chiark / gitweb /
udp.c: call buffer_init
[secnet.git] / site.c
diff --git a/site.c b/site.c
index 98bd6b678a7bc73f0d2b903e2931e560cc4933f8..909e8e9fa5a9903967fc700d93b4c2cabf70a620 100644 (file)
--- a/site.c
+++ b/site.c
@@ -89,6 +89,8 @@
 #define SITE_SENTMSG5 7
 #define SITE_WAIT     8
 
+int32_t site_max_start_pad = 4*4;
+
 static cstring_t state_name(uint32_t state)
 {
     switch (state) {
@@ -239,11 +241,13 @@ struct site {
     struct random_if *random;
     struct rsaprivkey_if *privkey;
     struct rsapubkey_if *pubkey;
-    struct transform_if *transform;
+    struct transform_if **transforms;
+    int ntransforms;
     struct dh_if *dh;
     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 +279,8 @@ 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;
+    struct transform_if *chosen_transform;
     uint32_t setup_session_id;
     transport_peers setup_peers;
     uint8_t localN[NONCELEN]; /* Nonces for key exchange */
@@ -285,10 +291,12 @@ struct site {
     uint64_t timeout; /* Timeout for current state */
     uint8_t *dhsecret;
     uint8_t *sharedsecret;
-    uint32_t sharedsecretlen;
+    uint32_t sharedsecretlen, sharedsecretallocd;
     struct transform_inst_if *new_transform; /* For key setup/verify */
 };
 
+static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
+FORMAT(printf,3,4);
 static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
 {
     va_list ap;
@@ -314,7 +322,7 @@ static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
        }
 
        vsnprintf(buf,sizeof(buf),msg,ap);
-       st->log->log(st->log->st,class,"%s: %s",st->tunname,buf);
+       slilog(st->log,class,"%s: %s",st->tunname,buf);
     }
     va_end(ap);
 }
@@ -332,11 +340,42 @@ static bool_t enter_new_state(struct site *st,uint32_t next);
 static void enter_state_wait(struct site *st);
 static void activate_new_key(struct site *st);
 
+static bool_t is_transform_valid(struct transform_inst_if *transform)
+{
+    return transform && transform->valid(transform->st);
+}
+
 static bool_t current_valid(struct site *st)
 {
-    return st->current.transform->valid(st->current.transform->st);
+    return is_transform_valid(st->current.transform);
+}
+
+#define DEFINE_CALL_TRANSFORM(fwdrev)                                  \
+static int call_transform_##fwdrev(struct site *st,                    \
+                                  struct transform_inst_if *transform, \
+                                  struct buffer_if *buf,               \
+                                  const char **errmsg)                 \
+{                                                                      \
+    if (!is_transform_valid(transform)) {                              \
+       *errmsg="transform not set up";                                 \
+       return 1;                                                       \
+    }                                                                  \
+    return transform->fwdrev(transform->st,buf,errmsg);                        \
 }
 
+DEFINE_CALL_TRANSFORM(forwards)
+DEFINE_CALL_TRANSFORM(reverse)
+
+static void dispose_transform(struct transform_inst_if **transform_var)
+{
+    struct transform_inst_if *transform=*transform_var;
+    if (transform) {
+       transform->delkey(transform->st);
+       transform->destroy(transform->st);
+    }
+    *transform_var = 0;
+}    
+
 #define CHECK_AVAIL(b,l) do { if ((b)->size<(l)) return False; } while(0)
 #define CHECK_EMPTY(b) do { if ((b)->size!=0) return False; } while(0)
 #define CHECK_TYPE(b,t) do { uint32_t type; \
@@ -347,8 +386,7 @@ 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 +395,8 @@ struct msg {
     uint32_t source;
     struct parsedname remote;
     struct parsedname local;
+    uint32_t remote_capabilities;
+    int capab_transformnum;
     uint8_t *nR;
     uint8_t *nL;
     int32_t pklen;
@@ -366,6 +406,63 @@ struct msg {
     char *sig;
 };
 
+static void set_new_transform(struct site *st, char *pk)
+{
+    /* Make room for the shared key */
+    st->sharedsecretlen=st->chosen_transform->keylen?:st->dh->ceil_len;
+    assert(st->sharedsecretlen);
+    if (st->sharedsecretlen > st->sharedsecretallocd) {
+       st->sharedsecretallocd=st->sharedsecretlen;
+       st->sharedsecret=realloc(st->sharedsecret,st->sharedsecretallocd);
+    }
+    if (!st->sharedsecret) fatal_perror("site:sharedsecret");
+
+    /* Generate the shared key */
+    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,pk,
+                      st->sharedsecret,st->sharedsecretlen);
+
+    /* Set up the transform */
+    struct transform_if *generator=st->chosen_transform;
+    struct transform_inst_if *generated=generator->create(generator->st);
+    generated->setkey(generated->st,st->sharedsecret,
+                     st->sharedsecretlen,st->setup_priority);
+    dispose_transform(&st->new_transform);
+    st->new_transform=generated;
+
+    slog(st,LOG_SETUP_INIT,"key exchange negotiated transform"
+        " %d (capabilities ours=%#"PRIx32" theirs=%#"PRIx32")",
+        st->chosen_transform->capab_transformnum,
+        st->local_capabilities, st->remote_capabilities);
+}
+
+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 +478,14 @@ 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;
@@ -390,6 +494,9 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
 
     if (hacky_par_mid_failnow()) return False;
 
+    if (type==LABEL_MSG3BIS)
+       buf_append_uint8(&st->buffer,st->chosen_transform->capab_transformnum);
+
     dhpub=st->dh->makepublic(st->dh->st,st->dhsecret,st->dh->len);
     buf_append_string(&st->buffer,dhpub);
     free(dhpub);
@@ -412,11 +519,9 @@ 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;
@@ -425,6 +530,7 @@ static bool_t unpick_name(struct buffer_if *msg, struct parsedname *nm)
 static bool_t unpick_msg(struct site *st, uint32_t type,
                         struct buffer_if *msg, struct msg *m)
 {
+    m->capab_transformnum=-1;
     m->hashstart=msg->start;
     CHECK_AVAIL(msg,4);
     m->dest=buf_unprepend_uint32(msg);
@@ -432,6 +538,11 @@ 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);
@@ -445,6 +556,12 @@ static bool_t unpick_msg(struct site *st, uint32_t type,
        CHECK_EMPTY(msg);
        return True;
     }
+    if (type==LABEL_MSG3BIS) {
+       CHECK_AVAIL(msg,1);
+       m->capab_transformnum = buf_unprepend_uint8(msg);
+    } else {
+       m->capab_transformnum = CAPAB_TRANSFORMNUM_ANCIENT;
+    }
     CHECK_AVAIL(msg,2);
     m->pklen=buf_unprepend_uint16(msg);
     CHECK_AVAIL(msg,m->pklen);
@@ -490,7 +607,13 @@ static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
        *error="wrong remotely-generated nonce";
        return False;
     }
-    if (type==LABEL_MSG3) return True;
+    /* MSG3 has complicated rules about capabilities, which are
+     * handled in process_msg3. */
+    if (type==LABEL_MSG3 || type==LABEL_MSG3BIS) 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 +634,7 @@ 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 +657,30 @@ 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;
+
+    /* Select the transform to use */
+
+    uint32_t remote_transforms = st->remote_capabilities & CAPAB_TRANSFORM_MASK;
+    if (!remote_transforms)
+       /* old secnets only had this one transform */
+       remote_transforms = 1UL << CAPAB_TRANSFORMNUM_ANCIENT;
+
+    struct transform_if *ti;
+    int i;
+    for (i=0; i<st->ntransforms; i++) {
+       ti=st->transforms[i];
+       if ((1UL << ti->capab_transformnum) & remote_transforms)
+           goto transform_found;
+    }
+    slog(st,LOG_ERROR,"no transforms in common"
+        " (us %#"PRIx32"; them: %#"PRIx32")",
+        st->local_capabilities & CAPAB_TRANSFORM_MASK,
+        remote_transforms);
+    return False;
+ transform_found:
+    st->chosen_transform=ti;
+
     memcpy(st->remoteN,m.nR,NONCELEN);
     return True;
 }
@@ -542,22 +690,49 @@ static bool_t generate_msg3(struct site *st)
     /* Now we have our nonce and their nonce. Think of a secret key,
        and create message number 3. */
     st->random->generate(st->random->st,st->dh->len,st->dhsecret);
-    return generate_msg(st,LABEL_MSG3,"site:MSG3");
+    return generate_msg(st,
+                       (st->remote_capabilities & CAPAB_TRANSFORM_MASK
+                        ? LABEL_MSG3BIS : LABEL_MSG3),
+                       "site:MSG3");
 }
 
 static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
-                          const struct comm_addr *src)
+                          const struct comm_addr *src, uint32_t msgtype)
 {
     struct msg m;
     uint8_t *hash;
     void *hst;
     cstring_t err;
 
-    if (!unpick_msg(st,LABEL_MSG3,msg3,&m)) return False;
-    if (!check_msg(st,LABEL_MSG3,&m,&err)) {
+    assert(msgtype==LABEL_MSG3 || msgtype==LABEL_MSG3BIS);
+
+    if (!unpick_msg(st,msgtype,msg3,&m)) return False;
+    if (!check_msg(st,msgtype,&m,&err)) {
        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;
+
+    struct transform_if *ti;
+    int i;
+    for (i=0; i<st->ntransforms; i++) {
+       ti=st->transforms[i];
+       if (ti->capab_transformnum == m.capab_transformnum)
+           goto transform_found;
+    }
+    slog(st,LOG_SEC,"peer chose unknown-to-us transform %d!",
+        m.capab_transformnum);
+    return False;
+ transform_found:
+    st->chosen_transform=ti;
 
     /* Check signature and store g^x mod m */
     hash=safe_malloc(st->hash->len, "process_msg3");
@@ -578,13 +753,8 @@ static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
     /* Invent our DH secret key */
     st->random->generate(st->random->st,st->dh->len,st->dhsecret);
 
-    /* Generate the shared key */
-    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,m.pk,
-                      st->sharedsecret,st->sharedsecretlen);
-
-    /* Set up the transform */
-    st->new_transform->setkey(st->new_transform->st,st->sharedsecret,
-                             st->sharedsecretlen,st->setup_priority);
+    /* Generate the shared key and set up the transform */
+    set_new_transform(st,m.pk);
 
     return True;
 }
@@ -626,12 +796,9 @@ static bool_t process_msg4(struct site *st, struct buffer_if *msg4,
 
     /* Terminate their DH public key with a '0' */
     m.pk[m.pklen]=0;
-    /* Generate the shared key */
-    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,m.pk,
-                      st->sharedsecret,st->sharedsecretlen);
-    /* Set up the transform */
-    st->new_transform->setkey(st->new_transform->st,st->sharedsecret,
-                             st->sharedsecretlen,st->setup_priority);
+
+    /* Generate the shared key and set up the transform */
+    set_new_transform(st,m.pk);
 
     return True;
 }
@@ -661,12 +828,13 @@ static bool_t generate_msg5(struct site *st)
 
     BUF_ALLOC(&st->buffer,"site:MSG5");
     /* We are going to add four words to the message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*4));
+    buffer_init(&st->buffer,calculate_max_start_pad());
     /* Give the netlink code an opportunity to put its own stuff in the
        message (configuration information, etc.) */
     buf_prepend_uint32(&st->buffer,LABEL_MSG5);
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-                               &transform_err);
+    if (call_transform_forwards(st,st->new_transform,
+                               &st->buffer,&transform_err))
+       return False;
     buf_prepend_uint32(&st->buffer,LABEL_MSG5);
     buf_prepend_uint32(&st->buffer,st->index);
     buf_prepend_uint32(&st->buffer,st->setup_session_id);
@@ -684,7 +852,7 @@ static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
 
     if (!unpick_msg0(st,msg5,&m)) return False;
 
-    if (transform->reverse(transform->st,msg5,&transform_err)) {
+    if (call_transform_reverse(st,transform,msg5,&transform_err)) {
        /* There's a problem */
        slog(st,LOG_SEC,"process_msg5: transform: %s",transform_err);
        return False;
@@ -707,11 +875,13 @@ static void create_msg6(struct site *st, struct transform_inst_if *transform,
 
     BUF_ALLOC(&st->buffer,"site:MSG6");
     /* We are going to add four words to the message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*4));
+    buffer_init(&st->buffer,calculate_max_start_pad());
     /* Give the netlink code an opportunity to put its own stuff in the
        message (configuration information, etc.) */
     buf_prepend_uint32(&st->buffer,LABEL_MSG6);
-    transform->forwards(transform->st,&st->buffer,&transform_err);
+    int problem = call_transform_forwards(st,transform,
+                                         &st->buffer,&transform_err);
+    assert(!problem);
     buf_prepend_uint32(&st->buffer,LABEL_MSG6);
     buf_prepend_uint32(&st->buffer,st->index);
     buf_prepend_uint32(&st->buffer,session_id);
@@ -719,6 +889,8 @@ static void create_msg6(struct site *st, struct transform_inst_if *transform,
 
 static bool_t generate_msg6(struct site *st)
 {
+    if (!is_transform_valid(st->new_transform))
+       return False;
     create_msg6(st,st->new_transform,st->setup_session_id);
     st->retries=1; /* Peer will retransmit MSG5 if this packet gets lost */
     return True;
@@ -732,8 +904,7 @@ static bool_t process_msg6(struct site *st, struct buffer_if *msg6,
 
     if (!unpick_msg0(st,msg6,&m)) return False;
 
-    if (st->new_transform->reverse(st->new_transform->st,
-                                  msg6,&transform_err)) {
+    if (call_transform_reverse(st,st->new_transform,msg6,&transform_err)) {
        /* There's a problem */
        slog(st,LOG_SEC,"process_msg6: transform: %s",transform_err);
        return False;
@@ -761,8 +932,8 @@ static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
     /* Keep a copy so we can try decrypting it with multiple keys */
     buffer_copy(&st->scratch, msg0);
 
-    problem = st->current.transform->reverse(st->current.transform->st,
-                                            msg0,&transform_err);
+    problem = call_transform_reverse(st,st->current.transform,
+                                    msg0,&transform_err);
     if (!problem) {
        if (!st->auxiliary_is_new)
            delete_one_key(st,&st->auxiliary_key,
@@ -773,8 +944,8 @@ static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
        goto skew;
 
     buffer_copy(msg0, &st->scratch);
-    problem = st->auxiliary_key.transform->reverse
-       (st->auxiliary_key.transform->st,msg0,&auxkey_err);
+    problem = call_transform_reverse(st,st->auxiliary_key.transform,
+                                    msg0,&auxkey_err);
     if (problem==0) {
        slog(st,LOG_DROP,"processing packet which uses auxiliary key");
        if (st->auxiliary_is_new) {
@@ -799,8 +970,8 @@ static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
 
     if (st->state==SITE_SENTMSG5) {
        buffer_copy(msg0, &st->scratch);
-       problem = st->new_transform->reverse(st->new_transform->st,
-                                            msg0,&newkey_err);
+       problem = call_transform_reverse(st,st->new_transform,
+                                        msg0,&newkey_err);
        if (!problem) {
            /* It looks like we didn't get the peer's MSG6 */
            /* This is like a cut-down enter_new_state(SITE_RUN) */
@@ -859,9 +1030,9 @@ static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
 static void dump_packet(struct site *st, struct buffer_if *buf,
                        const struct comm_addr *addr, bool_t incoming)
 {
-    uint32_t dest=ntohl(*(uint32_t *)buf->start);
-    uint32_t source=ntohl(*(uint32_t *)(buf->start+4));
-    uint32_t msgtype=ntohl(*(uint32_t *)(buf->start+8));
+    uint32_t dest=get_uint32(buf->start);
+    uint32_t source=get_uint32(buf->start+4);
+    uint32_t msgtype=get_uint32(buf->start+8);
 
     if (st->log_events & LOG_DUMP)
        slilog(st->log,M_DEBUG,"%s: %s: %08x<-%08x: %08x:",
@@ -890,8 +1061,8 @@ static bool_t send_msg(struct site *st)
        t=st->auxiliary_key.transform;
        st->auxiliary_key.transform=st->new_transform;
        st->new_transform=t;
+       dispose_transform(&st->new_transform);
 
-       t->delkey(t->st);
        st->auxiliary_is_new=1;
        st->auxiliary_key.key_timeout=st->now+st->key_lifetime;
        st->auxiliary_renegotiate_key_time=st->now+st->key_renegotiate_time;
@@ -960,8 +1131,8 @@ static void activate_new_key(struct site *st)
     st->auxiliary_key.transform=st->current.transform;
     st->current.transform=st->new_transform;
     st->new_transform=t;
+    dispose_transform(&st->new_transform);
 
-    t->delkey(t->st);
     st->timeout=0;
     st->auxiliary_is_new=0;
     st->auxiliary_key.key_timeout=st->current.key_timeout;
@@ -977,9 +1148,9 @@ static void activate_new_key(struct site *st)
 static void delete_one_key(struct site *st, struct data_key *key,
                           cstring_t reason, cstring_t which, uint32_t loglevel)
 {
-    if (!key->transform->valid(key->transform->st)) return;
+    if (!is_transform_valid(key->transform)) return;
     if (reason) slog(st,loglevel,"%s deleted (%s)",which,reason);
-    key->transform->delkey(key->transform->st);
+    dispose_transform(&key->transform);
     key->key_timeout=0;
 }
 
@@ -1004,7 +1175,7 @@ static void enter_state_stop(struct site *st)
     st->state=SITE_STOP;
     st->timeout=0;
     delete_keys(st,"entering state STOP",LOG_TIMEOUT_KEY);
-    st->new_transform->delkey(st->new_transform->st);
+    dispose_transform(&st->new_transform);
 }
 
 static void set_link_quality(struct site *st)
@@ -1034,7 +1205,7 @@ static void enter_state_run(struct site *st)
     transport_peers_clear(st,&st->setup_peers);
     memset(st->localN,0,NONCELEN);
     memset(st->remoteN,0,NONCELEN);
-    st->new_transform->delkey(st->new_transform->st);
+    dispose_transform(&st->new_transform);
     memset(st->dhsecret,0,st->dh->len);
     memset(st->sharedsecret,0,st->sharedsecretlen);
     set_link_quality(st);
@@ -1125,16 +1296,18 @@ static bool_t send_msg7(struct site *st, cstring_t reason)
     if (current_valid(st) && st->buffer.free
        && transport_peers_valid(&st->peers)) {
        BUF_ALLOC(&st->buffer,"site:MSG7");
-       buffer_init(&st->buffer,st->transform->max_start_pad+(4*3));
+       buffer_init(&st->buffer,calculate_max_start_pad());
        buf_append_uint32(&st->buffer,LABEL_MSG7);
        buf_append_string(&st->buffer,reason);
-       st->current.transform->forwards(st->current.transform->st,
-                                       &st->buffer, &transform_err);
+       if (call_transform_forwards(st, st->current.transform,
+                                   &st->buffer, &transform_err))
+           goto free_out;
        buf_prepend_uint32(&st->buffer,LABEL_MSG0);
        buf_prepend_uint32(&st->buffer,st->index);
        buf_prepend_uint32(&st->buffer,st->current.remote_session_id);
        transport_xmit(st,&st->peers,&st->buffer,True);
        BUF_FREE(&st->buffer);
+    free_out:
        return True;
     }
     return False;
@@ -1231,13 +1404,15 @@ static void site_outgoing(void *sst, struct buffer_if *buf)
        /* Transform it and send it */
        if (buf->size>0) {
            buf_prepend_uint32(buf,LABEL_MSG9);
-           st->current.transform->forwards(st->current.transform->st,
-                                           buf, &transform_err);
+           if (call_transform_forwards(st, st->current.transform,
+                                       buf, &transform_err))
+               goto free_out;
            buf_prepend_uint32(buf,LABEL_MSG0);
            buf_prepend_uint32(buf,st->index);
            buf_prepend_uint32(buf,st->current.remote_session_id);
            transport_xmit(st,&st->peers,buf,False);
        }
+    free_out:
        BUF_FREE(buf);
        return;
     }
@@ -1268,8 +1443,8 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 
     if (buf->size < 12) return False;
 
-    uint32_t msgtype=ntohl(get_uint32(buf->start+8));
-    uint32_t dest=ntohl(*(uint32_t *)buf->start);
+    uint32_t dest=get_uint32(buf->start);
+    uint32_t msgtype=get_uint32(buf->start+8);
     struct msg named_msg;
 
     if (msgtype==LABEL_MSG1) {
@@ -1350,10 +1525,11 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
            }
            break;
        case LABEL_MSG3:
+       case LABEL_MSG3BIS:
            /* Setup packet: expected only in state SENTMSG2 */
            if (st->state!=SITE_SENTMSG2) {
                slog(st,LOG_UNEXPECTED,"unexpected MSG3");
-           } else if (process_msg3(st,buf,source)) {
+           } else if (process_msg3(st,buf,source,msgtype)) {
                transport_setup_msgok(st,source);
                enter_new_state(st,SITE_SENTMSG4);
            } else {
@@ -1493,21 +1669,28 @@ 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");
-    if (!comms_cfg) cfgfatal(loc,"site","closure list \"comm\" not found\n");
-    st->ncomms=list_length(comms_cfg);
-    st->comms=safe_malloc_ary(sizeof(*st->comms),st->ncomms,"comms");
-    assert(st->ncomms);
-    for (i=0; i<st->ncomms; i++) {
-       item_t *item=list_elem(comms_cfg,i);
-       if (item->type!=t_closure)
-           cfgfatal(loc,"site","comm is not a closure\n");
-       closure_t *cl=item->data.closure;
-       if (cl->type!=CL_COMM) cfgfatal(loc,"site","comm closure wrong type\n");
-       st->comms[i]=cl->interface;
-    }
+#define GET_CLOSURE_LIST(dictkey,things,nthings,CL_TYPE) do{           \
+    list_t *things##_cfg=dict_lookup(dict,dictkey);                    \
+    if (!things##_cfg)                                                 \
+       cfgfatal(loc,"site","closure list \"%s\" not found\n",dictkey); \
+    st->nthings=list_length(things##_cfg);                             \
+    st->things=safe_malloc_ary(sizeof(*st->things),st->nthings,dictkey "s"); \
+    assert(st->nthings);                                               \
+    for (i=0; i<st->nthings; i++) {                                    \
+       item_t *item=list_elem(things##_cfg,i);                         \
+       if (item->type!=t_closure)                                      \
+           cfgfatal(loc,"site","%s is not a closure\n",dictkey);       \
+       closure_t *cl=item->data.closure;                               \
+       if (cl->type!=CL_TYPE)                                          \
+           cfgfatal(loc,"site","%s closure wrong type\n",dictkey);     \
+       st->things[i]=cl->interface;                                    \
+    }                                                                  \
+}while(0)
+
+    GET_CLOSURE_LIST("comm",comms,ncomms,CL_COMM);
 
     st->resolver=find_cl_if(dict,"resolver",CL_RESOLVER,True,"site",loc);
     st->log=find_cl_if(dict,"log",CL_LOG,True,"site",loc);
@@ -1520,8 +1703,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     else st->remoteport=0;
     st->pubkey=find_cl_if(dict,"key",CL_RSAPUBKEY,True,"site",loc);
 
-    st->transform=
-       find_cl_if(dict,"transform",CL_TRANSFORM,True,"site",loc);
+    GET_CLOSURE_LIST("transform",transforms,ntransforms,CL_TRANSFORM);
 
     st->dh=find_cl_if(dict,"dh",CL_DH,True,"site",loc);
     st->hash=find_cl_if(dict,"hash",CL_HASH,True,"site",loc);
@@ -1579,38 +1761,35 @@ 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->chosen_transform=0;
     st->current.key_timeout=0;
     st->auxiliary_key.key_timeout=0;
     transport_peers_clear(st,&st->peers);
     transport_peers_clear(st,&st->setup_peers);
     /* XXX mlock these */
     st->dhsecret=safe_malloc(st->dh->len,"site:dhsecret");
-    st->sharedsecretlen=st->transform->keylen?:st->dh->ceil_len;
-    st->sharedsecret=safe_malloc(st->sharedsecretlen,"site:sharedsecret");
-
-    /* We need to compute some properties of our comms */
-#define COMPUTE_WORST(pad)                     \
-    int worst_##pad=0;                         \
-    for (i=0; i<st->ncomms; i++) {             \
-       int thispad=st->comms[i]->pad;          \
-       if (thispad > worst_##pad)              \
-           worst_##pad=thispad;                \
+    st->sharedsecretlen=st->sharedsecretallocd=0;
+    st->sharedsecret=0;
+
+    for (i=0; i<st->ntransforms; i++) {
+       struct transform_if *ti=st->transforms[i];
+       uint32_t capbit = 1UL << ti->capab_transformnum;
+       if (st->local_capabilities & capbit)
+           slog(st,LOG_ERROR,"transformnum capability bit"
+                " %d (%#"PRIx32") reused", ti->capab_transformnum, capbit);
+       st->local_capabilities |= capbit;
     }
-    COMPUTE_WORST(min_start_pad)
-    COMPUTE_WORST(min_end_pad)
 
     /* We need to register the remote networks with the netlink device */
-    st->netlink->reg(st->netlink->st, site_outgoing, st,
-                    st->transform->max_start_pad+(4*4)+
-                    worst_min_start_pad,
-                    st->transform->max_end_pad+worst_min_end_pad);
+    st->netlink->reg(st->netlink->st, site_outgoing, st);
     
     for (i=0; i<st->ncomms; i++)
        st->comms[i]->request_notify(st->comms[i]->st, st, site_incoming);
 
-    st->current.transform=st->transform->create(st->transform->st);
-    st->auxiliary_key.transform=st->transform->create(st->transform->st);
-    st->new_transform=st->transform->create(st->transform->st);
+    st->current.transform=0;
+    st->auxiliary_key.transform=0;
+    st->new_transform=0;
     st->auxiliary_is_new=0;
 
     enter_state_stop(st);
@@ -1718,7 +1897,7 @@ static bool_t transport_compute_setupinit_peers(struct site *st,
     slog(st,LOG_SETUP_INIT,
         (!configured_addr ? "using only %d old peer address(es)"
          : "using configured address, and/or perhaps %d old peer address(es)"),
-        st->peers);
+        st->peers.npeers);
 
     /* Non-mobile peers havve st->peers.npeers==0 or ==1, since they
      * have transport_peers_max==1.  The effect is that this code