mirror of
https://github.com/topjohnwu/Magisk.git
synced 2024-11-24 18:45:28 +00:00
313 lines
8.2 KiB
C
313 lines
8.2 KiB
C
/* magiskinit.c - Workaround for skip_initramfs devices
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*
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* This code has to be compiled statically to work properly.
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*
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* Magiskinit will mount sysfs, parse through uevent files to make the system block device,
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* then it'll mount the system partition and clone rootfs except files under /system.
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* Folders placed in "overlay" will then be overlayed to the root.
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* Lastly, before giving control back to the real init, it'll patch the root files,
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* extract (or compile if needed) sepolicy and patch it to load Magisk.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/mount.h>
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#include <sys/mman.h>
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#include <sys/sendfile.h>
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#include <sys/sysmacros.h>
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#include <cil/cil.h>
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#include "utils.h"
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#include "magiskpolicy.h"
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struct cmdline {
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int skip_initramfs;
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char slot[3];
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};
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struct device {
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dev_t major;
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dev_t minor;
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char devname[32];
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char partname[32];
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char path[64];
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};
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extern policydb_t *policydb;
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extern void mmap_ro(const char *filename, void **buf, size_t *size);
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extern void mmap_rw(const char *filename, void **buf, size_t *size);
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extern void *patch_init_rc(char *data, uint32_t *size);
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static void parse_cmdline(struct cmdline *cmd) {
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char *tok;
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char buffer[4096];
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mkdir("/proc", 0555);
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mount("proc", "/proc", "proc", 0, NULL);
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int fd = open("/proc/cmdline", O_RDONLY | O_CLOEXEC);
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ssize_t size = read(fd, buffer, sizeof(buffer));
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buffer[size] = '\0';
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close(fd);
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umount("/proc");
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tok = strtok(buffer, " ");
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cmd->skip_initramfs = 0;
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cmd->slot[0] = '\0';
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while (tok != NULL) {
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if (strncmp(tok, "androidboot.slot_suffix", 23) == 0) {
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sscanf(tok, "androidboot.slot_suffix=%s", cmd->slot);
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} else if (strcmp(tok, "skip_initramfs") == 0) {
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cmd->skip_initramfs = 1;
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break;
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}
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tok = strtok(NULL, " ");
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}
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}
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static void parse_device(struct device *dev, char *uevent) {
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char *tok;
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tok = strtok(uevent, "\n");
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while (tok != NULL) {
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if (strncmp(tok, "MAJOR", 5) == 0) {
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sscanf(tok, "MAJOR=%ld", (long*) &dev->major);
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} else if (strncmp(tok, "MINOR", 5) == 0) {
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sscanf(tok, "MINOR=%ld", (long*) &dev->minor);
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} else if (strncmp(tok, "DEVNAME", 7) == 0) {
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sscanf(tok, "DEVNAME=%s", dev->devname);
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} else if (strncmp(tok, "PARTNAME", 8) == 0) {
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sscanf(tok, "PARTNAME=%s", dev->partname);
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}
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tok = strtok(NULL, "\n");
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}
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}
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static int setup_block(struct device *dev, const char *partname) {
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char buffer[1024], path[128];
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struct dirent *entry;
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DIR *dir = opendir("/sys/dev/block");
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if (dir == NULL)
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return 1;
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int found = 0;
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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snprintf(path, sizeof(path), "/sys/dev/block/%s/uevent", entry->d_name);
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int fd = open(path, O_RDONLY | O_CLOEXEC);
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ssize_t size = read(fd, buffer, sizeof(buffer));
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buffer[size] = '\0';
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close(fd);
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parse_device(dev, buffer);
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if (strcmp(dev->partname, partname) == 0) {
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snprintf(dev->path, sizeof(dev->path), "/dev/block/%s", dev->devname);
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found = 1;
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break;
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}
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}
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closedir(dir);
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if (!found)
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return 1;
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mkdir("/dev", 0755);
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mkdir("/dev/block", 0755);
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mknod(dev->path, S_IFBLK | 0600, makedev(dev->major, dev->minor));
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return 0;
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}
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static void patch_ramdisk() {
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void *addr;
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size_t size;
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mmap_rw("/init", &addr, &size);
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for (int i = 0; i < size; ++i) {
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if (memcmp(addr + i, "/system/etc/selinux/plat_sepolicy.cil", 37) == 0) {
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memcpy(addr + i, "/system/etc/selinux/plat_sepolicy.xxx", 37);
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break;
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}
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}
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munmap(addr, size);
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mmap_rw("/init.rc", &addr, &size);
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uint32_t new_size = size;
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void *init_rc = patch_init_rc(addr, &new_size);
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munmap(addr, size);
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int fd = open("/init.rc", O_WRONLY | O_TRUNC | O_CLOEXEC);
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write(fd, init_rc, new_size);
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close(fd);
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free(init_rc);
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}
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static int strend(const char *s1, const char *s2) {
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int l1 = strlen(s1);
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int l2 = strlen(s2);
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return strcmp(s1 + l1 - l2, s2);
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}
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static void patch_sepolicy() {
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DIR *dir;
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struct dirent *entry;
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char *sepolicy = NULL, path[128];
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if (access("/system_root/sepolicy", R_OK) == 0)
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sepolicy = "/system_root/sepolicy";
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if (sepolicy == NULL && access("/vendor/etc/selinux/precompiled_sepolicy", R_OK) == 0) {
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void *sys_sha = NULL, *ven_sha = NULL;
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size_t sys_size = 0, ven_size = 0;
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if ((dir = opendir("/vendor/etc/selinux")) == NULL)
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goto check_done;
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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if (strend(entry->d_name, ".sha256") == 0) {
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snprintf(path, sizeof(path), "/vendor/etc/selinux/%s", entry->d_name);
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mmap_ro(path, &ven_sha, &ven_size);
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break;
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}
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}
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closedir(dir);
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if ((dir = opendir("/system/etc/selinux")) == NULL)
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goto check_done;
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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if (strend(entry->d_name, ".sha256") == 0) {
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snprintf(path, sizeof(path), "/system/etc/selinux/%s", entry->d_name);
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mmap_ro(path, &sys_sha, &sys_size);
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break;
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}
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}
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closedir(dir);
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if (sys_size == ven_size && memcmp(sys_sha, ven_sha, sys_size) == 0)
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sepolicy = "/vendor/etc/selinux/precompiled_sepolicy";
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munmap(sys_sha, sys_size);
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munmap(ven_sha, ven_size);
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}
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check_done:
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if (sepolicy) {
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load_policydb(sepolicy);
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} else {
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// Compile cil
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struct cil_db *db = NULL;
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sepol_policydb_t *pdb = NULL;
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void *addr;
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size_t size;
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cil_db_init(&db);
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cil_set_mls(db, 1);
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cil_set_target_platform(db, SEPOL_TARGET_SELINUX);
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cil_set_policy_version(db, POLICYDB_VERSION_XPERMS_IOCTL);
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cil_set_attrs_expand_generated(db, 0);
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mmap_ro("/system/etc/selinux/plat_sepolicy.cil", &addr, &size);
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cil_add_file(db, "/system/etc/selinux/plat_sepolicy.cil", addr, size);
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munmap(addr, size);
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dir = opendir("/system/etc/selinux/mapping");
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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if (strend(entry->d_name, ".cil") == 0) {
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snprintf(path, sizeof(path), "/system/etc/selinux/mapping/%s", entry->d_name);
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mmap_ro(path, &addr, &size);
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cil_add_file(db, path, addr, size);
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munmap(addr, size);
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}
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}
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closedir(dir);
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dir = opendir("/vendor/etc/selinux");
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while ((entry = readdir(dir))) {
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if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
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continue;
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if (strend(entry->d_name, ".cil") == 0) {
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snprintf(path, sizeof(path), "/vendor/etc/selinux/%s", entry->d_name);
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mmap_ro(path, &addr, &size);
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cil_add_file(db, path, addr, size);
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munmap(addr, size);
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}
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}
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closedir(dir);
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cil_compile(db);
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cil_build_policydb(db, &pdb);
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cil_db_destroy(&db);
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policydb = &pdb->p;
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}
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// Magisk patches
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sepol_min_rules();
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dump_policydb("/sepolicy");
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destroy_policydb();
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}
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int main(int argc, char *argv[]) {
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umask(0);
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struct cmdline cmd;
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parse_cmdline(&cmd);
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if (cmd.skip_initramfs) {
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// Normal boot mode
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// Clear rootfs
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int root = open("/", O_RDONLY | O_CLOEXEC);
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// Exclude overlay folder
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excl_list = (char *[]) { "overlay", NULL };
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frm_rf(root);
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mkdir("/sys", 0755);
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mount("sysfs", "/sys", "sysfs", 0, NULL);
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char partname[32];
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snprintf(partname, sizeof(partname), "system%s", cmd.slot);
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struct device dev;
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setup_block(&dev, partname);
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mkdir("/system_root", 0755);
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mount(dev.path, "/system_root", "ext4", MS_RDONLY, NULL);
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int system_root = open("/system_root", O_RDONLY | O_CLOEXEC);
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// Exclude system folder
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excl_list = (char *[]) { "system", NULL };
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clone_dir(system_root, root);
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mkdir("/system", 0755);
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mount("/system_root/system", "/system", NULL, MS_BIND, NULL);
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int overlay = open("/overlay", O_RDONLY | O_CLOEXEC);
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if (overlay > 0)
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mv_dir(overlay, root);
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snprintf(partname, sizeof(partname), "vendor%s", cmd.slot);
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// We need to mount independent vendor partition
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if (setup_block(&dev, partname) == 0)
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mount(dev.path, "/vendor", "ext4", MS_RDONLY, NULL);
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patch_ramdisk();
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patch_sepolicy();
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close(root);
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close(system_root);
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close(overlay);
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rmdir("/overlay");
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umount("/vendor");
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} else {
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// Recovery mode
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// Revert original init binary
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unlink("/init");
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rename("/.backup/init", "/init");
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}
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execv("/init", argv);
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return 0;
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}
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