ref: a79465e118a0469bbda928f86b9eef6b42d18593
dir: /sys/src/cmd/auth/cron.c/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <libsec.h>
#include <auth.h>
#include <authsrv.h>
#include "authcmdlib.h"
char CRONLOG[] = "cron";
enum {
Minute = 60,
Hour = 60 * Minute,
Day = 24 * Hour,
};
typedef struct Job Job;
typedef struct Time Time;
typedef struct User User;
struct Time{ /* bit masks for each valid time */
uvlong min;
ulong hour;
ulong mday;
ulong wday;
ulong mon;
};
struct Job{
char *host; /* where ... */
Time time; /* when ... */
char *cmd; /* and what to execute */
Job *next;
};
struct User{
Qid lastqid; /* of last read /cron/user/cron */
char *name; /* who ... */
Job *jobs; /* wants to execute these jobs */
};
User *users;
int nuser;
int maxuser;
char *savec;
char *savetok;
int tok;
int debug;
ulong lexval;
void rexec(User*, Job*);
void readalljobs(void);
Job *readjobs(char*, User*);
int getname(char**);
uvlong gettime(int, int);
int gettok(int, int);
void initcap(void);
void pushtok(void);
void usage(void);
void freejobs(Job*);
User *newuser(char*);
void *emalloc(ulong);
void *erealloc(void*, ulong);
int myauth(int, char*);
void createuser(void);
int mkcmd(char*, char*, int);
void printjobs(void);
int qidcmp(Qid, Qid);
int becomeuser(char*);
ulong
minute(ulong tm)
{
return tm - tm%Minute; /* round down to the minute */
}
int
sleepuntil(ulong tm)
{
ulong now = time(0);
if (now < tm)
return sleep((tm - now)*1000);
else
return 0;
}
#pragma varargck argpos clog 1
#pragma varargck argpos fatal 1
static void
clog(char *fmt, ...)
{
char msg[256];
va_list arg;
va_start(arg, fmt);
vseprint(msg, msg + sizeof msg, fmt, arg);
va_end(arg);
syslog(0, CRONLOG, msg);
}
static void
fatal(char *fmt, ...)
{
char msg[256];
va_list arg;
va_start(arg, fmt);
vseprint(msg, msg + sizeof msg, fmt, arg);
va_end(arg);
clog("%s", msg);
error("%s", msg);
}
static int
openlock(char *file)
{
return create(file, ORDWR, 0600);
}
static int
mklock(char *file)
{
int fd, try;
Dir *dir;
fd = openlock(file);
if (fd >= 0) {
/* make it a lock file if it wasn't */
dir = dirfstat(fd);
if (dir == nil)
error("%s vanished: %r", file);
dir->mode |= DMEXCL;
dir->qid.type |= QTEXCL;
dirfwstat(fd, dir);
free(dir);
/* reopen in case it wasn't a lock file at last open */
close(fd);
}
for (try = 0; try < 65 && (fd = openlock(file)) < 0; try++)
sleep(10*1000);
return fd;
}
void
main(int argc, char *argv[])
{
Job *j;
Tm tm;
Time t;
ulong now, last; /* in seconds */
int i, lock;
debug = 0;
ARGBEGIN{
case 'c':
createuser();
exits(0);
case 'd':
debug = 1;
break;
default:
usage();
}ARGEND
if(debug){
readalljobs();
printjobs();
exits(0);
}
initcap(); /* do this early, before cpurc removes it */
switch(fork()){
case -1:
fatal("can't fork: %r");
case 0:
break;
default:
exits(0);
}
/*
* it can take a few minutes before the file server notices that
* we've rebooted and gives up the lock.
*/
lock = mklock("/cron/lock");
if (lock < 0)
fatal("cron already running: %r");
argv0 = "cron";
last = time(0);
for(;;){
readalljobs();
/*
* the system's notion of time may have jumped forward or
* backward an arbitrary amount since the last call to time().
*/
now = time(0);
/*
* if time has jumped backward, just note it and adapt.
* if time has jumped forward more than a day,
* just execute one day's jobs.
*/
if (now < last) {
clog("time went backward");
last = now;
} else if (now - last > Day) {
clog("time advanced more than a day");
last = now - Day;
}
now = minute(now);
for(last = minute(last); last <= now; last += Minute){
tm = *localtime(last);
t.min = 1ULL << tm.min;
t.hour = 1 << tm.hour;
t.wday = 1 << tm.wday;
t.mday = 1 << tm.mday;
t.mon = 1 << (tm.mon + 1);
for(i = 0; i < nuser; i++)
for(j = users[i].jobs; j; j = j->next)
if(j->time.min & t.min
&& j->time.hour & t.hour
&& j->time.wday & t.wday
&& j->time.mday & t.mday
&& j->time.mon & t.mon)
rexec(&users[i], j);
}
seek(lock, 0, 0);
write(lock, "x", 1); /* keep the lock alive */
/*
* if we're not at next minute yet, sleep until a second past
* (to allow for sleep intervals being approximate),
* which synchronises with minute roll-over as a side-effect.
*/
sleepuntil(now + Minute + 1);
}
/* not reached */
}
void
createuser(void)
{
Dir d;
char file[128], *user;
int fd;
user = getuser();
snprint(file, sizeof file, "/cron/%s", user);
fd = create(file, OREAD, 0755|DMDIR);
if(fd < 0)
fatal("couldn't create %s: %r", file);
nulldir(&d);
d.gid = user;
dirfwstat(fd, &d);
close(fd);
snprint(file, sizeof file, "/cron/%s/cron", user);
fd = create(file, OREAD, 0644);
if(fd < 0)
fatal("couldn't create %s: %r", file);
nulldir(&d);
d.gid = user;
dirfwstat(fd, &d);
close(fd);
}
void
readalljobs(void)
{
User *u;
Dir *d, *du;
char file[128];
int i, n, fd;
fd = open("/cron", OREAD);
if(fd < 0)
fatal("can't open /cron: %r");
while((n = dirread(fd, &d)) > 0){
for(i = 0; i < n; i++){
if(strcmp(d[i].name, "log") == 0 ||
!(d[i].qid.type & QTDIR))
continue;
if(strcmp(d[i].name, d[i].uid) != 0){
syslog(1, CRONLOG, "cron for %s owned by %s",
d[i].name, d[i].uid);
continue;
}
u = newuser(d[i].name);
snprint(file, sizeof file, "/cron/%s/cron", d[i].name);
du = dirstat(file);
if(du == nil || qidcmp(u->lastqid, du->qid) != 0){
freejobs(u->jobs);
u->jobs = readjobs(file, u);
}
free(du);
}
free(d);
}
close(fd);
}
/*
* parse user's cron file
* other lines: minute hour monthday month weekday host command
*/
Job *
readjobs(char *file, User *user)
{
Biobuf *b;
Job *j, *jobs;
Dir *d;
int line;
d = dirstat(file);
if(!d)
return nil;
b = Bopen(file, OREAD);
if(!b){
free(d);
return nil;
}
jobs = nil;
user->lastqid = d->qid;
free(d);
for(line = 1; savec = Brdline(b, '\n'); line++){
savec[Blinelen(b) - 1] = '\0';
while(*savec == ' ' || *savec == '\t')
savec++;
if(*savec == '#' || *savec == '\0')
continue;
if(strlen(savec) > 1024){
clog("%s: line %d: line too long", user->name, line);
continue;
}
j = emalloc(sizeof *j);
j->time.min = gettime(0, 59);
if(j->time.min && (j->time.hour = gettime(0, 23))
&& (j->time.mday = gettime(1, 31))
&& (j->time.mon = gettime(1, 12))
&& (j->time.wday = gettime(0, 6))
&& getname(&j->host)){
j->cmd = emalloc(strlen(savec) + 1);
strcpy(j->cmd, savec);
j->next = jobs;
jobs = j;
}else{
clog("%s: line %d: syntax error", user->name, line);
free(j);
}
}
Bterm(b);
return jobs;
}
void
printjobs(void)
{
char buf[8*1024];
Job *j;
int i;
for(i = 0; i < nuser; i++){
print("user %s\n", users[i].name);
for(j = users[i].jobs; j; j = j->next)
if(!mkcmd(j->cmd, buf, sizeof buf))
print("\tbad job %s on host %s\n",
j->cmd, j->host);
else
print("\tjob %s on host %s\n", buf, j->host);
}
}
User *
newuser(char *name)
{
int i;
for(i = 0; i < nuser; i++)
if(strcmp(users[i].name, name) == 0)
return &users[i];
if(nuser == maxuser){
maxuser += 32;
users = erealloc(users, maxuser * sizeof *users);
}
memset(&users[nuser], 0, sizeof(users[nuser]));
users[nuser].name = strdup(name);
users[nuser].jobs = 0;
users[nuser].lastqid.type = QTFILE;
users[nuser].lastqid.path = ~0LL;
users[nuser].lastqid.vers = ~0L;
return &users[nuser++];
}
void
freejobs(Job *j)
{
Job *next;
for(; j; j = next){
next = j->next;
free(j->cmd);
free(j->host);
free(j);
}
}
int
getname(char **namep)
{
int c;
char buf[64], *p;
if(!savec)
return 0;
while(*savec == ' ' || *savec == '\t')
savec++;
for(p = buf; (c = *savec) && c != ' ' && c != '\t'; p++){
if(p >= buf+sizeof buf -1)
return 0;
*p = *savec++;
}
*p = '\0';
*namep = strdup(buf);
if(*namep == 0){
clog("internal error: strdup failure");
_exits(0);
}
while(*savec == ' ' || *savec == '\t')
savec++;
return p > buf;
}
/*
* return the next time range (as a bit vector) in the file:
* times: '*'
* | range
* range: number
* | number '-' number
* | range ',' range
* a return of zero means a syntax error was discovered
*/
uvlong
gettime(int min, int max)
{
uvlong n, m, e;
if(gettok(min, max) == '*')
return ~0ULL;
n = 0;
while(tok == '1'){
m = 1ULL << lexval;
n |= m;
if(gettok(0, 0) == '-'){
if(gettok(lexval, max) != '1')
return 0;
e = 1ULL << lexval;
for( ; m <= e; m <<= 1)
n |= m;
gettok(min, max);
}
if(tok != ',')
break;
if(gettok(min, max) != '1')
return 0;
}
pushtok();
return n;
}
void
pushtok(void)
{
savec = savetok;
}
int
gettok(int min, int max)
{
char c;
savetok = savec;
if(!savec)
return tok = 0;
while((c = *savec) == ' ' || c == '\t')
savec++;
switch(c){
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
lexval = strtoul(savec, &savec, 10);
if(lexval < min || lexval > max)
return tok = 0;
return tok = '1';
case '*': case '-': case ',':
savec++;
return tok = c;
default:
return tok = 0;
}
}
/*
* convert command to run properly on the remote machine
* need to escape the quotes so they don't get stripped
*/
int
mkcmd(char *cmd, char *buf, int len)
{
char *p;
int n, m;
n = sizeof "exec rc -c '" -1;
if(n >= len)
return 0;
strcpy(buf, "exec rc -c '");
while(p = utfrune(cmd, L'\'')){
p++;
m = p - cmd;
if(n + m + 1 >= len)
return 0;
strncpy(&buf[n], cmd, m);
n += m;
buf[n++] = '\'';
cmd = p;
}
m = strlen(cmd);
if(n + m + sizeof "'</dev/null>/dev/null>[2=1]" >= len)
return 0;
strcpy(&buf[n], cmd);
strcpy(&buf[n+m], "'</dev/null>/dev/null>[2=1]");
return 1;
}
void
rexec(User *user, Job *j)
{
char buf[8*1024];
switch(rfork(RFPROC|RFNOWAIT|RFNAMEG|RFENVG|RFFDG)){
case 0:
break;
case -1:
clog("can't fork a job for %s: %r\n", user->name);
default:
return;
}
if(!mkcmd(j->cmd, buf, sizeof buf)){
clog("internal error: cmd buffer overflow");
_exits(0);
}
if(becomeuser(user->name) < 0){
clog("%s: can't change uid for %s on %s: %r",
user->name, j->cmd, j->host);
_exits(0);
}
clog("%s: ran '%s' on %s", user->name, j->cmd, j->host);
close(0);
close(1);
close(2);
open("/dev/null", OREAD);
open("/dev/null", OWRITE);
open("/dev/null", OWRITE);
if(strcmp(j->host, "local") == 0){
putenv("service", "rx");
execl("/bin/rc", "rc", "-lc", buf, nil);
} else {
execl("/bin/rx", "rx", j->host, buf, nil);
}
clog("%s: exec failed for %s on %s: %r", user->name, j->cmd, j->host);
_exits(0);
}
void *
emalloc(ulong n)
{
void *p;
if(p = mallocz(n, 1))
return p;
fatal("out of memory");
return 0;
}
void *
erealloc(void *p, ulong n)
{
if(p = realloc(p, n))
return p;
fatal("out of memory");
return 0;
}
void
usage(void)
{
fprint(2, "usage: cron [-c]\n");
exits("usage");
}
int
qidcmp(Qid a, Qid b)
{
/* might be useful to know if a > b, but not for cron */
return(a.path != b.path || a.vers != b.vers);
}
/*
* keep caphash fd open since opens of it could be disabled
*/
static int caphashfd;
void
initcap(void)
{
caphashfd = open("/dev/caphash", OCEXEC|OWRITE);
if(caphashfd < 0)
fprint(2, "%s: opening /dev/caphash: %r\n", argv0);
}
/*
* create a change uid capability
*/
char*
mkcap(char *from, char *to)
{
uchar rand[20];
char *cap;
char *key;
int nfrom, nto, ncap;
uchar hash[SHA1dlen];
if(caphashfd < 0)
return nil;
/* create the capability */
nto = strlen(to);
nfrom = strlen(from);
ncap = nfrom + 1 + nto + 1 + sizeof(rand)*3 + 1;
cap = emalloc(ncap);
snprint(cap, ncap, "%s@%s", from, to);
genrandom(rand, sizeof(rand));
key = cap+nfrom+1+nto+1;
enc64(key, sizeof(rand)*3, rand, sizeof(rand));
/* hash the capability */
hmac_sha1((uchar*)cap, strlen(cap), (uchar*)key, strlen(key), hash, nil);
/* give the kernel the hash */
key[-1] = '@';
if(write(caphashfd, hash, SHA1dlen) < 0){
free(cap);
return nil;
}
return cap;
}
int
usecap(char *cap)
{
int fd, rv;
fd = open("/dev/capuse", OCEXEC|OWRITE);
if(fd < 0)
return -1;
rv = write(fd, cap, strlen(cap));
close(fd);
return rv;
}
int
becomeuser(char *new)
{
char *cap;
int rv;
cap = mkcap(getuser(), new);
if(cap == nil)
return -1;
rv = usecap(cap);
free(cap);
newns(new, nil);
return rv;
}