/* backend.c -- IMAP server proxy for Cyrus Murder
 *
 * Copyright (c) 1998-2003 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any other legal
 *    details, please contact  
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: backend.c,v 1.14 2003/02/13 20:15:23 rjs3 Exp $ */

#include <config.h>

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <signal.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <syslog.h>
#include <com_err.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>

#include <sasl/sasl.h>
#include <sasl/saslutil.h>

#include "prot.h"
#include "backend.h"
#include "imapconf.h"
#include "xmalloc.h"
#include "iptostring.h"
#include "util.h"

/* In SASL 2.1.6 and prior, SASL_NEED_PROXY was not available, and thus 
 * proxyds could get a mechanism such as CRAM-MD5 which wouldn't convey the
 * authzid to the backend server, thus resulting in a proxyed connection as the
 * proxy user, and not as the real user */
#ifndef SASL_NEED_PROXY
#warning This version of the SASL library offers no way to ensure that we get a mechanism that allows proxying.
#define SASL_NEED_PROXY 0
#endif

static void get_capability(struct backend *s)
{
    static int cap_tag_num = 0;
    char tag[64];
    char resp[1024];
    int st = 0;

    cap_tag_num++;
    snprintf(tag, sizeof(tag), "C%d", cap_tag_num);

    prot_printf(s->out, "%s Capability\r\n",tag);
    do {
	if (!prot_fgets(resp, sizeof(resp), s->in)) return;
	if (!strncasecmp(resp, "* Capability ", 13)) {
	    st++; /* increment state */
	    if (strstr(resp, "IDLE")) s->capability |= IDLE;
	    if (strstr(resp, "MUPDATE")) s->capability |= MUPDATE;
	} else {
	    /* line we weren't expecting. hmmm. */
	}
    } while (st == 0);
    do {
	if (!prot_fgets(resp, sizeof(resp), s->in)) return;
	if (!strncmp(resp, tag, strlen(tag))) {
	    st++; /* increment state */
	} else {
	    /* line we weren't expecting. hmmm. */
	}
    } while (st == 1);
}

static int mysasl_getauthline(struct protstream *p, char *tag,
			      char **line, unsigned int *linelen)
{
    char buf[2096];
    char *str = (char *) buf;
    
    if (!prot_fgets(str, sizeof(buf), p)) {
	return SASL_FAIL;
    }
    if (!strncmp(str, tag, strlen(tag))) {
	str += strlen(tag) + 1;
	if (!strncasecmp(str, "OK ", 3)) { return SASL_OK; }
	if (!strncasecmp(str, "NO ", 3)) { return SASL_BADAUTH; }
	return SASL_FAIL; /* huh? */
    } else if (str[0] == '+' && str[1] == ' ') {
	unsigned buflen;
	str += 2; /* jump past the "+ " */

	buflen = strlen(str) + 1;

	*line = xmalloc(buflen);
	if (*str != '\r') {	/* decode it */
	    int r;
	    
	    r = sasl_decode64(str, strlen(str), *line, buflen, linelen);
	    if (r != SASL_OK) {
		return r;
	    }
	    
	    return SASL_CONTINUE;
	} else {		/* blank challenge */
	    *line = NULL;
	    *linelen = 0;

	    return SASL_CONTINUE;
	}
    } else {
	/* huh??? */
	return SASL_FAIL;
    }
}

static char *parsemechlist(char *str)
{
    char *tmp;
    int num=0;
    char *ret=xmalloc(strlen(str)+1);
    
    ret[0] = '\0';
    
    while ((tmp=strstr(str,"AUTH="))!=NULL)
    {
	char *end=tmp+5;
	tmp+=5;
	
	while(((*end)!=' ') && ((*end)!='\0'))
	    end++;
	
	(*end)='\0';
	
	/* add entry to list */
	if (num>0)
	    strcat(ret," ");
	strcat(ret, tmp);
	num++;
	
	/* reset the string */
	str=end+1;
    }
    
    return ret;
}

static char *ask_capability(struct protstream *pout, struct protstream *pin)
{
    char str[4096];
    char *ret;
    
    /* request capabilities of server */
    prot_printf(pout, "C01 CAPABILITY\r\n");
    prot_flush(pout);
    
    do { /* look for the * CAPABILITY response */
	if (prot_fgets(str,sizeof(str),pin) == NULL) {
	    return NULL;
	}
    } while (strncasecmp(str, "* CAPABILITY", 12));
    
    ret=parsemechlist(str);
    
    do { /* look for TAG */
	if (prot_fgets(str, sizeof(str), pin) == NULL) {
	    free(ret);
	    return NULL;
	}
    } while (strncmp(str, "C01", strlen("C01")));
    
    return ret;
}

extern sasl_callback_t *mysasl_callbacks(const char *username,
					 const char *authname,
					 const char *realm,
					 const char *password);
extern void free_callbacks(sasl_callback_t *in);

static int backend_authenticate(struct backend *s, const char *userid)
{
    int r;
    sasl_security_properties_t *secprops = NULL;
    struct sockaddr_storage saddr_l, saddr_r;
    char remoteip[60], localip[60];
    socklen_t addrsize;
    sasl_callback_t *cb;
    char buf[2048];
    char optstr[128];
    char *in, *p;
    const char *out;
    unsigned int inlen, outlen;
    const char *mech_conf, *mechusing;
    char *mechlist;
    unsigned b64len;
    const char *pass;

    strcpy(optstr, s->hostname);
    p = strchr(optstr, '.');
    if (p) *p = '\0';
    strcat(optstr, "_password");
    pass = config_getstring(optstr, NULL);
    cb = mysasl_callbacks(userid, 
			  config_getstring("proxy_authname", "proxy"),
			  config_getstring("proxy_realm", NULL),
			  pass);

    /* set the IP addresses */
    addrsize=sizeof(struct sockaddr_storage);
    if (getpeername(s->sock, (struct sockaddr *)&saddr_r, &addrsize) != 0)
	return SASL_FAIL;
    if(iptostring((struct sockaddr *)&saddr_r, addrsize, remoteip, 60) != 0)
	return SASL_FAIL;
  
    addrsize=sizeof(struct sockaddr_storage);
    if (getsockname(s->sock, (struct sockaddr *)&saddr_l, &addrsize)!=0)
	return SASL_FAIL;
    if(iptostring((struct sockaddr *)&saddr_l, addrsize, localip, 60) != 0)
	return SASL_FAIL;

    /* Require proxying if we have an "interesting" userid (authzid) */
    r = sasl_client_new("imap", s->hostname, localip, remoteip,
			cb, (userid  && *userid ? SASL_NEED_PROXY : 0),
			&s->saslconn);
    if (r != SASL_OK) {
	return r;
    }

    secprops = mysasl_secprops(0);
    r = sasl_setprop(s->saslconn, SASL_SEC_PROPS, secprops);
    if (r != SASL_OK) {
	return r;
    }

    /* read the initial greeting */
    if (!prot_fgets(buf, sizeof(buf), s->in)) {
	syslog(LOG_ERR,
	       "backend_authenticate(): couldn't read initial greeting: %s",
	       s->in->error ? s->in->error : "(null)");
	return SASL_FAIL;
    }

    /* Get SASL mechanism list */
    /* We can force a particular mechanism using a <shorthost>_mechs option */
    strcpy(buf, s->hostname);
    p = strchr(buf, '.');
    if (p) *p = '\0';
    strcat(buf, "_mechs");
    mech_conf = config_getstring(buf, NULL);
    
    /* If we don't have a mech_conf, ask the server what it can do */
    if(!mech_conf) {
	mechlist = ask_capability(s->out, s->in);
    } else {
	mechlist = xstrdup(mech_conf);
    }

    /* we now do the actual SASL exchange */
    r = sasl_client_start(s->saslconn, mechlist,
			  NULL, NULL, NULL, &mechusing);

    /* garbage collect */
    free(mechlist);
    mechlist = NULL;

    if ((r != SASL_OK) && (r != SASL_CONTINUE)) {
	return r;
    }
    prot_printf(s->out, "A01 AUTHENTICATE %s\r\n", mechusing);

    in = NULL;
    inlen = 0;
    r = mysasl_getauthline(s->in, "A01", &in, &inlen);
    while (r == SASL_CONTINUE) {
	r = sasl_client_step(s->saslconn, in, inlen, NULL, &out, &outlen);
	if (in) { 
	    free(in);
	}
	if (r != SASL_OK && r != SASL_CONTINUE) {
	    return r;
	}

	r = sasl_encode64(out, outlen, buf, sizeof(buf), &b64len);
	if (r != SASL_OK) {
	    return r;
	}

	prot_write(s->out, buf, b64len);
	prot_printf(s->out, "\r\n");

	r = mysasl_getauthline(s->in, "A01", &in, &inlen);
    }

    /* xxx unclear that this is correct */
    free_callbacks(cb);

    if (r == SASL_OK) {
	prot_setsasl(s->in, s->saslconn);
	prot_setsasl(s->out, s->saslconn);
    }

    /* r == SASL_OK on success */
    return r;
}

struct backend *findserver(struct backend *ret, const char *server,
			   const char *userid) 
{
    /* need to (re)establish connection to server or create one */
    int sock = -1;
    int r;
    int err;
    struct addrinfo hints, *res0 = NULL, *res;

    if (!ret) {
	ret = xmalloc(sizeof(struct backend));
	memset(ret, 0, sizeof(struct backend));
	strlcpy(ret->hostname, server, sizeof(ret->hostname));
	ret->timeout = NULL;
    }

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = PF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    err = getaddrinfo(server, "143", &hints, &res0);
    if (err) {
	syslog(LOG_ERR, "getaddrinfo(%s) failed: %s",
	       server, gai_strerror(err));
	free(ret);
	return NULL;
    }
    for (res = res0; res; res = res->ai_next) {
	sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
	if (sock < 0)
	    continue;
	if (connect(sock, res->ai_addr, res->ai_addrlen) >= 0)
	    break;
	close(sock);
	sock = -1;
    }
    if (sock < 0) {
	freeaddrinfo(res0);
	syslog(LOG_ERR, "connect(%s) failed: %m", server);
	free(ret);
	return NULL;
    }
    memcpy(&ret->addr, res->ai_addr, res->ai_addrlen);
    freeaddrinfo(res0);
    
    ret->in = prot_new(sock, 0);
    ret->out = prot_new(sock, 1);
    ret->sock = sock;
    prot_setflushonread(ret->in, ret->out);
    
    /* now need to authenticate to backend server */
    if ((r = backend_authenticate(ret,userid))) {
	syslog(LOG_ERR, "couldn't authenticate to backend server: %s",
	       sasl_errstring(r, NULL, NULL));
	free(ret);
        close(sock);
	return NULL;
    }
    
    /* find the capabilities of the server */
    get_capability(ret);
    
    return ret;
}

void downserver(struct backend *s) 
{
    char buf[1024];
    if(!s) return;
    
    prot_printf(s->out, "L01 LOGOUT\r\n");
    prot_flush(s->out);

    while (prot_fgets(buf, sizeof(buf), s->in)) {
	if (!strncmp("L01", buf, 3)) {
	    break;
	}
	if (!strncmp("* BAD", buf, 5)) {
	    syslog(LOG_ERR, "got BAD in response to LOGOUT command sent to %s",
		   s->hostname);
	    break;
	}
    }

    /* Flush the incoming buffer */
    prot_NONBLOCK(s->in);
    prot_fill(s->in);

    /* close/free socket & prot layer */
    cyrus_close_sock(s->sock);
    s->sock = -1;
    
    prot_free(s->in);
    prot_free(s->out);
    s->in = s->out = NULL;

    /* Free saslconn */
    if(s->saslconn) {
	sasl_dispose(&(s->saslconn));
	s->saslconn = NULL;
    }
}