Magisk/core/jni/magiskboot/ramdisk.c

#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <utils.h>
#include <sys/mman.h>
#include <fcntl.h>

#include "magiskboot.h"
#include "cpio.h"

int check_verity_pattern(const char *s) {
	int pos = 0;
	if (s[0] == ',') ++pos;
	if (strncmp(s + pos, "verify", 6) == 0)
		pos += 6;
	else if (strncmp(s + pos, "avb", 3) == 0)
		pos += 3;
	else
		return -1;

	if (s[pos] == '=') {
		while (s[pos] != '\0' && s[pos] != ' ' && s[pos] != '\n' && s[pos] != ',') ++pos;
	}
	return pos;
}

int check_encryption_pattern(const char *s) {
	const char *encrypt_list[] = { "forceencrypt", "forcefdeorfbe", NULL };
	for (int i = 0 ; encrypt_list[i]; ++i) {
		int len = strlen(encrypt_list[i]);
		if (strncmp(s, encrypt_list[i], len) == 0)
			return len;
	}
	return -1;
}

void cpio_patch(struct vector *v, int keepverity, int keepforceencrypt) {
	cpio_entry *f;
	int skip, write;
	vec_for_each(v, f) {
		if (!keepverity) {
			if (strstr(f->filename, "fstab") != NULL && S_ISREG(f->mode)) {
				write = 0;
				for (int read = 0; read < f->filesize; ++write, ++read) {
					if ((skip = check_verity_pattern(f->data + read)) > 0) {
						fprintf(stderr, "Remove pattern [%.*s] in [%s]\n", skip, f->data + read, f->filename);
						read += skip;
					}
					f->data[write] = f->data[read];
				}
				f->filesize = write;
			} else if (strcmp(f->filename, "verity_key") == 0) {
				fprintf(stderr, "Remove [verity_key]\n");
				f->remove = 1;
			}
		}
		if (!keepforceencrypt) {
			if (strstr(f->filename, "fstab") != NULL && S_ISREG(f->mode)) {
				write = 0;
				for (int read = 0; read < f->filesize; ++write, ++read) {
					if ((skip = check_encryption_pattern(f->data + read)) > 0) {
						// assert(skip > 11)!
						fprintf(stderr, "Replace pattern [%.*s] with [encryptable] in [%s]\n", skip, f->data + read, f->filename);
						memcpy(f->data + write, "encryptable", 11);
						write += 11;
						read += skip;
					}
					f->data[write] = f->data[read];
				}
				f->filesize = write;
			}
		}
	}
}

static void restore_high_compress(struct vector *v, const char *incpio) {
	// Check if the ramdisk is in high compression mode
	if (cpio_extract(v, "ramdisk.cpio.xz", incpio) == 0) {
		void *addr, *xz;
		size_t size;
		mmap_ro(incpio, &addr, &size);
		xz = xmalloc(size);
		memcpy(xz, addr, size);
		munmap(addr, size);
		int fd = creat(incpio, 0644);
		lzma(0, fd, xz, size);
		close(fd);
		cpio_rm(v, 0, "ramdisk.cpio.xz");
		cpio_rm(v, 0, "init");
		struct vector vv;
		vec_init(&vv);
		parse_cpio(&vv, incpio);
		cpio_entry *e;
		vec_for_each(&vv, e)
			vec_push_back(v, e);
		vec_destroy(&vv);
	}
}

static void enable_high_compress(struct vector *v, struct vector *b, const char *incpio) {
	cpio_entry *e, *magiskinit, *init;

	// Swap magiskinit with original init
	vec_for_each(b, e) {
		if (strcmp(e->filename, ".backup/init") == 0) {
			free(e->filename);
			e->filename = strdup("init");
			init = e;
			vec_for_each(v, e) {
				if (strcmp(e->filename, "init") == 0) {
					magiskinit = e;
					vec_cur(v) = init;
					break;
				}
			}
			vec_cur(b) = NULL;
			break;
		}
	}

	dump_cpio(v, incpio);
	cpio_vec_destroy(v);
	void *addr, *cpio;
	size_t size;
	mmap_ro(incpio, &addr, &size);
	cpio = xmalloc(size);
	memcpy(cpio, addr, size);
	munmap(addr, size);
	int fd = creat(incpio, 0644);
	lzma(1, fd, cpio, size);
	close(fd);
	vec_init(v);
	vec_push_back(v, magiskinit);
	cpio_add(v, 0, "ramdisk.cpio.xz", incpio);
}

int cpio_commands(const char *command, int argc, char *argv[]) {
	char *incpio = argv[0];
	++argv;
	--argc;
	struct vector v;
	vec_init(&v);
	parse_cpio(&v, incpio);

	if (strcmp(command, "test") == 0) {
		exit(cpio_test(&v));
	} else if (strcmp(command, "restore") == 0) {
		restore_high_compress(&v, incpio);
		cpio_restore(&v);
	} else if (strcmp(command, "stocksha1") == 0) {
		printf("%s\n", cpio_stocksha1(&v));
		return 0;
	} else if (argc >= 2 && strcmp(command, "backup") == 0) {
		struct vector *back;
		cpio_entry *e;
		back = cpio_backup(&v, argv[0], argc > 2 ? argv[2] : NULL);

		// Enable high compression mode
		if (strcmp(argv[1], "true") == 0)
			enable_high_compress(&v, back, incpio);

		vec_for_each(back, e)
			if (e) vec_push_back(&v, e);

	} else if (argc > 0 && strcmp(command, "rm") == 0) {
		int recursive = 0;
		if (argc == 2 && strcmp(argv[0], "-r") == 0) {
			recursive = 1;
			++argv;
		}
		cpio_rm(&v, recursive, argv[0]);
	} else if (argc == 2 && strcmp(command, "mv") == 0) {
		if (cpio_mv(&v, argv[0], argv[1]))
			return 1;
	} else if (argc == 2 && strcmp(command, "patch") == 0) {
		cpio_patch(&v, strcmp(argv[0], "true") == 0, strcmp(argv[1], "true") == 0);
	} else if (strcmp(command, "extract") == 0) {
		if (argc == 2) {
			return cpio_extract(&v, argv[0], argv[1]);
		} else {
			cpio_extract_all(&v);
			return 0;
		}
	} else if (argc == 2 && strcmp(command, "mkdir") == 0) {
		cpio_mkdir(&v, strtoul(argv[0], NULL, 8), argv[1]);
	} else if (argc == 2 && strcmp(command, "ln") == 0) {
		cpio_ln(&v, argv[0], argv[1]);
	} else if (argc == 3 && strcmp(command, "add") == 0) {
		cpio_add(&v, strtoul(argv[0], NULL, 8), argv[1], argv[2]);
	} else {
		return 1;
	}

	dump_cpio(&v, incpio);
	cpio_vec_destroy(&v);
	exit(0);
}