init.c

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <linux/vm_sockets.h>

#include "jsmn.h"

#ifdef SEV
#include "tee/snp_attest.h"
#endif

#define KRUN_MAGIC "KRUN"
#define KRUN_FOOTER_LEN 12
#define CMDLINE_SECRET_PATH "/sfs/secrets/coco/cmdline"
#define CONFIG_FILE_PATH "/.krun_config.json"
#define MAX_ARGS 32
#define MAX_PASS_SIZE 512
#define MAX_TOKENS 16384

static int jsoneq(const char *, jsmntok_t *, const char *);

#ifdef SEV
static char *sev_get_luks_passphrase(int *);
static char *snp_get_luks_passphrase(char *, char *, char *, int *);
#endif

char DEFAULT_KRUN_INIT[] = "/bin/sh";

static void set_rlimits(const char *rlimits)
{
    unsigned long long int lim_id, lim_cur, lim_max;
    struct rlimit rlim;
    char *item = (char *)rlimits;

    while (1) {
        lim_id = lim_cur = lim_max = ULLONG_MAX;

        lim_id = strtoull(item, &item, 10);
        if (lim_id == ULLONG_MAX) {
            printf("Invalid rlimit ID\n");
            break;
        }

        item++;
        lim_cur = strtoull(item, &item, 10);
        item++;
        lim_max = strtoull(item, &item, 10);

        rlim.rlim_cur = lim_cur;
        rlim.rlim_max = lim_max;
        if (setrlimit(lim_id, &rlim) != 0) {
            printf("Error setting rlimit for ID=%lld\n", lim_id);
        }

        if (*item != '\0') {
            item++;
        } else {
            break;
        }
    }
}

#ifdef SEV
/*
 * The LUKS passphrase is obtained from a KBS attestation server, complete an
 * SNP attestation to get the passphrase.
 */
static char *get_luks_passphrase(int *pass_len)
{
    int fd, ret, num_tokens, wid_found, url_found, tee_found, tee_data_found;
    uint64_t dev_size, tc_size;
    char wid[256], url[256], *tc_json, *tok_start, *tok_end;
    char footer[KRUN_FOOTER_LEN], tee[256], tee_data[256], *return_str;
    jsmn_parser parser;
    jsmntok_t *tokens;
    size_t tok_size;

    return_str = NULL;

    /*
     * If a user registered the TEE config data disk with
     * krun_set_data_disk(), it would appear as /dev/vdb in the guest.
     * Mount this device and read the config.
     */
    if (mkdir("/dev", 0755) < 0 && errno != EEXIST) {
        perror("mkdir(/dev)");
        goto finish;
    }

    if (mount("devtmpfs", "/dev", "devtmpfs", MS_RELATIME, NULL) < 0 &&
        errno != EBUSY) {
        perror("mount(devtmpfs)");

        goto rmdir_dev;
    }

    fd = open("/dev/vda", O_RDONLY);
    if (fd < 0) {
        perror("open(/dev/vda)");

        goto umount_dev;
    }

    ret = ioctl(fd, BLKGETSIZE64, &dev_size);
    if (ret != 0) {
        perror("ioctl(BLKGETSIZE64)");

        goto close_dev;
    }

    if (lseek(fd, dev_size - KRUN_FOOTER_LEN, SEEK_SET) == -1) {
        perror("lseek(END - KRUN_FOOTER_LEN)");

        goto close_dev;
    }

    ret = read(fd, &footer[0], KRUN_FOOTER_LEN);
    if (ret != KRUN_FOOTER_LEN) {
        perror("read(KRUN_FOOTER_LEN)");

        goto close_dev;
    }

    if (memcmp(&footer[0], KRUN_MAGIC, 4) != 0) {
        printf("Couldn't find KRUN footer signature, falling back to SEV\n");
        return_str = sev_get_luks_passphrase(pass_len);

        goto close_dev;
    }

    tc_size = *(uint64_t *)&footer[4];

    if (lseek(fd, dev_size - tc_size - KRUN_FOOTER_LEN, SEEK_SET) == -1) {
        perror("lseek(END - tc_size - KRUN_FOOTER_LEN)");

        goto close_dev;
    }

    tc_json = malloc(tc_size + 1);
    if (tc_json == NULL) {
        perror("malloc(tc_size)");

        goto close_dev;
    }

    ret = read(fd, tc_json, tc_size);
    if (ret != tc_size) {
        perror("read(tc_size)");

        goto free_mem;
    }
    tc_json[tc_size] = '\0';

    /*
     * Parse the TEE config's workload_id and attestation_url field.
     */
    jsmn_init(&parser);

    tokens = (jsmntok_t *)malloc(sizeof(jsmntok_t) * MAX_TOKENS);
    if (tokens == NULL) {
        perror("malloc(jsmntok_t)");

        goto free_mem;
    }

    num_tokens =
        jsmn_parse(&parser, tc_json, strlen(tc_json), tokens, MAX_TOKENS);
    if (num_tokens < 0) {
        printf("Unable to allocate JSON tokens\n");

        goto free_mem;
    } else if (num_tokens < 1 || tokens[0].type != JSMN_OBJECT) {
        printf("Unable to find object in TEE configuration file\n");

        goto free_mem;
    }

    wid_found = url_found = tee_found = tee_data_found = 0;

    for (int i = 1; i < num_tokens - 1; ++i) {
        tok_start = tc_json + tokens[i + 1].start;
        tok_end = tc_json + tokens[i + 1].end;
        tok_size = tok_end - tok_start;
        if (!jsoneq(tc_json, &tokens[i], "workload_id")) {
            strncpy(wid, tok_start, tok_size);
            wid_found = 1;
        } else if (!jsoneq(tc_json, &tokens[i], "attestation_url")) {
            strncpy(url, tok_start, tok_size);
            url_found = 1;
        } else if (!jsoneq(tc_json, &tokens[i], "tee")) {
            strncpy(tee, tok_start, tok_size);
            tee_found = 1;
        } else if (!jsoneq(tc_json, &tokens[i], "tee_data")) {
            strncpy(tee_data, tok_start, tok_size);
            tee_data_found = 1;
        }
    }

    if (!wid_found) {
        printf("Unable to find attestation workload ID\n");

        goto free_mem;
    } else if (!url_found) {
        printf("Unable to find attestation server URL\n");

        goto free_mem;
    } else if (!tee_found) {
        printf("Unable to find TEE generation server URL\n");

        goto free_mem;
    }

    if (strcmp(tee, "snp") == 0) {
        if (tee_data_found == 0) {
            printf("Unable to find SNP generation\n");
            goto free_mem;
        }

        return_str = snp_get_luks_passphrase(url, wid, tee_data, pass_len);
    } else if (strcmp(tee, "sev") == 0) {
        return_str = sev_get_luks_passphrase(pass_len);
    }

free_mem:
    free(tc_json);

close_dev:
    close(fd);

umount_dev:
    umount("/dev");

rmdir_dev:
    rmdir("/dev");

finish:
    return return_str;
}

static char *snp_get_luks_passphrase(char *url, char *wid, char *tee_data,
                                     int *pass_len)
{
    char *pass;

    pass = (char *)malloc(MAX_PASS_SIZE);
    if (pass == NULL) {
        return NULL;
    }

    if (snp_attest(pass, url, wid, tee_data) == 0) {
        *pass_len = strlen(pass);
        return pass;
    }

    free(pass);

    return NULL;
}

static char *sev_get_luks_passphrase(int *pass_len)
{
    char *pass = NULL;
    int len;
    int fd;

    pass = getenv("KRUN_PASS");
    if (pass) {
        *pass_len = strnlen(pass, MAX_PASS_SIZE);
        return pass;
    }
    if (mkdir("/sfs", 0755) < 0 && errno != EEXIST) {
        perror("mkdir(/sfs)");
        return NULL;
    }

    if (mount("securityfs", "/sfs", "securityfs",
              MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/sfs)");
        goto cleanup_dir;
    }

    fd = open(CMDLINE_SECRET_PATH, O_RDONLY);
    if (fd < 0) {
        goto cleanup_sfs;
    }

    pass = malloc(MAX_PASS_SIZE);
    if (!pass) {
        goto cleanup_fd;
    }

    if ((len = read(fd, pass, MAX_PASS_SIZE)) < 0) {
        free(pass);
        pass = NULL;
    } else {
        *pass_len = len;
        unlink(CMDLINE_SECRET_PATH);
    }

cleanup_fd:
    close(fd);
cleanup_sfs:
    umount("/sfs");
cleanup_dir:
    rmdir("/sfs");

    return pass;
}

static int chroot_luks()
{
    char *pass;
    int pass_len;
    int pid;
    int pipefd[2];
    int wstatus;

    pass = get_luks_passphrase(&pass_len);
    if (!pass) {
        printf("Couldn't find LUKS passphrase\n");
        return -1;
    }

    printf("Unlocking LUKS root filesystem\n");

    if (mount("proc", "/proc", "proc",
              MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/proc)");
        return -1;
    }

    pipe(pipefd);

    pid = fork();
    if (pid == 0) {
        close(pipefd[1]);
        dup2(pipefd[0], 0);
        close(pipefd[0]);

        if (execl("/sbin/cryptsetup", "cryptsetup", "open", "/dev/vda",
                  "luksroot", "-", NULL) < 0) {
            perror("execl");
            return -1;
        }
    } else {
        write(pipefd[1], pass, strnlen(pass, pass_len));
        close(pipefd[1]);
        waitpid(pid, &wstatus, 0);
    }

    memset(pass, 0, pass_len);

    printf("Mounting LUKS root filesystem\n");

    if (mount("/dev/mapper/luksroot", "/luksroot", "ext4", 0, NULL) < 0) {
        perror("mount(/luksroot)");
        return -1;
    }

    chdir("/luksroot");

    if (mount(".", "/", NULL, MS_MOVE, NULL)) {
        perror("remount root");
        return -1;
    }
    chroot(".");

    return 0;
}
#endif

static int mount_filesystems()
{
    char *const DIRS_LEVEL1[] = {"/dev", "/proc", "/sys"};
    char *const DIRS_LEVEL2[] = {"/dev/pts", "/dev/shm"};
    int i;

    for (i = 0; i < 3; ++i) {
        if (mkdir(DIRS_LEVEL1[i], 0755) < 0 && errno != EEXIST) {
            printf("Error creating directory (%s)\n", DIRS_LEVEL1[i]);
            return -1;
        }
    }

    if (mount("devtmpfs", "/dev", "devtmpfs", MS_RELATIME, NULL) < 0 &&
        errno != EBUSY) {
        perror("mount(/dev)");
        return -1;
    }

    if (mount("proc", "/proc", "proc",
              MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/proc)");
        return -1;
    }

    if (mount("sysfs", "/sys", "sysfs",
              MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/sys)");
        return -1;
    }

    if (mount("cgroup2", "/sys/fs/cgroup", "cgroup2",
              MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/sys/fs/cgroup)");
        return -1;
    }

    for (i = 0; i < 2; ++i) {
        if (mkdir(DIRS_LEVEL2[i], 0755) < 0 && errno != EEXIST) {
            printf("Error creating directory (%s)\n", DIRS_LEVEL2[i]);
            return -1;
        }
    }

    if (mount("devpts", "/dev/pts", "devpts",
              MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) {
        perror("mount(/dev/pts)");
        return -1;
    }

    if (mount("tmpfs", "/dev/shm", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_RELATIME,
              NULL) < 0) {
        perror("mount(/dev/shm)");
        return -1;
    }

    /* May fail if already exists and that's fine. */
    symlink("/proc/self/fd", "/dev/fd");

    return 0;
}

/*
 * hexToDigit, Utf32toUtf8 and parts of unescape_string are taken from libyajl:
 *
 * Copyright (c) 2007-2014, Lloyd Hilaiel <me@lloyd.io>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
static void hexToDigit(unsigned int *val, const unsigned char *hex)
{
    unsigned int i;
    for (i = 0; i < 4; i++) {
        unsigned char c = hex[i];
        if (c >= 'A')
            c = (c & ~0x20) - 7;
        c -= '0';
        *val = (*val << 4) | c;
    }
}

static void Utf32toUtf8(unsigned int codepoint, char *utf8Buf)
{
    if (codepoint < 0x80) {
        utf8Buf[0] = (char)codepoint;
        utf8Buf[1] = 0;
    } else if (codepoint < 0x0800) {
        utf8Buf[0] = (char)((codepoint >> 6) | 0xC0);
        utf8Buf[1] = (char)((codepoint & 0x3F) | 0x80);
        utf8Buf[2] = 0;
    } else if (codepoint < 0x10000) {
        utf8Buf[0] = (char)((codepoint >> 12) | 0xE0);
        utf8Buf[1] = (char)(((codepoint >> 6) & 0x3F) | 0x80);
        utf8Buf[2] = (char)((codepoint & 0x3F) | 0x80);
        utf8Buf[3] = 0;
    } else if (codepoint < 0x200000) {
        utf8Buf[0] = (char)((codepoint >> 18) | 0xF0);
        utf8Buf[1] = (char)(((codepoint >> 12) & 0x3F) | 0x80);
        utf8Buf[2] = (char)(((codepoint >> 6) & 0x3F) | 0x80);
        utf8Buf[3] = (char)((codepoint & 0x3F) | 0x80);
        utf8Buf[4] = 0;
    } else {
        utf8Buf[0] = '?';
        utf8Buf[1] = 0;
    }
}

/* Do not worry about invalid JSON, it was already parsed by jsmn.  */
static void unescape_string(char *string, int len)
{
    unsigned char *val = (unsigned char *)string;
    unsigned char *end;
    int i = 0;

    end = val + len;
    while (val < end) {
        if (*val != '\\') {
            string[i++] = *val++;
            continue;
        }
        switch (*++val) {
        case 'n':
            string[i++] = '\n';
            break;
        case 't':
            string[i++] = '\t';
            break;
        case 'r':
            string[i++] = '\r';
            break;
        case 'b':
            string[i++] = '\b';
            break;
        case 'f':
            string[i++] = '\f';
            break;
        case '\\':
            string[i++] = '\\';
            break;
        case '\"':
            string[i++] = '\"';
            break;
        case '/':
            string[i++] = '/';
            break;
        case 'u': {
            const char *unescaped = "?";
            char utf8Buf[5];
            unsigned int codepoint = 0;
            hexToDigit(&codepoint, val++);
            val += 3;
            /* check if this is a surrogate */
            if ((codepoint & 0xFC00) == 0xD800) {
                val++;
                if (val[0] == '\\' && val[1] == 'u') {
                    unsigned int surrogate = 0;
                    hexToDigit(&surrogate, val + 2);
                    codepoint = (((codepoint & 0x3F) << 10) |
                                 ((((codepoint >> 6) & 0xF) + 1) << 16) |
                                 (surrogate & 0x3FF));
                    val += 5;
                } else {
                    unescaped = "?";
                    break;
                }
            }

            Utf32toUtf8(codepoint, utf8Buf);
            unescaped = utf8Buf;

            if (codepoint == 0) {
                memcpy(&string[i++], unescaped, 1);
                continue;
            }
            memcpy(&string[i], unescaped, (unsigned int)strlen(unescaped));
            break;
        }
        }
    }
    string[i] = '\0';
}

static void config_parse_env(char *data, jsmntok_t *token)
{
    jsmntok_t *tenv;
    char *env, *env_val;
    int len;
    int i;

    for (i = 0; i < token->size; i++) {
        tenv = &token[i + 1];

        env = data + tenv->start;
        len = tenv->end - tenv->start;

        unescape_string(env, len);

        env_val = strstr(env, "=");
        if (!env_val) {
            continue;
        }

        env[len] = '\0';
        *env_val = '\0';
        env_val++;

        if ((strcmp(env, "HOME") == 0) || (strcmp(env, "TERM") == 0)) {
            setenv(env, env_val, 1);
        } else {
            setenv(env, env_val, 0);
        }
    }
}

static char **config_parse_args(char *data, jsmntok_t *token)
{
    jsmntok_t *targ;
    char *arg, *value;
    char **argv;
    int len;
    int i, j;

    argv = malloc(MAX_ARGS * sizeof(char *));
    j = 0;

    for (i = 0; i < token->size; i++) {
        targ = &token[i + 1];

        value = data + targ->start;
        len = targ->end - targ->start;

        arg = malloc(len + 1);
        memcpy(arg, value, len);
        arg[len] = '\0';

        unescape_string(arg, len);

        argv[j] = arg;
        j++;
    }

    if (j == 0) {
        free(argv);
        argv = NULL;
    } else {
        argv[j] = NULL;
    }

    return argv;
}

static char *config_parse_string(char *data, jsmntok_t *token)
{
    char *string;
    char *val;
    int len;

    val = data + token->start;
    len = token->end - token->start;
    if (!len) {
        return NULL;
    }

    string = malloc(len + 1);

    if (!string) {
        return NULL;
    }
    memcpy(string, val, len);
    string[len] = '\0';

    unescape_string(string, len);

    return string;
}

static int jsoneq(const char *json, jsmntok_t *tok, const char *s)
{
    if (tok->type == JSMN_STRING && (int)strlen(s) == tok->end - tok->start &&
        strncasecmp(json + tok->start, s, tok->end - tok->start) == 0) {
        return 0;
    }
    return -1;
}

char **concat_entrypoint_argv(char **entrypoint, char **config_argv)
{
    char **argv;
    int i, j;

    argv = malloc(MAX_ARGS * sizeof(char *));

    for (i = 0; i < MAX_ARGS && entrypoint[i]; i++) {
        argv[i] = entrypoint[i];
    }

    for (j = 0; j < MAX_ARGS && config_argv[j]; i++, j++) {
        argv[i] = config_argv[j];
    }

    argv[i] = NULL;

    return argv;
}

static int config_parse_file(char ***argv, char **workdir)
{
    jsmn_parser parser;
    jsmntok_t *tokens;
    struct stat stat;
    char *data;
    char *config_file;
    char **config_argv;
    char **entrypoint;
    int parsed_env, parsed_workdir, parsed_args, parsed_entrypoint;
    int num_tokens;
    int ret = -1;
    int fd;
    int i;

    config_file = getenv("KRUN_CONFIG");
    if (!config_file) {
        config_file = CONFIG_FILE_PATH;
    }

    fd = open(config_file, O_RDONLY);
    if (fd < 0) {
        return ret;
    }

    if (fstat(fd, &stat) != 0) {
        perror("Couldn't stat config file");
        goto cleanup_fd;
    }

    data = malloc(stat.st_size);
    if (!data) {
        perror("Couldn't allocate memory");
        goto cleanup_fd;
    }

    if (read(fd, data, stat.st_size) < 0) {
        perror("Error reading config file");
        goto cleanup_data;
    }

    tokens = malloc(MAX_TOKENS * sizeof(jsmntok_t));
    if (!tokens) {
        perror("Couldn't allocate memory");
        goto cleanup_data;
    }

    jsmn_init(&parser);
    num_tokens = jsmn_parse(&parser, data, strlen(data), tokens, MAX_TOKENS);
    if (num_tokens < 0) {
        printf("Error parsing config file\n");
        goto cleanup_tokens;
    }

    if (num_tokens < 1 || tokens[0].type != JSMN_OBJECT) {
        printf("Couldn't find object in config file\n");
        goto cleanup_tokens;
    }

    config_argv = NULL;
    entrypoint = NULL;
    parsed_env = parsed_workdir = parsed_args = parsed_entrypoint = 0;

    for (i = 1; i < num_tokens && (!parsed_env || !parsed_args ||
                                   !parsed_workdir || !parsed_entrypoint);
         i++) {
        if (!parsed_env && jsoneq(data, &tokens[i], "Env") == 0 &&
            (i + 1) < num_tokens && tokens[i + 1].type == JSMN_ARRAY) {
            config_parse_env(data, &tokens[i + 1]);
            parsed_env = 1;
        }

        if (!parsed_args && jsoneq(data, &tokens[i], "args") == 0 &&
            (i + 1) < num_tokens) {
            config_argv = config_parse_args(data, &tokens[i + 1]);
            parsed_args = 1;
        }

        if (!parsed_args && jsoneq(data, &tokens[i], "Cmd") == 0 &&
            (i + 1) < num_tokens) {
            config_argv = config_parse_args(data, &tokens[i + 1]);
            parsed_args = 1;
        }

        if (!parsed_workdir && jsoneq(data, &tokens[i], "WorkingDir") == 0 &&
            (i + 1) < num_tokens) {
            *workdir = config_parse_string(data, &tokens[i + 1]);
            parsed_workdir = 1;
        }

        if (!parsed_workdir && jsoneq(data, &tokens[i], "Cwd") == 0 &&
            (i + 1) < num_tokens) {
            *workdir = config_parse_string(data, &tokens[i + 1]);
            parsed_workdir = 1;
        }

        if (!parsed_entrypoint && jsoneq(data, &tokens[i], "Entrypoint") == 0 &&
            (i + 1) < num_tokens) {
            entrypoint = config_parse_args(data, &tokens[i + 1]);
            parsed_entrypoint = 1;
        }
    }

    if (config_argv && entrypoint) {
        *argv = concat_entrypoint_argv(entrypoint, config_argv);
    } else {
        *argv = config_argv;
    }

    ret = 0;

cleanup_tokens:
    free(tokens);
cleanup_data:
    free(data);
cleanup_fd:
    close(fd);

    return ret;
}

#ifdef __TIMESYNC__

#define TSYNC_PORT 123
#define BUFSIZE 8
#define NANOS_IN_SECOND 1000000000
/* Set clock if delta is bigger than 100ms */
#define DELTA_SYNC 100000000

void clock_worker()
{
    int sockfd, n;
    struct sockaddr_vm serveraddr;
    char buf[BUFSIZE];
    struct timespec gtime;
    struct timespec htime;
    uint64_t gtime_ns;
    uint64_t htime_ns;

    sockfd = socket(AF_VSOCK, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("Couldn't create timesync socket\n");
        return;
    }

    bzero((char *)&serveraddr, sizeof(serveraddr));
    serveraddr.svm_family = AF_VSOCK;
    serveraddr.svm_port = TSYNC_PORT;
    serveraddr.svm_cid = 3;

    bzero(buf, BUFSIZE);

    n = bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
    if (n < 0) {
        printf("Couldn't bind timesync socket\n");
        return;
    }

    while (1) {
        n = recv(sockfd, buf, BUFSIZE, 0);
        if (n < 0) {
            perror("Error in timesync recv\n");
            return;
        } else if (n != 8) {
            printf("Ignoring bogus timesync packet\n");
            continue;
        }

        htime_ns = *(uint64_t *)&buf[0];
        clock_gettime(CLOCK_REALTIME, &gtime);
        gtime_ns = gtime.tv_sec * NANOS_IN_SECOND;
        gtime_ns += gtime.tv_nsec;

        if (llabs(htime_ns - gtime_ns) > DELTA_SYNC) {
            htime.tv_sec = htime_ns / NANOS_IN_SECOND;
            htime.tv_nsec = htime_ns % NANOS_IN_SECOND;
            clock_settime(CLOCK_REALTIME, &htime);
        }
    }
}
#endif

int reopen_fd(int fd, char *path, int flags)
{
    int newfd = open(path, flags);
    if (newfd < 0) {
        printf("Failed to open '%s': %s\n", path, strerror(errno));
        return -1;
    }

    close(fd);
    if (dup2(newfd, fd) < 0) {
        perror("dup2");
        close(newfd);
        return -1;
    }
    close(newfd);
    return 0;
}

int setup_redirects()
{
    DIR *ports_dir = opendir("/sys/class/virtio-ports");
    if (ports_dir == NULL) {
        printf("Unable to open ports directory!\n");
        return -4;
    }

    char path[2048];
    char name_buf[1024];

    struct dirent *entry = NULL;
    while ((entry = readdir(ports_dir))) {
        char *port_identifier = entry->d_name;
        int result_len =
            snprintf(path, sizeof(path), "/sys/class/virtio-ports/%s/name",
                     port_identifier);

        // result was truncated
        if (result_len > sizeof(name_buf) - 1) {
            printf("Path buffer too small");
            return -1;
        }

        FILE *port_name_file = fopen(path, "r");
        if (port_name_file == NULL) {
            continue;
        }

        char *port_name = fgets(name_buf, sizeof(name_buf), port_name_file);
        fclose(port_name_file);

        if (port_name != NULL && strcmp(port_name, "krun-stdin\n") == 0) {
            // if previous snprintf didn't fail, this one cannot fail either
            snprintf(path, sizeof(path), "/dev/%s", port_identifier);
            reopen_fd(STDIN_FILENO, path, O_RDONLY);
        } else if (port_name != NULL &&
                   strcmp(port_name, "krun-stdout\n") == 0) {
            snprintf(path, sizeof(path), "/dev/%s", port_identifier);
            reopen_fd(STDOUT_FILENO, path, O_WRONLY);
        } else if (port_name != NULL &&
                   strcmp(port_name, "krun-stderr\n") == 0) {
            snprintf(path, sizeof(path), "/dev/%s", port_identifier);
            reopen_fd(STDERR_FILENO, path, O_WRONLY);
        }
    }

    closedir(ports_dir);
    return 0;
}

int main(int argc, char **argv)
{
    struct ifreq ifr;
    int sockfd;
    char localhost[] = "localhost\0";
    char *hostname;
    char *krun_home;
    char *krun_term;
    char *krun_init;
    char *config_workdir, *env_workdir;
    char *rlimits;
    char **config_argv, **exec_argv;

#ifdef SEV
    if (chroot_luks() < 0) {
        printf("Couldn't switch to LUKS volume, bailing out\n");
        exit(-1);
    }
#endif
    if (mount_filesystems() < 0) {
        printf("Couldn't mount filesystems, bailing out\n");
        exit(-2);
    }

    setsid();
    ioctl(0, TIOCSCTTY, 1);

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd >= 0) {
        memset(&ifr, 0, sizeof ifr);
        strncpy(ifr.ifr_name, "lo", IFNAMSIZ);
        ifr.ifr_flags |= IFF_UP;
        ioctl(sockfd, SIOCSIFFLAGS, &ifr);
        close(sockfd);
    }

    config_argv = NULL;
    config_workdir = NULL;

    config_parse_file(&config_argv, &config_workdir);

    krun_home = getenv("KRUN_HOME");
    if (krun_home) {
        setenv("HOME", krun_home, 1);
    }

    krun_term = getenv("KRUN_TERM");
    if (krun_term) {
        setenv("TERM", krun_term, 1);
    }

    hostname = getenv("HOSTNAME");
    if (hostname) {
        sethostname(hostname, strlen(hostname));
    } else {
        sethostname(&localhost[0], strlen(localhost));
    }

    rlimits = getenv("KRUN_RLIMITS");
    if (rlimits) {
        set_rlimits(rlimits);
    }

    env_workdir = getenv("KRUN_WORKDIR");
    if (env_workdir) {
        chdir(env_workdir);
    } else if (config_workdir) {
        chdir(config_workdir);
    }

    exec_argv = argv;
    krun_init = getenv("KRUN_INIT");
    if (krun_init) {
        exec_argv[0] = krun_init;
    } else if (config_argv) {
        exec_argv = config_argv;
    } else {
        exec_argv[0] = &DEFAULT_KRUN_INIT[0];
    }

#ifdef __TIMESYNC__
    if (fork() == 0) {
        clock_worker();
    }
#endif

    // We need to fork ourselves, because pid 1 cannot doesn't receive SIGINT
    // signal
    int pid = fork();
    if (pid < 0) {
        perror("fork");
        exit(-3);
    }
    if (pid == 0) { // child
        if (setup_redirects() < 0) {
            exit(-4);
        }
        if (execvp(exec_argv[0], exec_argv) < 0) {
            printf("Couldn't execute '%s' inside the vm: %s\n", exec_argv[0],
                   strerror(errno));
            exit(-3);
        }
    } else { // parent
        // tell the kernel we don't want to be notified on SIGCHLD so it'll reap
        // our children for us
        signal(SIGCHLD, SIG_IGN);
        // wait for children since we can't exit init
        waitpid(pid, NULL, 0);
    }

    return 0;
}