sandbox.c

#include <errno.h>
#include <seccomp.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char* argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <command> [args...]\n", argv[0]);
        return EXIT_FAILURE;
    }

    scmp_filter_ctx ctx;

    // Initialize the seccomp filter in blocklist mode
    ctx = seccomp_init(SCMP_ACT_ALLOW);
    if (ctx == NULL) {
        perror("seccomp_init");
        return EXIT_FAILURE;
    }

    // Block relevant network-related syscalls, so as to block egress internet access

    // We cannot deny these calls as they are needed by cuda
    // This should not be a big deal for our use case if what we want is to block egress network access
    // (just blocking connect should actually be enough)

    // seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(socket), 0);
    // seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(bind), 0);
    // seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(listen), 0);

    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(connect), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(accept), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(send), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(sendto), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(sendmsg), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(recv), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(recvfrom), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(recvmsg), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(setsockopt), 0);
    seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(getsockopt), 0);

    // Load the filter into the kernel
    if (seccomp_load(ctx) < 0) {
        perror("seccomp_load");
        seccomp_release(ctx);
        return EXIT_FAILURE;
    }

#ifdef DEBUG
    printf("seccomp filter installed. Network access is blocked.\n");
#endif

    // Execute the target program
    execvp(argv[1], argv + 1);

    seccomp_release(ctx);
    return EXIT_SUCCESS;
}