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Refactor ecdh_kex into an organised vtable.

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This is already slightly nice because it lets me separate the
Weierstrass and Montgomery code more completely, without having to
have a vtable tucked into dh->extra. But more to the point, it will
allow completely different kex methods to fit into the same framework
later.

To that end, I've moved more of the descriptive message generation
into the vtable, and also provided the constructor with a flag that
will let it do different things in client and server.

Also, following on from a previous commit, I've arranged that the new
API returns arbitrary binary data for the exchange hash, rather than
an mp_int. An upcoming implementation of this interface will want to
return an encoded string instead of an encoded mp_int.
This commit is contained in:
Simon Tatham
2022-04-14 07:04:33 +01:00
parent 422a89e208
commit e59ee96554
9 changed files with 207 additions and 168 deletions
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22
ssh/kex2-client.c
View File

@ -185,13 +185,14 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
mp_free(s->p); s->p = NULL;
}
} else if (s->kex_alg->main_type == KEXTYPE_ECDH) {
ppl_logevent("Doing ECDH key exchange with curve %s and hash %s",
ssh_ecdhkex_curve_textname(s->kex_alg),
char *desc = ecdh_keyalg_description(s->kex_alg);
ppl_logevent("Doing %s, using hash %s", desc,
ssh_hash_alg(s->exhash)->text_name);
sfree(desc);
s->ppl.bpp->pls->kctx = SSH2_PKTCTX_ECDHKEX;
s->ecdh_key = ssh_ecdhkex_newkey(s->kex_alg);
s->ecdh_key = ecdh_key_new(s->kex_alg, false);
if (!s->ecdh_key) {
ssh_sw_abort(s->ppl.ssh, "Unable to generate key for ECDH");
*aborted = true;
@ -201,7 +202,7 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
pktout = ssh_bpp_new_pktout(s->ppl.bpp, SSH2_MSG_KEX_ECDH_INIT);
{
strbuf *pubpoint = strbuf_new();
ssh_ecdhkex_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
ecdh_key_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
put_stringsb(pktout, pubpoint);
}
@ -224,7 +225,7 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
{
strbuf *pubpoint = strbuf_new();
ssh_ecdhkex_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
ecdh_key_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
put_string(s->exhash, pubpoint->u, pubpoint->len);
strbuf_free(pubpoint);
}
@ -232,15 +233,14 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
{
ptrlen keydata = get_string(pktin);
put_stringpl(s->exhash, keydata);
mp_int *K = ssh_ecdhkex_getkey(s->ecdh_key, keydata);
if (!get_err(pktin) && !K) {
bool ok = ecdh_key_getkey(s->ecdh_key, keydata,
BinarySink_UPCAST(s->kex_shared_secret));
if (!get_err(pktin) && !ok) {
ssh_proto_error(s->ppl.ssh, "Received invalid elliptic curve "
"point in ECDH reply");
*aborted = true;
return;
}
put_mp_ssh2(s->kex_shared_secret, K);
mp_free(K);
}
s->sigdata = get_string(pktin);
@ -250,7 +250,7 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
return;
}
ssh_ecdhkex_freekey(s->ecdh_key);
ecdh_key_free(s->ecdh_key);
s->ecdh_key = NULL;
#ifndef NO_GSSAPI
} else if (s->kex_alg->main_type == KEXTYPE_GSS) {

19
ssh/kex2-server.c
View File

@ -191,12 +191,12 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
mp_free(s->p); s->p = NULL;
}
} else if (s->kex_alg->main_type == KEXTYPE_ECDH) {
ppl_logevent("Doing ECDH key exchange with curve %s and hash %s",
ssh_ecdhkex_curve_textname(s->kex_alg),
char *desc = ecdh_keyalg_description(s->kex_alg);
ppl_logevent("Doing %s, using hash %s", desc,
ssh_hash_alg(s->exhash)->text_name);
s->ppl.bpp->pls->kctx = SSH2_PKTCTX_ECDHKEX;
sfree(desc);
s->ecdh_key = ssh_ecdhkex_newkey(s->kex_alg);
s->ecdh_key = ecdh_key_new(s->kex_alg, true);
if (!s->ecdh_key) {
ssh_sw_abort(s->ppl.ssh, "Unable to generate key for ECDH");
*aborted = true;
@ -219,29 +219,28 @@ void ssh2kex_coroutine(struct ssh2_transport_state *s, bool *aborted)
ptrlen keydata = get_string(pktin);
put_stringpl(s->exhash, keydata);
mp_int *K = ssh_ecdhkex_getkey(s->ecdh_key, keydata);
if (!get_err(pktin) && !K) {
bool ok = ecdh_key_getkey(s->ecdh_key, keydata,
BinarySink_UPCAST(s->kex_shared_secret));
if (!get_err(pktin) && !ok) {
ssh_proto_error(s->ppl.ssh, "Received invalid elliptic curve "
"point in ECDH initial packet");
*aborted = true;
return;
}
put_mp_ssh2(s->kex_shared_secret, K);
mp_free(K);
}
pktout = ssh_bpp_new_pktout(s->ppl.bpp, SSH2_MSG_KEX_ECDH_REPLY);
put_stringpl(pktout, s->hostkeydata);
{
strbuf *pubpoint = strbuf_new();
ssh_ecdhkex_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
ecdh_key_getpublic(s->ecdh_key, BinarySink_UPCAST(pubpoint));
put_string(s->exhash, pubpoint->u, pubpoint->len);
put_stringsb(pktout, pubpoint);
}
put_stringsb(pktout, finalise_and_sign_exhash(s));
pq_push(s->ppl.out_pq, pktout);
ssh_ecdhkex_freekey(s->ecdh_key);
ecdh_key_free(s->ecdh_key);
s->ecdh_key = NULL;
} else if (s->kex_alg->main_type == KEXTYPE_GSS) {
ssh_sw_abort(s->ppl.ssh, "GSS key exchange not supported in server");

2
ssh/transport2.c
View File

@ -227,7 +227,7 @@ static void ssh2_transport_free(PacketProtocolLayer *ppl)
sfree(s->rsa_kex_key);
}
if (s->ecdh_key)
ssh_ecdhkex_freekey(s->ecdh_key);
ecdh_key_free(s->ecdh_key);
if (s->exhash)
ssh_hash_free(s->exhash);
strbuf_free(s->outgoing_kexinit);