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/* popen.c secure popen: code mix from Richard Stevens and ntop source
*
* 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 <sys/wait.h>
#include <limits.h>
#include <fcntl.h>
#include "ipband.h"
#define __SEC_POPEN_TOKEN " "
static pid_t *childpid = NULL; /* ptr to array allocated at run-time */
static int maxfd;
/* popen() substitute */
FILE * sec_popen(const char *cmd, const char *type) {
char **argv, *ptr, *strtokState;
char *cmdcpy = NULL;
int i, pfd[2];
pid_t pid;
FILE *fp;
if(cmd == NULL || cmd == "")
return(NULL);
if ((type[0] != 'r' && type[0] != 'w') || type[1] != 0) {
errno = EINVAL; /* required by POSIX.2 */
return(NULL);
}
if((cmdcpy = strdup(cmd)) == NULL)
return(NULL);
argv = NULL;
if((ptr = strtok_r(cmdcpy, __SEC_POPEN_TOKEN, &strtokState)) == NULL) {
free(cmdcpy);
return(NULL);
}
for(i = 0;; i++) {
if((argv = (char **)realloc(argv, (i+1) * sizeof(char*))) == NULL) {
free(cmdcpy);
return(NULL);
}
if((*(argv+i) = (char*)malloc((strlen(ptr)+1) * sizeof(char))) == NULL) {
free(cmdcpy);
return(NULL);
}
strcpy(argv[i], ptr);
if((ptr = strtok_r(NULL, __SEC_POPEN_TOKEN, &strtokState)) == NULL) {
if((argv = (char **) realloc(argv, (i+2) * sizeof(char*))) == NULL) {
free(cmdcpy);
return(NULL);
}
argv[i+1] = NULL;
break;
}
}
free(cmdcpy);
if (childpid == NULL) { /* first time through */
/* allocate zeroed out array for child pids */
maxfd = open_max();
if ( (childpid = calloc(maxfd, sizeof(pid_t))) == NULL)
return(NULL);
}
if (pipe(pfd) < 0)
return(NULL); /* errno set by pipe() */
if ( (pid = fork()) < 0)
return(NULL); /* errno set by fork() */
else if (pid == 0) { /* child */
if((getuid() != geteuid()) || (getgid() != getegid())) {
/* setuid binary, drop privileges */
if (setgid(getgid()) != 0 || setuid(getuid()) != 0)
err_sys("Error dropping privileges");
}
if (*type == 'r') {
close(pfd[0]);
if (pfd[1] != STDOUT_FILENO) {
dup2(pfd[1], STDOUT_FILENO);
close(pfd[1]);
}
} else {
close(pfd[1]);
if (pfd[0] != STDIN_FILENO) {
dup2(pfd[0], STDIN_FILENO);
close(pfd[0]);
}
}
/* close all descriptors in childpid[] */
for (i = 0; i < maxfd; i++)
if (childpid[i] > 0)
close(i);
if(strchr(argv[0], '/') == NULL)
execvp(argv[0], argv); /* search in $PATH */
else
execv(argv[0], argv);
_exit(127);
} /* parent */
if (*type == 'r') {
close(pfd[1]);
if ( (fp = fdopen(pfd[0], type)) == NULL)
return(NULL);
} else {
close(pfd[0]);
if ( (fp = fdopen(pfd[1], type)) == NULL)
return(NULL);
}
childpid[fileno(fp)] = pid; /* remember child pid for this fd */
return(fp);
}
int sec_pclose(FILE *fp) {
int fd, stat;
pid_t pid;
if (childpid == NULL)
return(-1); /* popen() has never been called */
fd = fileno(fp);
if ( (pid = childpid[fd]) == 0)
return(-1); /* fp wasn't opened by popen() */
childpid[fd] = 0;
if (fclose(fp) == EOF)
return(-1);
while (waitpid(pid, &stat, 0) < 0)
if (errno != EINTR)
return(-1); /* error other than EINTR from waitpid() */
return(stat); /* return child's termination status */
}
/* Determine maximum number of open files */
#ifdef OPEN_MAX
static int openmax = OPEN_MAX;
#else
static int openmax = 0;
#endif
#define OPEN_MAX_GUESS 256 /* if OPEN_MAX is indeterminate */
/* we're not guaranteed this is adequate */
int open_max(void)
{
if (openmax == 0) { /* first time through */
errno = 0;
if ( (openmax = sysconf(_SC_OPEN_MAX)) < 0) {
if (errno == 0)
openmax = OPEN_MAX_GUESS; /* it's indeterminate */
else
err_sys("sysconf error for _SC_OPEN_MAX");
}
}
return(openmax);
}
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