[ashd.git] / src / userplex.c

/*
    ashd - A Sane HTTP Daemon
    Copyright (C) 2008  Fredrik Tolf <fredrik@dolda2000.com>

    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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <errno.h>
#include <pwd.h>
#include <grp.h>

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <utils.h>
#include <log.h>
#include <req.h>
#include <resp.h>

struct user {
    struct user *next, *prev;
    char *name;
    int fd;
};

static int ignore = 0;
static char *mgroup = NULL;
static char *dirname = NULL;
static char **childspec;
static uid_t minuid = 0;
static int usesyslog = 0;
static struct user *users = NULL;

static void login(struct passwd *pwd)
{
    int fd;
    
    if(getuid() == 0) {
	if(initgroups(pwd->pw_name, pwd->pw_gid)) {
	    flog(LOG_ERR, "could not init group list for %s: %s", pwd->pw_name, strerror(errno));
	    exit(1);
	}
	if(setgid(pwd->pw_gid)) {
	    flog(LOG_ERR, "could not switch group for %s: %s", pwd->pw_name, strerror(errno));
	    exit(1);
	}
	if(setuid(pwd->pw_uid)) {
	    flog(LOG_ERR, "could not switch user to %s: %s", pwd->pw_name, strerror(errno));
	    exit(1);
	}
    } else {
	if(getuid() != pwd->pw_uid)
	    exit(1);
    }
    if(chdir(pwd->pw_dir)) {
	flog(LOG_ERR, "could not change to home directory for %s: %s", pwd->pw_name, strerror(errno));
	exit(1);
    }
    if(usesyslog)
	putenv("ASHD_USESYSLOG=1");
    else
	unsetenv("ASHD_USESYSLOG");
    putenv(sprintf2("HOME=%s", pwd->pw_dir));
    putenv(sprintf2("SHELL=%s", pwd->pw_shell));
    putenv(sprintf2("USER=%s", pwd->pw_name));
    putenv(sprintf2("LOGNAME", pwd->pw_name));
    /* There's whole load of other stuff one could want to do here --
     * getting Kerberos credentials, running PAM session modules, and
     * who knows what. I'll add them along as I find them useful. */
    if(((fd = open(".ashd/output", O_WRONLY | O_APPEND)) >= 0) ||
       ((fd = open("/dev/null", 0)) >= 0)) {
	dup2(fd, 1);
	close(fd);
    }
    if(((fd = open(".ashd/error", O_WRONLY | O_APPEND)) >= 0) ||
       ((fd = open("/dev/null", 0)) >= 0)) {
	dup2(fd, 2);
	close(fd);
    }
}

static void execchild(struct passwd *pwd)
{
    if(!ignore)
	execl(".ashd/handler", ".ashd/handler", NULL);
    if(dirname != NULL) {
	if(access(dirname, X_OK | R_OK))
	    return;
    }
    execvp(childspec[0], childspec);
}

static int forkchild(char *usrnm)
{
    struct passwd *pwd;
    pid_t pid;
    int i, fd[2];
    
    /* XXX: There should be a way for the child to report errors (like
     * 404 when htpub doesn't exist), but for now I don't bother with
     * that. I might return to it at some later time. */
    if(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fd))
	return(-1);
    if((pwd = getpwnam(usrnm)) == NULL) {
	flog(LOG_ERR, "already discovered user `%s' has disappeared", usrnm);
	return(-1);
    }
    if((pid = fork()) < 0)
	return(-1);
    if(pid == 0) {
	for(i = 3; i < FD_SETSIZE; i++) {
	    if(i != fd[0])
		close(i);
	}
	dup2(fd[0], 0);
	close(fd[0]);
	login(pwd);
	execchild(pwd);
	exit(127);
    }
    close(fd[0]);
    return(fd[1]);
}

static void serve2(struct user *usr, struct hthead *req, int fd)
{
    if(usr->fd < 0)
	usr->fd = forkchild(usr->name);
    if(sendreq(usr->fd, req, fd)) {
	if((errno == EPIPE) || (errno == ECONNRESET)) {
	    /* Assume that the child has crashed and restart it. */
	    close(usr->fd);
	    usr->fd = forkchild(usr->name);
	    if(!sendreq(usr->fd, req, fd))
		return;
	}
	flog(LOG_ERR, "could not pass on request to user `%s': %s", usr->name, strerror(errno));
	close(usr->fd);
	usr->fd = -1;
	simpleerror(fd, 500, "User Error", "The request handler for that user keeps crashing.");
    }
}

static void initnew(struct hthead *req, int fd, char *usrnm)
{
    struct user *usr;
    struct passwd *pwd;
    struct group *grp;
    int i, valid;

    pwd = getpwnam(usrnm);
    if(pwd == NULL) {
	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	return;
    }
    if(pwd->pw_uid < minuid) {
	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	return;
    }
    if(mgroup) {
	if((grp = getgrnam(mgroup)) == NULL) {
	    flog(LOG_ERR, "unknown group %s specified to userplex", mgroup);
	    simpleerror(fd, 500, "Configuration Error", "The server has been erroneously configured.");
	    return;
	}
	valid = 0;
	if(grp->gr_gid == pwd->pw_gid) {
	    valid = 1;
	} else {
	    for(i = 0; grp->gr_mem[i] != NULL; i++) {
		if(!strcmp(grp->gr_mem[i], usrnm)) {
		    valid = 1;
		    break;
		}
	    }
	}
	if(!valid) {
	    simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	    return;
	}
    }
    omalloc(usr);
    usr->name = sstrdup(usrnm);
    usr->fd = -1;
    usr->next = users;
    usr->prev = NULL;
    if(users != NULL)
	users->prev = usr;
    users = usr;
    serve2(usr, req, fd);
}

static void serve(struct hthead *req, int fd)
{
    struct user *usr;
    char *usrnm, *p;
    
    if((p = strchr(req->rest, '/')) == NULL) {
	if(*req->rest)
	    stdredir(req, fd, 301, sprintf3("%s/", req->url));
	else
	    simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	return;
    }
    *(p++) = 0;
    usrnm = sstrdup(req->rest);
    replrest(req, p);
    for(usr = users; usr != NULL; usr = usr->next) {
	if(!strcmp(usr->name, usrnm)) {
	    serve2(usr, req, fd);
	    goto out;
	}
    }
    initnew(req, fd, usrnm);
    
out:
    free(usrnm);
}

static void sighandler(int sig)
{
}

static void usage(FILE *out)
{
    fprintf(out, "usage: userplex [-hIs] [-g GROUP] [-m MIN-UID] [-d PUB-DIR] [PROGRAM ARGS...]\n");
}

int main(int argc, char **argv)
{
    struct hthead *req;
    int c;
    int fd;
    struct charvbuf csbuf;
    
    while((c = getopt(argc, argv, "+hIsg:m:d:")) >= 0) {
	switch(c) {
	case 'I':
	    ignore = 1;
	    break;
	case 's':
	    usesyslog = 1;
	    break;
	case 'm':
	    if((minuid = atoi(optarg)) < 1) {
		fprintf(stderr, "userplex: argument to -m must be greater than 0\n");
		exit(1);
	    }
	    break;
	case 'g':
	    mgroup = optarg;
	    break;
	case 'd':
	    dirname = optarg;
	    break;
	case 'h':
	    usage(stdout);
	    exit(0);
	default:
	    usage(stderr);
	    exit(1);
	}
    }
    if(optind < argc) {
	childspec = argv + optind;
    } else {
	if(dirname == NULL)
	    dirname = "htpub";
	bufinit(csbuf);
	bufadd(csbuf, "dirplex");
	bufadd(csbuf, dirname);
	bufadd(csbuf, NULL);
	childspec = csbuf.b;
    }
    signal(SIGCHLD, SIG_IGN);
    signal(SIGPIPE, sighandler);
    while(1) {
	if((fd = recvreq(0, &req)) < 0) {
	    if(errno != 0)
		flog(LOG_ERR, "recvreq: %s", strerror(errno));
	    break;
	}
	serve(req, fd);
	freehthead(req);
	close(fd);
    }
    return(0);
}
Commit	Line	Data
	1	/*
	2	ashd - A Sane HTTP Daemon
	3	Copyright (C) 2008 Fredrik Tolf <fredrik@dolda2000.com>
	4
	5	This program is free software: you can redistribute it and/or modify
	6	it under the terms of the GNU General Public License as published by
	7	the Free Software Foundation, either version 3 of the License, or
	8	(at your option) any later version.
	9
	10	This program is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	GNU General Public License for more details.
	14
	15	You should have received a copy of the GNU General Public License
	16	along with this program. If not, see <http://www.gnu.org/licenses/>.
	17	*/
	18
	19	#include <stdlib.h>
	20	#include <stdio.h>
	21	#include <unistd.h>
	22	#include <fcntl.h>
	23	#include <string.h>
	24	#include <signal.h>
	25	#include <sys/socket.h>
	26	#include <errno.h>
	27	#include <pwd.h>
	28	#include <grp.h>
	29
	30	#ifdef HAVE_CONFIG_H
	31	#include <config.h>
	32	#endif
	33	#include <utils.h>
	34	#include <log.h>
	35	#include <req.h>
	36	#include <resp.h>
	37
	38	struct user {
	39	struct user next, prev;
	40	char *name;
	41	int fd;
	42	};
	43
	44	static int ignore = 0;
	45	static char *mgroup = NULL;
	46	static char *dirname = NULL;
	47	static char **childspec;
	48	static uid_t minuid = 0;
	49	static int usesyslog = 0;
	50	static struct user *users = NULL;
	51
	52	static void login(struct passwd *pwd)
	53	{
	54	int fd;
	55
	56	if(getuid() == 0) {
	57	if(initgroups(pwd->pw_name, pwd->pw_gid)) {
	58	flog(LOG_ERR, "could not init group list for %s: %s", pwd->pw_name, strerror(errno));
	59	exit(1);
	60	}
	61	if(setgid(pwd->pw_gid)) {
	62	flog(LOG_ERR, "could not switch group for %s: %s", pwd->pw_name, strerror(errno));
	63	exit(1);
	64	}
	65	if(setuid(pwd->pw_uid)) {
	66	flog(LOG_ERR, "could not switch user to %s: %s", pwd->pw_name, strerror(errno));
	67	exit(1);
	68	}
	69	} else {
	70	if(getuid() != pwd->pw_uid)
	71	exit(1);
	72	}
	73	if(chdir(pwd->pw_dir)) {
	74	flog(LOG_ERR, "could not change to home directory for %s: %s", pwd->pw_name, strerror(errno));
	75	exit(1);
	76	}
	77	if(usesyslog)
	78	putenv("ASHD_USESYSLOG=1");
	79	else
	80	unsetenv("ASHD_USESYSLOG");
	81	putenv(sprintf2("HOME=%s", pwd->pw_dir));
	82	putenv(sprintf2("SHELL=%s", pwd->pw_shell));
	83	putenv(sprintf2("USER=%s", pwd->pw_name));
	84	putenv(sprintf2("LOGNAME", pwd->pw_name));
	85	/* There's whole load of other stuff one could want to do here --
	86	* getting Kerberos credentials, running PAM session modules, and
	87	* who knows what. I'll add them along as I find them useful. */
	88	if(((fd = open(".ashd/output", O_WRONLY \| O_APPEND)) >= 0) \|\|
	89	((fd = open("/dev/null", 0)) >= 0)) {
	90	dup2(fd, 1);
	91	close(fd);
	92	}
	93	if(((fd = open(".ashd/error", O_WRONLY \| O_APPEND)) >= 0) \|\|
	94	((fd = open("/dev/null", 0)) >= 0)) {
	95	dup2(fd, 2);
	96	close(fd);
	97	}
	98	}
	99
	100	static void execchild(struct passwd *pwd)
	101	{
	102	if(!ignore)
	103	execl(".ashd/handler", ".ashd/handler", NULL);
	104	if(dirname != NULL) {
	105	if(access(dirname, X_OK \| R_OK))
	106	return;
	107	}
	108	execvp(childspec[0], childspec);
	109	}
	110
	111	static int forkchild(char *usrnm)
	112	{
	113	struct passwd *pwd;
	114	pid_t pid;
	115	int i, fd[2];
	116
	117	/* XXX: There should be a way for the child to report errors (like
	118	* 404 when htpub doesn't exist), but for now I don't bother with
	119	* that. I might return to it at some later time. */
	120	if(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fd))
	121	return(-1);
	122	if((pwd = getpwnam(usrnm)) == NULL) {
	123	flog(LOG_ERR, "already discovered user `%s' has disappeared", usrnm);
	124	return(-1);
	125	}
	126	if((pid = fork()) < 0)
	127	return(-1);
	128	if(pid == 0) {
	129	for(i = 3; i < FD_SETSIZE; i++) {
	130	if(i != fd[0])
	131	close(i);
	132	}
	133	dup2(fd[0], 0);
	134	close(fd[0]);
	135	login(pwd);
	136	execchild(pwd);
	137	exit(127);
	138	}
	139	close(fd[0]);
	140	return(fd[1]);
	141	}
	142
	143	static void serve2(struct user usr, struct hthead req, int fd)
	144	{
	145	if(usr->fd < 0)
	146	usr->fd = forkchild(usr->name);
	147	if(sendreq(usr->fd, req, fd)) {
	148	if((errno == EPIPE) \|\| (errno == ECONNRESET)) {
	149	/* Assume that the child has crashed and restart it. */
	150	close(usr->fd);
	151	usr->fd = forkchild(usr->name);
	152	if(!sendreq(usr->fd, req, fd))
	153	return;
	154	}
	155	flog(LOG_ERR, "could not pass on request to user `%s': %s", usr->name, strerror(errno));
	156	close(usr->fd);
	157	usr->fd = -1;
	158	simpleerror(fd, 500, "User Error", "The request handler for that user keeps crashing.");
	159	}
	160	}
	161
	162	static void initnew(struct hthead req, int fd, char usrnm)
	163	{
	164	struct user *usr;
	165	struct passwd *pwd;
	166	struct group *grp;
	167	int i, valid;
	168
	169	pwd = getpwnam(usrnm);
	170	if(pwd == NULL) {
	171	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	172	return;
	173	}
	174	if(pwd->pw_uid < minuid) {
	175	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	176	return;
	177	}
	178	if(mgroup) {
	179	if((grp = getgrnam(mgroup)) == NULL) {
	180	flog(LOG_ERR, "unknown group %s specified to userplex", mgroup);
	181	simpleerror(fd, 500, "Configuration Error", "The server has been erroneously configured.");
	182	return;
	183	}
	184	valid = 0;
	185	if(grp->gr_gid == pwd->pw_gid) {
	186	valid = 1;
	187	} else {
	188	for(i = 0; grp->gr_mem[i] != NULL; i++) {
	189	if(!strcmp(grp->gr_mem[i], usrnm)) {
	190	valid = 1;
	191	break;
	192	}
	193	}
	194	}
	195	if(!valid) {
	196	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	197	return;
	198	}
	199	}
	200	omalloc(usr);
	201	usr->name = sstrdup(usrnm);
	202	usr->fd = -1;
	203	usr->next = users;
	204	usr->prev = NULL;
	205	if(users != NULL)
	206	users->prev = usr;
	207	users = usr;
	208	serve2(usr, req, fd);
	209	}
	210
	211	static void serve(struct hthead *req, int fd)
	212	{
	213	struct user *usr;
	214	char usrnm, p;
	215
	216	if((p = strchr(req->rest, '/')) == NULL) {
	217	if(*req->rest)
	218	stdredir(req, fd, 301, sprintf3("%s/", req->url));
	219	else
	220	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
	221	return;
	222	}
	223	*(p++) = 0;
	224	usrnm = sstrdup(req->rest);
	225	replrest(req, p);
	226	for(usr = users; usr != NULL; usr = usr->next) {
	227	if(!strcmp(usr->name, usrnm)) {
	228	serve2(usr, req, fd);
	229	goto out;
	230	}
	231	}
	232	initnew(req, fd, usrnm);
	233
	234	out:
	235	free(usrnm);
	236	}
	237
	238	static void sighandler(int sig)
	239	{
	240	}
	241
	242	static void usage(FILE *out)
	243	{
	244	fprintf(out, "usage: userplex [-hIs] [-g GROUP] [-m MIN-UID] [-d PUB-DIR] [PROGRAM ARGS...]\n");
	245	}
	246
	247	int main(int argc, char **argv)
	248	{
	249	struct hthead *req;
	250	int c;
	251	int fd;
	252	struct charvbuf csbuf;
	253
	254	while((c = getopt(argc, argv, "+hIsg:m:d:")) >= 0) {
	255	switch(c) {
	256	case 'I':
	257	ignore = 1;
	258	break;
	259	case 's':
	260	usesyslog = 1;
	261	break;
	262	case 'm':
	263	if((minuid = atoi(optarg)) < 1) {
	264	fprintf(stderr, "userplex: argument to -m must be greater than 0\n");
	265	exit(1);
	266	}
	267	break;
	268	case 'g':
	269	mgroup = optarg;
	270	break;
	271	case 'd':
	272	dirname = optarg;
	273	break;
	274	case 'h':
	275	usage(stdout);
	276	exit(0);
	277	default:
	278	usage(stderr);
	279	exit(1);
	280	}
	281	}
	282	if(optind < argc) {
	283	childspec = argv + optind;
	284	} else {
	285	if(dirname == NULL)
	286	dirname = "htpub";
	287	bufinit(csbuf);
	288	bufadd(csbuf, "dirplex");
	289	bufadd(csbuf, dirname);
	290	bufadd(csbuf, NULL);
	291	childspec = csbuf.b;
	292	}
	293	signal(SIGCHLD, SIG_IGN);
	294	signal(SIGPIPE, sighandler);
	295	while(1) {
	296	if((fd = recvreq(0, &req)) < 0) {
	297	if(errno != 0)
	298	flog(LOG_ERR, "recvreq: %s", strerror(errno));
	299	break;
	300	}
	301	serve(req, fd);
	302	freehthead(req);
	303	close(fd);
	304	}
	305	return(0);
	306	}