/* seitan - Syscall Expressive Interpreter, Transformer and Notifier
*
* operations.c - Execution of bytecode operations
*
* Copyright 2023 Red Hat GmbH
* Authors: Alice Frosi <afrosi@redhat.com>
* Stefano Brivio <sbrivio@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.id.pid, ns_name);
break;
case NS_SPEC_PATH:
snprintf(path, sizeof(path), "%s", ns.id.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);
}
static int op_load(struct seccomp_notif *req, int notifier, struct gluten *g,
struct op_load *load)
{
char path[PATH_MAX];
int fd, ret = 0;
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");
ret = -1;
goto out;
}
memcpy(gluten_write_ptr(g, load->dst),
gluten_ptr(&req->data, g, load->src),
load->size);
out:
close(fd);
return ret;
}
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, struct gluten *g,
const struct op_inject *a,
struct seccomp_notif_addfd *resp)
{
resp->flags = SECCOMP_ADDFD_FLAG_SETFD;
resp->id = id;
memcpy(&resp->newfd, gluten_ptr(NULL, g, a->new_fd),
sizeof(resp->newfd));
memcpy(&resp->srcfd, gluten_ptr(NULL, g, a->new_fd),
sizeof(resp->srcfd));
resp->newfd_flags = 0;
}
static int op_cmp(struct seccomp_notif *req, int notifier, struct gluten *g,
struct op_cmp *op)
{
int res = memcmp(gluten_ptr(&req->data, g, op->x),
gluten_ptr(&req->data, g, op->y), op->size);
enum op_cmp_type cmp = op->cmp;
(void)notifier;
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 op->jmp;
return -1;
}
int do_operations(struct gluten *g, struct op *ops, struct seccomp_notif *req,
unsigned int n_ops, int notifyfd)
{
struct seccomp_notif_addfd resp_fd;
struct seccomp_notif_resp resp;
struct arg_clone c;
unsigned int i;
struct op *op;
int ret;
for (i = 0, op = ops; i < n_ops; i++, op++) {
switch (op->type) {
case OP_CALL:
resp.id = req->id;
resp.val = 0;
resp.flags = 0;
c.args = &ops[i].op.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 (ops[i].op.call.has_ret) {
memcpy(gluten_write_ptr(g, op->op.call.ret),
&c.ret, sizeof(c.ret));
}
break;
case OP_BLOCK:
resp.id = req->id;
resp.val = 0;
resp.flags = 0;
resp.error = ops[i].op.block.error;
if (send_target(&resp, notifyfd) == -1)
return -1;
break;
case OP_RETURN:
resp.id = req->id;
resp.flags = 0;
resp.error = 0;
memcpy(&resp.val,
gluten_ptr(&req->data, g, op->op.ret.val),
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, g, &ops[i].op.inject,
&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, g, &ops[i].op.inject,
&resp_fd);
if (send_inject_target(&resp_fd, notifyfd) == -1)
return -1;
break;
case OP_LOAD:
if (op_load(req, notifyfd, g, &op->op.load))
return -1;
break;
case OP_END:
return 0;
case OP_CMP:
ret = op_cmp(req, notifyfd, g, (struct op_cmp *)op);
if (ret == -1)
return -1;
i = ret;
break;
case OP_RESOLVEDFD:
ret = resolve_fd(g->data, &ops[i].op.resfd, req->pid);
if (ret == -1)
return -1;
else if (ret == 1)
i = ops[i].op.resfd.jmp;
break;
default:
fprintf(stderr, "unknown operation %d \n", ops[i].type);
}
}
return 0;
}