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/*
*****************************************************************************
*
* File: extcmd.c
*
* Author: Damien Stuart (dstuart@dstuart.org)
*
* Purpose: Routines for executing and processing external commands.
*
* Copyright 2010 Damien Stuart (dstuart@dstuart.org)
*
* License (GNU Public License):
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*****************************************************************************
*/
#include "fwknopd_common.h"
#include "extcmd.h"
#include "log_msg.h"
#include "utils.h"
/*
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/select.h>
*/
#include <errno.h>
#include <signal.h>
#if HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
/*
static sig_atomic_t got_sigalrm;
*/
/* Takes a file descriptor and makes it non-blocking.
static int
set_nonblock(int fd)
{
int val;
if((val = fcntl(fd, F_GETFL, 0)) < 0)
{
perror("fcntl F_GETFL error:");
return(-1);
}
val |= O_NONBLOCK;
if(fcntl(fd, F_SETFL, val) < 0)
{
perror("fcntl F_SETFL error setting O_NONBLOCK");
return(-1);
}
return(0);
}
static void
alarm_handler(int sig)
{
got_sigalrm = 1;
}
*/
/* Run en external command returning exit status, and optionally filling
* provided buffer with STDOUT output up to the size provided.
*
* Note: XXX: We are not using the timeout parameter at present. We still need
* to implement a reliable timeout mechanism.
*/
static int
_run_extcmd(uid_t user_uid, const char *cmd, char *so_buf, const size_t so_buf_sz, const int timeout)
{
FILE *ipt;
int retval = 0;
char so_read_buf[IO_READ_BUF_LEN];
pid_t pid;
int res;
if(so_buf == NULL)
{
/* Since we do not have to capture output, we will fork here (which we
* would have to do anyway if we are running as another user as well).
*/
pid = fork();
if(pid == -1)
{
log_msg(LOG_ERR, "run_extcmd: fork failed: %s", strerror(errno));
return(EXTCMD_FORK_ERROR);
}
else if (pid == 0)
{
/* We are the child */
/* If user is not null, then we setuid to that user before running the
* command.
*/
if(user_uid > 0)
{
if(setuid(user_uid) < 0)
{
exit(EXTCMD_SETUID_ERROR);
}
}
res = system(cmd);
exit(WEXITSTATUS(res));
}
/* Retval is forced to 0 as we don't care about the exit status of
* the child (for now)>
*/
retval = 0;
}
else
{
/* Looking for output use popen and fill the buffer to its limit.
*/
ipt = popen(cmd, "r");
if(ipt == NULL)
{
log_msg(LOG_ERR, "Got popen error %i: %s", errno, strerror(errno));
retval = -1;
}
else
{
memset(so_buf, 0x0, so_buf_sz);
while((fgets(so_read_buf, IO_READ_BUF_LEN, ipt)) != NULL)
{
if(so_buf == NULL)
continue;
strlcat(so_buf, so_read_buf, so_buf_sz);
if(strlen(so_buf) >= so_buf_sz-1)
break;
}
pclose(ipt);
}
}
return(retval);
}
#if 0 /* --DSS the original method that did not work on some systems */
/* Create the pipes we will use for getting stdout and stderr
* from the child process.
*/
if(pipe(so) != 0)
return(EXTCMD_PIPE_ERROR);
if(pipe(se) != 0)
return(EXTCMD_PIPE_ERROR);
/* Fork off a child process to run the command and provide its outputs.
*/
pid = fork();
if(pid == -1)
{
return(EXTCMD_FORK_ERROR);
}
else if (pid == 0)
{
/* We are the child, so we dup stdout and stderr to our respective
* write-end of the pipes, close stdin and the read-end of the pipes
* (since we don't need them here). Then use system() to run the
* command and exit with the exit status of that command so we can
* grab it from the waitpid call in the parent.
*/
close(fileno(stdin));
dup2(so[1], fileno(stdout));
dup2(se[1], fileno(stderr));
close(so[0]);
close(se[0]);
/* If user is not null, then we setuid to that user before running the
* command.
*/
if(user_uid > 0)
{
if(setuid(user_uid) < 0)
{
exit(EXTCMD_SETUID_ERROR);
}
}
/* --DSS XXX: Would it be more efficient to use one of the exec()
* calls (i.e. 'return(execvp(ext_cmd, &argv[1]));')?
* For now, we use system() and exit with the external
* command exit status.
*/
exit(WEXITSTATUS(system(cmd)));
}
/* Parent from here */
/* Give the exit status an initial value of -1.
*/
*status = -1;
/* Close the write-end of the pipes (we are only reading).
*/
close(so[1]);
close(se[1]);
/* Set our pipes to non-blocking
*/
set_nonblock(so[0]);
set_nonblock(se[0]);
tv.tv_sec = EXTCMD_DEF_TIMEOUT;
tv.tv_usec = 0;
/* Initialize and setup our file descriptor sets for select.
*/
FD_ZERO(&rfds);
FD_ZERO(&efds);
FD_SET(so[0], &rfds);
FD_SET(se[0], &rfds);
FD_SET(so[0], &efds);
FD_SET(se[0], &efds);
/* Start with fully clear buffers.
*/
memset(so_buf, 0x0, so_buf_sz);
memset(se_buf, 0x0, se_buf_sz);
/* Read both stdout and stderr piped from the child until we get eof,
* fill the buffers, or error out.
*/
while(so_buf_remaining > 0 || se_buf_remaining > 0)
{
selval = select(8, &rfds, NULL, &efds, &tv);
if(selval == -1)
{
/* Select error - so kill the child and bail.
*/
kill(pid, SIGTERM);
retval |= EXTCMD_SELECT_ERROR;
break;
}
if(selval == 0)
{
/* Timeout - so kill the child and bail
*/
kill(pid, SIGTERM);
retval |= EXTCMD_EXECUTION_TIMEOUT;
break;
}
/* The stdout pipe...
*/
bytes_read = read(so[0], so_read_buf, IO_READ_BUF_LEN);
if(so_buf_remaining > 0)
{
if(bytes_read > 0)
{
/* We have data, so process it...
*/
if(bytes_read > so_buf_remaining)
{
bytes_read = so_buf_remaining;
retval |= EXTCMD_SUCCESS_PARTIAL_STDOUT;
}
memcpy(so_buf, so_read_buf, bytes_read);
so_buf += bytes_read;
so_buf_remaining -= bytes_read;
}
else if(bytes_read < 0)
{
/* Anything other than EAGAIN or EWOULDBLOCK is conisdered
* error enough to bail. We are done here so we force the
* buf_remaining value to 0.
*/
if(errno != EAGAIN && errno != EWOULDBLOCK)
{
retval |= EXTCMD_STDOUT_READ_ERROR;
so_buf_remaining = 0;
}
}
else
{
/* Bytes read was 0 which indicate end of file. So we are
* done.
*/
so_buf_remaining = 0;
}
}
else
break;
/* The stderr pipe...
*/
bytes_read = read(se[0], se_read_buf, IO_READ_BUF_LEN);
if(se_buf_remaining > 0)
{
if(bytes_read > 0)
{
/* We have data, so process it...
*/
if(bytes_read > se_buf_remaining)
{
bytes_read = se_buf_remaining;
retval |= EXTCMD_SUCCESS_PARTIAL_STDERR;
}
memcpy(se_buf, se_read_buf, bytes_read);
se_buf += bytes_read;
se_buf_remaining -= bytes_read;
}
else if(bytes_read < 0)
{
/* Anything other than EAGAIN or EWOULDBLOCK is conisdered
* error enough to bail. We are done here so we force the
* buf_remaining value to 0.
*/
if(errno != EAGAIN && errno != EWOULDBLOCK)
{
retval |= EXTCMD_STDERR_READ_ERROR;
se_buf_remaining = 0;
}
}
else
{
/* Bytes read was 0 which indicate end of file. So we are
* done.
*/
se_buf_remaining = 0;
}
}
else
break;
}
close(so[0]);
close(se[0]);
/* Wait for the external command to finish and capture its exit status.
*/
waitpid(pid, status, 0);
if(*status != 0)
retval != EXTCMD_EXECUTION_ERROR;
/* Return the our status of this operation command.
*/
return(retval);
}
#endif
/* Run an external command. This is wrapper around _run_extcmd()
*/
int
run_extcmd(const char *cmd, char *so_buf, const size_t so_buf_sz, const int timeout)
{
return _run_extcmd(0, cmd, so_buf, so_buf_sz, timeout);
}
/* Run an external command as the specified user. This is wrapper around _run_extcmd()
*/
int
run_extcmd_as(uid_t user_uid, const char *cmd, char *so_buf, const size_t so_buf_sz, const int timeout)
{
return _run_extcmd(user_uid, cmd, so_buf, so_buf_sz, timeout);
}
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