Magisk/jni/daemon/socket_trans.c
2017-04-22 17:12:54 +08:00

149 lines
3.5 KiB
C

/* socket_trans.c - Functions to transfer data through socket
*/
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "magisk.h"
#include "utils.h"
#include "daemon.h"
/*
* Receive a file descriptor from a Unix socket.
* Contributed by @mkasick
*
* Returns the file descriptor on success, or -1 if a file
* descriptor was not actually included in the message
*
* On error the function terminates by calling exit(-1)
*/
int recv_fd(int sockfd) {
// Need to receive data from the message, otherwise don't care about it.
char iovbuf;
struct iovec iov = {
.iov_base = &iovbuf,
.iov_len = 1,
};
char cmsgbuf[CMSG_SPACE(sizeof(int))];
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsgbuf,
.msg_controllen = sizeof(cmsgbuf),
};
xrecvmsg(sockfd, &msg, MSG_WAITALL);
// Was a control message actually sent?
switch (msg.msg_controllen) {
case 0:
// No, so the file descriptor was closed and won't be used.
return -1;
case sizeof(cmsgbuf):
// Yes, grab the file descriptor from it.
break;
default:
goto error;
}
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg == NULL ||
cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
cmsg->cmsg_level != SOL_SOCKET ||
cmsg->cmsg_type != SCM_RIGHTS) {
error:
LOGE("unable to read fd");
exit(-1);
}
return *(int *)CMSG_DATA(cmsg);
}
/*
* Send a file descriptor through a Unix socket.
* Contributed by @mkasick
*
* On error the function terminates by calling exit(-1)
*
* fd may be -1, in which case the dummy data is sent,
* but no control message with the FD is sent.
*/
void send_fd(int sockfd, int fd) {
// Need to send some data in the message, this will do.
struct iovec iov = {
.iov_base = "",
.iov_len = 1,
};
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
};
char cmsgbuf[CMSG_SPACE(sizeof(int))];
if (fd != -1) {
// Is the file descriptor actually open?
if (fcntl(fd, F_GETFD) == -1) {
if (errno != EBADF) {
PLOGE("unable to send fd");
}
// It's closed, don't send a control message or sendmsg will EBADF.
} else {
// It's open, send the file descriptor in a control message.
msg.msg_control = cmsgbuf;
msg.msg_controllen = sizeof(cmsgbuf);
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
*(int *)CMSG_DATA(cmsg) = fd;
}
}
xsendmsg(sockfd, &msg, 0);
}
int read_int(int fd) {
int val;
xxread(fd, &val, sizeof(int));
return val;
}
void write_int(int fd, int val) {
if (fd < 0) return;
xwrite(fd, &val, sizeof(int));
}
char* read_string(int fd) {
int len = read_int(fd);
if (len > PATH_MAX || len < 0) {
LOGE("invalid string length %d", len);
exit(1);
}
char* val = xmalloc(sizeof(char) * (len + 1));
xxread(fd, val, len);
val[len] = '\0';
return val;
}
void write_string(int fd, const char* val) {
if (fd < 0) return;
int len = strlen(val);
write_int(fd, len);
xwrite(fd, val, len);
}