freebsd-skq/sys/netinet/ip_ftp_pxy.c
2000-07-19 14:02:09 +00:00

766 lines
16 KiB
C

/*
* Simple FTP transparent proxy for in-kernel use. For use with the NAT
* code.
* $FreeBSD$
*/
#if SOLARIS && defined(_KERNEL)
extern kmutex_t ipf_rw;
#endif
#define isdigit(x) ((x) >= '0' && (x) <= '9')
#define isupper(x) (((unsigned)(x) >= 'A') && ((unsigned)(x) <= 'Z'))
#define islower(x) (((unsigned)(x) >= 'a') && ((unsigned)(x) <= 'z'))
#define isalpha(x) (isupper(x) || islower(x))
#define toupper(x) (isupper(x) ? (x) : (x) - 'a' + 'A')
#define IPF_FTP_PROXY
#define IPF_MINPORTLEN 18
#define IPF_MAXPORTLEN 30
#define IPF_MIN227LEN 39
#define IPF_MAX227LEN 51
#define IPF_FTPBUFSZ 96 /* This *MUST* be >= 53! */
int ippr_ftp_client __P((fr_info_t *, ip_t *, nat_t *, ftpinfo_t *, int));
int ippr_ftp_complete __P((char *, size_t));
int ippr_ftp_in __P((fr_info_t *, ip_t *, ap_session_t *, nat_t *));
int ippr_ftp_init __P((void));
int ippr_ftp_new __P((fr_info_t *, ip_t *, ap_session_t *, nat_t *));
int ippr_ftp_out __P((fr_info_t *, ip_t *, ap_session_t *, nat_t *));
int ippr_ftp_pasv __P((fr_info_t *, ip_t *, nat_t *, ftpside_t *, int));
int ippr_ftp_port __P((fr_info_t *, ip_t *, nat_t *, ftpside_t *, int));
int ippr_ftp_process __P((fr_info_t *, ip_t *, nat_t *, ftpinfo_t *, int));
int ippr_ftp_server __P((fr_info_t *, ip_t *, nat_t *, ftpinfo_t *, int));
int ippr_ftp_valid __P((char *, size_t));
u_short ippr_ftp_atoi __P((char **));
static frentry_t natfr;
int ippr_ftp_pasvonly = 0;
int ippr_ftp_insecure = 0;
/*
* Initialize local structures.
*/
int ippr_ftp_init()
{
bzero((char *)&natfr, sizeof(natfr));
natfr.fr_ref = 1;
natfr.fr_flags = FR_INQUE|FR_PASS|FR_QUICK|FR_KEEPSTATE;
return 0;
}
int ippr_ftp_new(fin, ip, aps, nat)
fr_info_t *fin;
ip_t *ip;
ap_session_t *aps;
nat_t *nat;
{
ftpinfo_t *ftp;
ftpside_t *f;
KMALLOC(ftp, ftpinfo_t *);
if (ftp == NULL)
return -1;
aps->aps_data = ftp;
aps->aps_psiz = sizeof(ftpinfo_t);
bzero((char *)ftp, sizeof(*ftp));
f = &ftp->ftp_side[0];
f->ftps_rptr = f->ftps_buf;
f->ftps_wptr = f->ftps_buf;
f = &ftp->ftp_side[1];
f->ftps_rptr = f->ftps_buf;
f->ftps_wptr = f->ftps_buf;
return 0;
}
int ippr_ftp_port(fin, ip, nat, f, dlen)
fr_info_t *fin;
ip_t *ip;
nat_t *nat;
ftpside_t *f;
int dlen;
{
tcphdr_t *tcp, tcph, *tcp2 = &tcph;
char newbuf[IPF_FTPBUFSZ], *s;
u_short a5, a6, sp, dp;
u_int a1, a2, a3, a4;
struct in_addr swip;
size_t nlen, olen;
fr_info_t fi;
int inc, off;
nat_t *ipn;
mb_t *m;
#if SOLARIS
mb_t *m1;
#endif
tcp = (tcphdr_t *)fin->fin_dp;
/*
* Check for client sending out PORT message.
*/
if (dlen < IPF_MINPORTLEN)
return 0;
off = fin->fin_hlen + (tcp->th_off << 2);
/*
* Skip the PORT command + space
*/
s = f->ftps_rptr + 5;
/*
* Pick out the address components, two at a time.
*/
a1 = ippr_ftp_atoi(&s);
if (!s)
return 0;
a2 = ippr_ftp_atoi(&s);
if (!s)
return 0;
/*
* check that IP address in the PORT/PASV reply is the same as the
* sender of the command - prevents using PORT for port scanning.
*/
a1 <<= 16;
a1 |= a2;
if (a1 != ntohl(nat->nat_inip.s_addr))
return 0;
a5 = ippr_ftp_atoi(&s);
if (!s)
return 0;
if (*s == ')')
s++;
/*
* check for CR-LF at the end.
*/
if (*s == '\n')
s--;
if ((*s == '\r') && (*(s + 1) == '\n')) {
s += 2;
a6 = a5 & 0xff;
} else
return 0;
a5 >>= 8;
/*
* Calculate new address parts for PORT command
*/
a1 = ntohl(ip->ip_src.s_addr);
a2 = (a1 >> 16) & 0xff;
a3 = (a1 >> 8) & 0xff;
a4 = a1 & 0xff;
a1 >>= 24;
olen = s - f->ftps_rptr;
/* DO NOT change this to sprintf! */
(void) sprintf(newbuf, "%s %u,%u,%u,%u,%u,%u\r\n",
"PORT", a1, a2, a3, a4, a5, a6);
nlen = strlen(newbuf);
inc = nlen - olen;
if ((inc + ip->ip_len) > 65535)
return 0;
#if SOLARIS
m = fin->fin_qfm;
for (m1 = m; m1->b_cont; m1 = m1->b_cont)
;
if ((inc > 0) && (m1->b_datap->db_lim - m1->b_wptr < inc)) {
mblk_t *nm;
/* alloc enough to keep same trailer space for lower driver */
nm = allocb(nlen, BPRI_MED);
PANIC((!nm),("ippr_ftp_out: allocb failed"));
nm->b_band = m1->b_band;
nm->b_wptr += nlen;
m1->b_wptr -= olen;
PANIC((m1->b_wptr < m1->b_rptr),
("ippr_ftp_out: cannot handle fragmented data block"));
linkb(m1, nm);
} else {
if (m1->b_datap->db_struiolim == m1->b_wptr)
m1->b_datap->db_struiolim += inc;
m1->b_datap->db_struioflag &= ~STRUIO_IP;
m1->b_wptr += inc;
}
copyin_mblk(m, off, nlen, newbuf);
#else
m = *((mb_t **)fin->fin_mp);
if (inc < 0)
m_adj(m, inc);
/* the mbuf chain will be extended if necessary by m_copyback() */
m_copyback(m, off, nlen, newbuf);
# ifdef M_PKTHDR
if (!(m->m_flags & M_PKTHDR))
m->m_pkthdr.len += inc;
# endif
#endif
if (inc != 0) {
#if SOLARIS || defined(__sgi)
register u_32_t sum1, sum2;
sum1 = ip->ip_len;
sum2 = ip->ip_len + inc;
/* Because ~1 == -2, We really need ~1 == -1 */
if (sum1 > sum2)
sum2--;
sum2 -= sum1;
sum2 = (sum2 & 0xffff) + (sum2 >> 16);
fix_outcksum(&ip->ip_sum, sum2, 0);
#endif
ip->ip_len += inc;
}
/*
* Add skeleton NAT entry for connection which will come back the
* other way.
*/
sp = htons(a5 << 8 | a6);
/*
* Don't allow the PORT command to specify a port < 1024 due to
* security crap.
*/
if (ntohs(sp) < 1024)
return 0;
/*
* The server may not make the connection back from port 20, but
* it is the most likely so use it here to check for a conflicting
* mapping.
*/
dp = htons(fin->fin_data[1] - 1);
ipn = nat_outlookup(fin->fin_ifp, IPN_TCP, nat->nat_p, nat->nat_inip,
ip->ip_dst, (dp << 16) | sp);
if (ipn == NULL) {
int slen;
slen = ip->ip_len;
ip->ip_len = fin->fin_hlen + sizeof(*tcp2);
bcopy((char *)fin, (char *)&fi, sizeof(fi));
bzero((char *)tcp2, sizeof(*tcp2));
tcp2->th_win = htons(8192);
tcp2->th_sport = sp;
tcp2->th_off = 5;
tcp2->th_dport = 0; /* XXX - don't specify remote port */
fi.fin_data[0] = ntohs(sp);
fi.fin_data[1] = 0;
fi.fin_dp = (char *)tcp2;
swip = ip->ip_src;
ip->ip_src = nat->nat_inip;
ipn = nat_new(nat->nat_ptr, ip, &fi, IPN_TCP|FI_W_DPORT,
NAT_OUTBOUND);
if (ipn != NULL) {
ipn->nat_age = fr_defnatage;
(void) fr_addstate(ip, &fi, FI_W_DPORT);
}
ip->ip_len = slen;
ip->ip_src = swip;
}
return inc;
}
int ippr_ftp_client(fin, ip, nat, ftp, dlen)
fr_info_t *fin;
nat_t *nat;
ftpinfo_t *ftp;
ip_t *ip;
int dlen;
{
char *rptr, *wptr, cmd[6], c;
ftpside_t *f;
int inc, i;
inc = 0;
f = &ftp->ftp_side[0];
rptr = f->ftps_rptr;
wptr = f->ftps_wptr;
for (i = 0; (i < 5) && (i < dlen); i++) {
c = rptr[i];
if (isalpha(c)) {
cmd[i] = toupper(c);
} else {
cmd[i] = c;
}
}
cmd[i] = '\0';
if ((ftp->ftp_passok == 0) && !strncmp(cmd, "USER ", 5))
ftp->ftp_passok = 1;
else if ((ftp->ftp_passok == 2) && !strncmp(cmd, "PASS ", 5))
ftp->ftp_passok = 3;
else if ((ftp->ftp_passok == 4) && !ippr_ftp_pasvonly &&
!strncmp(cmd, "PORT ", 5)) {
inc = ippr_ftp_port(fin, ip, nat, f, dlen);
} else if (ippr_ftp_insecure && !ippr_ftp_pasvonly &&
!strncmp(cmd, "PORT ", 5)) {
inc = ippr_ftp_port(fin, ip, nat, f, dlen);
}
while ((*rptr++ != '\n') && (rptr < wptr))
;
f->ftps_rptr = rptr;
return inc;
}
int ippr_ftp_pasv(fin, ip, nat, f, dlen)
fr_info_t *fin;
ip_t *ip;
nat_t *nat;
ftpside_t *f;
int dlen;
{
tcphdr_t *tcp, tcph, *tcp2 = &tcph;
struct in_addr swip, swip2;
u_short a5, a6, sp, dp;
u_int a1, a2, a3, a4;
fr_info_t fi;
nat_t *ipn;
int inc;
char *s;
/*
* Check for PASV reply message.
*/
if (dlen < IPF_MIN227LEN)
return 0;
else if (strncmp(f->ftps_rptr, "227 Entering Passive Mode", 25))
return 0;
tcp = (tcphdr_t *)fin->fin_dp;
/*
* Skip the PORT command + space
*/
s = f->ftps_rptr + 25;
while (*s && !isdigit(*s))
s++;
/*
* Pick out the address components, two at a time.
*/
a1 = ippr_ftp_atoi(&s);
if (!s)
return 0;
a2 = ippr_ftp_atoi(&s);
if (!s)
return 0;
/*
* check that IP address in the PORT/PASV reply is the same as the
* sender of the command - prevents using PORT for port scanning.
*/
a1 <<= 16;
a1 |= a2;
if (a1 != ntohl(nat->nat_oip.s_addr))
return 0;
a5 = ippr_ftp_atoi(&s);
if (!s)
return 0;
if (*s == ')')
s++;
if (*s == '\n')
s--;
/*
* check for CR-LF at the end.
*/
if ((*s == '\r') && (*(s + 1) == '\n')) {
s += 2;
a6 = a5 & 0xff;
} else
return 0;
a5 >>= 8;
/*
* Calculate new address parts for 227 reply
*/
a1 = ntohl(ip->ip_src.s_addr);
a2 = (a1 >> 16) & 0xff;
a3 = (a1 >> 8) & 0xff;
a4 = a1 & 0xff;
a1 >>= 24;
inc = 0;
#if 0
olen = s - f->ftps_rptr;
(void) sprintf(newbuf, "%s %u,%u,%u,%u,%u,%u\r\n",
"227 Entering Passive Mode", a1, a2, a3, a4, a5, a6);
nlen = strlen(newbuf);
inc = nlen - olen;
if ((inc + ip->ip_len) > 65535)
return 0;
#if SOLARIS
m = fin->fin_qfm;
for (m1 = m; m1->b_cont; m1 = m1->b_cont)
;
if ((inc > 0) && (m1->b_datap->db_lim - m1->b_wptr < inc)) {
mblk_t *nm;
/* alloc enough to keep same trailer space for lower driver */
nm = allocb(nlen, BPRI_MED);
PANIC((!nm),("ippr_ftp_out: allocb failed"));
nm->b_band = m1->b_band;
nm->b_wptr += nlen;
m1->b_wptr -= olen;
PANIC((m1->b_wptr < m1->b_rptr),
("ippr_ftp_out: cannot handle fragmented data block"));
linkb(m1, nm);
} else {
m1->b_wptr += inc;
}
/*copyin_mblk(m, off, nlen, newbuf);*/
#else /* SOLARIS */
m = *((mb_t **)fin->fin_mp);
if (inc < 0)
m_adj(m, inc);
/* the mbuf chain will be extended if necessary by m_copyback() */
/*m_copyback(m, off, nlen, newbuf);*/
#endif /* SOLARIS */
if (inc != 0) {
#if SOLARIS || defined(__sgi)
register u_32_t sum1, sum2;
sum1 = ip->ip_len;
sum2 = ip->ip_len + inc;
/* Because ~1 == -2, We really need ~1 == -1 */
if (sum1 > sum2)
sum2--;
sum2 -= sum1;
sum2 = (sum2 & 0xffff) + (sum2 >> 16);
fix_outcksum(&ip->ip_sum, sum2, 0);
#endif /* SOLARIS || defined(__sgi) */
ip->ip_len += inc;
}
#endif /* 0 */
/*
* Add skeleton NAT entry for connection which will come back the
* other way.
*/
sp = 0;
dp = htons(fin->fin_data[1] - 1);
ipn = nat_outlookup(fin->fin_ifp, IPN_TCP, nat->nat_p, nat->nat_inip,
ip->ip_dst, (dp << 16) | sp);
if (ipn == NULL) {
int slen;
slen = ip->ip_len;
ip->ip_len = fin->fin_hlen + sizeof(*tcp2);
bcopy((char *)fin, (char *)&fi, sizeof(fi));
bzero((char *)tcp2, sizeof(*tcp2));
tcp2->th_win = htons(8192);
tcp2->th_sport = 0; /* XXX - fake it for nat_new */
tcp2->th_off = 5;
fi.fin_data[0] = a5 << 8 | a6;
tcp2->th_dport = htons(fi.fin_data[0]);
fi.fin_data[1] = 0;
fi.fin_dp = (char *)tcp2;
swip = ip->ip_src;
swip2 = ip->ip_dst;
ip->ip_dst = ip->ip_src;
ip->ip_src = nat->nat_inip;
ipn = nat_new(nat->nat_ptr, ip, &fi, IPN_TCP|FI_W_SPORT,
NAT_OUTBOUND);
if (ipn != NULL) {
ipn->nat_age = fr_defnatage;
(void) fr_addstate(ip, &fi, FI_W_SPORT);
}
ip->ip_len = slen;
ip->ip_src = swip;
ip->ip_dst = swip2;
}
return inc;
}
int ippr_ftp_server(fin, ip, nat, ftp, dlen)
fr_info_t *fin;
ip_t *ip;
nat_t *nat;
ftpinfo_t *ftp;
int dlen;
{
char *rptr, *wptr;
ftpside_t *f;
int inc;
inc = 0;
f = &ftp->ftp_side[1];
rptr = f->ftps_rptr;
wptr = f->ftps_wptr;
if ((ftp->ftp_passok == 1) && !strncmp(rptr, "331", 3))
ftp->ftp_passok = 2;
else if ((ftp->ftp_passok == 3) && !strncmp(rptr, "230", 3))
ftp->ftp_passok = 4;
else if ((ftp->ftp_passok == 3) && !strncmp(rptr, "530", 3))
ftp->ftp_passok = 0;
else if ((ftp->ftp_passok == 4) && !strncmp(rptr, "227 ", 4)) {
inc = ippr_ftp_pasv(fin, ip, nat, f, dlen);
} else if (ippr_ftp_insecure && !strncmp(rptr, "227 ", 4)) {
inc = ippr_ftp_pasv(fin, ip, nat, f, dlen);
}
while ((*rptr++ != '\n') && (rptr < wptr))
;
f->ftps_rptr = rptr;
return inc;
}
/*
* Look to see if the buffer starts with something which we recognise as
* being the correct syntax for the FTP protocol.
*/
int ippr_ftp_valid(buf, len)
char *buf;
size_t len;
{
register char *s, c;
register size_t i = len;
if (i < 5)
return 2;
s = buf;
c = *s++;
i--;
if (isdigit(c)) {
c = *s++;
i--;
if (isdigit(c)) {
c = *s++;
i--;
if (isdigit(c)) {
c = *s++;
i--;
if ((c != '-') && (c != ' '))
return 1;
} else
return 1;
} else
return 1;
} else if (isalpha(c)) {
c = *s++;
i--;
if (isalpha(c)) {
c = *s++;
i--;
if (isalpha(c)) {
c = *s++;
i--;
if (isalpha(c)) {
c = *s++;
i--;
if ((c != ' ') && (c != '\r'))
return 1;
} else if ((c != ' ') && (c != '\r'))
return 1;
} else
return 1;
} else
return 1;
} else
return 1;
for (; i; i--) {
c = *s++;
if (c == '\n')
return 0;
}
return 2;
}
int ippr_ftp_process(fin, ip, nat, ftp, rv)
fr_info_t *fin;
ip_t *ip;
nat_t *nat;
ftpinfo_t *ftp;
int rv;
{
int mlen, len, off, inc, i, sel;
char *rptr, *wptr;
ftpside_t *f, *t;
tcphdr_t *tcp;
mb_t *m;
tcp = (tcphdr_t *)fin->fin_dp;
off = fin->fin_hlen + (tcp->th_off << 2);
#if SOLARIS
m = fin->fin_qfm;
#else
m = *((mb_t **)fin->fin_mp);
#endif
#if SOLARIS
mlen = msgdsize(m) - off;
#else
mlen = mbufchainlen(m) - off;
#endif
t = &ftp->ftp_side[1 - rv];
if (!mlen) {
t->ftps_seq = ntohl(tcp->th_ack);
return 0;
}
inc = 0;
f = &ftp->ftp_side[rv];
rptr = f->ftps_rptr;
wptr = f->ftps_wptr;
sel = nat->nat_aps->aps_sel[1 - rv];
if (rv)
i = nat->nat_aps->aps_ackoff[sel];
else
i = nat->nat_aps->aps_seqoff[sel];
/*
* XXX - Ideally, this packet should get dropped because we now know
* that it is out of order (and there is no real danger in doing so
* apart from causing packets to go through here ordered).
*/
if (ntohl(tcp->th_seq) + i != f->ftps_seq) {
return APR_ERR(-1);
}
while (mlen > 0) {
len = MIN(mlen, FTP_BUFSZ / 2);
#if SOLARIS
copyout_mblk(m, off, len, wptr);
#else
m_copydata(m, off, len, wptr);
#endif
mlen -= len;
off += len;
wptr += len;
f->ftps_wptr = wptr;
if (f->ftps_junk == 2)
f->ftps_junk = ippr_ftp_valid(rptr, wptr - rptr);
while ((f->ftps_junk == 0) && (wptr > rptr)) {
f->ftps_junk = ippr_ftp_valid(rptr, wptr - rptr);
if (f->ftps_junk == 0) {
len = wptr - rptr;
f->ftps_rptr = rptr;
if (rv)
inc += ippr_ftp_server(fin, ip, nat,
ftp, len);
else
inc += ippr_ftp_client(fin, ip, nat,
ftp, len);
rptr = f->ftps_rptr;
}
}
while ((f->ftps_junk == 1) && (rptr < wptr)) {
while ((rptr < wptr) && (*rptr != '\r'))
rptr++;
if ((*rptr == '\r') && (rptr + 1 < wptr)) {
if (*(rptr + 1) == '\n') {
rptr += 2;
f->ftps_junk = 0;
} else
rptr++;
}
f->ftps_rptr = rptr;
}
if (rptr == wptr) {
rptr = wptr = f->ftps_buf;
} else {
if ((wptr > f->ftps_buf + FTP_BUFSZ / 2)) {
i = wptr - rptr;
if ((rptr == f->ftps_buf) ||
(wptr - rptr > FTP_BUFSZ / 2)) {
f->ftps_junk = 1;
rptr = wptr = f->ftps_buf;
} else {
bcopy(rptr, f->ftps_buf, i);
wptr = f->ftps_buf + i;
rptr = f->ftps_buf;
}
}
f->ftps_rptr = rptr;
f->ftps_wptr = wptr;
}
}
t->ftps_seq = ntohl(tcp->th_ack);
f->ftps_rptr = rptr;
f->ftps_wptr = wptr;
return inc;
}
int ippr_ftp_out(fin, ip, aps, nat)
fr_info_t *fin;
ip_t *ip;
ap_session_t *aps;
nat_t *nat;
{
ftpinfo_t *ftp;
ftp = aps->aps_data;
if (ftp == NULL)
return 0;
return ippr_ftp_process(fin, ip, nat, ftp, 0);
}
int ippr_ftp_in(fin, ip, aps, nat)
fr_info_t *fin;
ip_t *ip;
ap_session_t *aps;
nat_t *nat;
{
ftpinfo_t *ftp;
ftp = aps->aps_data;
if (ftp == NULL)
return 0;
return ippr_ftp_process(fin, ip, nat, ftp, 1);
}
/*
* ippr_ftp_atoi - implement a version of atoi which processes numbers in
* pairs separated by commas (which are expected to be in the range 0 - 255),
* returning a 16 bit number combining either side of the , as the MSB and
* LSB.
*/
u_short ippr_ftp_atoi(ptr)
char **ptr;
{
register char *s = *ptr, c;
register u_char i = 0, j = 0;
while ((c = *s++) && isdigit(c)) {
i *= 10;
i += c - '0';
}
if (c != ',') {
*ptr = NULL;
return 0;
}
while ((c = *s++) && isdigit(c)) {
j *= 10;
j += c - '0';
}
*ptr = s;
return (i << 8) | j;
}