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/*
* Windows implementation of SSH connection-sharing IPC setup.
*/
#include <stdio.h>
#include <assert.h>
#define DEFINE_PLUG_METHOD_MACROS
#include "tree234.h"
#include "putty.h"
#include "network.h"
#include "proxy.h"
#include "ssh.h"
#if !defined NO_SECURITY
#include "winsecur.h"
#define CONNSHARE_PIPE_PREFIX "\\\\.\\pipe\\putty-connshare"
#define CONNSHARE_MUTEX_PREFIX "Local\\putty-connshare-mutex"
static char *obfuscate_name(const char *realname)
{
/*
* Windows's named pipes all live in the same namespace, so one
* user can see what pipes another user has open. This is an
* undesirable privacy leak and in particular permits one user to
* know what username@host another user is SSHing to, so we
* protect that information by using CryptProtectMemory (which
* uses a key built in to each user's account).
*/
char *cryptdata;
int cryptlen;
SHA256_State sha;
unsigned char lenbuf[4];
unsigned char digest[32];
char retbuf[65];
int i;
cryptlen = strlen(realname) + 1;
cryptlen += CRYPTPROTECTMEMORY_BLOCK_SIZE - 1;
cryptlen /= CRYPTPROTECTMEMORY_BLOCK_SIZE;
cryptlen *= CRYPTPROTECTMEMORY_BLOCK_SIZE;
cryptdata = snewn(cryptlen, char);
memset(cryptdata, 0, cryptlen);
strcpy(cryptdata, realname);
/*
* CRYPTPROTECTMEMORY_CROSS_PROCESS causes CryptProtectMemory to
* use the same key in all processes with this user id, meaning
* that the next PuTTY process calling this function with the same
* input will get the same data.
*
* (Contrast with CryptProtectData, which invents a new session
* key every time since its API permits returning more data than
* was input, so calling _that_ and hashing the output would not
* be stable.)
*
* We don't worry too much if this doesn't work for some reason.
* Omitting this step still has _some_ privacy value (in that
* another user can test-hash things to confirm guesses as to
* where you might be connecting to, but cannot invert SHA-256 in
* the absence of any plausible guess). So we don't abort if we
* can't call CryptProtectMemory at all, or if it fails.
*/
if (got_crypt())
p_CryptProtectMemory(cryptdata, cryptlen,
CRYPTPROTECTMEMORY_CROSS_PROCESS);
/*
* We don't want to give away the length of the hostname either,
* so having got it back out of CryptProtectMemory we now hash it.
*/
SHA256_Init(&sha);
PUT_32BIT_MSB_FIRST(lenbuf, cryptlen);
SHA256_Bytes(&sha, lenbuf, 4);
SHA256_Bytes(&sha, cryptdata, cryptlen);
SHA256_Final(&sha, digest);
sfree(cryptdata);
/*
* Finally, make printable.
*/
for (i = 0; i < 32; i++) {
sprintf(retbuf + 2*i, "%02x", digest[i]);
/* the last of those will also write the trailing NUL */
}
return dupstr(retbuf);
}
static char *make_name(const char *prefix, const char *name)
{
char *username, *retname;
username = get_username();
retname = dupprintf("%s.%s.%s", prefix, username, name);
sfree(username);
return retname;
}
Socket new_named_pipe_client(const char *pipename, Plug plug);
Socket new_named_pipe_listener(const char *pipename, Plug plug);
int platform_ssh_share(const char *pi_name, Conf *conf,
Plug downplug, Plug upplug, Socket *sock,
char **logtext, char **ds_err, char **us_err,
int can_upstream, int can_downstream)
{
char *name, *mutexname, *pipename;
HANDLE mutex;
Socket retsock;
PSECURITY_DESCRIPTOR psd;
PACL acl;
/*
* Transform the platform-independent version of the connection
* identifier into the obfuscated version we'll use for our
* Windows named pipe and mutex. A side effect of doing this is
* that it also eliminates any characters illegal in Windows pipe
* names.
*/
name = obfuscate_name(pi_name);
if (!name) {
*logtext = dupprintf("Unable to call CryptProtectMemory: %s",
win_strerror(GetLastError()));
return SHARE_NONE;
}
/*
* Make a mutex name out of the connection identifier, and lock it
* while we decide whether to be upstream or downstream.
*/
{
SECURITY_ATTRIBUTES sa;
mutexname = make_name(CONNSHARE_MUTEX_PREFIX, name);
if (!make_private_security_descriptor(MUTEX_ALL_ACCESS,
&psd, &acl, logtext)) {
sfree(mutexname);
return SHARE_NONE;
}
memset(&sa, 0, sizeof(sa));
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = psd;
sa.bInheritHandle = FALSE;
mutex = CreateMutex(&sa, FALSE, mutexname);
if (!mutex) {
*logtext = dupprintf("CreateMutex(\"%s\") failed: %s",
mutexname, win_strerror(GetLastError()));
sfree(mutexname);
LocalFree(psd);
LocalFree(acl);
return SHARE_NONE;
}
sfree(mutexname);
LocalFree(psd);
LocalFree(acl);
WaitForSingleObject(mutex, INFINITE);
}
pipename = make_name(CONNSHARE_PIPE_PREFIX, name);
*logtext = NULL;
if (can_downstream) {
retsock = new_named_pipe_client(pipename, downplug);
if (sk_socket_error(retsock) == NULL) {
sfree(*logtext);
*logtext = pipename;
*sock = retsock;
sfree(name);
ReleaseMutex(mutex);
CloseHandle(mutex);
return SHARE_DOWNSTREAM;
}
sfree(*ds_err);
*ds_err = dupprintf("%s: %s", pipename, sk_socket_error(retsock));
sk_close(retsock);
}
if (can_upstream) {
retsock = new_named_pipe_listener(pipename, upplug);
if (sk_socket_error(retsock) == NULL) {
sfree(*logtext);
*logtext = pipename;
*sock = retsock;
sfree(name);
ReleaseMutex(mutex);
CloseHandle(mutex);
return SHARE_UPSTREAM;
}
sfree(*us_err);
*us_err = dupprintf("%s: %s", pipename, sk_socket_error(retsock));
sk_close(retsock);
}
/* One of the above clauses ought to have happened. */
assert(*logtext || *ds_err || *us_err);
sfree(pipename);
sfree(name);
ReleaseMutex(mutex);
CloseHandle(mutex);
return SHARE_NONE;
}
void platform_ssh_share_cleanup(const char *name)
{
}
#else /* !defined NO_SECURITY */
#include "noshare.c"
#endif /* !defined NO_SECURITY */
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