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4ba0d54794
openssh/sshkey.h
djm@openbsd.org 4ba0d54794 upstream: Improve strictness and control over RSA-SHA2 signature 
In ssh, when an agent fails to return a RSA-SHA2 signature when
requested and falls back to RSA-SHA1 instead, retry the signature to
ensure that the public key algorithm sent in the SSH_MSG_USERAUTH
matches the one in the signature itself.

In sshd, strictly enforce that the public key algorithm sent in the
SSH_MSG_USERAUTH message matches what appears in the signature.

Make the sshd_config PubkeyAcceptedKeyTypes and
HostbasedAcceptedKeyTypes options control accepted signature algorithms
(previously they selected supported key types). This allows these
options to ban RSA-SHA1 in favour of RSA-SHA2.

Add new signature algorithms "rsa-sha2-256-cert-v01@openssh.com" and
"rsa-sha2-512-cert-v01@openssh.com" to force use of RSA-SHA2 signatures
with certificate keys.

feedback and ok markus@

OpenBSD-Commit-ID: c6e9f6d45eed8962ad502d315d7eaef32c419dde
2018-07-03 23:26:36 +10:00

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/* $OpenBSD: sshkey.h,v 1.25 2018/07/03 11:39:54 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SSHKEY_H
#define SSHKEY_H
#include <sys/types.h>
#ifdef WITH_OPENSSL
#include <openssl/rsa.h>
#include <openssl/dsa.h>
# ifdef OPENSSL_HAS_ECC
# include <openssl/ec.h>
# else /* OPENSSL_HAS_ECC */
# define EC_KEY void
# define EC_GROUP void
# define EC_POINT void
# endif /* OPENSSL_HAS_ECC */
#else /* WITH_OPENSSL */
# define RSA void
# define DSA void
# define EC_KEY void
# define EC_GROUP void
# define EC_POINT void
#endif /* WITH_OPENSSL */
#define SSH_RSA_MINIMUM_MODULUS_SIZE 1024
#define SSH_KEY_MAX_SIGN_DATA_SIZE (1 << 20)
struct sshbuf;
/* Key types */
enum sshkey_types {
KEY_RSA,
KEY_DSA,
KEY_ECDSA,
KEY_ED25519,
KEY_RSA_CERT,
KEY_DSA_CERT,
KEY_ECDSA_CERT,
KEY_ED25519_CERT,
KEY_XMSS,
KEY_XMSS_CERT,
KEY_UNSPEC
};
/* Default fingerprint hash */
#define SSH_FP_HASH_DEFAULT SSH_DIGEST_SHA256
/* Fingerprint representation formats */
enum sshkey_fp_rep {
SSH_FP_DEFAULT = 0,
SSH_FP_HEX,
SSH_FP_BASE64,
SSH_FP_BUBBLEBABBLE,
SSH_FP_RANDOMART
};
/* Private key serialisation formats, used on the wire */
enum sshkey_serialize_rep {
SSHKEY_SERIALIZE_DEFAULT = 0,
SSHKEY_SERIALIZE_STATE = 1,
SSHKEY_SERIALIZE_FULL = 2,
SSHKEY_SERIALIZE_INFO = 254,
};
/* key is stored in external hardware */
#define SSHKEY_FLAG_EXT 0x0001
#define SSHKEY_CERT_MAX_PRINCIPALS 256
/* XXX opaquify? */
struct sshkey_cert {
struct sshbuf *certblob; /* Kept around for use on wire */
u_int type; /* SSH2_CERT_TYPE_USER or SSH2_CERT_TYPE_HOST */
u_int64_t serial;
char *key_id;
u_int nprincipals;
char **principals;
u_int64_t valid_after, valid_before;
struct sshbuf *critical;
struct sshbuf *extensions;
struct sshkey *signature_key;
};
/* XXX opaquify? */
struct sshkey {
int type;
int flags;
RSA *rsa;
DSA *dsa;
int ecdsa_nid; /* NID of curve */
EC_KEY *ecdsa;
u_char *ed25519_sk;
u_char *ed25519_pk;
char *xmss_name;
char *xmss_filename; /* for state file updates */
void *xmss_state; /* depends on xmss_name, opaque */
u_char *xmss_sk;
u_char *xmss_pk;
struct sshkey_cert *cert;
};
#define ED25519_SK_SZ crypto_sign_ed25519_SECRETKEYBYTES
#define ED25519_PK_SZ crypto_sign_ed25519_PUBLICKEYBYTES
struct sshkey *sshkey_new(int);
int sshkey_add_private(struct sshkey *);
struct sshkey *sshkey_new_private(int);
void sshkey_free(struct sshkey *);
int sshkey_demote(const struct sshkey *, struct sshkey **);
int sshkey_equal_public(const struct sshkey *,
const struct sshkey *);
int sshkey_equal(const struct sshkey *, const struct sshkey *);
char *sshkey_fingerprint(const struct sshkey *,
int, enum sshkey_fp_rep);
int sshkey_fingerprint_raw(const struct sshkey *k,
int, u_char **retp, size_t *lenp);
const char *sshkey_type(const struct sshkey *);
const char *sshkey_cert_type(const struct sshkey *);
int sshkey_format_text(const struct sshkey *, struct sshbuf *);
int sshkey_write(const struct sshkey *, FILE *);
int sshkey_read(struct sshkey *, char **);
u_int sshkey_size(const struct sshkey *);
int sshkey_generate(int type, u_int bits, struct sshkey **keyp);
int sshkey_from_private(const struct sshkey *, struct sshkey **);
int sshkey_type_from_name(const char *);
int sshkey_is_cert(const struct sshkey *);
int sshkey_type_is_cert(int);
int sshkey_type_plain(int);
int sshkey_to_certified(struct sshkey *);
int sshkey_drop_cert(struct sshkey *);
int sshkey_cert_copy(const struct sshkey *, struct sshkey *);
int sshkey_cert_check_authority(const struct sshkey *, int, int,
const char *, const char **);
size_t sshkey_format_cert_validity(const struct sshkey_cert *,
char *, size_t) __attribute__((__bounded__(__string__, 2, 3)));
int sshkey_certify(struct sshkey *, struct sshkey *, const char *);
/* Variant allowing use of a custom signature function (e.g. for ssh-agent) */
typedef int sshkey_certify_signer(const struct sshkey *, u_char **, size_t *,
const u_char *, size_t, const char *, u_int, void *);
int sshkey_certify_custom(struct sshkey *, struct sshkey *, const char *,
sshkey_certify_signer *, void *);
int sshkey_ecdsa_nid_from_name(const char *);
int sshkey_curve_name_to_nid(const char *);
const char * sshkey_curve_nid_to_name(int);
u_int sshkey_curve_nid_to_bits(int);
int sshkey_ecdsa_bits_to_nid(int);
int sshkey_ecdsa_key_to_nid(EC_KEY *);
int sshkey_ec_nid_to_hash_alg(int nid);
int sshkey_ec_validate_public(const EC_GROUP *, const EC_POINT *);
int sshkey_ec_validate_private(const EC_KEY *);
const char *sshkey_ssh_name(const struct sshkey *);
const char *sshkey_ssh_name_plain(const struct sshkey *);
int sshkey_names_valid2(const char *, int);
char *sshkey_alg_list(int, int, int, char);
int sshkey_from_blob(const u_char *, size_t, struct sshkey **);
int sshkey_fromb(struct sshbuf *, struct sshkey **);
int sshkey_froms(struct sshbuf *, struct sshkey **);
int sshkey_to_blob(const struct sshkey *, u_char **, size_t *);
int sshkey_to_base64(const struct sshkey *, char **);
int sshkey_putb(const struct sshkey *, struct sshbuf *);
int sshkey_puts(const struct sshkey *, struct sshbuf *);
int sshkey_puts_opts(const struct sshkey *, struct sshbuf *,
enum sshkey_serialize_rep);
int sshkey_plain_to_blob(const struct sshkey *, u_char **, size_t *);
int sshkey_putb_plain(const struct sshkey *, struct sshbuf *);
int sshkey_sign(const struct sshkey *, u_char **, size_t *,
const u_char *, size_t, const char *, u_int);
int sshkey_verify(const struct sshkey *, const u_char *, size_t,
const u_char *, size_t, const char *, u_int);
int sshkey_check_sigtype(const u_char *, size_t, const char *);
/* for debug */
void sshkey_dump_ec_point(const EC_GROUP *, const EC_POINT *);
void sshkey_dump_ec_key(const EC_KEY *);
/* private key parsing and serialisation */
int sshkey_private_serialize(const struct sshkey *key, struct sshbuf *buf);
int sshkey_private_serialize_opt(const struct sshkey *key, struct sshbuf *buf,
enum sshkey_serialize_rep);
int sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **keyp);
/* private key file format parsing and serialisation */
int sshkey_private_to_fileblob(struct sshkey *key, struct sshbuf *blob,
const char *passphrase, const char *comment,
int force_new_format, const char *new_format_cipher, int new_format_rounds);
int sshkey_parse_private_fileblob(struct sshbuf *buffer,
const char *passphrase, struct sshkey **keyp, char **commentp);
int sshkey_parse_private_fileblob_type(struct sshbuf *blob, int type,
const char *passphrase, struct sshkey **keyp, char **commentp);
/* XXX should be internal, but used by ssh-keygen */
int ssh_rsa_generate_additional_parameters(struct sshkey *);
/* stateful keys (e.g. XMSS) */
#ifdef NO_ATTRIBUTE_ON_PROTOTYPE_ARGS
typedef void sshkey_printfn(const char *, ...);
#else
typedef void sshkey_printfn(const char *, ...) __attribute__((format(printf, 1, 2)));
#endif
int sshkey_set_filename(struct sshkey *, const char *);
int sshkey_enable_maxsign(struct sshkey *, u_int32_t);
u_int32_t sshkey_signatures_left(const struct sshkey *);
int sshkey_forward_state(const struct sshkey *, u_int32_t, sshkey_printfn *);
int sshkey_private_serialize_maxsign(const struct sshkey *key, struct sshbuf *buf,
u_int32_t maxsign, sshkey_printfn *pr);
#ifdef SSHKEY_INTERNAL
int ssh_rsa_sign(const struct sshkey *key,
u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
const char *ident);
int ssh_rsa_verify(const struct sshkey *key,
const u_char *sig, size_t siglen, const u_char *data, size_t datalen,
const char *alg);
int ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat);
int ssh_dss_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, u_int compat);
int ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat);
int ssh_ecdsa_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, u_int compat);
int ssh_ed25519_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat);
int ssh_ed25519_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, u_int compat);
int ssh_xmss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat);
int ssh_xmss_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, u_int compat);
#endif
#if !defined(WITH_OPENSSL)
# undef RSA
# undef DSA
# undef EC_KEY
# undef EC_GROUP
# undef EC_POINT
#elif !defined(OPENSSL_HAS_ECC)
# undef EC_KEY
# undef EC_GROUP
# undef EC_POINT
#endif
#endif /* SSHKEY_H */
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