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Refuse RSA keys <1024 bits in length. Improve reporting
for keys that do not meet this requirement. ok markus@

Upstream-ID: b385e2a7b13b1484792ee681daaf79e1e203df6c
This commit is contained in:
djm@openbsd.org 2017-05-07 23:15:59 +00:00 committed by Damien Miller
parent 70c1218fc4
commit bd636f4091
7 changed files with 54 additions and 25 deletions
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24
ssh-keygen.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-keygen.c,v 1.302 2017/04/30 23:18:44 djm Exp $ */
/* $OpenBSD: ssh-keygen.c,v 1.303 2017/05/07 23:15:59 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@ -226,13 +226,21 @@ type_bits_valid(int type, const char *name, u_int32_t *bitsp)
OPENSSL_DSA_MAX_MODULUS_BITS : OPENSSL_RSA_MAX_MODULUS_BITS;
if (*bitsp > maxbits)
fatal("key bits exceeds maximum %d", maxbits);
if (type == KEY_DSA && *bitsp != 1024)
fatal("DSA keys must be 1024 bits");
else if (type != KEY_ECDSA && type != KEY_ED25519 && *bitsp < 1024)
fatal("Key must at least be 1024 bits");
else if (type == KEY_ECDSA && sshkey_ecdsa_bits_to_nid(*bitsp) == -1)
fatal("Invalid ECDSA key length - valid lengths are "
"256, 384 or 521 bits");
switch (type) {
case KEY_DSA:
if (*bitsp != 1024)
fatal("Invalid DSA key length: must be 1024 bits");
break;
case KEY_RSA:
if (*bitsp < SSH_RSA_MINIMUM_MODULUS_SIZE)
fatal("Invalid RSA key length: minimum is %d bits",
SSH_RSA_MINIMUM_MODULUS_SIZE);
break;
case KEY_ECDSA:
if (sshkey_ecdsa_bits_to_nid(*bitsp) == -1)
fatal("Invalid ECDSA key length: valid lengths are "
"256, 384 or 521 bits");
}
#endif
}

10
ssh-rsa.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-rsa.c,v 1.60 2016/09/12 23:39:34 djm Exp $ */
/* $OpenBSD: ssh-rsa.c,v 1.61 2017/05/07 23:15:59 djm Exp $ */
/*
* Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
*
@ -99,9 +99,10 @@ ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
else
hash_alg = rsa_hash_alg_from_ident(alg_ident);
if (key == NULL || key->rsa == NULL || hash_alg == -1 ||
sshkey_type_plain(key->type) != KEY_RSA ||
BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
sshkey_type_plain(key->type) != KEY_RSA)
return SSH_ERR_INVALID_ARGUMENT;
if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
return SSH_ERR_KEY_LENGTH;
slen = RSA_size(key->rsa);
if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM)
return SSH_ERR_INVALID_ARGUMENT;
@ -172,9 +173,10 @@ ssh_rsa_verify(const struct sshkey *key,
if (key == NULL || key->rsa == NULL ||
sshkey_type_plain(key->type) != KEY_RSA ||
BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE ||
sig == NULL || siglen == 0)
return SSH_ERR_INVALID_ARGUMENT;
if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
return SSH_ERR_KEY_LENGTH;
if ((b = sshbuf_from(sig, siglen)) == NULL)
return SSH_ERR_ALLOC_FAIL;

5
ssh.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh.h,v 1.86 2017/05/03 21:08:09 naddy Exp $ */
/* $OpenBSD: ssh.h,v 1.87 2017/05/07 23:15:59 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -98,8 +98,5 @@
#define SSH_PRIVSEP_USER "sshd"
#endif
/* Minimum modulus size (n) for RSA keys. */
#define SSH_RSA_MINIMUM_MODULUS_SIZE 768
/* Listen backlog for sshd, ssh-agent and forwarding sockets */
#define SSH_LISTEN_BACKLOG 128

4
ssherr.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssherr.c,v 1.5 2015/09/13 14:39:16 tim Exp $ */
/* $OpenBSD: ssherr.c,v 1.6 2017/05/07 23:15:59 djm Exp $ */
/*
* Copyright (c) 2011 Damien Miller
*
@ -135,6 +135,8 @@ ssh_err(int n)
return "Connection corrupted";
case SSH_ERR_PROTOCOL_ERROR:
return "Protocol error";
case SSH_ERR_KEY_LENGTH:
return "Invalid key length";
default:
return "unknown error";
}

3
ssherr.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssherr.h,v 1.3 2015/01/30 01:13:33 djm Exp $ */
/* $OpenBSD: ssherr.h,v 1.4 2017/05/07 23:15:59 djm Exp $ */
/*
* Copyright (c) 2011 Damien Miller
*
@ -77,6 +77,7 @@
#define SSH_ERR_CONN_TIMEOUT -53
#define SSH_ERR_CONN_CORRUPT -54
#define SSH_ERR_PROTOCOL_ERROR -55
#define SSH_ERR_KEY_LENGTH -56
/* Translate a numeric error code to a human-readable error string */
const char *ssh_err(int n);

29
sshkey.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: sshkey.c,v 1.48 2017/04/30 23:18:44 djm Exp $ */
/* $OpenBSD: sshkey.c,v 1.49 2017/05/07 23:15:59 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2008 Alexander von Gernler. All rights reserved.
@ -1392,10 +1392,11 @@ rsa_generate_private_key(u_int bits, RSA **rsap)
BIGNUM *f4 = NULL;
int ret = SSH_ERR_INTERNAL_ERROR;
if (rsap == NULL ||
bits < SSH_RSA_MINIMUM_MODULUS_SIZE ||
bits > SSHBUF_MAX_BIGNUM * 8)
if (rsap == NULL)
return SSH_ERR_INVALID_ARGUMENT;
if (bits < SSH_RSA_MINIMUM_MODULUS_SIZE ||
bits > SSHBUF_MAX_BIGNUM * 8)
return SSH_ERR_KEY_LENGTH;
*rsap = NULL;
if ((private = RSA_new()) == NULL || (f4 = BN_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
@ -1423,8 +1424,10 @@ dsa_generate_private_key(u_int bits, DSA **dsap)
DSA *private;
int ret = SSH_ERR_INTERNAL_ERROR;
if (dsap == NULL || bits != 1024)
if (dsap == NULL)
return SSH_ERR_INVALID_ARGUMENT;
if (bits != 1024)
return SSH_ERR_KEY_LENGTH;
if ((private = DSA_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
@ -1876,6 +1879,10 @@ sshkey_from_blob_internal(struct sshbuf *b, struct sshkey **keyp,
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
ret = SSH_ERR_KEY_LENGTH;
goto out;
}
#ifdef DEBUG_PK
RSA_print_fp(stderr, key->rsa, 8);
#endif
@ -2643,6 +2650,10 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
(r = sshbuf_get_bignum2(buf, k->rsa->q)) != 0 ||
(r = rsa_generate_additional_parameters(k->rsa)) != 0)
goto out;
if (BN_num_bits(k->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
r = SSH_ERR_KEY_LENGTH;
goto out;
}
break;
case KEY_RSA_CERT:
if ((r = sshkey_froms(buf, &k)) != 0 ||
@ -2653,6 +2664,10 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
(r = sshbuf_get_bignum2(buf, k->rsa->q)) != 0 ||
(r = rsa_generate_additional_parameters(k->rsa)) != 0)
goto out;
if (BN_num_bits(k->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
r = SSH_ERR_KEY_LENGTH;
goto out;
}
break;
#endif /* WITH_OPENSSL */
case KEY_ED25519:
@ -3427,6 +3442,10 @@ sshkey_parse_private_pem_fileblob(struct sshbuf *blob, int type,
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
if (BN_num_bits(prv->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
r = SSH_ERR_KEY_LENGTH;
goto out;
}
} else if (pk->type == EVP_PKEY_DSA &&
(type == KEY_UNSPEC || type == KEY_DSA)) {
if ((prv = sshkey_new(KEY_UNSPEC)) == NULL) {

4
sshkey.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: sshkey.h,v 1.17 2017/05/03 21:08:09 naddy Exp $ */
/* $OpenBSD: sshkey.h,v 1.18 2017/05/07 23:15:59 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
@ -46,7 +46,7 @@
# define EC_POINT void
#endif /* WITH_OPENSSL */
#define SSH_RSA_MINIMUM_MODULUS_SIZE 768
#define SSH_RSA_MINIMUM_MODULUS_SIZE 1024
#define SSH_KEY_MAX_SIGN_DATA_SIZE (1 << 20)
struct sshbuf;