fix: zygiskd companion, companion responses, write fd function and early client close

This commit fixes numerous issues in zygiskd code: The zygiskd companion code not loading the right entry, the companion not sending the correct responses, the write fd function not working properly and early client close when connecting to the companion.

zygiskd/src/utils.c

@@ -18,6 +18,10 @@
 
 #include "utils.h"
 
+/* INFO 50ms wait */
+// #define ALLOW_WAIT_ON_DEBUG() usleep(500 * 1000)
+#define ALLOW_WAIT_ON_DEBUG() {}
+
 bool switch_mount_namespace(pid_t pid) {
   char path[PATH_MAX];
   snprintf(path, sizeof(path), "/proc/%d/ns/mnt", pid);
@@ -192,82 +196,114 @@ int unix_listener_from_path(char *restrict path) {
   return socket_fd;
 }
 
-ssize_t send_fd(int sockfd, int fd) {
-  char control_buf[CMSG_SPACE(sizeof(int))];
-  memset(control_buf, 0, sizeof(control_buf));
-
-  int cnt = 1;
+ssize_t gwrite_fd(int fd, int sendfd) {
+  char cmsgbuf[CMSG_SPACE(sizeof(int))];
+  char buf[1] = { 0 };
+  
   struct iovec iov = {
-    .iov_base = &cnt,
-    .iov_len  = sizeof(cnt)
+    .iov_base = buf,
+    .iov_len = 1
   };
 
   struct msghdr msg = {
     .msg_iov = &iov,
     .msg_iovlen = 1,
-    .msg_control = control_buf,
-    .msg_controllen = sizeof(control_buf)
+    .msg_control = cmsgbuf,
+    .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;
-  cmsg->cmsg_len = CMSG_LEN(sizeof(int));
 
-  memcpy(CMSG_DATA(cmsg), &fd, sizeof(int));
+  memcpy(CMSG_DATA(cmsg), &sendfd, sizeof(int));
 
-  ssize_t sent_bytes = sendmsg(sockfd, &msg, 0);
-  if (sent_bytes == -1) {
-    LOGE("Failed to send fd: %s\n", strerror(errno));
+  ssize_t ret = sendmsg(fd, &msg, 0);
+  if (ret == -1) {
+    LOGE("sendmsg: %s\n", strerror(errno));
 
     return -1;
   }
 
-  return sent_bytes;
+  return ret;
 }
 
-ssize_t recv_fd(int sockfd, int *restrict fd) {
-  char control_buf[CMSG_SPACE(sizeof(int))];
-  memset(control_buf, 0, sizeof(control_buf));
-
-  int cnt = 1;
+int gread_fd(int fd) {
+  char cmsgbuf[CMSG_SPACE(sizeof(int))];
+  char buf[1] = { 0 };
+  
   struct iovec iov = {
-    .iov_base = &cnt,
-    .iov_len  = sizeof(cnt)
+    .iov_base = buf,
+    .iov_len = 1
   };
 
   struct msghdr msg = {
     .msg_iov = &iov,
     .msg_iovlen = 1,
-    .msg_control = control_buf,
-    .msg_controllen = sizeof(control_buf)
+    .msg_control = cmsgbuf,
+    .msg_controllen = sizeof(cmsgbuf)
   };
 
-  ssize_t received_bytes = recvmsg(sockfd, &msg, 0);
-  if (received_bytes == -1) {
-    LOGE("Failed to read fd: %s\n", strerror(errno));
+  ssize_t ret = recvmsg(fd, &msg, 0);
+  if (ret == -1) {
+    LOGE("recvmsg: %s\n", strerror(errno));
 
     return -1;
   }
 
   struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
-  memcpy(fd, CMSG_DATA(cmsg), sizeof(int));
-
-  return received_bytes;
-}
-
-ssize_t write_string(int fd, const char *restrict str) {
-  size_t len = strlen(str);
-
-  ssize_t written_bytes = write(fd, &len, sizeof(len));
-  if (written_bytes != sizeof(len)) {
-    LOGE("Failed to write string length: %s\n", strerror(errno));
+  if (cmsg == NULL) {
+    LOGE("CMSG_FIRSTHDR: %s\n", strerror(errno));
 
     return -1;
   }
 
-  written_bytes = write(fd, str, len);
-  if ((size_t)written_bytes != len) {
+  int sendfd;
+  memcpy(&sendfd, CMSG_DATA(cmsg), sizeof(int));
+
+  return sendfd;
+}
+
+#define write_func(type)                    \
+  ssize_t write_## type(int fd, type val) { \
+    ALLOW_WAIT_ON_DEBUG();                  \
+                                            \
+    return write(fd, &val, sizeof(type));   \
+  }
+
+#define read_func(type)                     \
+  ssize_t read_## type(int fd, type *val) { \
+    return read(fd, val, sizeof(type));     \
+  }
+
+write_func(int)
+read_func(int)
+
+write_func(size_t)
+read_func(size_t)
+
+write_func(uint32_t)
+read_func(uint32_t)
+
+write_func(uint8_t)
+read_func(uint8_t)
+
+ssize_t write_string(int fd, const char *restrict str) {
+  size_t len[1];
+  len[0] = strlen(str);
+
+  ALLOW_WAIT_ON_DEBUG();
+
+  ssize_t written_bytes = write(fd, &len, sizeof(size_t));
+  if (written_bytes != sizeof(size_t)) {
+    LOGE("Failed to write string length: Not all bytes were written (%zd != %zu).\n", written_bytes, sizeof(size_t));
+
+    return -1;
+  }
+
+  written_bytes = write(fd, str, len[0]);
+  if ((size_t)written_bytes != len[0]) {
     LOGE("Failed to write string: Not all bytes were written.\n");
 
     return -1;
@@ -279,9 +315,9 @@ ssize_t write_string(int fd, const char *restrict str) {
 ssize_t read_string(int fd, char *restrict str, size_t len) {
   size_t str_len_buf[1];
 
-  ssize_t read_bytes = read(fd, &str_len_buf, sizeof(str_len_buf));
-  if (read_bytes != (ssize_t)sizeof(str_len_buf)) {
-    LOGE("Failed to read string length: %s\n", strerror(errno));
+  ssize_t read_bytes = read(fd, &str_len_buf, sizeof(size_t));
+  if (read_bytes != (ssize_t)sizeof(size_t)) {
+    LOGE("Failed to read string length: Not all bytes were read (%zd != %zu).\n", read_bytes, sizeof(size_t));
 
     return -1;
   }
@@ -296,7 +332,7 @@ ssize_t read_string(int fd, char *restrict str, size_t len) {
 
   read_bytes = read(fd, str, str_len);
   if (read_bytes != (ssize_t)str_len) {
-    LOGE("Failed to read string: Not all bytes were read (%zd != %zu).\n", read_bytes, str_len);
+    LOGE("Failed to read string: Promised bytes doesn't exist (%zd != %zu).\n", read_bytes, str_len);
 
     return -1;
   }
@@ -349,7 +385,7 @@ bool check_unix_socket(int fd, bool block) {
   int timeout = block ? -1 : 0;
   poll(&pfd, 1, timeout);
 
-  return (pfd.revents & !POLLIN) != 0 ? false : true;
+  return pfd.revents & ~POLLIN ? false : true;
 }
 
 /* INFO: Cannot use restrict here as execv does not have restrict */