[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 = "htpub";
static char **childspec;
static uid_t minuid = 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);
    }
    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_APPEND)) >= 0) ||
       ((fd = open("/dev/null", 0)) >= 0)) {
	dup2(fd, 1);
	close(fd);
    }
    if(((fd = open(".ashd/error", 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) {
	    /* 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 usage(FILE *out)
{
    fprintf(out, "usage: userplex [-hI] [-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, "+hIg:m:d:")) >= 0) {
	switch(c) {
	case 'I':
	    ignore = 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;
	dirname = NULL;
    } else {
	bufinit(csbuf);
	bufadd(csbuf, "dirplex");
	bufadd(csbuf, dirname);
	bufadd(csbuf, NULL);
	childspec = csbuf.b;
    }
    signal(SIGCHLD, SIG_IGN);
    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
3b5e2f2d FT	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 = "htpub";
	47	static char **childspec;
	48	static uid_t minuid = 0;
	49	static struct user *users = NULL;
	50
	51	static void login(struct passwd *pwd)
	52	{
	53	int fd;
	54
	55	if(getuid() == 0) {
	56	if(initgroups(pwd->pw_name, pwd->pw_gid)) {
	57	flog(LOG_ERR, "could not init group list for %s: %s", pwd->pw_name, strerror(errno));
	58	exit(1);
	59	}
	60	if(setgid(pwd->pw_gid)) {
	61	flog(LOG_ERR, "could not switch group for %s: %s", pwd->pw_name, strerror(errno));
	62	exit(1);
	63	}
	64	if(setuid(pwd->pw_uid)) {
65	flog(LOG_ERR, "could not switch user to %s: %s", pwd->pw_name, strerror(errno));
66	exit(1);
67	}
68	} else {
69	if(getuid() != pwd->pw_uid)
70	exit(1);
71	}
72	if(chdir(pwd->pw_dir)) {
73	flog(LOG_ERR, "could not change to home directory for %s: %s", pwd->pw_name, strerror(errno));
74	exit(1);
75	}
76	putenv(sprintf2("HOME=%s", pwd->pw_dir));
77	putenv(sprintf2("SHELL=%s", pwd->pw_shell));
78	putenv(sprintf2("USER=%s", pwd->pw_name));
79	putenv(sprintf2("LOGNAME", pwd->pw_name));
80	/* There's whole load of other stuff one could want to do here --
81	* getting Kerberos credentials, running PAM session modules, and
82	* who knows what. I'll add them along as I find them useful. */
83	if(((fd = open(".ashd/output", O_APPEND)) >= 0) \|\|
84	((fd = open("/dev/null", 0)) >= 0)) {
85	dup2(fd, 1);
86	close(fd);
87	}
88	if(((fd = open(".ashd/error", O_APPEND)) >= 0) \|\|
89	((fd = open("/dev/null", 0)) >= 0)) {
90	dup2(fd, 2);
91	close(fd);
92	}
93	}
94
95	static void execchild(struct passwd *pwd)
96	{
97	if(!ignore)
98	execl(".ashd/handler", ".ashd/handler", NULL);
99	if(dirname != NULL) {
100	if(access(dirname, X_OK \| R_OK))
101	return;
102	}
103	execvp(childspec[0], childspec);
104	}
105
106	static int forkchild(char *usrnm)
107	{
108	struct passwd *pwd;
109	pid_t pid;
110	int i, fd[2];
111
112	/* XXX: There should be a way for the child to report errors (like
113	* 404 when htpub doesn't exist), but for now I don't bother with
114	* that. I might return to it at some later time. */
115	if(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fd))
116	return(-1);
117	if((pwd = getpwnam(usrnm)) == NULL) {
118	flog(LOG_ERR, "already discovered user `%s' has disappeared", usrnm);
119	return(-1);
120	}
121	if((pid = fork()) < 0)
122	return(-1);
123	if(pid == 0) {
124	for(i = 3; i < FD_SETSIZE; i++) {
125	if(i != fd[0])
126	close(i);
127	}
128	dup2(fd[0], 0);
129	close(fd[0]);
130	login(pwd);
131	execchild(pwd);
132	exit(127);
133	}
134	close(fd[0]);
135	return(fd[1]);
136	}
137
138	static void serve2(struct user usr, struct hthead req, int fd)
139	{
140	if(usr->fd < 0)
141	usr->fd = forkchild(usr->name);
142	if(sendreq(usr->fd, req, fd)) {
143	if(errno == EPIPE) {
144	/* Assume that the child has crashed and restart it. */
145	close(usr->fd);
146	usr->fd = forkchild(usr->name);
147	if(!sendreq(usr->fd, req, fd))
148	return;
149	}
150	flog(LOG_ERR, "could not pass on request to user `%s': %s", usr->name, strerror(errno));
151	close(usr->fd);
152	usr->fd = -1;
153	simpleerror(fd, 500, "User Error", "The request handler for that user keeps crashing.");
154	}
155	}
156
157	static void initnew(struct hthead req, int fd, char usrnm)
158	{
159	struct user *usr;
160	struct passwd *pwd;
161	struct group *grp;
162	int i, valid;
163
164	pwd = getpwnam(usrnm);
165	if(pwd == NULL) {
166	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
167	return;
168	}
169	if(pwd->pw_uid < minuid) {
170	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
171	return;
172	}
173	if(mgroup) {
174	if((grp = getgrnam(mgroup)) == NULL) {
175	flog(LOG_ERR, "unknown group %s specified to userplex", mgroup);
176	simpleerror(fd, 500, "Configuration Error", "The server has been erroneously configured.");
177	return;
178	}
179	valid = 0;
180	if(grp->gr_gid == pwd->pw_gid) {
181	valid = 1;
182	} else {
183	for(i = 0; grp->gr_mem[i] != NULL; i++) {
184	if(!strcmp(grp->gr_mem[i], usrnm)) {
185	valid = 1;
186	break;
187	}
188	}
189	}
190	if(!valid) {
191	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
192	return;
193	}
194	}
195	omalloc(usr);
196	usr->name = sstrdup(usrnm);
197	usr->fd = -1;
198	usr->next = users;
199	usr->prev = NULL;
200	if(users != NULL)
201	users->prev = usr;
202	users = usr;
203	serve2(usr, req, fd);
204	}
205
206	static void serve(struct hthead *req, int fd)
207	{
208	struct user *usr;
209	char usrnm, p;
210
211	if((p = strchr(req->rest, '/')) == NULL) {
212	if(*req->rest)
213	stdredir(req, fd, 301, sprintf3("%s/", req->url));
214	else
215	simpleerror(fd, 404, "Not Found", "No such resource could be found.");
216	return;
217	}
218	*(p++) = 0;
219	usrnm = sstrdup(req->rest);
220	replrest(req, p);
221	for(usr = users; usr != NULL; usr = usr->next) {
222	if(!strcmp(usr->name, usrnm)) {
223	serve2(usr, req, fd);
224	goto out;
225	}
226	}
227	initnew(req, fd, usrnm);
228
229	out:
230	free(usrnm);
231	}
232
233	static void usage(FILE *out)
234	{
b9e7ec7a	235	fprintf(out, "usage: userplex [-hI] [-g GROUP] [-m MIN-UID] [-d PUB-DIR] [PROGRAM ARGS...]\n");
3b5e2f2d FT	236	}
	237
	238	int main(int argc, char **argv)
	239	{
	240	struct hthead *req;
	241	int c;
	242	int fd;
	243	struct charvbuf csbuf;
	244
42384d2a	245	while((c = getopt(argc, argv, "+hIg:m:d:")) >= 0) {
3b5e2f2d FT	246	switch(c) {
	247	case 'I':
	248	ignore = 1;
	249	break;
	250	case 'm':
	251	if((minuid = atoi(optarg)) < 1) {
	252	fprintf(stderr, "userplex: argument to -m must be greater than 0\n");
	253	exit(1);
	254	}
	255	break;
	256	case 'g':
	257	mgroup = optarg;
	258	break;
	259	case 'd':
	260	dirname = optarg;
	261	break;
	262	case 'h':
	263	usage(stdout);
	264	exit(0);
	265	default:
	266	usage(stderr);
	267	exit(1);
	268	}
	269	}
	270	if(optind < argc) {
	271	childspec = argv + optind;
	272	dirname = NULL;
	273	} else {
	274	bufinit(csbuf);
	275	bufadd(csbuf, "dirplex");
	276	bufadd(csbuf, dirname);
	277	bufadd(csbuf, NULL);
	278	childspec = csbuf.b;
	279	}
	280	signal(SIGCHLD, SIG_IGN);
	281	while(1) {
	282	if((fd = recvreq(0, &req)) < 0) {
	283	if(errno != 0)
	284	flog(LOG_ERR, "recvreq: %s", strerror(errno));
	285	break;
	286	}
	287	serve(req, fd);
	288	freehthead(req);
	289	close(fd);
	290	}
	291	return(0);
	292	}