* Re: [9fans] nfactotum: mschap fix
2012-03-30 15:53 ` erik quanstrom
@ 2012-03-30 16:11 ` yaroslav
0 siblings, 0 replies; 4+ messages in thread
From: yaroslav @ 2012-03-30 16:11 UTC (permalink / raw)
To: quanstro; +Cc: 9fans
[-- Attachment #1: Type: text/plain, Size: 271 bytes --]
> surely you need to use the "user" attribute. if you don't please send
> a copy of chap that doesn't give compiler warnings.
The user attribute is available at the end of CR protocol, upon 'attr'
rpc request.
The attached chap.c compiles cleanly here.
- yk
[-- Attachment #2: chap.c --]
[-- Type: text/plain, Size: 8337 bytes --]
/*
* CHAP, MSCHAP
*
* The client does not authenticate the server, hence no CAI
*
* Protocol:
*
* S -> C: random 8-byte challenge
* C -> S: user in UTF-8
* C -> S: Chapreply or MSchapreply structure
* S -> C: ok or 'bad why'
*
* The chap protocol requires the client to give it id=%d, the id of
* the PPP message containing the challenge, which is used
* as part of the response. Because the client protocol is message-id
* specific, there is no point in looping to try multiple keys.
*
* The MS chap protocol actually uses two different hashes, an
* older insecure one called the LM (Lan Manager) hash, and a newer
* more secure one called the NT hash. By default we send back only
* the NT hash, because the LM hash can help an eavesdropper run
* a brute force attack. If the key has an lm attribute, then we send only the
* LM hash.
*/
#include "std.h"
#include "dat.h"
extern Proto chap, mschap;
enum {
ChapChallen = 8,
MShashlen = 16,
MSchallen = 8,
MSresplen = 24
};
static int
chapcheck(Key *k)
{
if(!strfindattr(k->attr, "user") || !strfindattr(k->privattr, "!password")){
werrstr("need user and !password attributes");
return -1;
}
return 0;
}
static void
nthash(uchar hash[MShashlen], char *passwd)
{
uchar buf[512];
int i;
for(i=0; *passwd && i<sizeof(buf); passwd++) {
buf[i++] = *passwd;
buf[i++] = 0;
}
memset(hash, 0, 16);
md4(buf, i, hash, 0);
}
static void
desencrypt(uchar data[8], uchar key[7])
{
ulong ekey[32];
key_setup(key, ekey);
block_cipher(ekey, data, 0);
}
static void
lmhash(uchar hash[MShashlen], char *passwd)
{
uchar buf[14];
char *stdtext = "KGS!@#$%";
int i;
strncpy((char*)buf, passwd, sizeof(buf));
for(i=0; i<sizeof(buf); i++)
if(buf[i] >= 'a' && buf[i] <= 'z')
buf[i] += 'A' - 'a';
memset(hash, 0, 16);
memcpy(hash, stdtext, 8);
memcpy(hash+8, stdtext, 8);
desencrypt(hash, buf);
desencrypt(hash+8, buf+7);
}
static void
mschalresp(uchar resp[MSresplen], uchar hash[MShashlen], uchar chal[MSchallen])
{
int i;
uchar buf[21];
memset(buf, 0, sizeof(buf));
memcpy(buf, hash, MShashlen);
for(i=0; i<3; i++) {
memmove(resp+i*MSchallen, chal, MSchallen);
desencrypt(resp+i*MSchallen, buf+i*7);
}
}
static int
chapclient(Conv *c)
{
int id, astype, nchal, npw, ret;
uchar *chal;
char *s, *pw, *res;
Attr *attr;
Key *k;
Chapreply cr;
MSchapreply mscr;
DigestState *ds;
ret = -1;
chal = nil;
res = nil;
k = nil;
attr = c->attr;
if(c->proto == &chap){
astype = AuthChap;
s = strfindattr(attr, "id");
if(s == nil || *s == 0){
werrstr("need id=n attr in start message");
goto out;
}
id = strtol(s, &s, 10);
if(*s != 0 || id < 0 || id >= 256){
werrstr("bad id=n attr in start message");
goto out;
}
cr.id = id;
}else if(c->proto == &mschap)
astype = AuthMSchap;
else{
werrstr("bad proto");
goto out;
}
c->state = "find key";
k = keyfetch(c, "%A %s", attr, c->proto->keyprompt);
if(k == nil)
goto out;
c->attr = addattrs(copyattr(attr), k->attr);
c->state = "read challenge";
if((nchal = convreadm(c, (char**)(void*)&chal)) < 0)
goto out;
if(strfindattr(k->attr, "user") == nil){
werrstr("key has no user (cannot happen?)");
goto out;
}
c->state = "write response";
if((pw = strfindattr(k->privattr, "!password")) == nil){
werrstr("key has no password (cannot happen?)");
goto out;
}
npw = strlen(pw);
if(astype == AuthChap){
ds = md5(&cr.id, 1, 0, 0);
md5((uchar*)pw, npw, 0, ds);
md5(chal, nchal, (uchar*)cr.resp, ds);
if(convwrite(c, &cr, sizeof cr) < 0)
goto out;
}else{
uchar hash[MShashlen];
memset(&mscr, 0, sizeof mscr);
if(strfindattr(k->attr, "lm")){
lmhash(hash, pw);
mschalresp((uchar*)mscr.LMresp, hash, chal);
}else{
nthash(hash, pw);
mschalresp((uchar*)mscr.NTresp, hash, chal);
}
if(convwrite(c, &mscr, sizeof mscr) < 0)
goto out;
}
c->state = "read result";
if(convreadm(c, &res) < 0)
goto out;
if(strcmp(res, "ok") == 0){
ret = 0;
werrstr("succeeded");
goto out;
}
if(strncmp(res, "bad ", 4) != 0){
werrstr("bad result: %s", res);
goto out;
}
c->state = "replace key";
keyevict(c, k, "%s", res+4);
werrstr("%s", res+4);
out:
free(res);
keyclose(k);
free(chal);
if(c->attr != attr)
freeattr(attr);
return ret;
}
/* shared with auth dialing routines */
typedef struct ServerState ServerState;
struct ServerState
{
int asfd;
Key *k;
Ticketreq tr;
Ticket t;
char *dom;
char *hostid;
};
static int chapchal(ServerState*, int, char[ChapChallen]);
static int chapresp(ServerState*, char*, char*);
static int
chapserver(Conv *c)
{
char chal[ChapChallen], *user, *resp;
ServerState s;
int astype, ret;
Attr *a;
ret = -1;
user = nil;
resp = nil;
memset(&s, 0, sizeof s);
s.asfd = -1;
if(c->proto == &chap)
astype = AuthChap;
else if(c->proto == &mschap)
astype = AuthMSchap;
else{
werrstr("bad proto");
goto out;
}
c->state = "find key";
if((s.k = plan9authkey(c->attr)) == nil)
goto out;
a = copyattr(s.k->attr);
a = delattr(a, "proto");
c->attr = addattrs(c->attr, a);
freeattr(a);
c->state = "authdial";
s.hostid = strfindattr(s.k->attr, "user");
s.dom = strfindattr(s.k->attr, "dom");
if((s.asfd = xioauthdial(nil, s.dom)) < 0){
werrstr("authdial %s: %r", s.dom);
goto out;
}
c->state = "authchal";
if(chapchal(&s, astype, chal) < 0)
goto out;
c->state = "write challenge";
if(convprint(c, "%s", chal) < 0)
goto out;
c->state = "read user";
if(convreadm(c, &user) < 0)
goto out;
c->state = "read response";
if(convreadm(c, &resp) < 0)
goto out;
c->state = "authwrite";
switch(chapresp(&s, user, resp)){
default:
fprint(2, "factotum: bad result from chapresp\n");
goto out;
case -1:
goto out;
case 0:
c->state = "write status";
if(convprint(c, "bad authentication failed") < 0)
goto out;
goto out;
case 1:
c->state = "write status";
if(convprint(c, "ok") < 0)
goto out;
goto ok;
}
ok:
ret = 0;
c->attr = addcap(c->attr, c->sysuser, &s.t);
out:
keyclose(s.k);
free(user);
free(resp);
/* xioclose(s.asfd); */
return ret;
}
static int
chapchal(ServerState *s, int astype, char chal[ChapChallen])
{
char trbuf[TICKREQLEN];
Ticketreq tr;
memset(&tr, 0, sizeof tr);
tr.type = astype;
if(strlen(s->hostid) >= sizeof tr.hostid){
werrstr("hostid too long");
return -1;
}
strcpy(tr.hostid, s->hostid);
if(strlen(s->dom) >= sizeof tr.authdom){
werrstr("domain too long");
return -1;
}
strcpy(tr.authdom, s->dom);
convTR2M(&tr, trbuf);
if(xiowrite(s->asfd, trbuf, TICKREQLEN) != TICKREQLEN)
return -1;
if(xioasrdresp(s->asfd, chal, ChapChallen) <= 5)
return -1;
s->tr = tr;
return 0;
}
static int
chapresp(ServerState *s, char *user, char *resp)
{
char tabuf[TICKETLEN+AUTHENTLEN];
char trbuf[TICKREQLEN];
int len;
Authenticator a;
Ticket t;
Ticketreq tr;
tr = s->tr;
if(memrandom(tr.chal, CHALLEN) < 0)
return -1;
if(strlen(user) >= sizeof tr.uid){
werrstr("uid too long");
return -1;
}
strcpy(tr.uid, user);
convTR2M(&tr, trbuf);
if(xiowrite(s->asfd, trbuf, TICKREQLEN) != TICKREQLEN)
return -1;
len = strlen(resp);
if(xiowrite(s->asfd, resp, len) != len)
return -1;
if(xioasrdresp(s->asfd, tabuf, TICKETLEN+AUTHENTLEN) != TICKETLEN+AUTHENTLEN)
return 0;
convM2T(tabuf, &t, s->k->priv);
if(t.num != AuthTs
|| memcmp(t.chal, tr.chal, sizeof tr.chal) != 0){
werrstr("key mismatch with auth server");
return -1;
}
convM2A(tabuf+TICKETLEN, &a, t.key);
if(a.num != AuthAc
|| memcmp(a.chal, tr.chal, sizeof a.chal) != 0
|| a.id != 0){
werrstr("key2 mismatch with auth server");
return -1;
}
s->t = t;
return 1;
}
static Role
chaproles[] =
{
"client", chapclient,
"server", chapserver,
0
};
Proto chap = {
"chap",
chaproles,
"user? !password?",
chapcheck
};
Proto mschap = {
"mschap",
chaproles,
"user? !password?",
chapcheck
};
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