putty/windows/winpgntc.c

/*
 * Pageant client code.
 */

#include <stdio.h>
#include <stdlib.h>

#include "putty.h"

#ifndef NO_SECURITY
#include <aclapi.h>
#endif

#define AGENT_COPYDATA_ID 0x804e50ba   /* random goop */
#define AGENT_MAX_MSGLEN  8192

int agent_exists(void)
{
    HWND hwnd;
    hwnd = FindWindow("Pageant", "Pageant");
    if (!hwnd)
	return FALSE;
    else
	return TRUE;
}

/*
 * Unfortunately, this asynchronous agent request mechanism doesn't
 * appear to work terribly well. I'm going to comment it out for
 * the moment, and see if I can come up with a better one :-/
 */
#ifdef WINDOWS_ASYNC_AGENT

struct agent_query_data {
    COPYDATASTRUCT cds;
    unsigned char *mapping;
    HANDLE handle;
    char *mapname;
    HWND hwnd;
    void (*callback)(void *, void *, int);
    void *callback_ctx;
};

DWORD WINAPI agent_query_thread(LPVOID param)
{
    struct agent_query_data *data = (struct agent_query_data *)param;
    unsigned char *ret;
    int id, retlen;

    id = SendMessage(data->hwnd, WM_COPYDATA, (WPARAM) NULL,
		     (LPARAM) &data->cds);
    ret = NULL;
    if (id > 0) {
	retlen = 4 + GET_32BIT(data->mapping);
	ret = snewn(retlen, unsigned char);
	if (ret) {
	    memcpy(ret, data->mapping, retlen);
	}
    }
    if (!ret)
	retlen = 0;
    UnmapViewOfFile(data->mapping);
    CloseHandle(data->handle);
    sfree(data->mapname);

    agent_schedule_callback(data->callback, data->callback_ctx, ret, retlen);

    return 0;
}

#endif

/*
 * Dynamically load advapi32.dll for SID manipulation. In its absence,
 * we degrade gracefully.
 */
#ifndef NO_SECURITY
int advapi_initialised = FALSE;
static HMODULE advapi;
DECL_WINDOWS_FUNCTION(static, BOOL, OpenProcessToken,
		      (HANDLE, DWORD, PHANDLE));
DECL_WINDOWS_FUNCTION(static, BOOL, GetTokenInformation,
		      (HANDLE, TOKEN_INFORMATION_CLASS,
                       LPVOID, DWORD, PDWORD));
DECL_WINDOWS_FUNCTION(static, BOOL, InitializeSecurityDescriptor,
		      (PSECURITY_DESCRIPTOR, DWORD));
DECL_WINDOWS_FUNCTION(static, BOOL, SetSecurityDescriptorOwner,
		      (PSECURITY_DESCRIPTOR, PSID, BOOL));
DECL_WINDOWS_FUNCTION(, DWORD, GetSecurityInfo,
		      (HANDLE, SE_OBJECT_TYPE, SECURITY_INFORMATION,
		       PSID *, PSID *, PACL *, PACL *,
		       PSECURITY_DESCRIPTOR *));
int init_advapi(void)
{
    advapi = load_system32_dll("advapi32.dll");
    return advapi &&
	GET_WINDOWS_FUNCTION(advapi, GetSecurityInfo) &&
        GET_WINDOWS_FUNCTION(advapi, OpenProcessToken) &&
	GET_WINDOWS_FUNCTION(advapi, GetTokenInformation) &&
	GET_WINDOWS_FUNCTION(advapi, InitializeSecurityDescriptor) &&
	GET_WINDOWS_FUNCTION(advapi, SetSecurityDescriptorOwner);
}

PSID get_user_sid(void)
{
    HANDLE proc = NULL, tok = NULL;
    TOKEN_USER *user = NULL;
    DWORD toklen, sidlen;
    PSID sid = NULL, ret = NULL;

    if ((proc = OpenProcess(MAXIMUM_ALLOWED, FALSE,
                            GetCurrentProcessId())) == NULL)
        goto cleanup;

    if (!p_OpenProcessToken(proc, TOKEN_QUERY, &tok))
        goto cleanup;

    if (!p_GetTokenInformation(tok, TokenUser, NULL, 0, &toklen) &&
        GetLastError() != ERROR_INSUFFICIENT_BUFFER)
        goto cleanup;

    if ((user = (TOKEN_USER *)LocalAlloc(LPTR, toklen)) == NULL)
        goto cleanup;

    if (!p_GetTokenInformation(tok, TokenUser, user, toklen, &toklen))
        goto cleanup;

    sidlen = GetLengthSid(user->User.Sid);

    sid = (PSID)smalloc(sidlen);

    if (!CopySid(sidlen, sid, user->User.Sid))
        goto cleanup;

    /* Success. Move sid into the return value slot, and null it out
     * to stop the cleanup code freeing it. */
    ret = sid;
    sid = NULL;

  cleanup:
    if (proc != NULL)
        CloseHandle(proc);
    if (tok != NULL)
        CloseHandle(tok);
    if (user != NULL)
        LocalFree(user);
    if (sid != NULL)
        sfree(sid);

    return ret;
}

#endif

int agent_query(void *in, int inlen, void **out, int *outlen,
		void (*callback)(void *, void *, int), void *callback_ctx)
{
    HWND hwnd;
    char *mapname;
    HANDLE filemap;
    unsigned char *p, *ret;
    int id, retlen;
    COPYDATASTRUCT cds;
    SECURITY_ATTRIBUTES sa, *psa;
    PSECURITY_DESCRIPTOR psd = NULL;
    PSID usersid = NULL;

    *out = NULL;
    *outlen = 0;

    hwnd = FindWindow("Pageant", "Pageant");
    if (!hwnd)
	return 1;		       /* *out == NULL, so failure */
    mapname = dupprintf("PageantRequest%08x", (unsigned)GetCurrentThreadId());

    psa = NULL;
#ifndef NO_SECURITY
    if (advapi_initialised || init_advapi()) {
        /*
         * Make the file mapping we create for communication with
         * Pageant owned by the user SID rather than the default. This
         * should make communication between processes with slightly
         * different contexts more reliable: in particular, command
         * prompts launched as administrator should still be able to
         * run PSFTPs which refer back to the owning user's
         * unprivileged Pageant.
         */
        usersid = get_user_sid();

        if (usersid) {
            psd = (PSECURITY_DESCRIPTOR)
                LocalAlloc(LPTR, SECURITY_DESCRIPTOR_MIN_LENGTH);
            if (psd) {
                if (p_InitializeSecurityDescriptor
                    (psd, SECURITY_DESCRIPTOR_REVISION) &&
                    p_SetSecurityDescriptorOwner(psd, usersid, FALSE)) {
                    sa.nLength = sizeof(sa);
                    sa.bInheritHandle = TRUE;
                    sa.lpSecurityDescriptor = psd;
                    psa = &sa;
                } else {
                    LocalFree(psd);
                    psd = NULL;
                }
            }
        }
    }
#endif /* NO_SECURITY */

    filemap = CreateFileMapping(INVALID_HANDLE_VALUE, psa, PAGE_READWRITE,
				0, AGENT_MAX_MSGLEN, mapname);
    if (filemap == NULL || filemap == INVALID_HANDLE_VALUE) {
        sfree(mapname);
	return 1;		       /* *out == NULL, so failure */
    }
    p = MapViewOfFile(filemap, FILE_MAP_WRITE, 0, 0, 0);
    memcpy(p, in, inlen);
    cds.dwData = AGENT_COPYDATA_ID;
    cds.cbData = 1 + strlen(mapname);
    cds.lpData = mapname;
#ifdef WINDOWS_ASYNC_AGENT
    if (callback != NULL && !(flags & FLAG_SYNCAGENT)) {
	/*
	 * We need an asynchronous Pageant request. Since I know of
	 * no way to stop SendMessage from blocking the thread it's
	 * called in, I see no option but to start a fresh thread.
	 * When we're done we'll PostMessage the result back to our
	 * main window, so that the callback is done in the primary
	 * thread to avoid concurrency.
	 */
	struct agent_query_data *data = snew(struct agent_query_data);
	DWORD threadid;
	data->mapping = p;
	data->handle = filemap;
	data->mapname = mapname;
	data->callback = callback;
	data->callback_ctx = callback_ctx;
	data->cds = cds;	       /* structure copy */
	data->hwnd = hwnd;
	if (CreateThread(NULL, 0, agent_query_thread, data, 0, &threadid))
	    return 0;
	sfree(mapname);
	sfree(data);
    }
#endif

    /*
     * The user either passed a null callback (indicating that the
     * query is required to be synchronous) or CreateThread failed.
     * Either way, we need a synchronous request.
     */
    id = SendMessage(hwnd, WM_COPYDATA, (WPARAM) NULL, (LPARAM) &cds);
    if (id > 0) {
	retlen = 4 + GET_32BIT(p);
	ret = snewn(retlen, unsigned char);
	if (ret) {
	    memcpy(ret, p, retlen);
	    *out = ret;
	    *outlen = retlen;
	}
    }
    UnmapViewOfFile(p);
    CloseHandle(filemap);
    sfree(mapname);
    if (psd)
        LocalFree(psd);
    sfree(usersid);
    return 1;
}