path: root/operations.c

/* SPDX-License-Identifier: GPL-3.0-or-later
 * Copyright 2023 Red Hat GmbH
 * Author: Alice Frosi <afrosi@redhat.com>
 */

#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 "operations.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 op_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 op_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 copy_args(struct seccomp_notif *req, struct op_copy_args *copy, void *data,
	      int notifier)
{
	char path[PATH_MAX];
	unsigned int i;
	ssize_t nread;
	void *dest;
	int fd;

	snprintf(path, sizeof(path), "/proc/%d/mem", req->pid);
	if ((fd = open(path, O_RDONLY | O_CLOEXEC)) < 0) {
		perror("open mem");
		return -1;
	}

	/*
         * Avoid the TOCTOU and check if the read mappings are still valid
         */
	if (!is_cookie_valid(notifier, req->id)) {
		fprintf(stderr, "the seccomp request isn't valid anymore\n");
		return -1;
	}
	for (i = 0; i < 6; i++) {
		if (copy->args[i].type == REFERENCE) {
			dest = (uint16_t *)data + copy->args[i].args_off;
			nread = pread(fd, dest, copy->args[i].size,
				      req->data.args[i]);
			if (nread < 0) {
				perror("pread");
				return -1;
			}
		} else {
			memcpy((uint16_t *)data + copy->args[i].args_off,
			       &req->data.args[i], copy->args[i].size);
		}
	}
	close(fd);
	return 0;
}

static int resolve_fd(void *data, struct op_resolvedfd *resfd, pid_t pid)
{
	char fdpath[PATH_MAX], buf[PATH_MAX];
	char *path = (char *)((uint16_t *)data + resfd->path_off);
	int *fd = (int *)((uint16_t *)data + resfd->fd_off);
	ssize_t nbytes;

	snprintf(fdpath, PATH_MAX, "/proc/%d/fd/%d", pid, *fd);
	if ((nbytes = readlink(fdpath, buf, resfd->path_size)) < 0) {
		fprintf(stderr, "error reading %s\n", fdpath);
		perror("readlink");
		return -1;
	}
	if (strcmp(path, buf) == 0)
		return 0;
	else
		return 1;
}

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;
}

static void set_inject_fields(uint64_t id, void *data, const struct op *a,
			      struct seccomp_notif_addfd *resp)
{
	const struct fd_type *new = &(a->inj).newfd;
	const struct fd_type *old = &(a->inj).oldfd;

	resp->flags = SECCOMP_ADDFD_FLAG_SETFD;
	resp->id = id;
	if (new->type == IMMEDIATE)
		resp->newfd = new->fd;
	else
		memcpy(&resp->newfd, (uint16_t *)data + new->fd_off,
		       sizeof(resp->newfd));

	if (old->type == IMMEDIATE)
		resp->srcfd = old->fd;
	else
		memcpy(&resp->srcfd, (uint16_t *)data + old->fd_off,
		       sizeof(resp->srcfd));
	resp->newfd_flags = 0;
}

static int op_cmp(void *data, const struct op_cmp *c)
{
	enum op_cmp_type cmp = c->cmp;
	int res = memcmp((uint16_t *)data + c->s1_off,
			 (uint16_t *)data + c->s2_off, c->size);
	if ((res == 0 && (cmp == CMP_EQ || cmp == CMP_LE || cmp == CMP_GE)) ||
	    (res < 0 && (cmp == CMP_LT || cmp == CMP_LE)) ||
	    (res > 0 && (cmp == CMP_GT || cmp == CMP_GE)))
		return c->jmp;
	else
		return -1;
}

int do_operations(void *data, struct op operations[], struct seccomp_notif *req,
		  unsigned int n_operations, int notifyfd)
{
	struct seccomp_notif_addfd resp_fd;
	struct seccomp_notif_resp resp;
	struct arg_clone c;
	unsigned int i;
	int ret;

	for (i = 0; i < n_operations; i++) {
		switch (operations[i].type) {
		case OP_CALL:
			resp.id = req->id;
			resp.val = 0;
			resp.flags = 0;
			c.args = &operations[i].call;
			c.pid = req->pid;
			if (do_call(&c) == -1) {
				resp.error = -1;
				if (send_target(&resp, notifyfd) == -1)
					return -1;
			}
			if (c.err != 0) {
				resp.error = -1;
				if (send_target(&resp, notifyfd) == -1)
					return c.err;
			}
			/*
			 * The result of the call needs to be save as
			 * reference
			 */
			if (operations[i].call.has_ret) {
				memcpy((uint16_t *)data +
					       operations[i].call.ret_off,
				       &c.ret, sizeof(c.ret));
			}
			break;
		case OP_BLOCK:
			resp.id = req->id;
			resp.val = 0;
			resp.flags = 0;
			resp.error = operations[i].block.error;
			if (send_target(&resp, notifyfd) == -1)
				return -1;
			break;
		case OP_RETURN:
			resp.id = req->id;
			resp.flags = 0;
			resp.error = 0;
			if (operations[i].ret.type == IMMEDIATE)
				resp.val = operations[i].ret.value;
			else
				memcpy(&resp.val,
				       (uint16_t *)data +
					       operations[i].ret.value_off,
				       sizeof(resp.val));

			if (send_target(&resp, notifyfd) == -1)
				return -1;
			break;

		case OP_CONT:
			resp.id = req->id;
			resp.flags = SECCOMP_USER_NOTIF_FLAG_CONTINUE;
			resp.error = 0;
			resp.val = 0;
			if (send_target(&resp, notifyfd) == -1)
				return -1;
			break;
		case OP_INJECT_A:
			set_inject_fields(req->id, data, &operations[i],
					  &resp_fd);
			resp_fd.flags |= SECCOMP_ADDFD_FLAG_SEND;
			if (send_inject_target(&resp_fd, notifyfd) == -1)
				return -1;
			break;
		case OP_INJECT:
			set_inject_fields(req->id, data, &operations[i],
					  &resp_fd);
			if (send_inject_target(&resp_fd, notifyfd) == -1)
				return -1;
			break;
		case OP_COPY_ARGS:
			if (copy_args(req, &operations[i].copy, data,
				      notifyfd) < 0)
				return -1;
			break;
		case OP_END:
			return 0;
		case OP_CMP:
			if ((ret = op_cmp(data, &operations[i].cmp)) != -1)
				i = ret;
			break;
		case OP_RESOLVEDFD:
			ret = resolve_fd(data, &operations[i].resfd, req->pid);
			if (ret == -1)
				return -1;
			else if (ret == 1)
				i = operations[i].resfd.jmp;
			break;
		default:
			fprintf(stderr, "unknow operation %d \n",
				operations[i].type);
		}
	}
	return 0;
}