seitan: action for the call

Perform the action action with the context. The action call executes a
syscall in the given namespaces or in caller context if non is
specified.

Signed-off-by: Alice Frosi <afrosi@redhat.com>

1 files changed, 193 insertions, 0 deletions

diff --git a/actions.c b/actions.c
new file mode 100644
index 0000000..edd7a8a
--- /dev/null
+++ b/actions.c
@@ -0,0 +1,193 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sched.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/wait.h>
+#include <linux/seccomp.h>
+#include <linux/filter.h>
+#include <linux/audit.h>
+#include <errno.h>
+
+#include "gluten.h"
+#include "actions.h"
+
+static bool is_cookie_valid(int notifyFd, uint64_t id)
+{
+	return ioctl(notifyFd, SECCOMP_IOCTL_NOTIF_ID_VALID, &id) == 0;
+}
+
+static int send_target(const struct seccomp_notif_resp *resp, int notifyfd)
+{
+	if (!is_cookie_valid(notifyfd, resp->id)) {
+		fprintf(stderr, "the response id isn't valid\ncheck if the targets has already terminated\n");
+		return -1;
+	}
+	if (ioctl(notifyfd, SECCOMP_IOCTL_NOTIF_SEND, resp) < 0) {
+		if (errno != EINPROGRESS) {
+			perror("sending the response");
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static int send_inject_target(const struct seccomp_notif_addfd *resp,
+			      int notifyfd)
+{
+	if (!is_cookie_valid(notifyfd, resp->id)) {
+		fprintf(stderr, "the response id isn't valid\ncheck if the targets has already terminated\n");
+		return -1;
+	}
+	if (ioctl(notifyfd, SECCOMP_IOCTL_NOTIF_ADDFD, resp) < 0) {
+		if (errno != EINPROGRESS) {
+			perror("sending the response");
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static void proc_ns_name(unsigned i, char *ns)
+{
+	switch (i) {
+	case NS_CGROUP:
+		snprintf(ns, PATH_MAX + 1, "cgroup");
+		break;
+	case NS_IPC:
+		snprintf(ns, PATH_MAX + 1, "ipc");
+		break;
+	case NS_NET:
+		snprintf(ns, PATH_MAX + 1, "net");
+		break;
+	case NS_MOUNT:
+		snprintf(ns, PATH_MAX + 1, "mnt");
+		break;
+	case NS_PID:
+		snprintf(ns, PATH_MAX + 1, "pid");
+		break;
+	case NS_USER:
+		snprintf(ns, PATH_MAX + 1, "user");
+		break;
+	case NS_UTS:
+		snprintf(ns, PATH_MAX + 1, "uts");
+		break;
+	case NS_TIME:
+		snprintf(ns, PATH_MAX + 1, "time");
+		break;
+	default:
+		fprintf(stderr, "unrecognized namespace index %d\n", i);
+	}
+}
+
+static int set_namespaces(const struct act_call *a, int tpid)
+{
+	char path[PATH_MAX + 1];
+	char ns_name[PATH_MAX / 2];
+	struct ns_spec ns;
+	int fd;
+	unsigned int i;
+
+	for (i = 0, ns = (a->context).ns[i]; i < sizeof(enum ns_type);
+	     i++, ns = (a->context).ns[i]) {
+		proc_ns_name(i, ns_name);
+		switch (ns.type) {
+		case NS_NONE:
+			continue;
+		case NS_SPEC_TARGET:
+			snprintf(path, sizeof(path), "/proc/%d/ns/%s", tpid,
+				 ns_name);
+			break;
+		case NS_SPEC_PID:
+			snprintf(path, sizeof(path), "/proc/%d/ns/%s", ns.pid,
+				 ns_name);
+			break;
+		case NS_SPEC_PATH:
+			snprintf(path, sizeof(path), "%s", ns.path);
+			break;
+		}
+
+		if ((fd = open(path, O_CLOEXEC)) < 0) {
+			fprintf(stderr, "open for file %s: %s", path,
+				strerror(errno));
+			return -1;
+		}
+
+		if (setns(fd, 0) != 0) {
+			perror("setns");
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static int execute_syscall(void *args)
+{
+	struct arg_clone *a = (struct arg_clone *)args;
+	const struct act_call *c = a->args;
+
+	if (set_namespaces(a->args, a->pid) < 0) {
+		exit(EXIT_FAILURE);
+	}
+	/* execute syscall */
+	a->ret = syscall(c->nr, c->args[0], c->args[1], c->args[2], c->args[3],
+			 c->args[4], c->args[5]);
+	a->err = errno;
+	if (a->ret < 0) {
+		perror("syscall");
+		exit(EXIT_FAILURE);
+	}
+	exit(0);
+}
+
+int do_call(struct arg_clone *c)
+{
+	char stack[STACK_SIZE];
+	pid_t child;
+
+	c->ret = -1;
+	c->err = 0;
+
+	/* Create a process that will be moved to the namespace */
+	child = clone(execute_syscall, stack + sizeof(stack),
+		      CLONE_FILES | CLONE_VM | SIGCHLD, (void *)c);
+	if (child == -1) {
+		perror("clone");
+		return -1;
+	}
+	wait(NULL);
+	return 0;
+}
+
+int do_actions(struct action actions[], unsigned int n_actions, int pid,
+	       int notifyfd, uint64_t id)
+{
+	struct seccomp_notif_resp resp;
+	struct arg_clone c;
+	unsigned int i;
+
+	for (i = 0; i < n_actions; i++) {
+		switch (actions[i].type) {
+		case A_CALL:
+			resp.id = id;
+			resp.val = 0;
+			resp.flags = 0;
+			c.args = &actions[i].call;
+			c.pid = pid;
+			if (do_call(&c) == -1) {
+				resp.error = c.err;
+				if (send_target(&resp, notifyfd) == -1)
+					return -1;
+			}
+			break;
+		default:
+			fprintf(stderr, "unknow action %d \n", actions[i].type);
+		}
+	}
+	return 0;
+}