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Support elliptic-curve Diffie-Hellman GSS KEX.

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This is surprisingly simple, because it wasn't necessary to touch the
GSS parts at all. Nothing changes about the message formats between
integer DH and ECDH in GSS KEX, except that the mpints sent back and
forth as part of integer DH are replaced by the opaque strings used in
ECDH. So I've invented a new KEXTYPE and made it control a bunch of
small conditionals in the middle of the GSS KEX code, leaving the rest
unchanged.
This commit is contained in:
Simon Tatham
2022-08-29 11:35:34 +01:00
parent 031d86ed5b
commit cec8c87626
6 changed files with 138 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
crypto/diffie-hellman.c
View File

@ -223,20 +223,6 @@ static const ssh_kex *const gex_list[] = {
const ssh_kexes ssh_diffiehellman_gex = { lenof(gex_list), gex_list };
/*
* Suffix on GSSAPI SSH protocol identifiers that indicates Kerberos 5
* as the mechanism.
*
* This suffix is the base64-encoded MD5 hash of the byte sequence
* 06 09 2A 86 48 86 F7 12 01 02 02, which in turn is the ASN.1 DER
* encoding of the object ID 1.2.840.113554.1.2.2 which designates
* Kerberos v5.
*
* (The same encoded OID, minus the two-byte DER header, is defined in
* ssh/pgssapi.c as GSS_MECH_KRB5.)
*/
#define GSS_KRB5_OID_HASH "toWM5Slw5Ew8Mqkay+al2g=="
static const ssh_kex ssh_gssk5_diffiehellman_gex_sha1 = {
.name = "gss-gex-sha1-" GSS_KRB5_OID_HASH,
.groupname = NULL,

43
crypto/ecc-ssh.c
View File

@ -1644,6 +1644,14 @@ const ssh_kex ssh_ec_kex_curve25519_libssh = {
.ecdh_vt = &ssh_ecdhkex_m_alg,
.extra = &kex_extra_curve25519,
};
/* GSSAPI variant */
static const ssh_kex ssh_ec_kex_curve25519_gss = {
.name = "gss-curve25519-sha256-" GSS_KRB5_OID_HASH,
.main_type = KEXTYPE_GSS_ECDH,
.hash = &ssh_sha256,
.ecdh_vt = &ssh_ecdhkex_m_alg,
.extra = &kex_extra_curve25519,
};
static const struct eckex_extra kex_extra_curve448 = { ec_curve448 };
const ssh_kex ssh_ec_kex_curve448 = {
@ -1669,6 +1677,14 @@ const ssh_kex ssh_ec_kex_nistp256 = {
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp256,
};
/* GSSAPI variant */
static const ssh_kex ssh_ec_kex_nistp256_gss = {
.name = "gss-nistp256-sha256-" GSS_KRB5_OID_HASH,
.main_type = KEXTYPE_GSS_ECDH,
.hash = &ssh_sha256,
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp256,
};
static const struct eckex_extra kex_extra_nistp384 = { ec_p384 };
const ssh_kex ssh_ec_kex_nistp384 = {
@ -1678,6 +1694,14 @@ const ssh_kex ssh_ec_kex_nistp384 = {
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp384,
};
/* GSSAPI variant */
static const ssh_kex ssh_ec_kex_nistp384_gss = {
.name = "gss-nistp384-sha384-" GSS_KRB5_OID_HASH,
.main_type = KEXTYPE_GSS_ECDH,
.hash = &ssh_sha384,
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp384,
};
static const struct eckex_extra kex_extra_nistp521 = { ec_p521 };
const ssh_kex ssh_ec_kex_nistp521 = {
@ -1687,6 +1711,14 @@ const ssh_kex ssh_ec_kex_nistp521 = {
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp521,
};
/* GSSAPI variant */
static const ssh_kex ssh_ec_kex_nistp521_gss = {
.name = "gss-nistp521-sha512-" GSS_KRB5_OID_HASH,
.main_type = KEXTYPE_GSS_ECDH,
.hash = &ssh_sha512,
.ecdh_vt = &ssh_ecdhkex_w_alg,
.extra = &kex_extra_nistp521,
};
static const ssh_kex *const ec_kex_list[] = {
&ssh_ec_kex_curve448,
@ -1699,6 +1731,17 @@ static const ssh_kex *const ec_kex_list[] = {
const ssh_kexes ssh_ecdh_kex = { lenof(ec_kex_list), ec_kex_list };
static const ssh_kex *const ec_gss_kex_list[] = {
&ssh_ec_kex_curve25519_gss,
&ssh_ec_kex_nistp521_gss,
&ssh_ec_kex_nistp384_gss,
&ssh_ec_kex_nistp256_gss,
};
const ssh_kexes ssh_gssk5_ecdh_kex = {
lenof(ec_gss_kex_list), ec_gss_kex_list
};
/* ----------------------------------------------------------------------
* Helper functions for finding key algorithms and returning auxiliary
* data.