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Dropping privileges when run as root (#21)
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* Dropping privileges when run as root, default to user nobody, group dialout
* configurable pidfile location
* add sigterm, sigint signal handlers, improved cleanup
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@speters
speters authored Jan 20, 2018
1 parent 9dbd14a commit 150a840
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Showing 6 changed files with 197 additions and 24 deletions.
15 changes: 15 additions & 0 deletions doc/man/vcontrold.rst
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Expand Up @@ -44,6 +44,21 @@ OPTIONS
-l <logfile>, \--logfile <logfile>
use <logfile> instead of syslog.

-P <pidfile>, \--pidfile <pidfile>
write process id to <pidfile> when started as a daemon.
When started as root, <pidfile> is written prior to dropping privileges.
This overrides the corresponding entry in the config file.

-U <username>, \--username <username>
when started by root, drop privileges to user <username>
instead of user nobody. This overrides the corresponding entry in the config file.
If using a serial link, ensure that user or group has access rights to the serial device.

-G <groupname>, \--groupname <groupname>
when started by root, drop privileges to group <groupname>
instead of group dialout. This overrides the corresponding entry in the config file.
If using a serial link, ensure that user or group has access rights to the serial device.

-n, \--nodaemon
do not fork. This is for testing purpose only. Normaly vcontrold
will detach from the controlling terminal and put itself into the
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8 changes: 1 addition & 7 deletions src/semaphore.c
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Expand Up @@ -101,14 +101,8 @@ int initsem(key_t key, int nsems)
return semid;
}

#ifdef _CYGWIN__
#define TMPFILENAME "vcontrol.lockXXXXXX"
#else
#define TMPFILENAME "/tmp/vcontrol.lockXXXXXX"
#endif

char tmpfilename[MAXPATHLEN + 1]; // account for the leading '\0'
int semid;
char tmpfilename[MAXPATHLEN + 1]; // account for the leading '\0'

int vcontrol_seminit()
{
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10 changes: 10 additions & 0 deletions src/semaphore.h
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Expand Up @@ -17,6 +17,16 @@
#ifndef SEMAPHORE_H
#define SEMAPHORE_H

#include <sys/param.h>

#ifdef _CYGWIN__
#define TMPFILENAME "vcontrol.lockXXXXXX"
#else
#define TMPFILENAME "/tmp/vcontrol.lockXXXXXX"
#endif

extern char tmpfilename[MAXPATHLEN + 1]; // account for the leading '\0'

int vcontrol_seminit();
int vcontrol_semfree();
int vcontrol_semget();
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146 changes: 129 additions & 17 deletions src/vcontrold.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
#include <string.h>
#include <time.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>

#include <sys/types.h>
#include <sys/stat.h>
Expand Down Expand Up @@ -84,6 +86,7 @@ void usage()
printf("usage: vcontrold [-x|--xmlfile xml-file] [-d|--device <device>]\n");
printf(" [-l|--logfile <logfile>] [-p|--port port] [-s|--syslog]\n");
printf(" [-n|--nodaemon] [-v|--verbose] [-V|--Version]\n");
printf(" [-U|--username <username>] [-G|--groupname <groupname>]\n");
printf(" [-?|--help] [-i|--vsim] [-g|--debug]\n");
printf(" [-4|--inet4] [-6|--inet6]\n\n");

Expand Down Expand Up @@ -632,10 +635,21 @@ static void sigHupHandler(int signo)
reloadConfig();
}

char *pidFile = NULL;

static void sigTermHandler(int signo)
{
logIT1(LOG_NOTICE, "Received SIGTERM");
if (signo == SIGTERM) {
logIT1(LOG_NOTICE, "Received SIGTERM");
} else if (signo == SIGINT) {
logIT1(LOG_NOTICE, "Received SIGINT");
} else if (signo == SIGQUIT) {
logIT1(LOG_NOTICE, "Received SIGQUIT");
} else {
logIT(LOG_NOTICE, "Received signal %d", signo);
}
vcontrol_semfree();
if (pidFile) { unlink(pidFile); }
exit(1);
}

Expand All @@ -646,6 +660,8 @@ int main(int argc, char *argv[])
char *device = NULL;
char *cmdfile = NULL;
char *logfile = NULL;
char *username = NULL;
char *groupname = NULL;
static int useSyslog = 0;
static int debug = 0;
static int verbose = 0;
Expand All @@ -660,6 +676,9 @@ int main(int argc, char *argv[])
{"debug", no_argument, &debug, 1 },
{"vsim", no_argument, &simuOut, 1 },
{"logfile", required_argument, 0, 'l'},
{"pidfile", required_argument, 0, 'P'},
{"username", required_argument, 0, 'U'},
{"groupname", required_argument, 0, 'G'},
{"nodaemon", no_argument, &makeDaemon, 0 },
{"port", required_argument, 0, 'p'},
{"syslog", no_argument, &useSyslog, 1 },
Expand All @@ -674,7 +693,7 @@ int main(int argc, char *argv[])

// getopt_long stores the option index here.
int option_index = 0;
opt = getopt_long (argc, argv, "c:d:gil:np:sx:vV46",
opt = getopt_long (argc, argv, "c:d:gil:P:U:G:np:sx:vV46",
long_options, &option_index);

// Detect the end of the options.
Expand Down Expand Up @@ -720,6 +739,15 @@ int main(int argc, char *argv[])
case 'l':
logfile = optarg;
break;
case 'P':
pidFile = optarg;
break;
case 'U':
username = optarg;
break;
case 'G':
groupname = optarg;
break;
case 'n':
makeDaemon = 0;
break;
Expand Down Expand Up @@ -769,6 +797,15 @@ int main(int argc, char *argv[])
if (! logfile) {
logfile = cfgPtr->logfile;
}
if (! pidFile) {
pidFile = cfgPtr->pidfile;
}
if (! username) {
username = cfgPtr->username;
}
if (! groupname) {
groupname = cfgPtr->groupname;
}
if (! useSyslog) {
useSyslog = cfgPtr->syslog;
}
Expand All @@ -787,6 +824,14 @@ int main(int argc, char *argv[])
}

if (signal(SIGQUIT, sigTermHandler) == SIG_ERR) {
logIT(LOG_ERR, "Error handling SIGQUIT: %s", strerror(errno));
exit(1);
}
if (signal(SIGINT, sigTermHandler) == SIG_ERR) {
logIT(LOG_ERR, "Error handling SIGINT: %s", strerror(errno));
exit(1);
}
if (signal(SIGTERM, sigTermHandler) == SIG_ERR) {
logIT(LOG_ERR, "Error handling SIGTERM: %s", strerror(errno));
exit(1);
}
Expand All @@ -810,7 +855,6 @@ int main(int argc, char *argv[])
int sid;
int pidFD = 0;
char str[10];
char *pidFile = "/var/run/vcontrold.pid";

if (tcpport) {
if (makeDaemon) {
Expand Down Expand Up @@ -846,21 +890,22 @@ int main(int argc, char *argv[])
logIT1(LOG_ERR, "chdir / failed");
exit(1);
}
pidFD = open(pidFile, O_RDWR | O_CREAT, 0600);
if (pidFD == -1) {
logIT(LOG_ERR, "Could not open PID lock file %s, exiting", pidFile);
exit(1);
}
if (lockf(pidFD, F_TLOCK, 0) == -1) {
logIT(LOG_ERR, "Could not lock PID lock file %s, exiting", pidFile);
exit(1);
}

sprintf(str, "%d\n", getpid());
write(pidFD, str, strlen(str));
}
if (pidFile) {
pidFD = open(pidFile, O_RDWR | O_CREAT, 0600);
if (pidFD == -1) {
logIT(LOG_ERR, "Could not open PID lock file %s, exiting", pidFile);
exit(1);
}
if (lockf(pidFD, F_TLOCK, 0) == -1) {
logIT(LOG_ERR, "Could not lock PID lock file %s, exiting", pidFile);
exit(1);
}

vcontrol_seminit();
sprintf(str, "%d\n", getpid());
write(pidFD, str, strlen(str));
}
}

int sockfd = -1;
int listenfd = -1;
Expand All @@ -875,6 +920,70 @@ int main(int argc, char *argv[])
}

listenfd = openSocket(tcpport);

// Drop privileges after binding
if (0 == getuid()) {
struct passwd *pw;
struct group *grp;
struct stat stb;

if (username == NULL) {
username = strdup("nobody");
}
pw = getpwnam(username);
if (pw == NULL) {
int errsv = errno;
logIT(LOG_ERR, "Error while dropping privileges: calling getpwnam(\"%s\") failed with errno %d", username, errsv);
exit(1);
}
if (groupname == NULL) {
groupname = strdup("dialout");
}
grp = getgrnam(groupname);
if (grp == NULL) {
int errsv = errno;
logIT(LOG_ERR, "Error while dropping privileges: calling getgrnam(\"%s\") failed with errno %d", groupname, errsv);
exit(1);
}

// Make logfile accessible to the anticipated user/group
if (stat(logfile, &stb) == 0) {
chmod(logfile, stb.st_mode | S_IRGRP | S_IWGRP);
chown(logfile, pw->pw_uid, grp->gr_gid);
}
// Make lock file accessible to the anticipated user/group
if (stat(tmpfilename, &stb) == 0) {
chmod(tmpfilename, stb.st_mode | S_IRGRP | S_IWGRP);
chown(tmpfilename, pw->pw_uid, grp->gr_gid);
}

if (setgroups(0, NULL) != 0) {
int errsv = errno;
logIT(LOG_ERR, "Error while dropping privileges: calling setgroups(0, NULL) failed with errno %d", errsv);
exit(1);
}

if (setgid(grp->gr_gid) != 0) {
int errsv = errno;
logIT(LOG_ERR, "Error while dropping privileges: calling setgid(%d) failed with errno %d", grp->gr_gid, errsv);
exit(1);
}

if (setuid(pw->pw_uid) != 0) {
int errsv = errno;
logIT(LOG_ERR, "Error while dropping privileges: calling setuid(%d) failed with errno %d", pw->pw_uid, errsv);
exit(1);
}

logIT(LOG_INFO, "Dropped privileges, now running with effective user ID %d, group ID %d", geteuid(), getegid());
} else {
if (username || groupname) {
logIT1(LOG_INFO, "Not started as root, username/groupname settings ignored");
}
}

vcontrol_seminit();

while (1) {
sockfd = listenToSocket(listenfd, makeDaemon, checkP);
if (signal(SIGPIPE, sigPipeHandler) == SIG_ERR) {
Expand Down Expand Up @@ -905,7 +1014,10 @@ int main(int argc, char *argv[])
vcontrol_semfree();

close(fd);
close(pidFD);
if (pidFile) {
close(pidFD);
unlink(pidFile);
};
logIT1(LOG_LOCAL0, "vcontrold terminated");

return 0;
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39 changes: 39 additions & 0 deletions src/xmlconfig.c
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Original file line number Diff line number Diff line change
Expand Up @@ -579,6 +579,45 @@ configPtr parseConfig(xmlNodePtr cur)
logFound = 1;
prevPtr = cur;
cur = cur->children;
} else if (strstr((char *)cur->name, "pidfile")) {
chrPtr = getTextNode(cur);
logIT(LOG_INFO, " (%d) Node::Name=%s Type:%d Content=%s",
cur->line, cur->name, cur->type, chrPtr);
if (chrPtr) {
cfgPtr->pidfile = calloc(strlen(chrPtr) + 1, sizeof(char));
strcpy(cfgPtr->pidfile, chrPtr);
} else {
nullIT(&cfgPtr->pidfile);
}

(cur->next && (! (cur->next->type == XML_TEXT_NODE) || cur->next->next))
? (cur = cur->next) : (cur = prevPtr->next);
} else if (strstr((char *)cur->name, "username")) {
chrPtr = getTextNode(cur);
logIT(LOG_INFO, " (%d) Node::Name=%s Type:%d Content=%s",
cur->line, cur->name, cur->type, chrPtr);
if (chrPtr) {
cfgPtr->username= calloc(strlen(chrPtr) + 1, sizeof(char));
strcpy(cfgPtr->username, chrPtr);
} else {
nullIT(&cfgPtr->username);
}

(cur->next && (! (cur->next->type == XML_TEXT_NODE) || cur->next->next))
? (cur = cur->next) : (cur = prevPtr->next);
} else if (strstr((char *)cur->name, "groupname")) {
chrPtr = getTextNode(cur);
logIT(LOG_INFO, " (%d) Node::Name=%s Type:%d Content=%s",
cur->line, cur->name, cur->type, chrPtr);
if (chrPtr) {
cfgPtr->groupname= calloc(strlen(chrPtr) + 1, sizeof(char));
strcpy(cfgPtr->groupname, chrPtr);
} else {
nullIT(&cfgPtr->groupname);
}

(cur->next && (! (cur->next->type == XML_TEXT_NODE) || cur->next->next))
? (cur = cur->next) : (cur = prevPtr->next);
} else if (strstr((char *)cur->name, "device")) {
chrPtr = getPropertyNode(cur->properties, (xmlChar *)"ID");
logIT(LOG_INFO, " Device ID=%s", chrPtr);
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3 changes: 3 additions & 0 deletions src/xmlconfig.h
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Expand Up @@ -58,6 +58,9 @@ struct config {
char *tty;
int port;
char *logfile;
char *pidfile;
char *username;
char *groupname;
char *devID;
devicePtr devPtr;
allowPtr aPtr;
Expand Down

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