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[原创]Netatalk CVE-2018-1160 复现及漏洞利用思路
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发表于: 2023-4-6 18:00
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author:cxing
Date:2023年4月6日
introduction：Netatalk 是一个 Apple Filing Protocol (AFP) 的开源实现。 它为 Unix 风格系统提供了与 Macintosh 文件共享的功能。AFP的数据流量包格式为DSI(Data Stream Interface)，DSI 在客户端和 AFP 服务器之间使用。
首先需要搭建netatalk的运行环境，这里使用docker搭建Ubuntu18.04，可以在docker Ubuntu18.04中进行环境复现。这里有两种方法，一是在docker中下载源码、安装依赖环境编译，二是在本机中下载源码、依赖编译。我这里选择了比较稳妥的的第一中。
运行Ubuntu 18.04的镜像，没有会自动从官方docker仓库中pull。
关于详细的安装步骤可以参考先知的这篇文章搭建环境，如果你想使用我的环境可以使用下面链接下载我的docker镜像。
链接：https://pan.baidu.com/s/1NJOfT9xS111RSmgcSbEW3Q
提取码：8r5i
你需要使用如下命令启动docker，以保证我docker中的设置正常运行。
netatalk处理请求类似于Apache，对于每一个用户请求都会为其fork一个子进程处理，而父进程则监控请求的处理情况。netatalk的关键运行模块主要有两个，主模块afpd和AFP协议流量包处理模块libnetatalk。其中afpd主要功能为初始化服务的环境、监听和接受处理请求并为之构建请求处理的环境，而libnetatalk是具体解析和处理dsi流量的。
注1：Netatalk的大部分功能性函数命名风格采用 模块命名空间_函数描述 的格式，如afp_exit、afp_over_dsi、dsi_opensession等。
注2: DSI流量包格式可以参考这篇wiki，Data_Stream_Interface。
对于理解Netatalk，需要用afp_start、afp_over_dsi为主线理解。
afp_start在main中被调用，通过阅读下面代码可以得知。第一个关键代码处调用了init_listening_sockets其目的是watch atp, dsi sockets and ipc parent/child file descriptor，也就是从这里开始监听APF请求了。继续往下看，我们发现了(child = dsi_start(&obj, (DSI *)(asev->data[i].private), server_children))这行代码，返货了进程描述符，这意味着从这里开始已经真正开始接收和处理请求了。
我们再来看afp_start函数。首先调用了dsi_getsession，并且forked后进入afp_over_dsi处理本次请求。我们先看dsi_getsession，我们可以看到在第一个数据包中只允许我们利用DSI中的command字段访问两个Command命令或者说函数，分别是DSIGetStatus和 DSIOpenSession。我们查阅一下，DSIOpenSession命令的分支即dsi_opensession函数。我们看到switch语句在解析DSI session options时，DSIOPT_ATTNQUANT分支中出现了一个memcpy(&dsi->attn_quantum, dsi->commands + i + 1, dsi->commands[i]);语句，这里存在一个越界写漏洞。在进入到dsi_opensession函数之前，会隐式的调用dsi_stream_receive函数，将我们发送的DSI数据包中的Payload字段 copy to dsi->commands中。而Payload字段是可控的，用户发包时自由指定，只要服务可以解析即可。因此，我们发现payload在这里实际上解析的格式是payload[0]:code, payload[1]:size, payload[2:size -1]:data，而memcpy拷贝至的dsi->attn_quantum变量却是一个uint32类型，也就说，只要我们合理设置size和data就可以触发越界写，覆盖&dsi->attn_quantum后面的字段。我们可以往后覆盖多少个字节呢？dsi->commands是一个uint8类型的指针，也就是解析格式中size最大值为255，我们可以往后覆盖255个字节。
DSI结构体如下，从attn_quantum字段往后溢出，我们最多可以溢出至data数组的部分空间（data数组非常大）。比较关键的是我们可以覆盖指针dsi->commands。在后面的漏洞分析小节，我们会纤细的讨论覆盖commands指针所导致的严重后果，这将使得我们可以RCE。afp_start->dsi_getsession->dsi_opensession这条路径我们分析至此。大意的作用从两个关键函数名也可以看出来，核心就是open session，配置一些东西并开启正式的连接会话，你可以理解为TCP建立连接前的三次握手，但是在配置过程中产生了越界写漏洞。
我们再继续从afp_start->afp_over_dsi开始看。afp_over_dsi处理正式连接的请求核心再这个while循环。首先第一行重要代码cmd = dsi_stream_receive(dsi);，Blocking read on the network socket，即阻塞地从socket连接中读取dsi steam，即会解析dsi流量填充dsi结构体，也就是反序列化dsi流量。我们进入快速阅读一下dsi_stream_receive函数，注意我们关注的是该函数如何从socket中读取数据填充dsi结构体。我们可以明显的发现block变量即是DSI Header，将block copy to dsi.header中。而其中关键的数据包的body也即payload或者说dsi data是同过一行if (dsi_stream_read(dsi, dsi->commands, dsi->cmdlen) != dsi->cmdlen)从dsi结构体的buffer中读取到dsi->commands指针指向的内存中，最后其返回值返回block[1]，也就是我们下图1中给出的DSI Header结构中的Command字段。至此我们了解该函数是如何把DSI流量数据填充进 dsi structure。
注3：这里我们就发现了任意地址写漏洞。我们最开始的越界写，第一次发包可以覆盖commands，而后续发包可以往commands中写入我们希望的数据，指针劫持并可控的写指针指向内存，并且我们发现我们可以写多少是由图1的total data length这个字段决定的，而这个字段是4字节大小且根据payload的长度计算值，因此我们可以写非常长的payload。
任意地址写漏洞是后续RCE的基。我们之所以可以如此是因为dsi->commands指针的生命周期与dsi结构体生命周期是一样的，存在于一次连接中。
我们继续回到afp_over_dsi的while循环中。再dsi_stream_receive函数返回时，其返回值同时也是本次请求的Command字段，该返回值进入Switch语句执行对应的command命令，而我们着重关注最核心的case DSIFUNC_CMD分支。这个分支的作用简而言之，就是根据我们DSI数据流中的Payload字段的数据，执行AFP回调函数。我们可以发现核心的afp_switch变量，通过全局搜索afp_switch =可以发现两处赋值（如图2所示）。通过变量名和两张回调函数表的内容，可以猜测，一个是未登入或未授权时走preauth_switch，一个是登入成功或授权时走postauth_switch。
注4：我们拥有了任意地址写，那么处理得当，我们可以为授权时通过任意地址写将afp_switch的值改成postauth_switch，我们将可以访问postauth_switch中的回调函数,即触发未授权访问。更进一步，我们将preauth_switch或postauth_switch表中的一些项改成我们希望的代码段地址、one_gadget等，将触发RCE。因此目前我们已经从漏洞点中分析出未授权访问和RCE两种利用方式了。
bingo，我们已经将两条主线分析完毕，也从中点出了漏洞点以及可能的利用方式，那么我们这一小节将根据我们的代码分析、漏洞点分析，讨论可能的利用思路和方式。具体的，我们会讨论越界写漏洞导致潜在任意地址写如何得以实现，即将潜在的变为真正的；我们将讨论任意地址写得以实现后，将详细分析如何RCE，简单的提一下如何进行未授权访问postauth_switch中的函数。
我们可以在第一次发送DSI数据包时，触发越界写，劫持commands指针，那么我们如何得以让commands指针写入我们希望的地址呢？在未开启ASLR时，这并不难，但现在我们开启了ASLR，我们没办法确定任意一个模块的base adress。这时我们不妨先，先看一看内存布局。尽管程序开启了ASLR，但是我们每次处理我们连接的是fork出来的子进程，而子进程的虚拟进程空间的内存布局与父进程是一致的，也就是说每次fork出来的子进程其地址在父进程生命周期内都是固定的。
注5：gdb附加容器进程进行调试请使用如下命令
sudo gdb -q -p `pgrep -n afp` --ex "set follow-fork-mode child"
如图3，通过观察，我们可以得知ASLR的Randomization主要是 0x00 00 7f ?? ?? ?? ?0 00，这样的随机化规律。那么，我们可以通过不断的写commands指针的地址试，逐个试探??，观察子进程是否crash。若commands指针地址不可写，那么后续读commands指针数据的操作将触发非法内存访问导致进程crash，无法响应我们的请求。也就是说，如果我们发的包修改的commands指针地址合法，我们会收到响应的数据包，如果没有那么就意味着我们写的commands指针地址非法。首先，commands指针原始的地址肯定是合法的、可写的。我们可以选择从0x00 00 7f ?? ?? ?? ?0 00的高字节逐字节往低试探(即上诉格式的从左往右消除问号)，每当我们收到响应包时，我们便确定了一个??，转之继续往下一个??试探，直至确定一个合法的可写地址。当我们确定一个合法的地址时，有什么用呢？ELF模块之间的相对位置通常是固定的，例如afpd永远是第一个加载的模块。由此当我们在内存中确定一个可写内存的位置时，其相对于其他模块、地址的偏移也是相对固定的，差也不会差太多。我们可以这样来爆破，我们从高地址开始逐渐向低地址爆破，然后每一个字节爆破的值从255->0开始，那么我们拿到的地址，几乎可以肯定的说落在地址最高的ELF模块中。同理，从低字节开始往高字节写，从0->255开始，把7f也当作??试探，几乎可以肯定你会得到一个落在afpd模块中的可读可写地址。由于后面我给出的Exploit是通过泄露libc，劫持__free_hook指针进行内存布局并RCE的。所以我的泄露地址思路是尽量泄露一个离libc近的地址，因为图5中libc地址足够高，因此我也选择泄露一个高地址。代码如下：该代码泄露出来的地址，落在最高的模块中。并且出于简单考虑，在这个形式中的泄露格式0x00 00 7f ?? ?? ?? ?0 00，我把最后两个字节默认抹除为0了，也即只需要泄露三个字节，并且我们泄露出来的地址是0x1000对齐的。
那么我们既然泄露出了一个可读可写的地址，如果我想写libc中的一些数据怎么办？或者我想写afpd中的一些数据结构怎么办？那么自然需要泄露对应的基地址。以libc写为例子，我给出的代码泄露出来的地址要么是位于ld-2.27.so中，要么是位于其下方的mmap内存中，我们可以大概的估算一下我们泄露的地址与libc之间的距离，一大步的靠近，然后一路小跑抵达libc基地址。例如我这里算出来的一大步是0x18040000~0x1880000这个区间，我们从直接一大步跨过0x18040000，然后以0x1000一小步一小步的跑向libc。afpd同理，甚至更加简单。
好了，现在我们解决了任意地址写的问题，那么我们来考虑如何进行RCE。泄露了libc以及可以任意地址写，那么常规的思路就是劫持函数指针获得控制流。注意下面的讲解一开始你可能有点困惑，但请看到这以小节的最后你再读一遍就会明白了。由三个gadgets可以完成这个思路。具体的，先看这一段gadgets，setcontext + 53(图4，红框)。我们可以看见只要我们能够控制rdi寄存器，那么我们就能控制几乎所有的寄存器，包括rsp和rip，也就是说我们就达成了劫持控制流、控制了几乎所有寄存器。这一段gadgets其实就是在进行SROP中 signal frame的构建，此时rdi相对于指向就是signal frame的顶部。因此，我们可以通过pwntools中的SigreturnFrame方便的控制这段代码对寄存器的赋值，只要我们可以控制rdi。
![image.png] 
为了控制rdi，我们需要另外两个gadgets。一个是__libc_dlopen_mode + 56，一个是fgetpos64+207，分别如图5、图6所示。
那么我如何控制dl_open_hook呢？在libc2.27中，_dl_open_hook地址比free_hook大约高0x2b00左右(不同版本编译器编译出来的libc2.27可能略有差别，但总体大约再0x2b00左右)。距离这么远，我们可以覆盖到吗？答案是，可以。（在Netatalk的代码分析小节的注3部分，我们讨论了一次性可以最多写入多大的数据）简言之，我们将commands指针覆盖至free_hook的地址处，随后根据三条gadgets的调用链，依次往后布局内存，使得我们最终能够控制rdi，进而控制程序流以及几乎所有寄存器，完成RCE。
未授权访问的核心是泄露afpd的基地址，然后获取其中的三个关键数据结构preauth_switch、postauth_switch和afp_switch，再通过任意地址写将afp_switch变量的值写成postauth_switch，即可进行未授权访问。!
https://gtrboy.github.io/posts/netatalk/#0x04-%E5%88%A9%E7%94%A8<br />https://xuanxuanblingbling.github.io/ctf/pwn/2021/11/06/netatalk/<br />https://medium.com/tenable-techblog/exploiting-an-18-year-old-bug-b47afe54172<br />https://en.wikipedia.org/wiki/Data_Stream_Interface#cite_note-2<br />https://xz.aliyun.com/t/3710
sudo docker run -it ubuntu:18.04 /bin/bash
sudo docker run -it ubuntu:18.04 /bin/bash
sudo docker run -p 548:548 -it --privileged=true temp-image:latest /sbin/init
sudo docker run -p 548:548 -it --privileged=true temp-image:latest /sbin/init
int main(int ac, char **av) {
...
/* watch atp, dsi sockets and ipc parent/child file descriptor. */
if (!(init_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: couldn't initialize socket handler");
afp_exit(EXITERR_CONF);
}
...
while (1) {
pthread_sigmask(SIG_UNBLOCK, &sigs, NULL);
ret = poll(asev->fdset, asev->used, -1);
pthread_sigmask(SIG_BLOCK, &sigs, NULL);
saveerrno = errno;
if (gotsigchld) {
gotsigchld = 0;
child_handler();
continue;
}
if (reloadconfig) {
nologin++;
if (!(reset_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: reset socket handlers");
afp_exit(EXITERR_CONF);
}
LOG(log_info, logtype_afpd, "re-reading configuration file");
configfree(&obj, NULL);
afp_config_free(&obj);
if (afp_config_parse(&obj, "afpd") != 0)
afp_exit(EXITERR_CONF);
if (configinit(&obj) != 0) {
LOG(log_error, logtype_afpd, "config re-read: no servers configured");
afp_exit(EXITERR_CONF);
}
if (!(init_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: couldn't initialize socket handler");
afp_exit(EXITERR_CONF);
}
nologin = 0;
reloadconfig = 0;
errno = saveerrno;
if (server_children) {
server_child_kill(server_children, SIGHUP);
}
continue;
}
if (ret == 0)
continue;
if (ret < 0) {
if (errno == EINTR)
continue;
LOG(log_error, logtype_afpd, "main: can't wait for input: %s", strerror(errno));
break;
}
for (int i = 0; i < asev->used; i++) {
if (asev->fdset[i].revents & (POLLIN | POLLERR | POLLHUP | POLLNVAL)) {
switch (asev->data[i].fdtype) {
case LISTEN_FD:
// here
if ((child = dsi_start(&obj, (DSI *)(asev->data[i].private), server_children))) {
if (!(asev_add_fd(asev, child->afpch_ipc_fd, IPC_FD, child))) {
LOG(log_error, logtype_afpd, "out of asev slots");
/*
* Close IPC fd here and mark it as unused
*/
close(child->afpch_ipc_fd);
child->afpch_ipc_fd = -1;
/*
* Being unfriendly here, but we really
* want to get rid of it. The 'child'
* handle gets cleaned up in the SIGCLD
* handler.
*/
kill(child->afpch_pid, SIGKILL);
}
}
break;
case IPC_FD:
child = (afp_child_t *)(asev->data[i].private);
LOG(log_debug, logtype_afpd, "main: IPC request from child[%u]", child->afpch_pid);
if (ipc_server_read(server_children, child->afpch_ipc_fd) != 0) {
if (!(asev_del_fd(asev, child->afpch_ipc_fd))) {
LOG(log_error, logtype_afpd, "child[%u]: no IPC fd");
}
close(child->afpch_ipc_fd);
child->afpch_ipc_fd = -1;
}
break;
default:
LOG(log_debug, logtype_afpd, "main: IPC request for unknown type");
break;
} /* switch */
} /* if */
} /* for (i)*/
} /* while (1) */
}
int main(int ac, char **av) {
...
/* watch atp, dsi sockets and ipc parent/child file descriptor. */
if (!(init_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: couldn't initialize socket handler");
afp_exit(EXITERR_CONF);
}
...
while (1) {
pthread_sigmask(SIG_UNBLOCK, &sigs, NULL);
ret = poll(asev->fdset, asev->used, -1);
pthread_sigmask(SIG_BLOCK, &sigs, NULL);
saveerrno = errno;
if (gotsigchld) {
gotsigchld = 0;
child_handler();
continue;
}
if (reloadconfig) {
nologin++;
if (!(reset_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: reset socket handlers");
afp_exit(EXITERR_CONF);
}
LOG(log_info, logtype_afpd, "re-reading configuration file");
configfree(&obj, NULL);
afp_config_free(&obj);
if (afp_config_parse(&obj, "afpd") != 0)
afp_exit(EXITERR_CONF);
if (configinit(&obj) != 0) {
LOG(log_error, logtype_afpd, "config re-read: no servers configured");
afp_exit(EXITERR_CONF);
}
if (!(init_listening_sockets(&obj))) {
LOG(log_error, logtype_afpd, "main: couldn't initialize socket handler");
afp_exit(EXITERR_CONF);
}
nologin = 0;
reloadconfig = 0;
errno = saveerrno;
if (server_children) {
server_child_kill(server_children, SIGHUP);
}
continue;
}
if (ret == 0)
continue;
if (ret < 0) {
if (errno == EINTR)
continue;
LOG(log_error, logtype_afpd, "main: can't wait for input: %s", strerror(errno));
break;
}
for (int i = 0; i < asev->used; i++) {
if (asev->fdset[i].revents & (POLLIN | POLLERR | POLLHUP | POLLNVAL)) {
switch (asev->data[i].fdtype) {
case LISTEN_FD:
// here
if ((child = dsi_start(&obj, (DSI *)(asev->data[i].private), server_children))) {
if (!(asev_add_fd(asev, child->afpch_ipc_fd, IPC_FD, child))) {
LOG(log_error, logtype_afpd, "out of asev slots");
/*
* Close IPC fd here and mark it as unused
*/
close(child->afpch_ipc_fd);
child->afpch_ipc_fd = -1;
/*
* Being unfriendly here, but we really
* want to get rid of it. The 'child'
* handle gets cleaned up in the SIGCLD
* handler.
*/
kill(child->afpch_pid, SIGKILL);
}
}
break;
case IPC_FD:
child = (afp_child_t *)(asev->data[i].private);
LOG(log_debug, logtype_afpd, "main: IPC request from child[%u]", child->afpch_pid);
if (ipc_server_read(server_children, child->afpch_ipc_fd) != 0) {
if (!(asev_del_fd(asev, child->afpch_ipc_fd))) {
LOG(log_error, logtype_afpd, "child[%u]: no IPC fd");
}
close(child->afpch_ipc_fd);
child->afpch_ipc_fd = -1;
}
break;
default:
LOG(log_debug, logtype_afpd, "main: IPC request for unknown type");
break;
} /* switch */
} /* if */
} /* for (i)*/
} /* while (1) */
}
static afp_child_t *dsi_start(AFPObj *obj, DSI *dsi, server_child_t *server_children)
{ afp_child_t *child = NULL;
if (dsi_getsession(dsi, server_children, obj->options.tickleval, &child) != 0) {
LOG(log_error, logtype_afpd, "dsi_start: session error: %s", strerror(errno));
return NULL;
}
// we've forked.
if (child == NULL) {
configfree(obj, dsi);
afp_over_dsi(obj); /* start a session */
exit (0);
}
return child;
}/*!
* Start a DSI session, fork an afpd process
** @param childp (w) after fork: parent return pointer to child, child returns NULL
* @returns 0 on sucess, any other value denotes failure
*/
/* DSI Commands */
#define DSIFUNC_CLOSE 1 /* DSICloseSession */#define DSIFUNC_CMD 2 /* DSICommand */#define DSIFUNC_STAT 3 /* DSIGetStatus */#define DSIFUNC_OPEN 4 /* DSIOpenSession */#define DSIFUNC_TICKLE 5 /* DSITickle */#define DSIFUNC_WRITE 6 /* DSIWrite */#define DSIFUNC_ATTN 8 /* DSIAttention */#define DSIFUNC_MAX 8 /* largest command */int dsi_getsession(DSI *dsi, server_child_t *serv_children, int tickleval, afp_child_t **childp)
{ switch (dsi->header.dsi_command) {
case DSIFUNC_STAT: /* send off status and return */
{
/* OpenTransport 1.1.2 bug workaround:
** OT code doesn't currently handle close sockets well. urk.
* the workaround: wait for the client to close its
* side. timeouts prevent indefinite resource use.
*/
static struct timeval timeout = {120, 0};
fd_set readfds;
dsi_getstatus(dsi);
FD_ZERO(&readfds);
FD_SET(dsi->socket, &readfds);
free(dsi);
select(FD_SETSIZE, &readfds, NULL, NULL, &timeout);
exit(0);
}
break;
case DSIFUNC_OPEN: /* setup session */
/* set up the tickle timer */
dsi->timer.it_interval.tv_sec = dsi->timer.it_value.tv_sec = tickleval;
dsi->timer.it_interval.tv_usec = dsi->timer.it_value.tv_usec = 0;
dsi_opensession(dsi);
*childp = NULL;
return 0;
default: /* just close */
LOG(log_info, logtype_dsi, "DSIUnknown %d", dsi->header.dsi_command);
dsi->proto_close(dsi);
exit(EXITERR_CLNT);
}
}/* DSI session options */
#define DSIOPT_SERVQUANT 0x00 /* server request quantum */#define DSIOPT_ATTNQUANT 0x01 /* attention quantum */#define DSIOPT_REPLCSIZE 0x02 /* AFP replaycache size supported by the server (that's us) *//* OpenSession. set up the connection */
void dsi_opensession(DSI *dsi)
{ uint32_t i = 0; /* this serves double duty. it must be 4-bytes long */
int offs;
if (setnonblock(dsi->socket, 1) < 0) {
LOG(log_error, logtype_dsi, "dsi_opensession: setnonblock: %s", strerror(errno));
AFP_PANIC("setnonblock error");
}
/* parse options */
while (i < dsi->cmdlen) {
switch (dsi->commands[i++]){
case DSIOPT_ATTNQUANT: // dsi_header.dsi_data[0]:code, dsi_header.dsi_data[1]:size, dsi_header.dsi_data[2:size -1]:data
memcpy(&dsi->attn_quantum, dsi->commands + i + 1, dsi->commands[i]); // 越界写，上层函数会执行 memcpy(dsi->commands, dsi_header->dsi_data) dsi_header是我们发包的内容
dsi->attn_quantum = ntohl(dsi->attn_quantum);
case DSIOPT_SERVQUANT: /* just ignore these */
default:
i += dsi->commands[i] + 1; /* forward past length tag + length */
break;
}
}
// ...
dsi_send(dsi);
}static afp_child_t *dsi_start(AFPObj *obj, DSI *dsi, server_child_t *server_children)
{ afp_child_t *child = NULL;
if (dsi_getsession(dsi, server_children, obj->options.tickleval, &child) != 0) {
LOG(log_error, logtype_afpd, "dsi_start: session error: %s", strerror(errno));
return NULL;
}
// we've forked.
if (child == NULL) {
configfree(obj, dsi);
afp_over_dsi(obj); /* start a session */
exit (0);
}
return child;
}/*!
* Start a DSI session, fork an afpd process
** @param childp (w) after fork: parent return pointer to child, child returns NULL
* @returns 0 on sucess, any other value denotes failure
*/
/* DSI Commands */
#define DSIFUNC_CLOSE 1 /* DSICloseSession */#define DSIFUNC_CMD 2 /* DSICommand */#define DSIFUNC_STAT 3 /* DSIGetStatus */#define DSIFUNC_OPEN 4 /* DSIOpenSession */#define DSIFUNC_TICKLE 5 /* DSITickle */#define DSIFUNC_WRITE 6 /* DSIWrite */#define DSIFUNC_ATTN 8 /* DSIAttention */#define DSIFUNC_MAX 8 /* largest command */int dsi_getsession(DSI *dsi, server_child_t *serv_children, int tickleval, afp_child_t **childp)
{ switch (dsi->header.dsi_command) {
case DSIFUNC_STAT: /* send off status and return */
{
/* OpenTransport 1.1.2 bug workaround:
** OT code doesn't currently handle close sockets well. urk.
* the workaround: wait for the client to close its
* side. timeouts prevent indefinite resource use.
*/
static struct timeval timeout = {120, 0};
fd_set readfds;
dsi_getstatus(dsi);
FD_ZERO(&readfds);
FD_SET(dsi->socket, &readfds);
free(dsi);
select(FD_SETSIZE, &readfds, NULL, NULL, &timeout);
exit(0);
}
break;
case DSIFUNC_OPEN: /* setup session */
/* set up the tickle timer */
dsi->timer.it_interval.tv_sec = dsi->timer.it_value.tv_sec = tickleval;
dsi->timer.it_interval.tv_usec = dsi->timer.it_value.tv_usec = 0;
dsi_opensession(dsi);
*childp = NULL;
return 0;
default: /* just close */
LOG(log_info, logtype_dsi, "DSIUnknown %d", dsi->header.dsi_command);
dsi->proto_close(dsi);
exit(EXITERR_CLNT);
}
}/* DSI session options */
#define DSIOPT_SERVQUANT 0x00 /* server request quantum */#define DSIOPT_ATTNQUANT 0x01 /* attention quantum */#define DSIOPT_REPLCSIZE 0x02 /* AFP replaycache size supported by the server (that's us) *//* OpenSession. set up the connection */
void dsi_opensession(DSI *dsi)
{ uint32_t i = 0; /* this serves double duty. it must be 4-bytes long */
int offs;
if (setnonblock(dsi->socket, 1) < 0) {
LOG(log_error, logtype_dsi, "dsi_opensession: setnonblock: %s", strerror(errno));
AFP_PANIC("setnonblock error");
}
/* parse options */
while (i < dsi->cmdlen) {
switch (dsi->commands[i++]){
case DSIOPT_ATTNQUANT: // dsi_header.dsi_data[0]:code, dsi_header.dsi_data[1]:size, dsi_header.dsi_data[2:size -1]:data
memcpy(&dsi->attn_quantum, dsi->commands + i + 1, dsi->commands[i]); // 越界写，上层函数会执行 memcpy(dsi->commands, dsi_header->dsi_data) dsi_header是我们发包的内容
dsi->attn_quantum = ntohl(dsi->attn_quantum);
case DSIOPT_SERVQUANT: /* just ignore these */
default:
i += dsi->commands[i] + 1; /* forward past length tag + length */
break;
}
}
// ...
dsi_send(dsi);
}typedef struct DSI { struct DSI *next; /* multiple listening addresses */
AFPObj *AFPobj;
int statuslen;
char status[1400];
char *signature;
struct dsi_block header;
struct sockaddr_storage server, client;
struct itimerval timer;
int tickle; /* tickle count */
int in_write; /* in the middle of writing multiple packets,
signal handlers can't write to the socket */
int msg_request; /* pending message to the client */
int down_request; /* pending SIGUSR1 down in 5 mn */
uint32_t attn_quantum, datasize, server_quantum;
uint16_t serverID, clientID;
uint8_t *commands; /* DSI recieve buffer */ //
uint8_t data[DSI_DATASIZ]; /* DSI reply buffer */
size_t datalen, cmdlen;
off_t read_count, write_count;
uint32_t flags; /* DSI flags like DSI_SLEEPING, DSI_DISCONNECTED */
int socket; /* AFP session socket */
int serversock; /* listening socket */
/* DSI readahead buffer used for buffered reads in dsi_peek */
size_t dsireadbuf; /* size of the DSI readahead buffer used in dsi_peek() */
char *buffer; /* buffer start */
char *start; /* current buffer head */
char *eof; /* end of currently used buffer */
char *end;
#ifdef USE_ZEROCONF char *bonjourname; /* server name as UTF8 maxlen MAXINSTANCENAMELEN */
int zeroconf_registered;
#endif /* protocol specific open/close, send/receive
* send/receive fill in the header and use dsi->commands.
* write/read just write/read data */
pid_t (*proto_open)(struct DSI *);
void (*proto_close)(struct DSI *);
} DSI;typedef struct DSI { struct DSI *next; /* multiple listening addresses */
AFPObj *AFPobj;
int statuslen;
char status[1400];
char *signature;
struct dsi_block header;
struct sockaddr_storage server, client;
struct itimerval timer;
int tickle; /* tickle count */
int in_write; /* in the middle of writing multiple packets,
signal handlers can't write to the socket */
int msg_request; /* pending message to the client */
int down_request; /* pending SIGUSR1 down in 5 mn */
uint32_t attn_quantum, datasize, server_quantum;
uint16_t serverID, clientID;
uint8_t *commands; /* DSI recieve buffer */ //
uint8_t data[DSI_DATASIZ]; /* DSI reply buffer */
size_t datalen, cmdlen;
off_t read_count, write_count;
uint32_t flags; /* DSI flags like DSI_SLEEPING, DSI_DISCONNECTED */
int socket; /* AFP session socket */
int serversock; /* listening socket */
/* DSI readahead buffer used for buffered reads in dsi_peek */
size_t dsireadbuf; /* size of the DSI readahead buffer used in dsi_peek() */
char *buffer; /* buffer start */
char *start; /* current buffer head */
char *eof; /* end of currently used buffer */
char *end;
#ifdef USE_ZEROCONF char *bonjourname; /* server name as UTF8 maxlen MAXINSTANCENAMELEN */
int zeroconf_registered;
#endif /* protocol specific open/close, send/receive
* send/receive fill in the header and use dsi->commands.
* write/read just write/read data */
pid_t (*proto_open)(struct DSI *);
void (*proto_close)(struct DSI *);
} DSI;void afp_over_dsi(AFPObj *obj)
{ DSI *dsi = (DSI *) obj->dsi;
// ...
while (1) {
if (sigsetjmp(recon_jmp, 1) != 0)
/* returning from SIGALARM handler for a primary reconnect */
continue;
/* Blocking read on the network socket */
cmd = dsi_stream_receive(dsi);
if (cmd == 0) {
/* cmd == 0 is the error condition */
if (dsi->flags & DSI_RECONSOCKET) {
/* we just got a reconnect so we immediately try again to receive on the new fd */
dsi->flags &= ~DSI_RECONSOCKET;
continue;
}
/* the client sometimes logs out (afp_logout) but doesn't close the DSI session */
if (dsi->flags & DSI_AFP_LOGGED_OUT) {
LOG(log_note, logtype_afpd, "afp_over_dsi: client logged out, terminating DSI session");
afp_dsi_close(obj);
exit(0);
}
if (dsi->flags & DSI_RECONINPROG) {
LOG(log_note, logtype_afpd, "afp_over_dsi: failed reconnect");
afp_dsi_close(obj);
exit(0);
}
/* Some error on the client connection, enter disconnected state */
if (dsi_disconnect(dsi) != 0)
afp_dsi_die(EXITERR_CLNT);
ipc_child_state(obj, DSI_DISCONNECTED);
while (dsi->flags & DSI_DISCONNECTED)
pause(); /* gets interrupted by SIGALARM or SIGURG tickle */
ipc_child_state(obj, DSI_RUNNING);
continue; /* continue receiving until disconnect timer expires
* or a primary reconnect succeeds */
}
if (!(dsi->flags & DSI_EXTSLEEP) && (dsi->flags & DSI_SLEEPING)) {
LOG(log_debug, logtype_afpd, "afp_over_dsi: got data, ending normal sleep");
dsi->flags &= ~DSI_SLEEPING;
dsi->tickle = 0;
ipc_child_state(obj, DSI_RUNNING);
}
if (reload_request) {
reload_request = 0;
load_volumes(AFPobj, LV_FORCE);
}
/* The first SIGINT enables debugging, the next restores the config */
if (debug_request) {
static int debugging = 0;
debug_request = 0;
dircache_dump();
uuidcache_dump();
if (debugging) {
if (obj->options.logconfig)
setuplog(obj->options.logconfig, obj->options.logfile);
else
setuplog("default:note", NULL);
debugging = 0;
} else {
char logstr[50];
debugging = 1;
sprintf(logstr, "/tmp/afpd.%u.XXXXXX", getpid());
setuplog("default:maxdebug", logstr);
}
}
dsi->flags |= DSI_DATA;
dsi->tickle = 0;
switch(cmd) {
case DSIFUNC_CLOSE:
LOG(log_debug, logtype_afpd, "DSI: close session request");
afp_dsi_close(obj);
LOG(log_note, logtype_afpd, "done");
exit(0);
case DSIFUNC_TICKLE:
dsi->flags &= ~DSI_DATA; /* thats no data in the sense we use it in alarm_handler */
LOG(log_debug, logtype_afpd, "DSI: client tickle");
/* timer is not every 30 seconds anymore, so we don't get killed on the client side. */
if ((dsi->flags & DSI_DIE))
dsi_tickle(dsi);
break;
case DSIFUNC_CMD:
#ifdef AFS if ( writtenfork ) {
if ( flushfork( writtenfork ) < 0 ) {
LOG(log_error, logtype_afpd, "main flushfork: %s", strerror(errno) );
}
writtenfork = NULL;
}
#endif /* AFS */ function = (u_char) dsi->commands[0];
/* AFP replay cache */
rc_idx = dsi->clientID % REPLAYCACHE_SIZE;
LOG(log_debug, logtype_dsi, "DSI request ID: %u", dsi->clientID);
if (replaycache[rc_idx].DSIreqID == dsi->clientID
&& replaycache[rc_idx].AFPcommand == function) {
LOG(log_note, logtype_afpd, "AFP Replay Cache match: id: %u / cmd: %s",
dsi->clientID, AfpNum2name(function));
err = replaycache[rc_idx].result;
/* AFP replay cache end */
} else {
/* send off an afp command. in a couple cases, we take advantage
* of the fact that we're a stream-based protocol. */
if (afp_switch[function]) {
dsi->datalen = DSI_DATASIZ;
dsi->flags |= DSI_RUNNING;
LOG(log_debug, logtype_afpd, "<== Start AFP command: %s", AfpNum2name(function));
AFP_AFPFUNC_START(function, (char *)AfpNum2name(function));
err = (*afp_switch[function])(obj,
(char *)dsi->commands, dsi->cmdlen,
(char *)&dsi->data, &dsi->datalen);
AFP_AFPFUNC_DONE(function, (char *)AfpNum2name(function));
LOG(log_debug, logtype_afpd, "==> Finished AFP command: %s -> %s",
AfpNum2name(function), AfpErr2name(err));
dir_free_invalid_q();
dsi->flags &= ~DSI_RUNNING;
/* Add result to the AFP replay cache */
replaycache[rc_idx].DSIreqID = dsi->clientID;
replaycache[rc_idx].AFPcommand = function;
replaycache[rc_idx].result = err;
} else {
LOG(log_maxdebug, logtype_afpd, "bad function %X", function);
dsi->datalen = 0;
err = AFPERR_NOOP;
}
}
/* single shot toggle that gets set by dsi_readinit. */
if (dsi->flags & DSI_NOREPLY) {
dsi->flags &= ~DSI_NOREPLY;
break;
} else if (!dsi_cmdreply(dsi, err)) {
LOG(log_error, logtype_afpd, "dsi_cmdreply(%d): %s", dsi->socket, strerror(errno) );
if (dsi_disconnect(dsi) != 0)
afp_dsi_die(EXITERR_CLNT);
}
break;
case DSIFUNC_WRITE: /* FPWrite and FPAddIcon */
function = (u_char) dsi->commands[0];
if ( afp_switch[ function ] != NULL ) {
dsi->datalen = DSI_DATASIZ;
dsi->flags |= DSI_RUNNING;
LOG(log_debug, logtype_afpd, "<== Start AFP command: %s", AfpNum2name(function));
AFP_AFPFUNC_START(function, (char *)AfpNum2name(function));
err = (*afp_switch[function])(obj,
(char *)dsi->commands, dsi->cmdlen,
(char *)&dsi->data, &dsi->datalen);
AFP_AFPFUNC_DONE(function, (char *)AfpNum2name(function));
LOG(log_debug, logtype_afpd, "==> Finished AFP command: %s -> %s",
AfpNum2name(function), AfpErr2name(err));
dsi->flags &= ~DSI_RUNNING;
} else {
LOG(log_error, logtype_afpd, "(write) bad function %x", function);
dsi->datalen = 0;
err = AFPERR_NOOP;
}
if (!dsi_wrtreply(dsi, err)) {
LOG(log_error, logtype_afpd, "dsi_wrtreply: %s", strerror(errno) );
if (dsi_disconnect(dsi) != 0)
afp_dsi_die(EXITERR_CLNT);
}
break;
case DSIFUNC_ATTN: /* attention replies */
break;
/* error. this usually implies a mismatch of some kind
* between server and client. if things are correct,
* we need to flush the rest of the packet if necessary. */
default:
LOG(log_info, logtype_afpd,"afp_dsi: spurious command %d", cmd);
dsi_writeinit(dsi, dsi->data, DSI_DATASIZ);
dsi_writeflush(dsi);
break;
}
pending_request(dsi);
fce_pending_events(obj);
}
}/*!
* Read DSI command and data
*
* @param dsi (rw) DSI handle
*
* @return DSI function on success, 0 on failure
*/
int dsi_stream_receive(DSI *dsi)
{ char block[DSI_BLOCKSIZ];
LOG(log_maxdebug, logtype_dsi, "dsi_stream_receive: START");
if (dsi->flags & DSI_DISCONNECTED)
return 0;
/* read in the header */
if (dsi_buffered_stream_read(dsi, (uint8_t *)block, sizeof(block)) != sizeof(block))
return 0;
dsi->header.dsi_flags = block[0];
dsi->header.dsi_command = block[1];
if (dsi->header.dsi_command == 0)
return 0;
memcpy(&dsi->header.dsi_requestID, block + 2, sizeof(dsi->header.dsi_requestID));
memcpy(&dsi->header.dsi_data.dsi_doff, block + 4, sizeof(dsi->header.dsi_data.dsi_doff));
dsi->header.dsi_data.dsi_doff = htonl(dsi->header.dsi_data.dsi_doff);
memcpy(&dsi->header.dsi_len, block + 8, sizeof(dsi->header.dsi_len));
memcpy(&dsi->header.dsi_reserved, block + 12, sizeof(dsi->header.dsi_reserved));
dsi->clientID = ntohs(dsi->header.dsi_requestID);
/* make sure we don't over-write our buffers. */
dsi->cmdlen = MIN(ntohl(dsi->header.dsi_len), dsi->server_quantum);
/* Receiving DSIWrite data is done in AFP function, not here */
if (dsi->header.dsi_data.dsi_doff) {
LOG(log_maxdebug, logtype_dsi, "dsi_stream_receive: write request");
dsi->cmdlen = dsi->header.dsi_data.dsi_doff;
}
// TCP fork dsi
if (dsi_stream_read(dsi, dsi->commands, dsi->cmdlen) != dsi->cmdlen)
return 0;
LOG(log_debug, logtype_dsi, "dsi_stream_receive: DSI cmdlen: %zd", dsi->cmdlen);
return block[1];
}void afp_over_dsi(AFPObj *obj)
{ DSI *dsi = (DSI *) obj->dsi;
// ...
while (1) {
if (sigsetjmp(recon_jmp, 1) != 0)
/* returning from SIGALARM handler for a primary reconnect */
continue;
/* Blocking read on the network socket */
cmd = dsi_stream_receive(dsi);
if (cmd == 0) {
/* cmd == 0 is the error condition */
if (dsi->flags & DSI_RECONSOCKET) {
/* we just got a reconnect so we immediately try again to receive on the new fd */
dsi->flags &= ~DSI_RECONSOCKET;
continue;
}
/* the client sometimes logs out (afp_logout) but doesn't close the DSI session */
if (dsi->flags & DSI_AFP_LOGGED_OUT) {
LOG(log_note, logtype_afpd, "afp_over_dsi: client logged out, terminating DSI session");
afp_dsi_close(obj);
exit(0);
}
if (dsi->flags & DSI_RECONINPROG) {
LOG(log_note, logtype_afpd, "afp_over_dsi: failed reconnect");
afp_dsi_close(obj);
exit(0);
}
/* Some error on the client connection, enter disconnected state */
if (dsi_disconnect(dsi) != 0)
afp_dsi_die(EXITERR_CLNT);
ipc_child_state(obj, DSI_DISCONNECTED);
while (dsi->flags & DSI_DISCONNECTED)
pause(); /* gets interrupted by SIGALARM or SIGURG tickle */
ipc_child_state(obj, DSI_RUNNING);
continue; /* continue receiving until disconnect timer expires
* or a primary reconnect succeeds */
}
if (!(dsi->flags & DSI_EXTSLEEP) && (dsi->flags & DSI_SLEEPING)) {
LOG(log_debug, logtype_afpd, "afp_over_dsi: got data, ending normal sleep");
dsi->flags &= ~DSI_SLEEPING;
dsi->tickle = 0;
ipc_child_state(obj, DSI_RUNNING);
}
if (reload_request) {
reload_request = 0;
load_volumes(AFPobj, LV_FORCE);
}
/* The first SIGINT enables debugging, the next restores the config */
if (debug_request) {
static int debugging = 0;
debug_request = 0;
dircache_dump();
uuidcache_dump();
if (debugging) {
if (obj->options.logconfig)
setuplog(obj->options.logconfig, obj->options.logfile);
else
setuplog("default:note", NULL);
debugging = 0;
} else {
char logstr[50];
debugging = 1;
sprintf(logstr, "/tmp/afpd.%u.XXXXXX", getpid());
setuplog("default:maxdebug", logstr);
}
}
dsi->flags |= DSI_DATA;
dsi->tickle = 0;
switch(cmd) {
case DSIFUNC_CLOSE:
LOG(log_debug, logtype_afpd, "DSI: close session request");
afp_dsi_close(obj);
LOG(log_note, logtype_afpd, "done");
exit(0);
case DSIFUNC_TICKLE:
dsi->flags &= ~DSI_DATA; /* thats no data in the sense we use it in alarm_handler */
LOG(log_debug, logtype_afpd, "DSI: client tickle");
/* timer is not every 30 seconds anymore, so we don't get killed on the client side. */
if ((dsi->flags & DSI_DIE))
dsi_tickle(dsi);
break;
case DSIFUNC_CMD:
#ifdef AFS if ( writtenfork ) {
if ( flushfork( writtenfork ) < 0 ) {
LOG(log_error, logtype_afpd, "main flushfork: %s", strerror(errno) );
}
writtenfork = NULL;
}
#endif /* AFS */ function = (u_char) dsi->commands[0];
/* AFP replay cache */
rc_idx = dsi->clientID % REPLAYCACHE_SIZE;
LOG(log_debug, logtype_dsi, "DSI request ID: %u", dsi->clientID);
if (replaycache[rc_idx].DSIreqID == dsi->clientID
&& replaycache[rc_idx].AFPcommand == function) {
LOG(log_note, logtype_afpd, "AFP Replay Cache match: id: %u / cmd: %s",
dsi->clientID, AfpNum2name(function));
err = replaycache[rc_idx].result;
/* AFP replay cache end */
} else {
/* send off an afp command. in a couple cases, we take advantage
* of the fact that we're a stream-based protocol. */
if (afp_switch[function]) {
dsi->datalen = DSI_DATASIZ;
dsi->flags |= DSI_RUNNING;
LOG(log_debug, logtype_afpd, "<== Start AFP command: %s", AfpNum2name(function));
AFP_AFPFUNC_START(function, (char *)AfpNum2name(function));
err = (*afp_switch[function])(obj,
(char *)dsi->commands, dsi->cmdlen,
(char *)&dsi->data, &dsi->datalen);
AFP_AFPFUNC_DONE(function, (char *)AfpNum2name(function));
LOG(log_debug, logtype_afpd, "==> Finished AFP command: %s -> %s",
AfpNum2name(function), AfpErr2name(err));
dir_free_invalid_q();
dsi->flags &= ~DSI_RUNNING;
/* Add result to the AFP replay cache */
replaycache[rc_idx].DSIreqID = dsi->clientID;
replaycache[rc_idx].AFPcommand = function;
replaycache[rc_idx].result = err;
} else {
LOG(log_maxdebug, logtype_afpd, "bad function %X", function);
dsi->datalen = 0;
err = AFPERR_NOOP;
}
}
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最后于 2023-4-6 18:02
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