[PATCH 30/41] site: interpret first 4 bytes of extrainfo as capabilities
Ian Jackson
ijackson at chiark.greenend.org.uk
Thu Jul 25 18:40:56 BST 2013
Define the first four bytes of the additional data (after the nul in
site names in MSG1..4) in the sender's name field to be a capability
bitmask. Currently no capability flags are defined.
To support this, replace extrainfo and its _len in struct parsedname
with a struct buffer_if.
We record the capabilities from MSG1 or MSG3, and check that they
haven't changed when processing MSG2..4, as applicable. (Because
older secnets don't cope with flags in MSG1, we have to define two
kinds of capability flag: ones expected to be in MSG1, and ones which
can appear later in the exchange.)
The support for "Early" capabilities is intended to be used in the
future to support algorithm agility in key exchange.
We also advertise our own capabilities (currently, all-bits-zero) in
our own messages.
Signed-off-by: Ian Jackson <ijackson at chiark.greenend.org.uk>
---
NOTES | 28 ++++++++++++++++++++++-
magic.h | 4 +++
site.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
3 files changed, 96 insertions(+), 9 deletions(-)
diff --git a/NOTES b/NOTES
index 3e9d71d..8619ee5 100644
--- a/NOTES
+++ b/NOTES
@@ -176,7 +176,7 @@ Definitions:
A is the originating gateway machine name
B is the destination gateway machine name
-A+ and B+ are the names with optional additional data, currently ignored
+A+ and B+ are the names with optional additional data, see below
PK_A is the public RSA key of A
PK_B is the public RSA key of B
PK_A^-1 is the private RSA key of A
@@ -194,7 +194,31 @@ i? is appropriate index for receiver
Note that 'i' may be re-used from one session to the next, whereas 'n'
is always fresh.
-The protocol version selection stuff is not yet implemented.
+The optional additional data after the sender's name consists of some
+initial subset of the following list of items:
+ * A 32-bit integer with a set of capability flags, representing the
+ abilities of the sender.
+ * More data which is yet to be defined and which must be ignored
+ by receivers.
+The optional additional data after the receiver's name is not
+currently used. If any is seen, it must be ignored.
+
+Capability flag bits must be in one the following two categories:
+
+1. Early capability flags must be advertised in MSG1 or MSG2, as
+ applicable. If MSG3 or MSG4 advertise any "early" capability bits,
+ MSG1 or MSG3 (as applicable) must have advertised them too. Sadly,
+ advertising an early capability flag will produce MSG1s which are
+ not understood by versions of secnet which predate the capability
+ mechanism.
+
+2. Late capability flags are advertised in MSG2 or MSG3, as
+ applicable. They may also appear in MSG1, but this is not
+ guaranteed. MSG4 must advertise the same set as MSG2.
+
+No capability flags are currently defined. Unknown capability flags
+should be treated as late ones.
+
Messages:
diff --git a/magic.h b/magic.h
index c2503a0..3ae7af4 100644
--- a/magic.h
+++ b/magic.h
@@ -15,4 +15,8 @@
#define LABEL_MSG8 0x08080808
#define LABEL_MSG9 0x09090909
+/* uses of the 32-bit capability bitmap */
+/* no flags currently defined */
+#define CAPAB_EARLY 0x00000000 /* no Early flags defined (see NOTES) */
+
#endif /* magic_h */
diff --git a/site.c b/site.c
index 5b071b2..0a02785 100644
--- a/site.c
+++ b/site.c
@@ -244,6 +244,7 @@ struct site {
struct hash_if *hash;
uint32_t index; /* Index of this site */
+ uint32_t local_capabilities;
int32_t setup_retries; /* How many times to send setup packets */
int32_t setup_retry_interval; /* Initial timeout for setup packets */
int32_t wait_timeout; /* How long to wait if setup unsuccessful */
@@ -275,6 +276,7 @@ struct site {
packet; we keep trying to continue the exchange, and have to
timeout before we can listen for another setup packet); perhaps
we should keep a list of 'bad' sources for setup packets. */
+ uint32_t remote_capabilities;
uint32_t setup_session_id;
transport_peers setup_peers;
uint8_t localN[NONCELEN]; /* Nonces for key exchange */
@@ -347,8 +349,7 @@ static bool_t current_valid(struct site *st)
struct parsedname {
int32_t len;
uint8_t *name;
- int32_t extrainfo_len;
- uint8_t *extrainfo;
+ struct buffer_if extrainfo;
};
struct msg {
@@ -357,6 +358,7 @@ struct msg {
uint32_t source;
struct parsedname remote;
struct parsedname local;
+ uint32_t remote_capabilities;
uint8_t *nR;
uint8_t *nL;
int32_t pklen;
@@ -366,6 +368,34 @@ struct msg {
char *sig;
};
+struct xinfoadd {
+ int32_t lenpos, afternul;
+};
+static void append_string_xinfo_start(struct buffer_if *buf,
+ struct xinfoadd *xia,
+ const char *str)
+ /* Helps construct one of the names with additional info as found
+ * in MSG1..4. Call this function first, then append all the
+ * desired extra info (not including the nul byte) to the buffer,
+ * then call append_string_xinfo_done. */
+{
+ xia->lenpos = buf->size;
+ buf_append_string(buf,str);
+ buf_append_uint8(buf,0);
+ xia->afternul = buf->size;
+}
+static void append_string_xinfo_done(struct buffer_if *buf,
+ struct xinfoadd *xia)
+{
+ /* we just need to adjust the string length */
+ if (buf->size == xia->afternul) {
+ /* no extra info, strip the nul too */
+ buf_unappend_uint8(buf);
+ } else {
+ put_uint16(buf->start+xia->lenpos, buf->size-(xia->lenpos+2));
+ }
+}
+
/* Build any of msg1 to msg4. msg5 and msg6 are built from the inside
out using a transform of config data supplied by netlink */
static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
@@ -381,7 +411,14 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
(type==LABEL_MSG1?0:st->setup_session_id));
buf_append_uint32(&st->buffer,st->index);
buf_append_uint32(&st->buffer,type);
- buf_append_string(&st->buffer,st->localname);
+
+ struct xinfoadd xia;
+ append_string_xinfo_start(&st->buffer,&xia,st->localname);
+ if ((st->local_capabilities & CAPAB_EARLY) || (type != LABEL_MSG1)) {
+ buf_append_uint32(&st->buffer,st->local_capabilities);
+ }
+ append_string_xinfo_done(&st->buffer,&xia);
+
buf_append_string(&st->buffer,st->remotename);
memcpy(buf_append(&st->buffer,NONCELEN),st->localN,NONCELEN);
if (type==LABEL_MSG1) return True;
@@ -412,11 +449,9 @@ static bool_t unpick_name(struct buffer_if *msg, struct parsedname *nm)
nm->name=buf_unprepend(msg,nm->len);
uint8_t *nul=memchr(nm->name,0,nm->len);
if (!nul) {
- nm->extrainfo_len=0;
- nm->extrainfo=0;
+ buffer_readonly_view(&nm->extrainfo,0,0);
} else {
- nm->extrainfo=nul+1;
- nm->extrainfo_len=msg->start-nm->extrainfo;
+ buffer_readonly_view(&nm->extrainfo, nul+1, msg->start-(nul+1));
nm->len=nul-nm->name;
}
return True;
@@ -432,6 +467,11 @@ static bool_t unpick_msg(struct site *st, uint32_t type,
m->source=buf_unprepend_uint32(msg);
CHECK_TYPE(msg,type);
if (!unpick_name(msg,&m->remote)) return False;
+ m->remote_capabilities=0;
+ if (m->remote.extrainfo.size) {
+ CHECK_AVAIL(&m->remote.extrainfo,4);
+ m->remote_capabilities=buf_unprepend_uint32(&m->remote.extrainfo);
+ }
if (!unpick_name(msg,&m->local)) return False;
CHECK_AVAIL(msg,NONCELEN);
m->nR=buf_unprepend(msg,NONCELEN);
@@ -490,7 +530,13 @@ static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
*error="wrong remotely-generated nonce";
return False;
}
+ /* MSG3 has complicated rules about capabilities, which are
+ * handled in process_msg3. */
if (type==LABEL_MSG3) return True;
+ if (m->remote_capabilities!=st->remote_capabilities) {
+ *error="remote capabilities changed";
+ return False;
+ }
if (type==LABEL_MSG4) return True;
*error="unknown message type";
return False;
@@ -511,6 +557,7 @@ static bool_t process_msg1(struct site *st, struct buffer_if *msg1,
transport_record_peer(st,&st->setup_peers,src,"msg1");
st->setup_session_id=m->source;
+ st->remote_capabilities=m->remote_capabilities;
memcpy(st->remoteN,m->nR,NONCELEN);
return True;
}
@@ -533,6 +580,7 @@ static bool_t process_msg2(struct site *st, struct buffer_if *msg2,
return False;
}
st->setup_session_id=m.source;
+ st->remote_capabilities=m.remote_capabilities;
memcpy(st->remoteN,m.nR,NONCELEN);
return True;
}
@@ -558,6 +606,15 @@ static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
slog(st,LOG_SEC,"msg3: %s",err);
return False;
}
+ uint32_t capab_adv_late = m.remote_capabilities
+ & ~st->remote_capabilities & CAPAB_EARLY;
+ if (capab_adv_late) {
+ slog(st,LOG_SEC,"msg3 impermissibly adds early capability flag(s)"
+ " %#"PRIx32" (was %#"PRIx32", now %#"PRIx32")",
+ capab_adv_late, st->remote_capabilities, m.remote_capabilities);
+ return False;
+ }
+ st->remote_capabilities|=m.remote_capabilities;
/* Check signature and store g^x mod m */
hash=safe_malloc(st->hash->len, "process_msg3");
@@ -1493,6 +1550,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
assert(index_sequence < 0xffffffffUL);
st->index = ++index_sequence;
+ st->local_capabilities = 0;
st->netlink=find_cl_if(dict,"link",CL_NETLINK,True,"site",loc);
list_t *comms_cfg=dict_lookup(dict,"comm");
@@ -1579,6 +1637,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
register_for_poll(st, site_beforepoll, site_afterpoll, 0, "site");
st->timeout=0;
+ st->remote_capabilities=0;
st->current.key_timeout=0;
st->auxiliary_key.key_timeout=0;
transport_peers_clear(st,&st->peers);
--
1.7.2.5
More information about the sgo-software-discuss
mailing list