ec3705f2ed
Introduce new domain `magisk_client` and new file type `magisk_exec`. Connection to magiskd's always-on socket is restricted to magisk_client only. Whitelisted process domains can transit to magisk_client through executing files labelled magisk_exec. The main magisk binary shall be the only file labelled as magisk_exec throughout the whole system. All processes thus are no longer allowed to connect to magiskd directly without going through the proper magisk binary. Connection failures are silenced from audit logs with dontaudit rules, so crazy processes which traverse through all unix domain sockets to try connection can no longer check logcat to know the actual reason behind EACCES, leaking the denied process policy (which is u:r:magisk:s0). This also allows us to remove many rules that open up holes in untrusted_app domains that were used to make remote shell work properly. Since all processes establishing the remote shell are now restricted to the magisk_client domain, all these rules are moved to magisk_client. This makes Magisk require fewer compromises in Android's security model. Note: as of this commit, requesting new root access via Magisk Manager will stop working as Magisk Manager can no longer communicate with magiskd directly. This will be addressed in a future commit that involves changes in both native and application side.
96 lines
2.4 KiB
C++
96 lines
2.4 KiB
C++
#include <string_view>
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#include <magisk.hpp>
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#include <selinux.hpp>
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#include <utils.hpp>
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using namespace std;
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#define UNLABEL_CON "u:object_r:unlabeled:s0"
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#define SYSTEM_CON "u:object_r:system_file:s0"
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#define ADB_CON "u:object_r:adb_data_file:s0"
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#define ROOT_CON "u:object_r:rootfs:s0"
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#define MAGISK_CON "u:object_r:" SEPOL_FILE_TYPE ":s0"
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#define EXEC_CON "u:object_r:" SEPOL_EXEC_TYPE ":s0"
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static void restore_syscon(int dirfd) {
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struct dirent *entry;
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DIR *dir;
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char *con;
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fgetfilecon(dirfd, &con);
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if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
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fsetfilecon(dirfd, SYSTEM_CON);
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freecon(con);
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dir = xfdopendir(dirfd);
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while ((entry = xreaddir(dir))) {
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int fd = openat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
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if (entry->d_type == DT_DIR) {
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restore_syscon(fd);
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} else if (entry->d_type == DT_REG) {
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fgetfilecon(fd, &con);
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if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
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fsetfilecon(fd, SYSTEM_CON);
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freecon(con);
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} else if (entry->d_type == DT_LNK) {
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getfilecon_at(dirfd, entry->d_name, &con);
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if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
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setfilecon_at(dirfd, entry->d_name, con);
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freecon(con);
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}
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close(fd);
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}
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}
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static void restore_magiskcon(int dirfd) {
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struct dirent *entry;
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DIR *dir;
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fsetfilecon(dirfd, MAGISK_CON);
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fchown(dirfd, 0, 0);
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dir = xfdopendir(dirfd);
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while ((entry = xreaddir(dir))) {
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int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
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if (entry->d_type == DT_DIR) {
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restore_magiskcon(fd);
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} else if (entry->d_type) {
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fsetfilecon(fd, MAGISK_CON);
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fchown(fd, 0, 0);
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}
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close(fd);
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}
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}
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void restorecon() {
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int fd = xopen(SELINUX_CONTEXT, O_WRONLY | O_CLOEXEC);
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if (write(fd, ADB_CON, sizeof(ADB_CON)) >= 0)
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lsetfilecon(SECURE_DIR, ADB_CON);
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close(fd);
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lsetfilecon(MODULEROOT, SYSTEM_CON);
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fd = xopen(MODULEROOT, O_RDONLY | O_CLOEXEC);
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restore_syscon(fd);
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close(fd);
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fd = xopen(DATABIN, O_RDONLY | O_CLOEXEC);
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restore_magiskcon(fd);
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close(fd);
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}
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void restore_tmpcon() {
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if (MAGISKTMP == "/sbin")
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setfilecon(MAGISKTMP.data(), ROOT_CON);
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else
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chmod(MAGISKTMP.data(), 0700);
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auto dir = xopen_dir(MAGISKTMP.data());
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int dfd = dirfd(dir.get());
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for (dirent *entry; (entry = xreaddir(dir.get()));) {
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if (entry->d_name == "magisk"sv)
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setfilecon_at(dfd, entry->d_name, EXEC_CON);
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else
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setfilecon_at(dfd, entry->d_name, SYSTEM_CON);
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}
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}
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