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/*

 * Various files from /sys/src/cmd/auth/secstore, just enough

 * to download a file at boot time.

 */

#include "dat.h"

#include <ip.h>

enum{ CHK = 16};

enum{ MAXFILESIZE = 10*1024*1024 };

enum{// PW status bits

	Enabled 	= (1<<0),

	STA 		= (1<<1),	// extra SecurID step

};

static char testmess[] = "__secstore\tPAK\nC=%s\nm=0\n";

int

havesecstore(void)

{

	int m, n, fd;

	uchar buf[500];

	n = snprint((char*)buf, sizeof buf, testmess, owner);

	hnputs(buf, 0x8000+n-2);

	fd = secdial();

	if(fd < 0)

		return 0;

	if(write(fd, buf, n) != n || readn(fd, buf, 2) != 2){

		close(fd);

		return 0;

	}

	n = ((buf[0]&0x7f)<<8) + buf[1];

	if(n+1 > sizeof buf){

		werrstr("implausibly large count %d", n);

		close(fd);

		return 0;

	}

	m = readn(fd, buf, n);

	close(fd);

	if(m != n){

		if(m >= 0)

			werrstr("short read from secstore");

		return 0;

	}

	buf[n] = 0;

	if(strcmp((char*)buf, "!account expired") == 0){

		werrstr("account expired");

		return 0;

	}

	return strcmp((char*)buf, "!account exists") == 0;

}

// delimited, authenticated, encrypted connection

enum{ Maxmsg=4096 };	// messages > Maxmsg bytes are truncated

typedef struct SConn SConn;

extern SConn* newSConn(int);	// arg is open file descriptor

struct SConn{

	void *chan;

	int secretlen;

	int (*secret)(SConn*, uchar*, int);// 

	int (*read)(SConn*, uchar*, int); // <0 if error;  errmess in buffer

	int (*write)(SConn*, uchar*, int);

	void (*free)(SConn*);		// also closes file descriptor

};

// secret(s,b,dir) sets secret for digest, encrypt, using the secretlen

//		bytes in b to form keys 	for the two directions;

//	  set dir=0 in client, dir=1 in server

// error convention: write !message in-band

#define readstr secstore_readstr

static void writerr(SConn*, char*);

static int readstr(SConn*, char*);  // call with buf of size Maxmsg+1

	// returns -1 upon error, with error message in buf

typedef struct ConnState {

	uchar secret[SHA1dlen];

	ulong seqno;

	RC4state rc4;

} ConnState;

typedef struct SS{

	int fd;		// file descriptor for read/write of encrypted data

	int alg;	// if nonzero, "alg sha rc4_128"

	ConnState in, out;

} SS;

static int

SC_secret(SConn *conn, uchar *sigma, int direction)

{

	SS *ss = (SS*)(conn->chan);

	int nsigma = conn->secretlen;

	if(direction != 0){

		hmac_sha1(sigma, nsigma, (uchar*)"one", 3, ss->out.secret, nil);

		hmac_sha1(sigma, nsigma, (uchar*)"two", 3, ss->in.secret, nil);

	}else{

		hmac_sha1(sigma, nsigma, (uchar*)"two", 3, ss->out.secret, nil);

		hmac_sha1(sigma, nsigma, (uchar*)"one", 3, ss->in.secret, nil);

	}

	setupRC4state(&ss->in.rc4, ss->in.secret, 16); // restrict to 128 bits

	setupRC4state(&ss->out.rc4, ss->out.secret, 16);

	ss->alg = 1;

	return 0;

}

static void

hash(uchar secret[SHA1dlen], uchar *data, int len, int seqno, uchar d[SHA1dlen])

{

	DigestState sha;

	uchar seq[4];

	seq[0] = seqno>>24;

	seq[1] = seqno>>16;

	seq[2] = seqno>>8;

	seq[3] = seqno;

	memset(&sha, 0, sizeof sha);

	sha1(secret, SHA1dlen, nil, &sha);

	sha1(data, len, nil, &sha);

	sha1(seq, 4, d, &sha);

}

static int

verify(uchar secret[SHA1dlen], uchar *data, int len, int seqno, uchar d[SHA1dlen])

{

	DigestState sha;

	uchar seq[4];

	uchar digest[SHA1dlen];

	seq[0] = seqno>>24;

	seq[1] = seqno>>16;

	seq[2] = seqno>>8;

	seq[3] = seqno;

	memset(&sha, 0, sizeof sha);

	sha1(secret, SHA1dlen, nil, &sha);

	sha1(data, len, nil, &sha);

	sha1(seq, 4, digest, &sha);

	return memcmp(d, digest, SHA1dlen);

}

static int

SC_read(SConn *conn, uchar *buf, int n)

{

	SS *ss = (SS*)(conn->chan);

	uchar count[2], digest[SHA1dlen];

	int len, nr;

	if(read(ss->fd, count, 2) != 2 || count[0]&0x80 == 0){

		werrstr("!SC_read invalid count");

		return -1;

	}

	len = (count[0]&0x7f)<<8 | count[1];	// SSL-style count; no pad

	if(ss->alg){

		len -= SHA1dlen;

		if(len <= 0 || readn(ss->fd, digest, SHA1dlen) != SHA1dlen){

			werrstr("!SC_read missing sha1");

			return -1;

		}

		if(len > n || readn(ss->fd, buf, len) != len){

			werrstr("!SC_read missing data");

			return -1;

		}

		rc4(&ss->in.rc4, digest, SHA1dlen);

		rc4(&ss->in.rc4, buf, len);

		if(verify(ss->in.secret, buf, len, ss->in.seqno, digest) != 0){

			werrstr("!SC_read integrity check failed");

			return -1;

		}

	}else{

		if(len <= 0 || len > n){

			werrstr("!SC_read implausible record length");

			return -1;

		}

		if( (nr = readn(ss->fd, buf, len)) != len){

			werrstr("!SC_read expected %d bytes, but got %d", len, nr);

			return -1;

		}

	}

	ss->in.seqno++;

	return len;

}

static int

SC_write(SConn *conn, uchar *buf, int n)

{

	SS *ss = (SS*)(conn->chan);

	uchar count[2], digest[SHA1dlen], enc[Maxmsg+1];

	int len;

	if(n <= 0 || n > Maxmsg+1){

		werrstr("!SC_write invalid n %d", n);

		return -1;

	}

	len = n;

	if(ss->alg)

		len += SHA1dlen;

	count[0] = 0x80 | len>>8;

	count[1] = len;

	if(write(ss->fd, count, 2) != 2){

		werrstr("!SC_write invalid count");

		return -1;

	}

	if(ss->alg){

		hash(ss->out.secret, buf, n, ss->out.seqno, digest);

		rc4(&ss->out.rc4, digest, SHA1dlen);

		memcpy(enc, buf, n);

		rc4(&ss->out.rc4, enc, n);

		if(write(ss->fd, digest, SHA1dlen) != SHA1dlen ||

				write(ss->fd, enc, n) != n){

			werrstr("!SC_write error on send");

			return -1;

		}

	}else{

		if(write(ss->fd, buf, n) != n){

			werrstr("!SC_write error on send");

			return -1;

		}

	}

	ss->out.seqno++;

	return n;

}

static void

SC_free(SConn *conn)

{

	SS *ss = (SS*)(conn->chan);

	close(ss->fd);

	free(ss);

	free(conn);

}

SConn*

newSConn(int fd)

{

	SS *ss;

	SConn *conn;

	if(fd < 0)

		return nil;

	ss = (SS*)emalloc(sizeof(*ss));

	conn = (SConn*)emalloc(sizeof(*conn));

	ss->fd  = fd;

	ss->alg = 0;

	conn->chan = (void*)ss;

	conn->secretlen = SHA1dlen;

	conn->free = SC_free;

	conn->secret = SC_secret;

	conn->read = SC_read;

	conn->write = SC_write;

	return conn;

}

static void

writerr(SConn *conn, char *s)

{

	char buf[Maxmsg];

	snprint(buf, Maxmsg, "!%s", s);

	conn->write(conn, (uchar*)buf, strlen(buf));

}

static int

readstr(SConn *conn, char *s)

{

	int n;

	n = conn->read(conn, (uchar*)s, Maxmsg);

	if(n >= 0){

		s[n] = 0;

		if(s[0] == '!'){

			memmove(s, s+1, n);

			n = -1;

		}

	}else{

		strcpy(s, "read error");

	}

	return n;

}

static int

getfile(SConn *conn, uchar *key, int nkey)

{

	char *buf;

	int nbuf, n, nr, len;

	char s[Maxmsg+1], *gf, *p, *q;

	uchar skey[SHA1dlen], ib[Maxmsg+CHK], *ibr, *ibw;

	AESstate aes;

	DigestState *sha;

	gf = "factotum";

	memset(&aes, 0, sizeof aes);

	snprint(s, Maxmsg, "GET %s\n", gf);

	conn->write(conn, (uchar*)s, strlen(s));

	/* get file size */

	s[0] = '\0';

	if(readstr(conn, s) < 0){

		werrstr("secstore: %r");

		return -1;

	}

	if((len = atoi(s)) < 0){

		werrstr("secstore: remote file %s does not exist", gf);

		return -1;

	}else if(len > MAXFILESIZE){//assert

		werrstr("secstore: implausible file size %d for %s", len, gf);

		return -1;

	}

	ibr = ibw = ib;

	buf = nil;

	nbuf = 0;

	for(nr=0; nr < len;){

		if((n = conn->read(conn, ibw, Maxmsg)) <= 0){

			werrstr("secstore: empty file chunk n=%d nr=%d len=%d: %r", n, nr, len);

			return -1;

		}

		nr += n;

		ibw += n;

		if(!aes.setup){ /* first time, read 16 byte IV */

			if(n < 16){

				werrstr("secstore: no IV in file");

				return -1;

			}

			sha = sha1((uchar*)"aescbc file", 11, nil, nil);

			sha1(key, nkey, skey, sha);

			setupAESstate(&aes, skey, AESbsize, ibr);

			memset(skey, 0, sizeof skey);

			ibr += AESbsize;

			n -= AESbsize;

		}

		aesCBCdecrypt(ibw-n, n, &aes);

		n = ibw-ibr-CHK;

		if(n > 0){

			buf = erealloc(buf, nbuf+n+1);

			memmove(buf+nbuf, ibr, n);

			nbuf += n;

			ibr += n;

		}

		memmove(ib, ibr, ibw-ibr);

		ibw = ib + (ibw-ibr);

		ibr = ib;

	}

	n = ibw-ibr;

	if((n != CHK) || (memcmp(ib, "XXXXXXXXXXXXXXXX", CHK) != 0)){

		werrstr("secstore: decrypted file failed to authenticate!");

		free(buf);

		return -1;

	}

	if(nbuf == 0){

		werrstr("secstore got empty file");

		return -1;

	}

	buf[nbuf] = '\0';

	p = buf;

	n = 0;

	while(p){

		if(q = strchr(p, '\n'))

			*q++ = '\0';

		n++;

		if(ctlwrite(p, 0) < 0)

			fprint(2, "factotum: secstore(%s) line %d: %r\n", gf, n);

		p = q;

	}

	free(buf);

	return 0;

}

static char VERSION[] = "secstore";

typedef struct PAKparams{

	mpint *q, *p, *r, *g;

} PAKparams;

static PAKparams *pak;

// This group was generated by the seed EB7B6E35F7CD37B511D96C67D6688CC4DD440E1E.

static void

initPAKparams(void)

{

	if(pak)

		return;

	pak = (PAKparams*)emalloc(sizeof(*pak));

	pak->q = strtomp("E0F0EF284E10796C5A2A511E94748BA03C795C13", nil, 16, nil);

	pak->p = strtomp("C41CFBE4D4846F67A3DF7DE9921A49D3B42DC33728427AB159CEC8CBBD"

		"B12B5F0C244F1A734AEB9840804EA3C25036AD1B61AFF3ABBC247CD4B384224567A86"

		"3A6F020E7EE9795554BCD08ABAD7321AF27E1E92E3DB1C6E7E94FAAE590AE9C48F96D9"

		"3D178E809401ABE8A534A1EC44359733475A36A70C7B425125062B1142D", nil, 16, nil);

	pak->r = strtomp("DF310F4E54A5FEC5D86D3E14863921E834113E060F90052AD332B3241CEF"

		"2497EFA0303D6344F7C819691A0F9C4A773815AF8EAECFB7EC1D98F039F17A32A7E887"

		"D97251A927D093F44A55577F4D70444AEBD06B9B45695EC23962B175F266895C67D21"

		"C4656848614D888A4", nil, 16, nil);

	pak->g = strtomp("2F1C308DC46B9A44B52DF7DACCE1208CCEF72F69C743ADD4D2327173444"

		"ED6E65E074694246E07F9FD4AE26E0FDDD9F54F813C40CB9BCD4338EA6F242AB94CD41"

		"0E676C290368A16B1A3594877437E516C53A6EEE5493A038A017E955E218E7819734E3E"

		"2A6E0BAE08B14258F8C03CC1B30E0DDADFCF7CEDF0727684D3D255F1", nil, 16, nil);

}

// H = (sha(ver,C,sha(passphrase)))^r mod p,

// a hash function expensive to attack by brute force.

static void

longhash(char *ver, char *C, uchar *passwd, mpint *H)

{

	uchar *Cp;

	int i, n, nver, nC;

	uchar buf[140], key[1];

	nver = strlen(ver);

	nC = strlen(C);

	n = nver + nC + SHA1dlen;

	Cp = (uchar*)emalloc(n);

	memmove(Cp, ver, nver);

	memmove(Cp+nver, C, nC);

	memmove(Cp+nver+nC, passwd, SHA1dlen);

	for(i = 0; i < 7; i++){

		key[0] = 'A'+i;

		hmac_sha1(Cp, n, key, sizeof key, buf+i*SHA1dlen, nil);

	}

	memset(Cp, 0, n);

	free(Cp);

	betomp(buf, sizeof buf, H);

	mpmod(H, pak->p, H);

	mpexp(H, pak->r, pak->p, H);

}

// Hi = H^-1 mod p

static char *

PAK_Hi(char *C, char *passphrase, mpint *H, mpint *Hi)

{

	uchar passhash[SHA1dlen];

	sha1((uchar *)passphrase, strlen(passphrase), passhash, nil);

	initPAKparams();

	longhash(VERSION, C, passhash, H);

	mpinvert(H, pak->p, Hi);

	return mptoa(Hi, 64, nil, 0);

}

// another, faster, hash function for each party to

// confirm that the other has the right secrets.

static void

shorthash(char *mess, char *C, char *S, char *m, char *mu, char *sigma, char *Hi, uchar *digest)

{

	SHA1state *state;

	state = sha1((uchar*)mess, strlen(mess), 0, 0);

	state = sha1((uchar*)C, strlen(C), 0, state);

	state = sha1((uchar*)S, strlen(S), 0, state);

	state = sha1((uchar*)m, strlen(m), 0, state);

	state = sha1((uchar*)mu, strlen(mu), 0, state);

	state = sha1((uchar*)sigma, strlen(sigma), 0, state);

	state = sha1((uchar*)Hi, strlen(Hi), 0, state);

	state = sha1((uchar*)mess, strlen(mess), 0, state);

	state = sha1((uchar*)C, strlen(C), 0, state);

	state = sha1((uchar*)S, strlen(S), 0, state);

	state = sha1((uchar*)m, strlen(m), 0, state);

	state = sha1((uchar*)mu, strlen(mu), 0, state);

	state = sha1((uchar*)sigma, strlen(sigma), 0, state);

	sha1((uchar*)Hi, strlen(Hi), digest, state);

}

// On input, conn provides an open channel to the server;

//	C is the name this client calls itself;

//	pass is the user's passphrase

// On output, session secret has been set in conn

//	(unless return code is negative, which means failure).

//    If pS is not nil, it is set to the (alloc'd) name the server calls itself.

static int

PAKclient(SConn *conn, char *C, char *pass, char **pS)

{

	char *mess, *mess2, *eol, *S, *hexmu, *ks, *hexm, *hexsigma = nil, *hexHi;

	char kc[2*SHA1dlen+1];

	uchar digest[SHA1dlen];

	int rc = -1, n;

	mpint *x, *m = mpnew(0), *mu = mpnew(0), *sigma = mpnew(0);

	mpint *H = mpnew(0), *Hi = mpnew(0);

	hexHi = PAK_Hi(C, pass, H, Hi);

	// random 1<=x<=q-1; send C, m=g**x H

	x = mprand(164, genrandom, nil);

	mpmod(x, pak->q, x);

	if(mpcmp(x, mpzero) == 0)

		mpassign(mpone, x);

	mpexp(pak->g, x, pak->p, m);

	mpmul(m, H, m);

	mpmod(m, pak->p, m);

	hexm = mptoa(m, 64, nil, 0);

	mess = (char*)emalloc(2*Maxmsg+2);

	mess2 = mess+Maxmsg+1;

	snprint(mess, Maxmsg, "%s\tPAK\nC=%s\nm=%s\n", VERSION, C, hexm);

	conn->write(conn, (uchar*)mess, strlen(mess));

	// recv g**y, S, check hash1(g**xy)

	if(readstr(conn, mess) < 0){

		fprint(2, "factotum: error: %s\n", mess);

		writerr(conn, "couldn't read g**y");

		goto done;

	}

	eol = strchr(mess, '\n');

	if(strncmp("mu=", mess, 3) != 0 || !eol || strncmp("\nk=", eol, 3) != 0){

		writerr(conn, "verifier syntax error");

		goto done;

	}

	hexmu = mess+3;

	*eol = 0;

	ks = eol+3;

	eol = strchr(ks, '\n');

	if(!eol || strncmp("\nS=", eol, 3) != 0){

		writerr(conn, "verifier syntax error for secstore 1.0");

		goto done;

	}

	*eol = 0;

	S = eol+3;

	eol = strchr(S, '\n');

	if(!eol){

		writerr(conn, "verifier syntax error for secstore 1.0");

		goto done;

	}

	*eol = 0;

	if(pS)

		*pS = estrdup(S);

	strtomp(hexmu, nil, 64, mu);

	mpexp(mu, x, pak->p, sigma);

	hexsigma = mptoa(sigma, 64, nil, 0);

	shorthash("server", C, S, hexm, hexmu, hexsigma, hexHi, digest);

	enc64(kc, sizeof kc, digest, SHA1dlen);

	if(strcmp(ks, kc) != 0){

		writerr(conn, "verifier didn't match");

		goto done;

	}

	// send hash2(g**xy)

	shorthash("client", C, S, hexm, hexmu, hexsigma, hexHi, digest);

	enc64(kc, sizeof kc, digest, SHA1dlen);

	snprint(mess2, Maxmsg, "k'=%s\n", kc);

	conn->write(conn, (uchar*)mess2, strlen(mess2));

	// set session key

	shorthash("session", C, S, hexm, hexmu, hexsigma, hexHi, digest);

	memset(hexsigma, 0, strlen(hexsigma));

	n = conn->secret(conn, digest, 0);

	memset(digest, 0, SHA1dlen);

	if(n < 0){//assert

		writerr(conn, "can't set secret");

		goto done;

	}

	rc = 0;

done:

	mpfree(x);

	mpfree(sigma);

	mpfree(mu);

	mpfree(m);

	mpfree(Hi);

	mpfree(H);

	free(hexsigma);

	free(hexHi);

	free(hexm);

	free(mess);

	return rc;

}

int

secstorefetch(char *password)

{

	int rv = -1, fd;

	char s[Maxmsg+1];

	SConn *conn;

	char *pass, *sta;

	sta = nil;

	conn = nil;

	if(password != nil && *password)

		pass = estrdup(password);

	else

		pass = readcons("secstore password", nil, 1);

	if(pass==nil || strlen(pass)==0){

		werrstr("cancel");

		goto Out;

	}

	if((fd = secdial()) < 0)

		goto Out;

	if((conn = newSConn(fd)) == nil)

		goto Out;

	if(PAKclient(conn, owner, pass, nil) < 0){

		werrstr("password mistyped?");

		goto Out;

	}

	if(readstr(conn, s) < 0)

		goto Out;

	if(strcmp(s, "STA") == 0){

		sta = readcons("STA PIN+SecureID", nil, 1);

		if(sta==nil || strlen(sta)==0){

			werrstr("cancel");

			goto Out;

		}

		if(strlen(sta) >= sizeof s - 3){

			werrstr("STA response too long");

			goto Out;

		}

		strcpy(s+3, sta);

		conn->write(conn, (uchar*)s, strlen(s));

		readstr(conn, s);

	}

	if(strcmp(s, "OK") !=0){

		werrstr("%s", s);

		goto Out;

	}

	if(getfile(conn, (uchar*)pass, strlen(pass)) < 0)

		goto Out;

	conn->write(conn, (uchar*)"BYE", 3);

	rv = 0;

Out:

	if(conn)

		conn->free(conn);

	if(pass)

		free(pass);

	if(sta)

		free(sta);

	return rv;

}