view signkey.c @ 1659:d32bcb5c557d

Add Ed25519 support (#91) * Add support for Ed25519 as a public key type Ed25519 is a elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance. It may be used for both user and host keys. OpenSSH key import and fuzzer are not supported yet. Initially inspired by Peter Szabo. * Add curve25519 and ed25519 fuzzers * Add import and export of Ed25519 keys
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Wed, 11 Mar 2020 21:09:45 +0500
parents 2f64cb3d3007
children ba6fc7afe1c5
line wrap: on
line source
/*
 * Dropbear - a SSH2 server
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. */

#include "includes.h"
#include "dbutil.h"
#include "signkey.h"
#include "buffer.h"
#include "ssh.h"
#include "ecdsa.h"

static const char * const signkey_names[DROPBEAR_SIGNKEY_NUM_NAMED] = {
#if DROPBEAR_RSA
	"ssh-rsa",
#endif
#if DROPBEAR_DSS
	"ssh-dss",
#endif
#if DROPBEAR_ECDSA
	"ecdsa-sha2-nistp256",
	"ecdsa-sha2-nistp384",
	"ecdsa-sha2-nistp521",
#endif /* DROPBEAR_ECDSA */
#if DROPBEAR_ED25519
	"ssh-ed25519",
#endif /* DROPBEAR_ED25519 */
};

/* malloc a new sign_key and set the dss and rsa keys to NULL */
sign_key * new_sign_key() {

	sign_key * ret;

	ret = (sign_key*)m_malloc(sizeof(sign_key));
	ret->type = DROPBEAR_SIGNKEY_NONE;
	ret->source = SIGNKEY_SOURCE_INVALID;
	return ret;
}

/* Returns key name corresponding to the type. Exits fatally
 * if the type is invalid */
const char* signkey_name_from_type(enum signkey_type type, unsigned int *namelen) {
	if (type >= DROPBEAR_SIGNKEY_NUM_NAMED) {
		dropbear_exit("Bad key type %d", type);
	}

	if (namelen) {
		*namelen = strlen(signkey_names[type]);
	}
	return signkey_names[type];
}

/* Returns DROPBEAR_SIGNKEY_NONE if none match */
enum signkey_type signkey_type_from_name(const char* name, unsigned int namelen) {
	int i;
	for (i = 0; i < DROPBEAR_SIGNKEY_NUM_NAMED; i++) {
		const char *fixed_name = signkey_names[i];
		if (namelen == strlen(fixed_name)
			&& memcmp(fixed_name, name, namelen) == 0) {

#if DROPBEAR_ECDSA
			/* Some of the ECDSA key sizes are defined even if they're not compiled in */
			if (0
#if !DROPBEAR_ECC_256
				|| i == DROPBEAR_SIGNKEY_ECDSA_NISTP256
#endif
#if !DROPBEAR_ECC_384
				|| i == DROPBEAR_SIGNKEY_ECDSA_NISTP384
#endif
#if !DROPBEAR_ECC_521
				|| i == DROPBEAR_SIGNKEY_ECDSA_NISTP521
#endif
				) {
				TRACE(("attempt to use ecdsa type %d not compiled in", i))
				return DROPBEAR_SIGNKEY_NONE;
			}
#endif

			return (enum signkey_type)i;
		}
	}

	TRACE(("signkey_type_from_name unexpected key type."))

	return DROPBEAR_SIGNKEY_NONE;
}

/* Returns a pointer to the key part specific to "type".
Be sure to check both (ret != NULL) and (*ret != NULL) */
void **
signkey_key_ptr(sign_key *key, enum signkey_type type) {
	switch (type) {
#if DROPBEAR_ED25519
		case DROPBEAR_SIGNKEY_ED25519:
			return (void**)&key->ed25519key;
#endif
#if DROPBEAR_ECDSA
#if DROPBEAR_ECC_256
		case DROPBEAR_SIGNKEY_ECDSA_NISTP256:
			return (void**)&key->ecckey256;
#endif
#if DROPBEAR_ECC_384
		case DROPBEAR_SIGNKEY_ECDSA_NISTP384:
			return (void**)&key->ecckey384;
#endif
#if DROPBEAR_ECC_521
		case DROPBEAR_SIGNKEY_ECDSA_NISTP521:
			return (void**)&key->ecckey521;
#endif
#endif /* DROPBEAR_ECDSA */
#if DROPBEAR_RSA
		case DROPBEAR_SIGNKEY_RSA:
			return (void**)&key->rsakey;
#endif
#if DROPBEAR_DSS
		case DROPBEAR_SIGNKEY_DSS:
			return (void**)&key->dsskey;
#endif
		default:
			return NULL;
	}
}

/* returns DROPBEAR_SUCCESS on success, DROPBEAR_FAILURE on fail.
 * type should be set by the caller to specify the type to read, and
 * on return is set to the type read (useful when type = _ANY) */
int buf_get_pub_key(buffer *buf, sign_key *key, enum signkey_type *type) {

	char *ident;
	unsigned int len;
	enum signkey_type keytype;
	int ret = DROPBEAR_FAILURE;

	TRACE2(("enter buf_get_pub_key"))

	ident = buf_getstring(buf, &len);
	keytype = signkey_type_from_name(ident, len);
	m_free(ident);

	if (*type != DROPBEAR_SIGNKEY_ANY && *type != keytype) {
		TRACE(("buf_get_pub_key bad type - got %d, expected %d", keytype, *type))
		return DROPBEAR_FAILURE;
	}
	
	TRACE2(("buf_get_pub_key keytype is %d", keytype))

	*type = keytype;

	/* Rewind the buffer back before "ssh-rsa" etc */
	buf_incrpos(buf, -len - 4);

#if DROPBEAR_DSS
	if (keytype == DROPBEAR_SIGNKEY_DSS) {
		dss_key_free(key->dsskey);
		key->dsskey = m_malloc(sizeof(*key->dsskey));
		ret = buf_get_dss_pub_key(buf, key->dsskey);
		if (ret == DROPBEAR_FAILURE) {
			dss_key_free(key->dsskey);
			key->dsskey = NULL;
		}
	}
#endif
#if DROPBEAR_RSA
	if (keytype == DROPBEAR_SIGNKEY_RSA) {
		rsa_key_free(key->rsakey);
		key->rsakey = m_malloc(sizeof(*key->rsakey));
		ret = buf_get_rsa_pub_key(buf, key->rsakey);
		if (ret == DROPBEAR_FAILURE) {
			rsa_key_free(key->rsakey);
			key->rsakey = NULL;
		}
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(keytype)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, keytype);
		if (eck) {
			if (*eck) {
				ecc_free(*eck);
				m_free(*eck);
				*eck = NULL;
			}
			*eck = buf_get_ecdsa_pub_key(buf);
			if (*eck) {
				ret = DROPBEAR_SUCCESS;
			}
		}
	}
#endif
#if DROPBEAR_ED25519
	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
		ed25519_key_free(key->ed25519key);
		key->ed25519key = m_malloc(sizeof(*key->ed25519key));
		ret = buf_get_ed25519_pub_key(buf, key->ed25519key);
		if (ret == DROPBEAR_FAILURE) {
			m_free(key->ed25519key);
			key->ed25519key = NULL;
		}
	}
#endif

	TRACE2(("leave buf_get_pub_key"))

	return ret;
}

/* returns DROPBEAR_SUCCESS on success, DROPBEAR_FAILURE on fail.
 * type should be set by the caller to specify the type to read, and
 * on return is set to the type read (useful when type = _ANY) */
int buf_get_priv_key(buffer *buf, sign_key *key, enum signkey_type *type) {

	char *ident;
	unsigned int len;
	enum signkey_type keytype;
	int ret = DROPBEAR_FAILURE;

	TRACE2(("enter buf_get_priv_key"))

	ident = buf_getstring(buf, &len);
	keytype = signkey_type_from_name(ident, len);
	m_free(ident);

	if (*type != DROPBEAR_SIGNKEY_ANY && *type != keytype) {
		TRACE(("wrong key type: %d %d", *type, keytype))
		return DROPBEAR_FAILURE;
	}

	*type = keytype;

	/* Rewind the buffer back before "ssh-rsa" etc */
	buf_incrpos(buf, -len - 4);

#if DROPBEAR_DSS
	if (keytype == DROPBEAR_SIGNKEY_DSS) {
		dss_key_free(key->dsskey);
		key->dsskey = m_malloc(sizeof(*key->dsskey));
		ret = buf_get_dss_priv_key(buf, key->dsskey);
		if (ret == DROPBEAR_FAILURE) {
			dss_key_free(key->dsskey);
			key->dsskey = NULL;
		}
	}
#endif
#if DROPBEAR_RSA
	if (keytype == DROPBEAR_SIGNKEY_RSA) {
		rsa_key_free(key->rsakey);
		key->rsakey = m_malloc(sizeof(*key->rsakey));
		ret = buf_get_rsa_priv_key(buf, key->rsakey);
		if (ret == DROPBEAR_FAILURE) {
			rsa_key_free(key->rsakey);
			key->rsakey = NULL;
		}
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(keytype)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, keytype);
		if (eck) {
			if (*eck) {
				ecc_free(*eck);
				m_free(*eck);
				*eck = NULL;
			}
			*eck = buf_get_ecdsa_priv_key(buf);
			if (*eck) {
				ret = DROPBEAR_SUCCESS;
			}
		}
	}
#endif
#if DROPBEAR_ED25519
	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
		ed25519_key_free(key->ed25519key);
		key->ed25519key = m_malloc(sizeof(*key->ed25519key));
		ret = buf_get_ed25519_priv_key(buf, key->ed25519key);
		if (ret == DROPBEAR_FAILURE) {
			m_free(key->ed25519key);
			key->ed25519key = NULL;
		}
	}
#endif

	TRACE2(("leave buf_get_priv_key"))

	return ret;
	
}

/* type is either DROPBEAR_SIGNKEY_DSS or DROPBEAR_SIGNKEY_RSA */
void buf_put_pub_key(buffer* buf, sign_key *key, enum signkey_type type) {

	buffer *pubkeys;

	TRACE2(("enter buf_put_pub_key"))
	pubkeys = buf_new(MAX_PUBKEY_SIZE);
	
#if DROPBEAR_DSS
	if (type == DROPBEAR_SIGNKEY_DSS) {
		buf_put_dss_pub_key(pubkeys, key->dsskey);
	}
#endif
#if DROPBEAR_RSA
	if (type == DROPBEAR_SIGNKEY_RSA) {
		buf_put_rsa_pub_key(pubkeys, key->rsakey);
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(type)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
		if (eck && *eck) {
			buf_put_ecdsa_pub_key(pubkeys, *eck);
		}
	}
#endif
#if DROPBEAR_ED25519
	if (type == DROPBEAR_SIGNKEY_ED25519) {
		buf_put_ed25519_pub_key(pubkeys, key->ed25519key);
	}
#endif
	if (pubkeys->len == 0) {
		dropbear_exit("Bad key types in buf_put_pub_key");
	}

	buf_putbufstring(buf, pubkeys);
	buf_free(pubkeys);
	TRACE2(("leave buf_put_pub_key"))
}

/* type is either DROPBEAR_SIGNKEY_DSS or DROPBEAR_SIGNKEY_RSA */
void buf_put_priv_key(buffer* buf, sign_key *key, enum signkey_type type) {

	TRACE(("enter buf_put_priv_key"))
	TRACE(("type is %d", type))

#if DROPBEAR_DSS
	if (type == DROPBEAR_SIGNKEY_DSS) {
		buf_put_dss_priv_key(buf, key->dsskey);
		TRACE(("leave buf_put_priv_key: dss done"))
		return;
	}
#endif
#if DROPBEAR_RSA
	if (type == DROPBEAR_SIGNKEY_RSA) {
		buf_put_rsa_priv_key(buf, key->rsakey);
		TRACE(("leave buf_put_priv_key: rsa done"))
		return;
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(type)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
		if (eck && *eck) {
			buf_put_ecdsa_priv_key(buf, *eck);
			TRACE(("leave buf_put_priv_key: ecdsa done"))
			return;
		}
	}
#endif
#if DROPBEAR_ED25519
	if (type == DROPBEAR_SIGNKEY_ED25519) {
		buf_put_ed25519_priv_key(buf, key->ed25519key);
		TRACE(("leave buf_put_priv_key: ed25519 done"))
		return;
	}
#endif
	dropbear_exit("Bad key types in put pub key");
}

void sign_key_free(sign_key *key) {

	TRACE2(("enter sign_key_free"))

#if DROPBEAR_DSS
	dss_key_free(key->dsskey);
	key->dsskey = NULL;
#endif
#if DROPBEAR_RSA
	rsa_key_free(key->rsakey);
	key->rsakey = NULL;
#endif
#if DROPBEAR_ECDSA
#if DROPBEAR_ECC_256
	if (key->ecckey256) {
		ecc_free(key->ecckey256);
		m_free(key->ecckey256);
		key->ecckey256 = NULL;
	}
#endif
#if DROPBEAR_ECC_384
	if (key->ecckey384) {
		ecc_free(key->ecckey384);
		m_free(key->ecckey384);
		key->ecckey384 = NULL;
	}
#endif
#if DROPBEAR_ECC_521
	if (key->ecckey521) {
		ecc_free(key->ecckey521);
		m_free(key->ecckey521);
		key->ecckey521 = NULL;
	}
#endif
#endif
#if DROPBEAR_ED25519
	ed25519_key_free(key->ed25519key);
	key->ed25519key = NULL;
#endif

	m_free(key->filename);

	m_free(key);
	TRACE2(("leave sign_key_free"))
}

static char hexdig(unsigned char x) {
	if (x > 0xf)
		return 'X';

	if (x < 10)
		return '0' + x;
	else
		return 'a' + x - 10;
}

/* Since we're not sure if we'll have md5 or sha1, we present both.
 * MD5 is used in preference, but sha1 could still be useful */
#if DROPBEAR_MD5_HMAC
static char * sign_key_md5_fingerprint(const unsigned char* keyblob,
		unsigned int keybloblen) {

	char * ret;
	hash_state hs;
	unsigned char hash[MD5_HASH_SIZE];
	unsigned int i;
	unsigned int buflen;

	md5_init(&hs);

	/* skip the size int of the string - this is a bit messy */
	md5_process(&hs, keyblob, keybloblen);

	md5_done(&hs, hash);

	/* "md5 hexfingerprinthere\0", each hex digit is "AB:" etc */
	buflen = 4 + 3*MD5_HASH_SIZE;
	ret = (char*)m_malloc(buflen);

	memset(ret, 'Z', buflen);
	strcpy(ret, "md5 ");

	for (i = 0; i < MD5_HASH_SIZE; i++) {
		unsigned int pos = 4 + i*3;
		ret[pos] = hexdig(hash[i] >> 4);
		ret[pos+1] = hexdig(hash[i] & 0x0f);
		ret[pos+2] = ':';
	}
	ret[buflen-1] = 0x0;

	return ret;
}

#else /* use SHA1 rather than MD5 for fingerprint */
static char * sign_key_sha1_fingerprint(const unsigned char* keyblob,
		unsigned int keybloblen) {

	char * ret;
	hash_state hs;
	unsigned char hash[SHA1_HASH_SIZE];
	unsigned int i;
	unsigned int buflen;

	sha1_init(&hs);

	/* skip the size int of the string - this is a bit messy */
	sha1_process(&hs, keyblob, keybloblen);

	sha1_done(&hs, hash);

	/* "sha1!! hexfingerprinthere\0", each hex digit is "AB:" etc */
	buflen = 7 + 3*SHA1_HASH_SIZE;
	ret = (char*)m_malloc(buflen);

	strcpy(ret, "sha1!! ");

	for (i = 0; i < SHA1_HASH_SIZE; i++) {
		unsigned int pos = 7 + 3*i;
		ret[pos] = hexdig(hash[i] >> 4);
		ret[pos+1] = hexdig(hash[i] & 0x0f);
		ret[pos+2] = ':';
	}
	ret[buflen-1] = 0x0;

	return ret;
}

#endif /* MD5/SHA1 switch */

/* This will return a freshly malloced string, containing a fingerprint
 * in either sha1 or md5 */
char * sign_key_fingerprint(const unsigned char* keyblob, unsigned int keybloblen) {

#if DROPBEAR_MD5_HMAC
	return sign_key_md5_fingerprint(keyblob, keybloblen);
#else
	return sign_key_sha1_fingerprint(keyblob, keybloblen);
#endif
}

void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type type, 
	const buffer *data_buf) {
	buffer *sigblob;
	sigblob = buf_new(MAX_PUBKEY_SIZE);

#if DROPBEAR_DSS
	if (type == DROPBEAR_SIGNKEY_DSS) {
		buf_put_dss_sign(sigblob, key->dsskey, data_buf);
	}
#endif
#if DROPBEAR_RSA
	if (type == DROPBEAR_SIGNKEY_RSA) {
		buf_put_rsa_sign(sigblob, key->rsakey, data_buf);
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(type)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
		if (eck && *eck) {
			buf_put_ecdsa_sign(sigblob, *eck, data_buf);
		}
	}
#endif
#if DROPBEAR_ED25519
	if (type == DROPBEAR_SIGNKEY_ED25519) {
		buf_put_ed25519_sign(sigblob, key->ed25519key, data_buf);
	}
#endif
	if (sigblob->len == 0) {
		dropbear_exit("Non-matching signing type");
	}
	buf_putbufstring(buf, sigblob);
	buf_free(sigblob);

}

#if DROPBEAR_SIGNKEY_VERIFY
/* Return DROPBEAR_SUCCESS or DROPBEAR_FAILURE.
 * If FAILURE is returned, the position of
 * buf is undefined. If SUCCESS is returned, buf will be positioned after the
 * signature blob */
int buf_verify(buffer * buf, sign_key *key, const buffer *data_buf) {
	
	char *type_name = NULL;
	unsigned int type_name_len = 0;
	enum signkey_type type;

	TRACE(("enter buf_verify"))

	buf_getint(buf); /* blob length */
	type_name = buf_getstring(buf, &type_name_len);
	type = signkey_type_from_name(type_name, type_name_len);
	m_free(type_name);

#if DROPBEAR_DSS
	if (type == DROPBEAR_SIGNKEY_DSS) {
		if (key->dsskey == NULL) {
			dropbear_exit("No DSS key to verify signature");
		}
		return buf_dss_verify(buf, key->dsskey, data_buf);
	}
#endif

#if DROPBEAR_RSA
	if (type == DROPBEAR_SIGNKEY_RSA) {
		if (key->rsakey == NULL) {
			dropbear_exit("No RSA key to verify signature");
		}
		return buf_rsa_verify(buf, key->rsakey, data_buf);
	}
#endif
#if DROPBEAR_ECDSA
	if (signkey_is_ecdsa(type)) {
		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
		if (eck && *eck) {
			return buf_ecdsa_verify(buf, *eck, data_buf);
		}
	}
#endif
#if DROPBEAR_ED25519
	if (type == DROPBEAR_SIGNKEY_ED25519) {
		if (key->ed25519key == NULL) {
			dropbear_exit("No Ed25519 key to verify signature");
		}
		return buf_ed25519_verify(buf, key->ed25519key, data_buf);
	}
#endif

	dropbear_exit("Non-matching signing type");
	return DROPBEAR_FAILURE;
}
#endif /* DROPBEAR_SIGNKEY_VERIFY */

#if DROPBEAR_KEY_LINES /* ie we're using authorized_keys or known_hosts */

/* Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE when given a buffer containing
 * a key, a key, and a type. The buffer is positioned at the start of the
 * base64 data, and contains no trailing data */
/* If fingerprint is non-NULL, it will be set to a malloc()ed fingerprint
   of the key if it is successfully decoded */
int cmp_base64_key(const unsigned char* keyblob, unsigned int keybloblen, 
					const unsigned char* algoname, unsigned int algolen, 
					const buffer * line, char ** fingerprint) {

	buffer * decodekey = NULL;
	int ret = DROPBEAR_FAILURE;
	unsigned int len, filealgolen;
	unsigned long decodekeylen;
	unsigned char* filealgo = NULL;

	/* now we have the actual data */
	len = line->len - line->pos;
	if (len == 0) {
		/* base64_decode doesn't like NULL argument */
		return DROPBEAR_FAILURE;
	}
	decodekeylen = len * 2; /* big to be safe */
	decodekey = buf_new(decodekeylen);

	if (base64_decode(buf_getptr(line, len), len,
				buf_getwriteptr(decodekey, decodekey->size),
				&decodekeylen) != CRYPT_OK) {
		TRACE(("checkpubkey: base64 decode failed"))
		goto out;
	}
	TRACE(("checkpubkey: base64_decode success"))
	buf_incrlen(decodekey, decodekeylen);
	
	if (fingerprint) {
		*fingerprint = sign_key_fingerprint(buf_getptr(decodekey, decodekeylen),
											decodekeylen);
	}
	
	/* compare the keys */
	if ( ( decodekeylen != keybloblen )
			|| memcmp( buf_getptr(decodekey, decodekey->len),
						keyblob, decodekey->len) != 0) {
		TRACE(("checkpubkey: compare failed"))
		goto out;
	}

	/* ... and also check that the algo specified and the algo in the key
	 * itself match */
	filealgolen = buf_getint(decodekey);
	filealgo = buf_getptr(decodekey, filealgolen);
	if (filealgolen != algolen || memcmp(filealgo, algoname, algolen) != 0) {
		TRACE(("checkpubkey: algo match failed")) 
		goto out;
	}

	/* All checks passed */
	ret = DROPBEAR_SUCCESS;

out:
	buf_free(decodekey);
	decodekey = NULL;
	return ret;
}
#endif

#if DROPBEAR_FUZZ
const char * const * fuzz_signkey_names = signkey_names;

#endif