ];
           mesonFlags = [
@@ -60,7 +61,7 @@ let
     enableParallelBuilding = true;
     outputs = [ "out" ];
     nativeBuildInputs = [ bash gitMinimal pcre pkg-config which ];
-    buildInputs = [ glibc glibc.static glib ];
+    buildInputs = [ glibc glibc.static glib libseccomp ];
     prePatch = ''
       export CFLAGS='-static -pthread'
       export LDFLAGS='-s -w -static-libgcc -static'

src/cli.c

@@ -50,6 +50,8 @@ gboolean opt_sync = FALSE;
 gboolean opt_no_sync_log = FALSE;
 char *opt_sdnotify_socket = NULL;
 gboolean opt_full_attach_path = FALSE;
+char *opt_seccomp_notify_socket = NULL;
+char *opt_seccomp_notify_plugins = NULL;
 GOptionEntry opt_entries[] = {
 	{"api-version", 0, 0, G_OPTION_ARG_NONE, &opt_api_version, "Conmon API version to use", NULL},
 	{"bundle", 'b', 0, G_OPTION_ARG_STRING, &opt_bundle_path, "Location of the OCI Bundle path", NULL},
@@ -100,6 +102,10 @@ GOptionEntry opt_entries[] = {
 	{"version", 0, 0, G_OPTION_ARG_NONE, &opt_version, "Print the version and exit", NULL},
 	{"full-attach", 0, 0, G_OPTION_ARG_NONE, &opt_full_attach_path,
 	 "Don't truncate the path to the attach socket. This option causes conmon to ignore --socket-dir-path", NULL},
+	{"seccomp-notify-socket", 0, 0, G_OPTION_ARG_STRING, &opt_seccomp_notify_socket,
+	 "Path to the socket where the seccomp notification fd is received", NULL},
+	{"seccomp-notify-plugins", 0, 0, G_OPTION_ARG_STRING, &opt_seccomp_notify_plugins,
+	 "Plugins to use for managing the seccomp notifications", NULL},
 	{NULL, 0, 0, 0, NULL, NULL, NULL}};
 
 
@@ -150,6 +156,9 @@ void process_cli()
 	if (opt_cuuid == NULL && (!opt_exec || opt_api_version >= 1))
 		nexit("Container UUID not provided. Use --cuuid");
 
+	if (opt_seccomp_notify_plugins == NULL)
+		opt_seccomp_notify_plugins = getenv("CONMON_SECCOMP_NOTIFY_PLUGINS");
+
 	if (opt_runtime_path == NULL)
 		nexit("Runtime path not provided. Use --runtime");
 	if (access(opt_runtime_path, X_OK) < 0)

src/cli.h

@@ -43,6 +43,8 @@ extern char *opt_log_tag;
 extern gboolean opt_no_sync_log;
 extern gboolean opt_sync;
 extern char *opt_sdnotify_socket;
+extern char *opt_seccomp_notify_socket;
+extern char *opt_seccomp_notify_plugins;
 extern GOptionEntry opt_entries[];
 extern gboolean opt_full_attach_path;
 

src/conmon.c

@@ -18,6 +18,7 @@
 #include "parent_pipe_fd.h"
 #include "ctr_exit.h"
 #include "close_fds.h"
+#include "seccomp_notify.h"
 #include "runtime_args.h"
 
 #include <sys/prctl.h>
@@ -131,6 +132,7 @@ int main(int argc, char *argv[])
 	}
 
 	_cleanup_free_ char *csname = NULL;
+	_cleanup_free_ char *seccomp_listener = NULL;
 	int workerfd_stdin = -1;
 	int workerfd_stdout = -1;
 	int workerfd_stderr = -1;
@@ -173,6 +175,12 @@ int main(int argc, char *argv[])
 			g_unix_fd_add(winsz_fd_r, G_IO_IN, ctrl_winsz_cb, NULL);
 	}
 
+	if (opt_seccomp_notify_socket != NULL) {
+		if (opt_seccomp_notify_plugins == NULL)
+			pexit("seccomp notify socket specified without any plugin");
+		seccomp_listener = setup_seccomp_socket(opt_seccomp_notify_socket);
+	}
+
 	/* We always create a stderr pipe, because that way we can capture
 	   runc stderr messages before the tty is created */
 	if (pipe2(fds, O_CLOEXEC) < 0)
@@ -315,6 +323,9 @@ int main(int argc, char *argv[])
 	if (workerfd_stderr > -1)
 		close(workerfd_stderr);
 
+	if (seccomp_listener != NULL)
+		g_unix_fd_add(seccomp_socket_fd, G_IO_IN, seccomp_accept_cb, csname);
+
 	if (csname != NULL) {
 		g_unix_fd_add(console_socket_fd, G_IO_IN, terminal_accept_cb, csname);
 		/* Process any SIGCHLD we may have missed before the signal handler was in place.  */
@@ -488,6 +499,8 @@ int main(int argc, char *argv[])
 		if (!g_file_set_contents(exit_file_path, status_str, -1, &err))
 			nexitf("Failed to write %s to exit file: %s", status_str, err->message);
 	}
+	if (seccomp_listener != NULL)
+		unlink(seccomp_listener);
 
 	/* Send the command exec exit code back to the parent */
 	if (opt_exec && sync_pipe_fd >= 0)

src/conn_sock.c

@@ -25,6 +25,7 @@ static gboolean local_sock_write_cb(G_GNUC_UNUSED int fd, G_GNUC_UNUSED GIOCondi
 static char *bind_unix_socket(char *socket_relative_name, int sock_type, mode_t perms, struct remote_sock_s *remote_sock,
 			      gboolean use_full_attach_path);
 static char *socket_parent_dir(gboolean use_full_attach_path, size_t desired_len);
+static char *setup_socket(int *fd, const char *path);
 /*
   Since our socket handling is abstract now, handling is based on sock_type, so we can pass around a structure
   that contains everything we need to handle I/O.  Callbacks used to handle IO, for example, and whether this
@@ -72,38 +73,79 @@ struct remote_sock_s remote_notify_sock = {
 };
 
 /* External */
+
 char *setup_console_socket(void)
+{
+	return setup_socket(&console_socket_fd, NULL);
+}
+
+char *setup_seccomp_socket(const char *socket)
+{
+	return setup_socket(&seccomp_socket_fd, socket);
+}
+       #include <libgen.h>
+
+static char *setup_socket(int *fd, const char *path)
 {
 	struct sockaddr_un addr = {0};
-	_cleanup_free_ const char *tmpdir = g_get_tmp_dir();
-	char *csname = g_build_filename(tmpdir, "conmon-term.XXXXXX", NULL);
-	/*
-	 * Generate a temporary name. Is this unsafe? Probably, but we can
-	 * replace it with a rename(2) setup if necessary.
-	 */
+	char *csname = NULL;
+	_cleanup_close_ int sfd = -1;
+	_cleanup_free_ char *dname_buf = NULL;
+	_cleanup_free_ char *bname_buf = NULL;
+	char *dname = NULL, *bname = NULL;
+
+	if (path != NULL) {
+		csname = strdup(path);
+		dname_buf = strdup(path);
+		bname_buf = strdup(path);
+		if (csname == NULL || dname_buf == NULL || bname_buf == NULL) {
+			pexit("Failed to allocate memory");
+			return NULL;
+		}
+		dname = dirname(dname_buf);
+		if (dname == NULL)
+			pexitf("Cannot get dirname for %s", csname);
 
-	int unusedfd = g_mkstemp(csname);
-	if (unusedfd < 0)
-		pexit("Failed to generate random path for console-socket");
-	close(unusedfd);
+		sfd = open(dname, O_CREAT|O_PATH, 0600);
+		if (sfd < 0)
+			pexit("Failed to create file for console-socket");
+
+		bname = basename(bname_buf);
+		if (bname == NULL)
+			pexitf("Cannot get basename for %s", csname);
+	} else {
+		_cleanup_free_ const char *tmpdir = g_get_tmp_dir();
+
+		csname = g_build_filename(tmpdir, "conmon-term.XXXXXX", NULL);
+		/*
+		 * Generate a temporary name. Is this unsafe? Probably, but we can
+		 * replace it with a rename(2) setup if necessary.
+		 */
+		sfd = g_mkstemp(csname);
+		if (sfd < 0)
+			pexit("Failed to generate random path for console-socket");
+		/* XXX: This should be handled with a rename(2). */
+		if (unlink(csname) < 0)
+			pexit("Failed to unlink temporary random path");
+	}
 
 	addr.sun_family = AF_UNIX;
-	strncpy(addr.sun_path, csname, sizeof(addr.sun_path) - 1);
+	if (bname)
+		snprintf(addr.sun_path, sizeof(addr.sun_path) - 1, "/proc/self/fd/%d/%s", sfd, bname);
+	else
+		strncpy(addr.sun_path, csname, sizeof(addr.sun_path) - 1);
 
 	ninfof("addr{sun_family=AF_UNIX, sun_path=%s}", addr.sun_path);
 
 	/* Bind to the console socket path. */
-	console_socket_fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
-	if (console_socket_fd < 0)
-		pexit("Failed to create console-socket");
-	if (fchmod(console_socket_fd, 0700))
+	*fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+	if (*fd < 0)
+		pexit("Failed to create socket");
+	if (fchmod(*fd, 0700))
 		pexit("Failed to change console-socket permissions");
-	/* XXX: This should be handled with a rename(2). */
-	if (unlink(csname) < 0)
-		pexit("Failed to unlink temporary random path");
-	if (bind(console_socket_fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
+	if (bind(*fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
 		pexit("Failed to bind to console-socket");
-	if (listen(console_socket_fd, 128) < 0)
+	if (listen(*fd, 128) < 0)
 		pexit("Failed to listen on console-socket");
 
 	return csname;

src/conn_sock.h

@@ -48,6 +48,7 @@ struct local_sock_s {
 };
 
 char *setup_console_socket(void);
+char *setup_seccomp_socket(const char *socket);
 char *setup_attach_socket(void);
 void setup_notify_socket(char *);
 void schedule_main_stdin_write();

src/ctrl.c

@@ -8,6 +8,7 @@
 #include "conn_sock.h"
 #include "cmsg.h"
 #include "cli.h" // opt_bundle_path
+#include "seccomp_notify.h"
 
 #include <sys/ioctl.h>
 #include <sys/socket.h>

src/globals.c

@@ -9,6 +9,7 @@ int mainfd_stderr = -1;
 
 int attach_socket_fd = -1;
 int console_socket_fd = -1;
+int seccomp_socket_fd = -1;
 int terminal_ctrl_fd = -1;
 int inotify_fd = -1;
 int winsz_fd_w = -1;

src/globals.h

@@ -14,6 +14,7 @@ extern int mainfd_stderr;
 
 extern int attach_socket_fd;
 extern int console_socket_fd;
+extern int seccomp_socket_fd;
 extern int terminal_ctrl_fd;
 extern int inotify_fd;
 extern int winsz_fd_w;