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openssh/sshkey.h
djm@openbsd.org 4f7a56d5e0 upstream: Add protection for private keys at rest in RAM against 
speculation and memory sidechannel attacks like Spectre, Meltdown, Rowhammer
and Rambleed. This change encrypts private keys when they are not in use with
a symmetic key that is derived from a relatively large "prekey" consisting of
random data (currently 16KB).

Attackers must recover the entire prekey with high accuracy before
they can attempt to decrypt the shielded private key, but the current
generation of attacks have bit error rates that, when applied
cumulatively to the entire prekey, make this unlikely.

Implementation-wise, keys are encrypted "shielded" when loaded and then
automatically and transparently unshielded when used for signatures or
when being saved/serialised.

Hopefully we can remove this in a few years time when computer
architecture has become less unsafe.

been in snaps for a bit already; thanks deraadt@

ok dtucker@ deraadt@

OpenBSD-Commit-ID: 19767213c312e46f94b303a512ef8e9218a39bd4
2019-06-21 14:24:35 +10:00

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/* $OpenBSD: sshkey.h,v 1.32 2019/06/21 04:21:05 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>
# include <openssl/ecdsa.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 BIGNUM void
# 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;
char *signature_type;
};
/* 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;
u_char *shielded_private;
size_t shielded_len;
u_char *shield_prekey;
size_t shield_prekey_len;
};
#define ED25519_SK_SZ crypto_sign_ed25519_SECRETKEYBYTES
#define ED25519_PK_SZ crypto_sign_ed25519_PUBLICKEYBYTES
struct sshkey *sshkey_new(int);
void sshkey_free(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_is_shielded(struct sshkey *);
int sshkey_shield_private(struct sshkey *);
int sshkey_unshield_private(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_check_cert_sigtype(const struct sshkey *, const char *);
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(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(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 *);
const char *sshkey_sigalg_by_name(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(struct sshkey *key, struct sshbuf *buf);
int sshkey_private_serialize_opt(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_complete_crt_parameters(struct sshkey *, const BIGNUM *);
/* 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(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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