/*----- Static variables --------------------------------------------------*/
static FILE *natfp; /* File handle for NAT table */
+static int randfd; /* File descriptor for random data */
+
+/*----- Miscellaneous system services -------------------------------------*/
+
+/* Fill the buffer at P with SZ random bytes. The buffer will be moderately
+ * large: this is intended to be a low-level interface, not a general-purpose
+ * utility.
+ */
+void fill_random(void *p, size_t sz)
+{
+ ssize_t n;
+
+ n = read(randfd, p, sz);
+ if (n < 0) fatal("error reading `/dev/urandom': %s", strerror(errno));
+ else if (n < sz) fatal("unexpected short read from `/dev/urandom'");
+}
/*----- Address-type operations -------------------------------------------*/
/* Open a netlink socket for interrogating the kernel. */
if ((fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
- die(1, "failed to create netlink socket: %s", strerror(errno));
+ fatal("failed to create netlink socket: %s", strerror(errno));
/* We want to read the routing table. There doesn't seem to be a good way
* to do this without just crawling through the whole thing.
rtgen->rtgen_family = af;
if (write(fd, nlmsg, nlmsg->nlmsg_len) < 0)
- die(1, "failed to send RTM_GETROUTE request: %s", strerror(errno));
+ fatal("failed to send RTM_GETROUTE request: %s", strerror(errno));
/* Now we try to parse the answer. */
for (;;) {
/* Not finished yet, so read another chunk of answer. */
if ((n = read(fd, buf, sizeof(buf))) < 0)
- die(1, "failed to read RTM_GETROUTE response: %s", strerror(errno));
+ fatal("failed to read RTM_GETROUTE response: %s", strerror(errno));
/* Start at the beginning of the response. */
nlmsg = (struct nlmsghdr *)buf;
return (rc);
}
-/* Find out who is responsible for the connection described in the query Q.
- * Write the answer to Q. Errors are logged and reported via the query
- * structure.
+/* Initially, PP points into a string containing whitespace-separated fields.
+ * Point P to the next field, null-terminate it, and advance PP so that we
+ * can read the next field in the next call.
*/
-void identify(struct query *q)
+#define NEXTFIELD do { \
+ for (p = pp; isspace((unsigned char)*p); p++); \
+ for (pp = p; *pp && !isspace((unsigned char)*pp); pp++); \
+ if (*pp) *pp++ = 0; \
+} while (0)
+
+/* Search the `tcp' connection table for the address family AO, looking for a
+ * connection between the addresses in QS. GWP is nonzero if the query's
+ * remote address is our gateway and we shouldn't expect the remote address
+ * in the system table to actually match it because of NAT. Return nonzero
+ * if we have filled in Q conclusively; return zero if the caller should try
+ * a different approach.
+ */
+static int search_tcp_file(struct query *q, int gwp,
+ const struct addrops *ao,
+ struct socket qs[NDIR])
{
FILE *fp = 0;
dstr d = DSTR_INIT;
char *p, *pp;
- struct socket s[4];
+ struct socket s[NDIR];
int i;
- int gwp = 0;
- unsigned fl;
-#define F_SADDR 1u
-#define F_SPORT 2u
-#define F_DADDR 4u
-#define F_DPORT 8u
-#define F_ALL (F_SADDR | F_SPORT | F_DADDR | F_DPORT)
-#define F_ESTAB 16u
uid_t uid;
enum { LOC, REM, ST, UID, NFIELD };
int f, ff[NFIELD];
-
- /* If we have a default gateway, and it matches the remote address then
- * this may be a proxy connection from our NAT, so remember this, and don't
- * inspect the remote addresses in the TCP tables.
- */
- if (!get_default_gw(q->ao->af, &s[0].addr) &&
- q->ao->addreq(&s[0].addr, &q->s[R].addr))
- gwp = 1;
+ int rc = 1;
/* Open the relevant TCP connection table. */
- if ((fp = fopen(q->ao->sys->procfile, "r")) == 0) {
+ if ((fp = fopen(ao->sys->procfile, "r")) == 0) {
logmsg(q, LOG_ERR, "failed to open `%s' for reading: %s",
- q->ao->sys->procfile, strerror(errno));
+ ao->sys->procfile, strerror(errno));
goto err_unk;
}
- /* Initially, PP points into a string containing whitespace-separated
- * fields. Point P to the next field, null-terminate it, and advance PP
- * so that we can read the next field in the next call.
- */
-#define NEXTFIELD do { \
- for (p = pp; isspace((unsigned char)*p); p++); \
- for (pp = p; *pp && !isspace((unsigned char)*pp); pp++); \
- if (*pp) *pp++ = 0; \
-} while (0)
-
/* Read the header line from the file. */
if (dstr_putline(&d, fp) == EOF) {
logmsg(q, LOG_ERR, "failed to read header line from `%s': %s",
- q->ao->sys->procfile,
+ ao->sys->procfile,
ferror(fp) ? strerror(errno) : "unexpected EOF");
goto err_unk;
}
for (i = 0; i < NFIELD; i++) {
if (ff[i] < 0) {
logmsg(q, LOG_ERR, "failed to find required fields in `%s'",
- q->ao->sys->procfile);
+ ao->sys->procfile);
goto err_unk;
}
}
* query is our gateway then don't check the remote address in the
* field (but do check the port number).
*/
- if (q->ao->sys->parseaddr(&p, &s[i].addr)) goto next_row;
- if (*p != ':') break; p++;
+ if (ao->sys->parseaddr(&p, &s[i].addr)) goto next_row;
+ if (*p != ':') break;
+ p++;
s[i].port = strtoul(p, 0, 16);
if ((i == R && gwp) ?
- q->s[R].port != s[i].port :
- !sockeq(q->ao, &q->s[i], &s[i]))
+ qs[R].port != s[i].port :
+ !sockeq(ao, &qs[i], &s[i]))
goto next_row;
}
if (uid != -1) {
q->resp = R_UID;
q->u.uid = uid;
- if (gwp) q->s[R].addr = s[i].addr;
+ if (gwp) qs[R].addr = s[i].addr;
goto done;
}
next_row:;
/* We got to the end of the file and didn't find anything. */
if (ferror(fp)) {
logmsg(q, LOG_ERR, "failed to read connection table `%s': %s",
- q->ao->sys->procfile, strerror(errno));
+ ao->sys->procfile, strerror(errno));
goto err_unk;
}
+ rc = 0;
+
+err_unk:
+ /* Something went wrong and the protocol can't express what. We should
+ * have logged what the problem actually was.
+ */
+ q->resp = R_ERROR;
+ q->u.error = E_UNKNOWN;
+
+done:
+ /* All done. */
+ dstr_destroy(&d);
+ if (fp) fclose(fp);
+ return (rc);
+}
+
+/* Convert the IPv4 socket address IN into the equivalent IPv4-mapped IPv6
+ * address OUT.
+ */
+static void map_v4(struct socket *out, const struct socket *in)
+{
+ unsigned i;
+ in_addr_t a4 = ntohl(in->addr.ipv4.s_addr);
+
+ for (i = 0; i < 10; i++) out->addr.ipv6.s6_addr[i] = 0;
+ for (i = 10; i < 12; i++) out->addr.ipv6.s6_addr[i] = 0xff;
+ for (i = 0; i < 4; i++) out->addr.ipv6.s6_addr[15 - i] = (a4 >> 8*i)&0xff;
+ out->port = in->port;
+}
+
+/* Convert the IPv4-mapped IPv6 socket address IN into the equivalent IPv4
+ * address OUT; return -1 if the IN address isn't actually IPv4-mapped.
+ */
+static int unmap_v4(struct socket *out, const struct socket *in)
+{
+ unsigned i;
+ in_addr_t a4 = 0;
+
+ for (i = 0; i < 10; i++) if (in->addr.ipv6.s6_addr[i] != 0) return (-1);
+ for (i = 10; i < 12; i++) if (in->addr.ipv6.s6_addr[i] != 0xff) return (-1);
+ for (i = 0; i < 4; i++) a4 |= in->addr.ipv6.s6_addr[15 - i] << 8*i;
+ out->addr.ipv4.s_addr = htonl(a4);
+ out->port = in->port;
+ return (0);
+}
+
+/* Find out who is responsible for the connection described in the query Q.
+ * Write the answer to Q. Errors are logged and reported via the query
+ * structure.
+ */
+void identify(struct query *q)
+{
+ FILE *fp = 0;
+ dstr d = DSTR_INIT;
+ char *p, *pp;
+ struct socket s[4];
+ int i;
+ int gwp = 0;
+ unsigned fl;
+#define F_SADDR 1u
+#define F_SPORT 2u
+#define F_DADDR 4u
+#define F_DPORT 8u
+#define F_ALL (F_SADDR | F_SPORT | F_DADDR | F_DPORT)
+#define F_ESTAB 16u
+
+ /* If we have a default gateway, and it matches the remote address then
+ * this may be a proxy connection from our NAT, so remember this, and don't
+ * inspect the remote addresses in the TCP tables.
+ */
+ if (!get_default_gw(q->ao->af, &s[0].addr) &&
+ q->ao->addreq(&s[0].addr, &q->s[R].addr))
+ gwp = 1;
+
+ /* Search the main `tcp' table. */
+ if (search_tcp_file(q, gwp, q->ao, q->s)) goto done;
+
+ /* Oh, dear. If this is IPv4, then the entry might actually be in the IPv6
+ * table, with weird addresses. So we must try again.
+ */
+ if (q->ao->af == AF_INET) {
+ map_v4(&s[L], &q->s[L]); map_v4(&s[R], &q->s[R]);
+ if (search_tcp_file(q, gwp, &addroptab[ADDR_IPV6], s)) {
+ if (gwp && unmap_v4(&q->s[R], &s[R])) {
+ logmsg(q, LOG_ERR, "can't unmap NATted destination address");
+ goto err_unk;
+ }
+ goto done;
+ }
+ }
/* If we opened the NAT table file, and we're using IPv4, then check to see
* whether we should proxy the connection. At least the addresses in this
!sockeq(q->ao, &s[i^1], &q->s[R]))
continue;
+ /* As a trap for the unwary, this file contains unhelpful entries which
+ * just mirror the source/destination addresses. If this is one of
+ * those, we'll be stuck in a cycle talking to ourselves.
+ */
+ if (sockeq(q->ao, &s[i], &s[i^3]))
+ continue;
+
/* We win. The remaining address must be the client host. We should
* proxy this query.
*/
}
}
-#undef NEXTFIELD
-
/* We didn't find a match anywhere. How unfortunate. */
logmsg(q, LOG_NOTICE, "connection not found");
q->resp = R_ERROR;
if (fp) fclose(fp);
}
+#undef NEXTFIELD
+
/* Initialize the system-specific code. */
void init_sys(void)
{
+ /* Open the NAT connection map. */
if ((natfp = fopen("/proc/net/nf_conntrack", "r")) == 0 &&
errno != ENOENT) {
die(1, "failed to open `/proc/net/nf_conntrack' for reading: %s",
strerror(errno));
}
+
+ /* Open the random data source. */
+ if ((randfd = open("/dev/urandom", O_RDONLY)) < 0) {
+ die(1, "failed to open `/dev/urandom' for reading: %s",
+ strerror(errno));
+ }
}
/*----- That's all, folks -------------------------------------------------*/
~mdw / yaid / blobdiff