- djm@cvs.openbsd.org 2010/09/09 10:45:45
[kex.c kex.h kexecdh.c key.c key.h monitor.c ssh-ecdsa.c]
ECDH/ECDSA compliance fix: these methods vary the hash function they use
(SHA256/384/512) depending on the length of the curve in use. The previous
code incorrectly used SHA256 in all cases.
This fix will cause authentication failure when using 384 or 521-bit curve
keys if one peer hasn't been upgraded and the other has. (256-bit curve
keys work ok). In particular you may need to specify HostkeyAlgorithms
when connecting to a server that has not been upgraded from an upgraded
client.
ok naddy@
diff --git a/ChangeLog b/ChangeLog
index 32f8236..87fee3b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -49,6 +49,19 @@
gcc, at least in earlier versions, but this does not forgive your current
transgressions) seen between zlib and openssl
ok djm
+ - djm@cvs.openbsd.org 2010/09/09 10:45:45
+ [kex.c kex.h kexecdh.c key.c key.h monitor.c ssh-ecdsa.c]
+ ECDH/ECDSA compliance fix: these methods vary the hash function they use
+ (SHA256/384/512) depending on the length of the curve in use. The previous
+ code incorrectly used SHA256 in all cases.
+
+ This fix will cause authentication failure when using 384 or 521-bit curve
+ keys if one peer hasn't been upgraded and the other has. (256-bit curve
+ keys work ok). In particular you may need to specify HostkeyAlgorithms
+ when connecting to a server that has not been upgraded from an upgraded
+ client.
+
+ ok naddy@
20100831
- OpenBSD CVS Sync
diff --git a/kex.c b/kex.c
index abe9b9f..7c87631 100644
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.84 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.85 2010/09/09 10:45:45 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
@@ -325,10 +325,10 @@
} else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
k->kex_type = KEX_DH_GEX_SHA256;
k->evp_md = evp_ssh_sha256();
- } else if (strncmp(k->name, KEX_ECDH_SHA256,
- sizeof(KEX_ECDH_SHA256) - 1) == 0) {
- k->kex_type = KEX_ECDH_SHA2;
- k->evp_md = evp_ssh_sha256();
+ } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
+ sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
+ k->kex_type = KEX_ECDH_SHA2;
+ k->evp_md = kex_ecdh_name_to_evpmd(k->name);
#endif
} else
fatal("bad kex alg %s", k->name);
diff --git a/kex.h b/kex.h
index a183ffd..f5dcc87 100644
--- a/kex.h
+++ b/kex.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.50 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: kex.h,v 1.51 2010/09/09 10:45:45 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
@@ -39,7 +39,7 @@
#define KEX_DHGEX_SHA256 "diffie-hellman-group-exchange-sha256"
#define KEX_RESUME "resume@appgate.com"
/* The following represents the family of ECDH methods */
-#define KEX_ECDH_SHA256 "ecdh-sha2-"
+#define KEX_ECDH_SHA2_STEM "ecdh-sha2-"
#define COMP_NONE 0
#define COMP_ZLIB 1
@@ -165,6 +165,7 @@
const BIGNUM *, u_char **, u_int *);
int kex_ecdh_name_to_nid(const char *);
+const EVP_MD *kex_ecdh_name_to_evpmd(const char *);
void
derive_ssh1_session_id(BIGNUM *, BIGNUM *, u_int8_t[8], u_int8_t[16]);
diff --git a/kexecdh.c b/kexecdh.c
index bd57181..f59d7b9 100644
--- a/kexecdh.c
+++ b/kexecdh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexecdh.c,v 1.1 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: kexecdh.c,v 1.2 2010/09/09 10:45:45 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -48,15 +48,23 @@
{
int ret;
- if (strlen(kexname) < sizeof(KEX_ECDH_SHA256) - 1)
+ if (strlen(kexname) < sizeof(KEX_ECDH_SHA2_STEM) - 1)
fatal("%s: kexname too short \"%s\"", __func__, kexname);
- ret = key_curve_name_to_nid(kexname + sizeof(KEX_ECDH_SHA256) - 1);
+ ret = key_curve_name_to_nid(kexname + sizeof(KEX_ECDH_SHA2_STEM) - 1);
if (ret == -1)
fatal("%s: unsupported curve negotiated \"%s\"", __func__,
kexname);
return ret;
}
+const EVP_MD *
+kex_ecdh_name_to_evpmd(const char *kexname)
+{
+ int nid = kex_ecdh_name_to_nid(kexname);
+
+ return key_ec_nid_to_evpmd(nid);
+}
+
void
kex_ecdh_hash(
const EVP_MD *evp_md,
diff --git a/key.c b/key.c
index 842280a..b9dc235 100644
--- a/key.c
+++ b/key.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: key.c,v 1.92 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: key.c,v 1.93 2010/09/09 10:45:45 djm Exp $ */
/*
* read_bignum():
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -978,17 +978,7 @@
return BN_num_bits(k->dsa->p);
case KEY_ECDSA:
case KEY_ECDSA_CERT:
- switch (k->ecdsa_nid) {
- case NID_X9_62_prime256v1:
- return 256;
- case NID_secp384r1:
- return 384;
- case NID_secp521r1:
- return 521;
- default:
- break;
- }
- break;
+ return key_curve_nid_to_bits(k->ecdsa_nid);
}
return 0;
}
@@ -1961,6 +1951,7 @@
}
}
+/* XXX: these are really begging for a table-driven approach */
int
key_curve_name_to_nid(const char *name)
{
@@ -1975,6 +1966,22 @@
return -1;
}
+u_int
+key_curve_nid_to_bits(int nid)
+{
+ switch (nid) {
+ case NID_X9_62_prime256v1:
+ return 256;
+ case NID_secp384r1:
+ return 384;
+ case NID_secp521r1:
+ return 521;
+ default:
+ error("%s: unsupported EC curve nid %d", __func__, nid);
+ return 0;
+ }
+}
+
const char *
key_curve_nid_to_name(int nid)
{
@@ -1989,6 +1996,22 @@
return NULL;
}
+const EVP_MD *
+key_ec_nid_to_evpmd(int nid)
+{
+ int kbits = key_curve_nid_to_bits(nid);
+
+ if (kbits == 0)
+ fatal("%s: invalid nid %d", __func__, nid);
+ /* RFC5656 section 6.2.1 */
+ if (kbits <= 256)
+ return EVP_sha256();
+ else if (kbits <= 384)
+ return EVP_sha384();
+ else
+ return EVP_sha512();
+}
+
int
key_ec_validate_public(const EC_GROUP *group, const EC_POINT *public)
{
diff --git a/key.h b/key.h
index 2eb1243..ba1a20c 100644
--- a/key.h
+++ b/key.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: key.h,v 1.31 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: key.h,v 1.32 2010/09/09 10:45:45 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
@@ -112,8 +112,10 @@
int key_ecdsa_nid_from_name(const char *);
int key_curve_name_to_nid(const char *);
const char * key_curve_nid_to_name(int);
+u_int key_curve_nid_to_bits(int);
int key_ecdsa_bits_to_nid(int);
int key_ecdsa_group_to_nid(const EC_GROUP *);
+const EVP_MD * key_ec_nid_to_evpmd(int nid);
int key_ec_validate_public(const EC_GROUP *, const EC_POINT *);
int key_ec_validate_private(const EC_KEY *);
diff --git a/monitor.c b/monitor.c
index 32395ee..29d987c 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.109 2010/08/31 11:54:45 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.110 2010/09/09 10:45:45 djm Exp $ */
/*
* Copyright 2002 Niels Provos <provos@citi.umich.edu>
* Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -590,10 +590,10 @@
p = buffer_get_string(m, &datlen);
/*
- * Supported KEX types will only return SHA1 (20 byte) or
- * SHA256 (32 byte) hashes
+ * Supported KEX types use SHA1 (20 bytes), SHA256 (32 bytes),
+ * SHA384 (48 bytes) and SHA512 (64 bytes).
*/
- if (datlen != 20 && datlen != 32)
+ if (datlen != 20 && datlen != 32 && datlen != 48 && datlen != 64)
fatal("%s: data length incorrect: %u", __func__, datlen);
/* save session id, it will be passed on the first call */
diff --git a/ssh-ecdsa.c b/ssh-ecdsa.c
index 0627ee5..5c4ce23 100644
--- a/ssh-ecdsa.c
+++ b/ssh-ecdsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD$ */
+/* $OpenBSD: ssh-ecdsa.c,v 1.4 2010/09/10 01:04:10 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -46,7 +46,7 @@
const u_char *data, u_int datalen)
{
ECDSA_SIG *sig;
- const EVP_MD *evp_md = EVP_sha256();
+ const EVP_MD *evp_md;
EVP_MD_CTX md;
u_char digest[EVP_MAX_MD_SIZE];
u_int len, dlen;
@@ -57,6 +57,7 @@
error("%s: no ECDSA key", __func__);
return -1;
}
+ evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, &dlen);
@@ -94,21 +95,22 @@
const u_char *data, u_int datalen)
{
ECDSA_SIG *sig;
- const EVP_MD *evp_md = EVP_sha256();
+ const EVP_MD *evp_md;
EVP_MD_CTX md;
u_char digest[EVP_MAX_MD_SIZE], *sigblob;
u_int len, dlen;
int rlen, ret;
Buffer b, bb;
+ char *ktype;
if (key == NULL || key->ecdsa == NULL ||
(key->type != KEY_ECDSA && key->type != KEY_ECDSA_CERT)) {
error("%s: no ECDSA key", __func__);
return -1;
}
+ evp_md = key_ec_nid_to_evpmd(key->ecdsa_nid);
/* fetch signature */
- char *ktype;
buffer_init(&b);
buffer_append(&b, signature, signaturelen);
ktype = buffer_get_string(&b, NULL);