progclient.cc

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/* Copyright 1999,2000,2001 BrightStation PLC
 * Copyright 2002 Ananova Ltd
 * Copyright 2003,2004,2005,2006,2007,2010,2011,2014,2019 Olly Betts
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */

#include <config.h>

#include "safefcntl.h"

#include "progclient.h"
#include <xapian/error.h>
#include "closefrom.h"
#include "debuglog.h"

#include <cerrno>
#include <string>
#include <vector>

#include <sys/types.h>
#ifndef __WIN32__
# include "safesyssocket.h"
# include <sys/wait.h>
#else
# include <cstdio> // For sprintf().
# include <io.h>
#endif

using namespace std;

#ifndef __WIN32__

static void
split_words(const string &text, vector<string> &words, char ws = ' ')
{
    size_t i = 0;
    if (i < text.length() && text[0] == ws) {
        i = text.find_first_not_of(ws, i);
    }
    while (i < text.length()) {
        size_t j = text.find_first_of(ws, i);
        words.push_back(text.substr(i, j - i));
        i = text.find_first_not_of(ws, j);
    }
}
#endif

ProgClient::ProgClient(const string &progname, const string &args,
                       double timeout_, bool writable, int flags)
        : RemoteDatabase(run_program(progname, args, child),
                         timeout_, get_progcontext(progname, args), writable,
                         flags)
{
    LOGCALL_CTOR(DB, "ProgClient", progname | args | timeout_ | writable | flags);
}

string
ProgClient::get_progcontext(const string &progname, const string &args)
{
    LOGCALL_STATIC(DB, string, "ProgClient::get_progcontext", progname | args);
    RETURN("remote:prog(" + progname + " " + args + ")");
}

int
ProgClient::run_program(const string &progname, const string &args,
#ifndef __WIN32__
                        pid_t& child
#else
                        HANDLE& child
#endif
                        )
{
    LOGCALL_STATIC(DB, int, "ProgClient::run_program", progname | args | Literal("[&child]"));

#if defined HAVE_SOCKETPAIR && defined HAVE_FORK
    /* socketpair() returns two sockets.  We keep sv[0] and give
     * sv[1] to the child process.
     */
    int sv[2];

    if (socketpair(PF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, sv) < 0) {
        throw Xapian::NetworkError(string("socketpair failed"), get_progcontext(progname, args), errno);
    }

    // Do the steps of splitting args into an argv[] array which need to
    // allocate memory before we call fork() since in a multi-threaded program
    // (which we might be used in) it's only safe to call async-signal-safe
    // functions in the child process after fork() until exec, and malloc, etc
    // aren't async-signal-safe.
    vector<string> argvec;
    split_words(args, argvec);
    const char **new_argv = new const char *[argvec.size() + 2];

    child = fork();

    if (child < 0) {
        delete [] new_argv;
        throw Xapian::NetworkError(string("fork failed"), get_progcontext(progname, args), errno);
    }

    if (child != 0) {
        // parent
        delete [] new_argv;
        // close the child's end of the socket
        ::close(sv[1]);
        RETURN(sv[0]);
    }

    /* child process:
     *   set up file descriptors and exec program
     */

#if defined F_SETFD && defined FD_CLOEXEC
    // Clear close-on-exec flag, if we set it when we called socketpair().
    // Clearing it here means there's no window where another thread in the
    // parent process could fork()+exec() and end up with this fd still
    // open (assuming close-on-exec is supported).
    //
    // We can't use a preprocessor check on the *value* of SOCK_CLOEXEC as
    // on Linux SOCK_CLOEXEC is an enum, with '#define SOCK_CLOEXEC
    // SOCK_CLOEXEC' to allow '#ifdef SOCK_CLOEXEC' to work.
    if (SOCK_CLOEXEC != 0)
        (void)fcntl(sv[1], F_SETFD, 0);
#endif

    // replace stdin and stdout with the socket
    // FIXME: check return values from dup2.
    if (sv[1] != 0) {
        dup2(sv[1], 0);
    }
    if (sv[1] != 1) {
        dup2(sv[1], 1);
    }

    // close unnecessary file descriptors
    closefrom(2);

    // Redirect stderr to /dev/null
    int stderrfd = open("/dev/null", O_WRONLY);
    if (stderrfd == -1) {
        _exit(-1);
    }
    if (stderrfd != 2) {
        // Not sure why it wouldn't be 2, but handle the situation anyway.
        dup2(stderrfd, 2);
        ::close(stderrfd);
    }

    new_argv[0] = progname.c_str();
    for (vector<string>::size_type i = 0; i < argvec.size(); ++i) {
        new_argv[i + 1] = argvec[i].c_str();
    }
    new_argv[argvec.size() + 1] = 0;
    execvp(progname.c_str(), const_cast<char *const *>(new_argv));

    // if we get here, then execvp failed.
    /* throwing an exception is a bad idea, since we're
     * not the original process. */
    _exit(-1);
#ifdef __xlC__
    // Avoid "missing return statement" warning.
    return 0;
#endif
#elif defined __WIN32__
    static unsigned int pipecount = 0;
    char pipename[256];
    sprintf(pipename, "\\\\.\\pipe\\xapian-remote-%lx-%lx-%x",
            static_cast<unsigned long>(GetCurrentProcessId()),
            static_cast<unsigned long>(GetCurrentThreadId()), pipecount++);
    // Create a pipe so we can read stdout from the child process.
    HANDLE hPipe = CreateNamedPipe(pipename,
                                   PIPE_ACCESS_DUPLEX|FILE_FLAG_OVERLAPPED,
                                   0,
                                   1, 4096, 4096, NMPWAIT_USE_DEFAULT_WAIT,
                                   NULL);

    if (hPipe == INVALID_HANDLE_VALUE) {
        throw Xapian::NetworkError("CreateNamedPipe failed",
                                   get_progcontext(progname, args),
                                   -int(GetLastError()));
    }

    HANDLE hClient = CreateFile(pipename,
                                GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING,
                                FILE_FLAG_OVERLAPPED, NULL);

    if (hClient == INVALID_HANDLE_VALUE) {
        throw Xapian::NetworkError("CreateFile failed",
                                   get_progcontext(progname, args),
                                   -int(GetLastError()));
    }

    if (!ConnectNamedPipe(hPipe, NULL) && GetLastError() != ERROR_PIPE_CONNECTED) {
        throw Xapian::NetworkError("ConnectNamedPipe failed",
                                   get_progcontext(progname, args),
                                   -int(GetLastError()));
    }

    // Set the appropriate handles to be inherited by the child process.
    SetHandleInformation(hClient, HANDLE_FLAG_INHERIT, 1);

    // Create the child process.
    PROCESS_INFORMATION procinfo;
    memset(&procinfo, 0, sizeof(PROCESS_INFORMATION));

    STARTUPINFO startupinfo;
    memset(&startupinfo, 0, sizeof(STARTUPINFO));
    startupinfo.cb = sizeof(STARTUPINFO);
    startupinfo.hStdError = hClient;
    startupinfo.hStdOutput = hClient;
    startupinfo.hStdInput = hClient;
    startupinfo.dwFlags |= STARTF_USESTDHANDLES;

    string cmdline{progname};
    cmdline += ' ';
    cmdline += args;
    // For some reason Windows wants a modifiable command line so we
    // pass `&cmdline[0]` rather than `cmdline.c_str()`.
    BOOL ok = CreateProcess(progname.c_str(), &cmdline[0], 0, 0, TRUE, 0, 0, 0,
                            &startupinfo, &procinfo);
    if (!ok) {
        throw Xapian::NetworkError("CreateProcess failed",
                                   get_progcontext(progname, args),
                                   -int(GetLastError()));
    }

    CloseHandle(hClient);
    CloseHandle(procinfo.hThread);
    child = procinfo.hProcess;
    RETURN(_open_osfhandle(intptr_t(hPipe), O_RDWR|O_BINARY));
#endif
}

ProgClient::~ProgClient()
{
    try {
        // Close the socket and reap the child.
        do_close();
    } catch (...) {
    }
#ifndef __WIN32__
    waitpid(child, 0, 0);
#else
    WaitForSingleObject(child, INFINITE);
#endif
}