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Add new config option to support thread token based agent process to … #133

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Add new config option to support thread token based agent process to …
masatma Nov 10, 2017
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masatma Nov 13, 2017
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7 changes: 7 additions & 0 deletions src/include/winpty_constants.h
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Original file line number Diff line number Diff line change
Expand Up @@ -76,11 +76,18 @@
* See https://github.com/rprichard/winpty/issues/58. */
#define WINPTY_FLAG_ALLOW_CURPROC_DESKTOP_CREATION 0x8ull

/* Create agent proces from the thread token instead of current process.
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s/proces/process

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done

* This is usefull when winpty.dll is called by Windows Service program to
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s/usefull/useful

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done

* impersonate to the original user from a remote process.
* See https://github.com/rprichard/winpty/issues/132. */
#define WINPTY_FLAG_IMPERSONATE_THREAD 0x10ull

#define WINPTY_FLAG_MASK (0ull \
| WINPTY_FLAG_CONERR \
| WINPTY_FLAG_PLAIN_OUTPUT \
| WINPTY_FLAG_COLOR_ESCAPES \
| WINPTY_FLAG_ALLOW_CURPROC_DESKTOP_CREATION \
| WINPTY_FLAG_IMPERSONATE_THREAD \
)

/* QuickEdit mode is initially disabled, and the agent does not send mouse
Expand Down
103 changes: 86 additions & 17 deletions src/libwinpty/winpty.cc
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Expand Up @@ -470,6 +470,7 @@ static bool shouldSpecifyHideFlag() {
}

static OwnedHandle startAgentProcess(
const winpty_config_t *cfg,
const std::wstring &desktop,
const std::wstring &controlPipeName,
const std::wstring &params,
Expand All @@ -494,24 +495,92 @@ static OwnedHandle startAgentProcess(
sui.dwFlags |= STARTF_USESHOWWINDOW;
sui.wShowWindow = SW_HIDE;
}

PROCESS_INFORMATION pi = {};
const BOOL success =
CreateProcessW(exePath.c_str(),
cmdlineV.data(),
nullptr, nullptr,
/*bInheritHandles=*/FALSE,
/*dwCreationFlags=*/creationFlags,
nullptr, nullptr,
&sui, &pi);
if (!success) {
const DWORD lastError = GetLastError();
const auto errStr =
(WStringBuilder(256)
<< L"winpty-agent CreateProcess failed: cmdline='" << cmdline
<< L"' err=0x" << whexOfInt(lastError)).str_moved();
throw LibWinptyException(
WINPTY_ERROR_AGENT_CREATION_FAILED, errStr.c_str());
if (cfg->flags & WINPTY_FLAG_IMPERSONATE_THREAD) {
HRESULT hr;
HANDLE token = nullptr;
if (!OpenThreadToken(
GetCurrentThread(),
TOKEN_QUERY | TOKEN_DUPLICATE | TOKEN_ASSIGN_PRIMARY,
FALSE,
&token))
{
const DWORD lastError = GetLastError();
const auto errStr =
(WStringBuilder(256)
<< L"winpty-agent OpenThreadToken failed: cmdline='" << cmdline
<< L"' err=0x" << whexOfInt(lastError)).str_moved();
throw LibWinptyException(
WINPTY_ERROR_AGENT_CREATION_FAILED, errStr.c_str());
}

HANDLE dupToken = nullptr;
if (!DuplicateTokenEx(
token,
TOKEN_QUERY | TOKEN_DUPLICATE | TOKEN_ASSIGN_PRIMARY,
NULL,
SecurityImpersonation,
TokenPrimary,
&dupToken))
{
CloseHandle(token);
const DWORD lastError = GetLastError();
const auto errStr =
(WStringBuilder(256)
<< L"winpty-agent DuplicateTokenEx failed: cmdline='" << cmdline
<< L"' err=0x" << whexOfInt(lastError)).str_moved();
throw LibWinptyException(
WINPTY_ERROR_AGENT_CREATION_FAILED, errStr.c_str());
}

DWORD exitCode = 0;
const BOOL success = CreateProcessAsUser(
dupToken,
exePath.c_str(),
cmdlineV.data(),
nullptr,
nullptr,
FALSE,
CREATE_DEFAULT_ERROR_MODE | CREATE_BREAKAWAY_FROM_JOB | CREATE_UNICODE_ENVIRONMENT | NORMAL_PRIORITY_CLASS,
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I'm curious about these creation flags.

  • startAgentProcess is already called with a creation flags parameter, which is currently only set to either DETACHED_PROCESS (for --create-desktop) or CREATE_NEW_CONSOLE (normal code path). This code doesn't ever use CREATE_NEW_CONSOLE, so I assume it reuses its parent's console, if it has one?
  • Regarding the specific flags:
    • CREATE_DEFAULT_ERROR_MODE: I wonder if this ought to be the default behavior for winpty -- there was a complaint a while ago about crash handling and winpty (When run in Terminal a programs unhandled exceptions don't produce debug dialog in win32  microsoft/vscode#32134), but I never looked into it. Maybe this creation flag fixes the problem?
    • CREATE_UNICODE_ENVIRONMENT: lpEnvironment is null; does this do anything?
    • CREATE_BREAKAWAY_FROM_JOB and NORMAL_PRIORITY_CLASS: I wonder if these flags should really be set by WINPTY_FLAG_IMPERSONATE_THREAD or whether they're orthogonal settings. Maybe winpty needs a way to specify arbitrary creation flags for the agent and/or the agent's child?

nullptr,
nullptr,
&sui,
&pi);
if (!success) {
CloseHandle(token);
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I'd prefer this code use RAII (i.e. OwnedHandle), but I can fix that up myself after merging the change.

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left as is.

CloseHandle(dupToken);
const DWORD lastError = GetLastError();
const auto errStr =
(WStringBuilder(256)
<< L"winpty-agent CreateProcessAsUser failed: cmdline='" << cmdline
<< L"' err=0x" << whexOfInt(lastError)).str_moved();
throw LibWinptyException(
WINPTY_ERROR_AGENT_CREATION_FAILED, errStr.c_str());
}

CloseHandle(token);
CloseHandle(dupToken);
} else {
const BOOL success =
CreateProcessW(exePath.c_str(),
cmdlineV.data(),
nullptr, nullptr,
/*bInheritHandles=*/FALSE,
/*dwCreationFlags=*/creationFlags,
nullptr, nullptr,
&sui, &pi);
if (!success) {
const DWORD lastError = GetLastError();
const auto errStr =
(WStringBuilder(256)
<< L"winpty-agent CreateProcess failed: cmdline='" << cmdline
<< L"' err=0x" << whexOfInt(lastError)).str_moved();
throw LibWinptyException(
WINPTY_ERROR_AGENT_CREATION_FAILED, errStr.c_str());
}
}

CloseHandle(pi.hThread);
TRACE("Created agent successfully, pid=%u, cmdline=%s",
static_cast<unsigned int>(pi.dwProcessId),
Expand Down Expand Up @@ -556,7 +625,7 @@ createAgentSession(const winpty_config_t *cfg,

DWORD agentPid = 0;
wp->agentProcess = startAgentProcess(
desktop, pipeName, params, creationFlags, agentPid);
cfg, desktop, pipeName, params, creationFlags, agentPid);
connectControlPipe(*wp.get());
verifyPipeClientPid(wp->controlPipe.get(), agentPid);

Expand Down