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Improve builtin selinux implementation

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This commit is contained in:
topjohnwu
2019-03-14 06:34:22 -04:00
parent b7e2e972c7
commit da0a72e8b0
5 changed files with 142 additions and 78 deletions
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122
native/jni/utils/selinux.cpp
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@@ -25,6 +25,13 @@ static int stub(const char *, char **ctx) {
return 0;
}
static int stub(int, const char *) { return 0; }
static int stub(int, char **ctx) {
*ctx = strdup("");
return 0;
}
// Builtin implementation
static void __freecon(char *s) {
@@ -44,25 +51,61 @@ static int __setcon(const char *ctx) {
static int __getfilecon(const char *path, char **ctx) {
char buf[1024];
int rc = syscall(__NR_getxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
if (rc > 0)
*ctx = strdup(buf);
if (rc < 0) {
errno = -rc;
return -1;
}
*ctx = strdup(buf);
return rc;
}
static int __lgetfilecon(const char *path, char **ctx) {
char buf[1024];
int rc = syscall(__NR_lgetxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
if (rc > 0)
*ctx = strdup(buf);
if (rc < 0) {
errno = -rc;
return -1;
}
*ctx = strdup(buf);
return rc;
}
static int __fgetfilecon(int fd, char **ctx) {
char buf[1024];
int rc = syscall(__NR_fgetxattr, fd, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
if (rc < 0) {
errno = -rc;
return -1;
}
*ctx = strdup(buf);
return rc;
}
static int __setfilecon(const char *path, const char *ctx) {
return syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
int rc = syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
if (rc) {
errno = -rc;
return -1;
}
return 0;
}
static int __lsetfilecon(const char *path, const char *ctx) {
return syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
int rc = syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
if (rc) {
errno = -rc;
return -1;
}
return 0;
}
static int __fsetfilecon(int fd, const char *ctx) {
int rc = syscall(__NR_fsetxattr, fd, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
if (rc) {
errno = -rc;
return -1;
}
return 0;
}
// Function pointers
@@ -71,15 +114,32 @@ void (*freecon)(char *) = __freecon;
int (*setcon)(const char *) = stub;
int (*getfilecon)(const char *, char **) = stub;
int (*lgetfilecon)(const char *, char **) = stub;
int (*fgetfilecon)(int, char **) = stub;
int (*setfilecon)(const char *, const char *) = stub;
int (*lsetfilecon)(const char *, const char *) = stub;
int (*fsetfilecon)(int, const char *) = stub;
void getfilecon_at(int dirfd, const char *name, char **con) {
char path[4096];
fd_pathat(dirfd, name, path, sizeof(path));
if (lgetfilecon(path, con))
*con = strdup("");
}
void setfilecon_at(int dirfd, const char *name, const char *con) {
char path[4096];
fd_pathat(dirfd, name, path, sizeof(path));
lsetfilecon(path, con);
}
void selinux_builtin_impl() {
setcon = __setcon;
getfilecon = __getfilecon;
lgetfilecon = __lgetfilecon;
fgetfilecon = __fgetfilecon;
setfilecon = __setfilecon;
lsetfilecon = __lsetfilecon;
fsetfilecon = __fsetfilecon;
}
void dload_selinux() {
@@ -95,33 +155,32 @@ void dload_selinux() {
static void restore_syscon(int dirfd) {
struct dirent *entry;
DIR *dir;
char *con;
char path[PATH_MAX], *con;
fd_getpath(dirfd, path, sizeof(path));
size_t len = strlen(path);
getfilecon(path, &con);
fgetfilecon(dirfd, &con);
if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
lsetfilecon(path, SYSTEM_CON);
fsetfilecon(dirfd, SYSTEM_CON);
freecon(con);
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
continue;
int fd = openat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
if (entry->d_type == DT_DIR) {
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
restore_syscon(fd);
close(fd);
} else {
path[len] = '/';
strcpy(path + len + 1, entry->d_name);
lgetfilecon(path, &con);
if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
lsetfilecon(path, SYSTEM_CON);
} else if (entry->d_type == DT_REG) {
fgetfilecon(fd, &con);
if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
fsetfilecon(fd, SYSTEM_CON);
freecon(con);
} else if (entry->d_type == DT_LNK) {
getfilecon_at(dirfd, entry->d_name, &con);
if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
setfilecon_at(dirfd, entry->d_name, con);
freecon(con);
path[len] = '\0';
}
close(fd);
}
}
@@ -129,28 +188,21 @@ static void restore_magiskcon(int dirfd) {
struct dirent *entry;
DIR *dir;
char path[PATH_MAX];
fd_getpath(dirfd, path, sizeof(path));
size_t len = strlen(path);
lsetfilecon(path, MAGISK_CON);
lchown(path, 0, 0);
fsetfilecon(dirfd, MAGISK_CON);
fchown(dirfd, 0, 0);
dir = xfdopendir(dirfd);
while ((entry = xreaddir(dir))) {
if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
continue;
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
if (entry->d_type == DT_DIR) {
int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
restore_magiskcon(fd);
close(fd);
} else {
path[len] = '/';
strcpy(path + len + 1, entry->d_name);
lsetfilecon(path, MAGISK_CON);
lchown(path, 0, 0);
path[len] = '\0';
} else if (entry->d_type) {
fsetfilecon(fd, MAGISK_CON);
fchown(fd, 0, 0);
}
close(fd);
}
}