我正在尝试将一个mach端口传递给在Mac OSX上使用fork创建的子进程。我看到了这个问题Sharing Mach ports with child processes，但它没有解决方案，只是描述了问题。查看此站点https://robert.sesek.com/2014/1/changes_to_xnu_mach_ipc.html它包含将mach端口传递给子进程的说明，但遗憾的是它们不是示例代码。
我尝试实现端口交换，但子进程无法接收父进程发送的消息，mach_msg内的recv_port失败并显示invalid name。以下是我到目前为止的情况。很抱歉这么多代码，马克思IPC很难简短。
那么，如果引导程序端口黑客不再起作用，我如何在Mac OSX上将一个mach端口传递给子进程？
我更改了代码示例以反映Ken Thomases在其答案中提出的要点，子进程创建一个具有发送权限的端口并将其发送给父级。但是，父进程无法接收由子进程创建和发送的端口，只能挂起recv_port。
#include <stdio.h>
#include <mach/mach.h>
#include <mach/error.h>
#include <mach/message.h>
#include <unistd.h>
static int32_t
send_port(mach_port_t remote_port, mach_port_t port)
{
kern_return_t err;
struct
{
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t task_port;
} msg;
msg.header.msgh_remote_port = remote_port;
msg.header.msgh_local_port = MACH_PORT_NULL;
msg.header.msgh_bits = MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND, 0) |
MACH_MSGH_BITS_COMPLEX;
msg.header.msgh_size = sizeof msg;
msg.body.msgh_descriptor_count = 1;
msg.task_port.name = port;
msg.task_port.disposition = MACH_MSG_TYPE_COPY_SEND;
msg.task_port.type = MACH_MSG_PORT_DESCRIPTOR;
err = mach_msg_send(&msg.header);
if(err != KERN_SUCCESS)
{
mach_error("Can't send mach msg\n", err);
return (-1);
}
return (0);
}
static int32_t
recv_port(mach_port_t recv_port, mach_port_t *port)
{
kern_return_t err;
struct
{
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t task_port;
mach_msg_trailer_t trailer;
} msg;
err = mach_msg(&msg.header, MACH_RCV_MSG,
0, sizeof msg, recv_port,
MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
if(err != KERN_SUCCESS)
{
mach_error("Can't recieve mach message\n", err);
return (-1);
}
*port = msg.task_port.name;
return 0;
}
static int32_t
setup_recv_port(mach_port_t *recv_port)
{
kern_return_t err;
mach_port_t port = MACH_PORT_NULL;
err = mach_port_allocate(mach_task_self (),
MACH_PORT_RIGHT_RECEIVE, &port);
if(err != KERN_SUCCESS)
{
mach_error("Can't allocate mach port\n", err);
return (-1);
}
err = mach_port_insert_right(mach_task_self (),
port,
port,
MACH_MSG_TYPE_MAKE_SEND);
if(err != KERN_SUCCESS)
{
mach_error("Can't insert port right\n", err);
return (-1);
}
(*recv_port) = port;
return (0);
}
pid_t
fork_pass_port(mach_port_t pass_port, int32_t (*child_start)(mach_port_t port, void *arg), void *arg)
{
pid_t pid = 0;
int32_t rtrn = 0;
kern_return_t err;
mach_port_t special_port = MACH_PORT_NULL;
/* Setup the mach port. */
if(setup_recv_port(&pass_port) != 0)
{
printf("Can't setup mach port\n");
return (-1);
}
/* Grab our current task's(process's) HOST_NAME special port. */
err = task_get_special_port(mach_task_self(), TASK_HOST_PORT, &special_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't get special port:\n", err);
return (-1);
}
/* Set the HOST_NAME special port as the parent recv port. */
err = task_set_special_port(mach_task_self(), TASK_HOST_PORT, pass_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't set special port:\n", err);
return (-1);
}
pid = fork();
if(pid == 0)
{
mach_port_t host_port = MACH_PORT_NULL;
mach_port_t port = MACH_PORT_NULL;
/* In the child process grab the port passed by the parent. */
err = task_get_special_port(mach_task_self(), TASK_HOST_PORT, &pass_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't get special port:\n", err);
return (-1);
}
/* Create a port with a send right. */
if(setup_recv_port(&port) != 0)
{
printf("Can't setup mach port\n");
return (-1);
}
/* Send port to parent. */
rtrn = send_port(pass_port, port);
if(rtrn < 0)
{
printf("Can't send port\n");
return (-1);
}
/* Now that were done passing the mach port, start the function passed by the caller. */
child_start(pass_port, arg);
/* Exit and clean up the child process. */
_exit(0);
}
else if(pid > 0)
{
mach_port_t child_port = MACH_PORT_NULL;
rtrn = recv_port(pass_port, &child_port);
if(rtrn < 0)
{
printf("Can't recv port\n");
return (-1);
}
/* Reset parents special port. */
err = task_set_special_port(mach_task_self(), TASK_HOST_PORT, special_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't set special port:\n", err);
return (-1);
}
return (0);
}
else
{
/* Error, so cleanup the mach port. */
err = mach_port_deallocate(mach_task_self(), pass_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't deallocate mach port\n", err);
return (-1);
}
perror("fork");
return (-1);
}
}
static int32_t start(mach_port_t port, void *arg)
{
printf("Started\n");
return (0);
}
int main(void)
{
char *arg = "argument";
mach_port_t port = MACH_PORT_NULL;
pid_t pid = fork_pass_port(port, start, arg);
if(pid < 0)
{
printf("Can't fork and pass msg port\n");
return (-1);
}
return (0);
}
答案 0 :(得分：3)
我想出了如何通过特殊端口继承传递mach端口。在调用fork之前，您必须暂时将TASK_BOOTSTRAP_PORT替换为要传递的端口。其他特殊端口以某种方式失败。下面是一个＆＃34;端口交换舞蹈的例子＆＃34;。
请注意，此代码仅在OSX 10.11.3上进行了测试，可能无法在OSX的早期版本或未来版本上运行。
#include <stdio.h>
#include <mach/mach.h>
#include <mach/error.h>
#include <mach/message.h>
#include <unistd.h>
#define SPECIAL_PORT TASK_BOOTSTRAP_PORT
static int32_t
send_port(mach_port_t remote_port, mach_port_t port)
{
kern_return_t err;
struct
{
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t task_port;
} msg;
msg.header.msgh_remote_port = remote_port;
msg.header.msgh_local_port = MACH_PORT_NULL;
msg.header.msgh_bits = MACH_MSGH_BITS (MACH_MSG_TYPE_COPY_SEND, 0) |
MACH_MSGH_BITS_COMPLEX;
msg.header.msgh_size = sizeof msg;
msg.body.msgh_descriptor_count = 1;
msg.task_port.name = port;
msg.task_port.disposition = MACH_MSG_TYPE_COPY_SEND;
msg.task_port.type = MACH_MSG_PORT_DESCRIPTOR;
err = mach_msg_send(&msg.header);
if(err != KERN_SUCCESS)
{
mach_error("Can't send mach msg\n", err);
return (-1);
}
return (0);
}
static int32_t
recv_port(mach_port_t recv_port, mach_port_t *port)
{
kern_return_t err;
struct
{
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t task_port;
mach_msg_trailer_t trailer;
} msg;
err = mach_msg(&msg.header, MACH_RCV_MSG,
0, sizeof msg, recv_port,
MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
if(err != KERN_SUCCESS)
{
mach_error("Can't recieve mach message\n", err);
return (-1);
}
(*port) = msg.task_port.name;
return 0;
}
static int32_t
setup_recv_port(mach_port_t *recv_port)
{
kern_return_t err;
mach_port_t port = MACH_PORT_NULL;
err = mach_port_allocate(mach_task_self (),
MACH_PORT_RIGHT_RECEIVE, &port);
if(err != KERN_SUCCESS)
{
mach_error("Can't allocate mach port\n", err);
return (-1);
}
err = mach_port_insert_right(mach_task_self (),
port,
port,
MACH_MSG_TYPE_MAKE_SEND);
if(err != KERN_SUCCESS)
{
mach_error("Can't insert port right\n", err);
return (-1);
}
(*recv_port) = port;
return (0);
}
static int32_t
start(mach_port_t port, void *arg)
{
return (0);
}
static pid_t
fork_pass_port(mach_port_t *pass_port,
int32_t (*child_start)(mach_port_t port, void *arg),
void *arg)
{
pid_t pid = 0;
int32_t rtrn = 0;
kern_return_t err;
mach_port_t special_port = MACH_PORT_NULL;
/* Allocate the mach port. */
if(setup_recv_port(pass_port) != 0)
{
printf("Can't setup mach port\n");
return (-1);
}
/* Grab our current process's bootstrap port. */
err = task_get_special_port(mach_task_self(), SPECIAL_PORT, &special_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't get special port:\n", err);
return (-1);
}
/* Set the special port as the parent recv port. */
err = task_set_special_port(mach_task_self(), SPECIAL_PORT, (*pass_port));
if(err != KERN_SUCCESS)
{
mach_error("Can't set special port:\n", err);
return (-1);
}
pid = fork();
if(pid == 0)
{
mach_port_t bootstrap_port = MACH_PORT_NULL;
mach_port_t port = MACH_PORT_NULL;
/* In the child process grab the port passed by the parent. */
err = task_get_special_port(mach_task_self(), SPECIAL_PORT, pass_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't get special port:\n", err);
return (-1);
}
/* Create a port with a send right. */
if(setup_recv_port(&port) != 0)
{
printf("Can't setup mach port\n");
return (-1);
}
/* Send port to parent. */
rtrn = send_port((*pass_port), port);
if(rtrn < 0)
{
printf("Can't send port\n");
return (-1);
}
/* Receive the real bootstrap port from the parent. */
rtrn = recv_port(port, &bootstrap_port);
if(rtrn < 0)
{
printf("Can't receive bootstrap port\n");
return (-1);
}
/* Set the bootstrap port back to normal. */
err = task_set_special_port(mach_task_self(), SPECIAL_PORT, bootstrap_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't set special port:\n", err);
return (-1);
}
/* Now that were done with the port dance, start the function passed by the caller. */
child_start((*pass_port), arg);
/* Exit and clean up the child process. */
_exit(0);
}
else if(pid > 0)
{
mach_port_t child_port = MACH_PORT_NULL;
/* Grab the child's recv port. */
rtrn = recv_port((*pass_port), &child_port);
if(rtrn < 0)
{
printf("Can't recv port\n");
return (-1);
}
/* Send the child the original bootstrap port. */
rtrn = send_port(child_port, special_port);
if(rtrn < 0)
{
printf("Can't send bootstrap port\n");
return (-1);
}
/* Reset parents special port. */
err = task_set_special_port(mach_task_self(), SPECIAL_PORT, special_port);
if(err != KERN_SUCCESS)
{
mach_error("Can't set special port:\n", err);
return (-1);
}
return (0);
}
else
{
/* Error, so cleanup the mach port. */
err = mach_port_deallocate(mach_task_self(), (*pass_port));
if(err != KERN_SUCCESS)
{
mach_error("Can't deallocate mach port\n", err);
return (-1);
}
perror("fork");
return (-1);
}
}
int main(void)
{
/* Argument to pass to the child process. */
char *arg = "argument";
/* Mach port we want to pass to the child. */
mach_port_t port = MACH_PORT_NULL;
pid_t pid = fork_pass_port(&port, start, arg);
if(pid < 0)
{
printf("Can't fork and pass msg port\n");
return (-1);
}
return (0);
}
答案 1 :(得分：2)
对于任何给定的端口，只有一个接收权限。父级具有其创建的端口的接收权限。特殊端口的继承仅适用于发送权限。因此，孩子只会继承你的通信端口的发送权。
您链接的文章暗示孩子通过此端口向父母发送消息。孩子应该创建自己的新端口并具有接收权限。它的消息将携带该端口的发送或发送一次权限给父节点，具体取决于您是否需要进行双工通信。孩子将把发送（-once）放在消息的msgh_local_port中;父母将在msgh_remote_port收到它。父母可以使用该发送（-once）权限进行回复，并且回复可以携带对原始主机端口的发送权限。孩子可以使用它来恢复其主机端口。
或者，您可以这样做：
mach_port_extract_right() 它还可以提取原始主机端口的发送权，而不是通过IPC接收它，这应该更简单。
所有这些都说，是什么让你认为主机端口比引导端口更安全？