CUMHOLE/extractor/cum_xct.c

/*
 * Copyright (c) 2026, Chloe M.
 * Provided under the BSD-3 clause.
 *
 * Description:  CUMHOLE extraction module
 * Author:       Chloe M.
 */

#include <sys/stat.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stddef.h>
#include <libgen.h>

#define REF_MAGIC "CUMHOLE"
#define REF_MAGIC_LEN 8
#define REF_PATH_LEN 256

/*
 * The offset table is made up of references, this
 * structure represents a reference.
 *
 * @magic:      Reference magic number
 * @path:       Path this reference refers to
 * @size:       Size of data being referenced
 * @data_off:   Offset to data being referenced
 */
struct hole_ref {
    char magic[REF_MAGIC_LEN];
    char path[REF_PATH_LEN];
    size_t size;
    size_t data_off;
} __attribute__((packed));

/* Globals */
static char *input_path = NULL;

static void
mkdir_recurse(const char *path)
{
    char buf[256];
    char *p = NULL;
    size_t len;

    snprintf(buf, sizeof(buf), "%s", path);
    len = strlen(buf);

    /* Strip trailing slash */
    if (buf[len - 1] == '/')
        buf[len - 1] = '\0';

    /* Make directory of each component */
    for (p = buf; *p != '\0'; ++p) {
        if (*p == '/') {
            *p = '\0';
            mkdir(buf, S_IRWXU);
            *p = '/';
        }
    }

    mkdir(buf, S_IRWXU);
}

static void
help(void)
{
    printf("usage: ./cumxct [flags]\n");
    printf("[-h]    Display this help menu\n");
    printf("[-i]    Input CUMHOLE bundle\n");
}

static int
push_file(const char *path, void *data, size_t size)
{
    int fd;

    if (path == NULL || data == NULL) {
        return -1;
    }

    fd = open(path, O_RDWR | O_CREAT, 0777);
    if (fd < 0) {
        printf("fatal: failed to open '%s'\n", path);
        perror("open");
        return -1;
    }

    write(fd, data, size);
    close(fd);
    return 0;
}

static void
do_parse(struct hole_ref *ref)
{
    const char *directory_name;
    struct hole_ref *ref_base = ref;
    char *path;
    void *data;

    if (ref == NULL) {
        return;
    }

    for (;;) {
        if (memcmp(ref->magic, REF_MAGIC, REF_MAGIC_LEN) != 0) {
            break;
        }

        path = strdup(ref->path);
        directory_name = dirname(path);
        mkdir_recurse(directory_name);

        printf("creating %s\n", ref->path);
        data = (void *)((char *)ref_base + ref->data_off);

        if (push_file(ref->path, data, ref->size) < 0) {
            free(path);
            return;
        }

        free(path);
        ++ref;
    }
}

static void
input_parse(void)
{
    int fd;
    char *data;
    size_t archive_size;
    ssize_t nret;

    fd = open(input_path, O_RDONLY);
    if (fd < 0) {
        printf("fatal: could not open input file\n");
        perror("open");
        return;
    }

    /* Obtain the size of the buffer */
    archive_size = lseek(fd, 0, SEEK_END);
    lseek(fd, 0, SEEK_SET);

    /* Allocate the actual buffer */
    data = malloc(archive_size);
    if (data == NULL) {
        printf("fatal: could not allocate archive buffer\n");
        close(fd);
        return;
    }

    /* Populate it with bytes */
    nret = read(fd, data, archive_size);
    if (nret <= 0) {
        printf("fatal: could not read archive\n");
        perror("read");
        return;
    }

    do_parse((struct hole_ref *)data);
    close(fd);
    free(data);
}

int
main(int argc, char **argv)
{
    int opt;

    if (argc < 2) {
        printf("fatal: too few arguments\n");
        help();
        return -1;
    }

    while ((opt = getopt(argc, argv, "hi:")) != -1) {
        switch (opt) {
        case 'h':
            help();
            return -1;
        case 'i':
            input_path = strdup(optarg);
            if (input_path == NULL) {
                printf("fatal: out of memory\n");
                return -1;
            }

            break;
        }
    }

    if (input_path == NULL) {
        printf("fatal: expected input bundle\n");
        help();
        return -1;
    }

    input_parse();
    free(input_path);
    return 0;
}