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- 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@
This commit is contained in:
Damien Miller 2010-09-10 11:23:34 +10:00
parent 3796ab47d3
commit 041ab7c1e7
8 changed files with 80 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
ChangeLog
View File

@ -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

10
kex.c
View File

@ -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 @@ choose_kex(Kex *k, char *client, char *server)
} 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);

5
kex.h
View File

@ -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 @@ kex_ecdh_hash(const EVP_MD *, const EC_GROUP *, char *, char *, char *, int,
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]);

14
kexecdh.c
View File

@ -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 @@ kex_ecdh_name_to_nid(const char *kexname)
{
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,

47
key.c
View File

@ -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 @@ key_size(const Key *k)
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 @@ key_cert_is_legacy(Key *k)
}
}
/* XXX: these are really begging for a table-driven approach */
int
key_curve_name_to_nid(const char *name)
{
@ -1975,6 +1966,22 @@ key_curve_name_to_nid(const char *name)
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 @@ key_curve_nid_to_name(int nid)
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)
{

4
key.h
View File

@ -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_cert_is_legacy(Key *);
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 *);

8
monitor.c
View File

@ -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 @@ mm_answer_sign(int sock, Buffer *m)
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 */

10
ssh-ecdsa.c
View File

@ -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 @@ ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
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 @@ ssh_ecdsa_sign(const Key *key, u_char **sigp, u_int *lenp,
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 @@ ssh_ecdsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
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);