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#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>
#include "SConn.h"
extern int verbose;
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){
snprint((char*)buf,n,"!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){
snprint((char*)buf,n,"!SC_read missing sha1");
return -1;
}
if(len > n || readn(ss->fd, buf, len) != len){
snprint((char*)buf,n,"!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){
snprint((char*)buf,n,"!SC_read integrity check failed");
return -1;
}
}else{
if(len <= 0 || len > n){
snprint((char*)buf,n,"!SC_read implausible record length");
return -1;
}
if( (nr = readn(ss->fd, buf, len)) != len){
snprint((char*)buf,n,"!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;
}
void
writerr(SConn *conn, char *s)
{
char buf[Maxmsg];
snprint(buf, Maxmsg, "!%s", s);
conn->write(conn, (uchar*)buf, strlen(buf));
}
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;
}
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