I was recently able to create my initramfs.img and run the following code in it:The idea is that I wanted to check certain data of the device on which the code is running and if everything matches, the system starts and if not, we don't. Plus, remembering the native device at the first launch of the system or script.
I wanted to rewrite this code in C and make it run through the main init. I got the following:To package the script, I installed:
And then packed it in:
The result is something like:
Later, I moved my init_checker to a folder, the folder tree is something like this:Then I write it in init:And I pack it in img:The first time I got an error like ‘can't open splash no such file or directory.’ . Someone recommended me to set the following value for the parameter in cmdline.txt - ‘quiet splash=0’. And now the only thing I get is an error:What could have gone wrong? Some of the recommendations I googled are checking whether the C script is packaged correctly and whether it is static and whether it matches the bit depth of the system, I checked it, it is packaged as 64-bit and I have the same system and everything indicates that it is static.
Code:
#!/bin/shecho "initramfs custom script activate!"echo "Checking system hardware ID..."sleep 10mkdir -p /proc /sys /dev /new_rootHW_INFO_FILE="/new_root/etc/hw_info"/bin/busybox mount -t proc none /proc/bin/busybox mount -t sysfs none /sys/bin/busybox mount -t devtmpfs none /devHW_ID=$(awk -F ': ' '/Serial/ {print $2}' /proc/cpuinfo)/bin/busybox mount -o ro /dev/mmcblk0p2 /new_root || { echo "ERROR: Failed to mount root filesystem!" exec /bin/busybox halt}if [ ! -f "$HW_INFO_FILE" ]; then echo "First boot detected. Saving hardware ID..." mkdir -p $(dirname "$HW_INFO_FILE") echo "$HW_ID" > "$HW_INFO_FILE"else SAVED_HW_ID=$(cat "$HW_INFO_FILE") if [ "$HW_ID" != "$SAVED_HW_ID" ]; then echo "ERROR: Hardware mismatch detected!" echo "This system was installed on different hardware." echo "Stopping boot process." exec /bin/busybox halt fifiecho "Hardware check passed. Continuing boot..."/bin/busybox mount -o remount,rw /new_rootexec /bin/busybox switch_root /new_root /sbin/init || { echo "ERROR: switch_root failed!" exec /bin/busybox sh}I wanted to rewrite this code in C and make it run through the main init. I got the following:
Code:
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/reboot.h>#include <sys/mount.h>#include <fcntl.h>#define HW_INFO_FILE "/new_root/etc/hw_info"#define REBOOT_DELAY 5 void infinite_reboot() { printf("ERROR: Hardware mismatch detected! Rebooting...\n"); sync(); sleep(REBOOT_DELAY); reboot(RB_AUTOBOOT);}void read_hw_id(char *buffer, size_t size) { FILE *cpuinfo = fopen("/proc/cpuinfo", "r"); if (!cpuinfo) { perror("Failed to open /proc/cpuinfo"); infinite_reboot(); } while (fgets(buffer, size, cpuinfo)) { if (strncmp(buffer, "Serial", 6) == 0) { char *id = strchr(buffer, ':'); if (id) { strncpy(buffer, id + 2, size); buffer[strcspn(buffer, "\n")] = 0; } break; } } fclose(cpuinfo);}int main() { printf("initramfs custom C program starting...\n"); mount("proc", "/proc", "proc", 0, NULL); mount("sysfs", "/sys", "sysfs", 0, NULL); mount("devtmpfs", "/dev", "devtmpfs", 0, NULL); char hw_id[32] = {0}; read_hw_id(hw_id, sizeof(hw_id)); if (mount("/dev/mmcblk0p2", "/new_root", "ext4", MS_RDONLY, NULL) < 0) { perror("ERROR: Failed to mount root filesystem"); infinite_reboot(); } FILE *file = fopen(HW_INFO_FILE, "r"); if (!file) { printf("First boot detected. Saving hardware ID...\n"); file = fopen(HW_INFO_FILE, "w"); if (!file) { perror("ERROR: Cannot write HW info"); infinite_reboot(); } fprintf(file, "%s\n", hw_id); fclose(file); } else { char saved_id[32] = {0}; fgets(saved_id, sizeof(saved_id), file); fclose(file); if (strcmp(hw_id, saved_id) != 0) { infinite_reboot(); } } printf("Hardware check passed. Continuing boot...\n"); mount("/dev/mmcblk0p2", "/new_root", "ext4", MS_REMOUNT, NULL); execl("/bin/busybox", "busybox", "switch_root", "/new_root", "/sbin/init", NULL); perror("ERROR: switch_root failed"); infinite_reboot(); return 0;}Code:
sudo apt install build-essential musl-tools busybox-staticCode:
musl-gcc -static -o init_checker init_checker.cCode:
init_checker: ELF 64-bit LSB executable, statically linkedCode:
/home/admin/initramfsbin:- busybox- echo -> busybox- init_checker- sh -> busybox- sleep -> busyboxetcinitprocsbinsysusr:- bin- sbinCode:
echo ‘#!/bin/shexec /bin/init_checker' > initramfs/initchmod +x initramfs/initCode:
find . | cpio -o -H newc --owner root:root | gzip > ~/initramfs.imgCode:
[ 2.904905] Failed to execute init (error -8)BusyBox v1.35.0 (Debian 1:1.35.0-4+b3) built-in shell (ash) Enter ‘help’ for a list of built-in commands./bin/sh: can't access tty: job control turned offStatistics: Posted by Araders — Sun Feb 16, 2025 9:08 pm — Replies 0 — Views 29