Magisk/native/jni/utils/selinux.cpp

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#include <sys/xattr.h>
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#include <utils.hpp>
#include <selinux.hpp>
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using namespace std;
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// Stub implementation
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static int stub(const char *) { return 0; }
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static int stub(const char *, const char *) { return 0; }
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static int stub(const char *, char **ctx) {
*ctx = strdup("");
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return 0;
}
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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) {
free(s);
}
static int __setcon(const char *ctx) {
int fd = open("/proc/self/attr/current", O_WRONLY | O_CLOEXEC);
if (fd < 0)
return fd;
size_t len = strlen(ctx) + 1;
int rc = write(fd, ctx, len);
close(fd);
return rc != len;
}
static int __getfilecon(const char *path, char **ctx) {
char buf[1024];
int rc = syscall(__NR_getxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
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if (rc >= 0)
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*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);
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if (rc >= 0)
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*ctx = strdup(buf);
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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);
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if (rc >= 0)
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*ctx = strdup(buf);
return rc;
}
static int __setfilecon(const char *path, const char *ctx) {
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return syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
}
static int __lsetfilecon(const char *path, const char *ctx) {
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return syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
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}
static int __fsetfilecon(int fd, const char *ctx) {
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return syscall(__NR_fsetxattr, fd, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
}
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// Function pointers
void (*freecon)(char *) = __freecon;
int (*setcon)(const char *) = stub;
int (*getfilecon)(const char *, char **) = stub;
int (*lgetfilecon)(const char *, char **) = stub;
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int (*fgetfilecon)(int, char **) = stub;
int (*setfilecon)(const char *, const char *) = stub;
int (*lsetfilecon)(const char *, const char *) = stub;
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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;
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fgetfilecon = __fgetfilecon;
setfilecon = __setfilecon;
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lsetfilecon = __lsetfilecon;
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fsetfilecon = __fsetfilecon;
}
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void dload_selinux() {
if (access("/system/lib/libselinux.so", F_OK))
return;
/* We only check whether libselinux.so exists but don't dlopen.
* For some reason calling symbols returned from dlsym
* will result to SEGV_ACCERR on some devices.
* Always use builtin implementations for SELinux stuffs. */
selinux_builtin_impl();
}