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Add support for certificate key types for users and hosts.

OpenSSH certificate key types are not X.509 certificates, but a much
simpler format that encodes a public key, identity information and
some validity constraints and signs it with a CA key. CA keys are
regular SSH keys. This certificate style avoids the attack surface
of X.509 certificates and is very easy to deploy.

Certified host keys allow automatic acceptance of new host keys
when a CA certificate is marked as trusted in ~/.ssh/known_hosts.
see VERIFYING HOST KEYS in ssh(1) for details.

Certified user keys allow authentication of users when the signing
CA key is marked as trusted in authorized_keys. See "AUTHORIZED_KEYS
FILE FORMAT" in sshd(8) for details.

Certificates are minted using ssh-keygen(1), documentation is in
the "CERTIFICATES" section of that manpage.

Documentation on the format of certificates is in the file
PROTOCOL.certkeys

feedback and ok markus@

/* $OpenBSD: key.c,v 1.83 2010/02/26 20:29:54 djm Exp $ */
/*
 * read_bignum():
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 *
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 * Copyright (c) 2008 Alexander von Gernler.  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.
 */

#include <sys/param.h>
#include <sys/types.h>

#include <openssl/evp.h>

#include <stdio.h>
#include <string.h>

#include "xmalloc.h"
#include "key.h"
#include "rsa.h"
#include "uuencode.h"
#include "buffer.h"
#include "log.h"
#include "ssh2.h"

static struct KeyCert *
cert_new(void)
{
	struct KeyCert *cert;

	cert = xcalloc(1, sizeof(*cert));
	buffer_init(&cert->certblob);
	buffer_init(&cert->constraints);
	cert->key_id = NULL;
	cert->principals = NULL;
	cert->signature_key = NULL;
	return cert;
}

Key *
key_new(int type)
{
	Key *k;
	RSA *rsa;
	DSA *dsa;
	k = xcalloc(1, sizeof(*k));
	k->type = type;
	k->dsa = NULL;
	k->rsa = NULL;
	k->cert = NULL;
	switch (k->type) {
	case KEY_RSA1:
	case KEY_RSA:
	case KEY_RSA_CERT:
		if ((rsa = RSA_new()) == NULL)
			fatal("key_new: RSA_new failed");
		if ((rsa->n = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		if ((rsa->e = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		k->rsa = rsa;
		break;
	case KEY_DSA:
	case KEY_DSA_CERT:
		if ((dsa = DSA_new()) == NULL)
			fatal("key_new: DSA_new failed");
		if ((dsa->p = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		if ((dsa->q = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		if ((dsa->g = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		if ((dsa->pub_key = BN_new()) == NULL)
			fatal("key_new: BN_new failed");
		k->dsa = dsa;
		break;
	case KEY_UNSPEC:
		break;
	default:
		fatal("key_new: bad key type %d", k->type);
		break;
	}

	if (key_is_cert(k))
		k->cert = cert_new();

	return k;
}

void
key_add_private(Key *k)
{
	switch (k->type) {
	case KEY_RSA1:
	case KEY_RSA:
	case KEY_RSA_CERT:
		if ((k->rsa->d = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		if ((k->rsa->iqmp = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		if ((k->rsa->q = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		if ((k->rsa->p = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		if ((k->rsa->dmq1 = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		if ((k->rsa->dmp1 = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		break;
	case KEY_DSA:
	case KEY_DSA_CERT:
		if ((k->dsa->priv_key = BN_new()) == NULL)
			fatal("key_new_private: BN_new failed");
		break;
	case KEY_UNSPEC:
		break;
	default:
		break;
	}
}

Key *
key_new_private(int type)
{
	Key *k = key_new(type);

	key_add_private(k);
	return k;
}

static void
cert_free(struct KeyCert *cert)
{
	u_int i;

	buffer_free(&cert->certblob);
	buffer_free(&cert->constraints);
	if (cert->key_id != NULL)
		xfree(cert->key_id);
	for (i = 0; i < cert->nprincipals; i++)
		xfree(cert->principals[i]);
	if (cert->principals != NULL)
		xfree(cert->principals);
	if (cert->signature_key != NULL)
		key_free(cert->signature_key);
}

void
key_free(Key *k)
{
	if (k == NULL)
		fatal("key_free: key is NULL");
	switch (k->type) {
	case KEY_RSA1:
	case KEY_RSA:
	case KEY_RSA_CERT:
		if (k->rsa != NULL)
			RSA_free(k->rsa);
		k->rsa = NULL;
		break;
	case KEY_DSA:
	case KEY_DSA_CERT:
		if (k->dsa != NULL)
			DSA_free(k->dsa);
		k->dsa = NULL;
		break;
	case KEY_UNSPEC:
		break;
	default:
		fatal("key_free: bad key type %d", k->type);
		break;
	}
	if (key_is_cert(k)) {
		if (k->cert != NULL)
			cert_free(k->cert);
		k->cert = NULL;
	}

	xfree(k);
}

static int
cert_compare(struct KeyCert *a, struct KeyCert *b)
{
	if (a == NULL && b == NULL)
		return 1;
	if (a == NULL || b == NULL)
		return 0;
	if (buffer_len(&a->certblob) != buffer_len(&b->certblob))
		return 0;
	if (memcmp(buffer_ptr(&a->certblob), buffer_ptr(&b->certblob),
	    buffer_len(&a->certblob)) != 0)
		return 0;
	return 1;
}

/*
 * Compare public portions of key only, allowing comparisons between
 * certificates and plain keys too.
 */
int
key_equal_public(const Key *a, const Key *b)
{
	if (a == NULL || b == NULL ||
	    key_type_plain(a->type) != key_type_plain(b->type))
		return 0;

	switch (a->type) {
	case KEY_RSA1:
	case KEY_RSA_CERT:
	case KEY_RSA:
		return a->rsa != NULL && b->rsa != NULL &&
		    BN_cmp(a->rsa->e, b->rsa->e) == 0 &&
		    BN_cmp(a->rsa->n, b->rsa->n) == 0;
	case KEY_DSA_CERT:
	case KEY_DSA:
		return a->dsa != NULL && b->dsa != NULL &&
		    BN_cmp(a->dsa->p, b->dsa->p) == 0 &&
		    BN_cmp(a->dsa->q, b->dsa->q) == 0 &&
		    BN_cmp(a->dsa->g, b->dsa->g) == 0 &&
		    BN_cmp(a->dsa->pub_key, b->dsa->pub_key) == 0;
	default:
		fatal("key_equal: bad key type %d", a->type);
	}
	/* NOTREACHED */
}

int
key_equal(const Key *a, const Key *b)
{
	if (a == NULL || b == NULL || a->type != b->type)
		return 0;
	if (key_is_cert(a)) {
		if (!cert_compare(a->cert, b->cert))
			return 0;
	}
	return key_equal_public(a, b);
}

u_char*
key_fingerprint_raw(Key *k, enum fp_type dgst_type, u_int *dgst_raw_length)
{
	const EVP_MD *md = NULL;
	EVP_MD_CTX ctx;
	u_char *blob = NULL;
	u_char *retval = NULL;
	u_int len = 0;
	int nlen, elen, otype;

	*dgst_raw_length = 0;

	switch (dgst_type) {
	case SSH_FP_MD5:
		md = EVP_md5();
		break;
	case SSH_FP_SHA1:
		md = EVP_sha1();
		break;
	default:
		fatal("key_fingerprint_raw: bad digest type %d",
		    dgst_type);
	}
	switch (k->type) {
	case KEY_RSA1:
		nlen = BN_num_bytes(k->rsa->n);
		elen = BN_num_bytes(k->rsa->e);
		len = nlen + elen;
		blob = xmalloc(len);
		BN_bn2bin(k->rsa->n, blob);
		BN_bn2bin(k->rsa->e, blob + nlen);
		break;
	case KEY_DSA:
	case KEY_RSA:
		key_to_blob(k, &blob, &len);
		break;
	case KEY_DSA_CERT:
	case KEY_RSA_CERT:
		/* We want a fingerprint of the _key_ not of the cert */
		otype = k->type;
		k->type = key_type_plain(k->type);
		key_to_blob(k, &blob, &len);
		k->type = otype;
		break;
	case KEY_UNSPEC:
		return retval;
	default:
		fatal("key_fingerprint_raw: bad key type %d", k->type);
		break;
	}
	if (blob != NULL) {
		retval = xmalloc(EVP_MAX_MD_SIZE);
		EVP_DigestInit(&ctx, md);
		EVP_DigestUpdate(&ctx, blob, len);
		EVP_DigestFinal(&ctx, retval, dgst_raw_length);
		memset(blob, 0, len);
		xfree(blob);
	} else {
		fatal("key_fingerprint_raw: blob is null");
	}
	return retval;
}

static char *
key_fingerprint_hex(u_char *dgst_raw, u_int dgst_raw_len)
{
	char *retval;
	u_int i;

	retval = xcalloc(1, dgst_raw_len * 3 + 1);
	for (i = 0; i < dgst_raw_len; i++) {
		char hex[4];
		snprintf(hex, sizeof(hex), "%02x:", dgst_raw[i]);
		strlcat(retval, hex, dgst_raw_len * 3 + 1);
	}

	/* Remove the trailing ':' character */
	retval[(dgst_raw_len * 3) - 1] = '\0';
	return retval;
}

static char *
key_fingerprint_bubblebabble(u_char *dgst_raw, u_int dgst_raw_len)
{
	char vowels[] = { 'a', 'e', 'i', 'o', 'u', 'y' };
	char consonants[] = { 'b', 'c', 'd', 'f', 'g', 'h', 'k', 'l', 'm',
	    'n', 'p', 'r', 's', 't', 'v', 'z', 'x' };
	u_int i, j = 0, rounds, seed = 1;
	char *retval;

	rounds = (dgst_raw_len / 2) + 1;
	retval = xcalloc((rounds * 6), sizeof(char));
	retval[j++] = 'x';
	for (i = 0; i < rounds; i++) {
		u_int idx0, idx1, idx2, idx3, idx4;
		if ((i + 1 < rounds) || (dgst_raw_len % 2 != 0)) {
			idx0 = (((((u_int)(dgst_raw[2 * i])) >> 6) & 3) +
			    seed) % 6;
			idx1 = (((u_int)(dgst_raw[2 * i])) >> 2) & 15;
			idx2 = ((((u_int)(dgst_raw[2 * i])) & 3) +
			    (seed / 6)) % 6;
			retval[j++] = vowels[idx0];
			retval[j++] = consonants[idx1];
			retval[j++] = vowels[idx2];
			if ((i + 1) < rounds) {
				idx3 = (((u_int)(dgst_raw[(2 * i) + 1])) >> 4) & 15;
				idx4 = (((u_int)(dgst_raw[(2 * i) + 1]))) & 15;
				retval[j++] = consonants[idx3];
				retval[j++] = '-';
				retval[j++] = consonants[idx4];
				seed = ((seed * 5) +
				    ((((u_int)(dgst_raw[2 * i])) * 7) +
				    ((u_int)(dgst_raw[(2 * i) + 1])))) % 36;
			}
		} else {
			idx0 = seed % 6;
			idx1 = 16;
			idx2 = seed / 6;
			retval[j++] = vowels[idx0];
			retval[j++] = consonants[idx1];
			retval[j++] = vowels[idx2];
		}
	}
	retval[j++] = 'x';
	retval[j++] = '\0';
	return retval;
}

/*
 * Draw an ASCII-Art representing the fingerprint so human brain can
 * profit from its built-in pattern recognition ability.
 * This technique is called "random art" and can be found in some
 * scientific publications like this original paper:
 *
 * "Hash Visualization: a New Technique to improve Real-World Security",
 * Perrig A. and Song D., 1999, International Workshop on Cryptographic
 * Techniques and E-Commerce (CrypTEC '99)
 * sparrow.ece.cmu.edu/~adrian/projects/validation/validation.pdf
 *
 * The subject came up in a talk by Dan Kaminsky, too.
 *
 * If you see the picture is different, the key is different.
 * If the picture looks the same, you still know nothing.
 *
 * The algorithm used here is a worm crawling over a discrete plane,
 * leaving a trace (augmenting the field) everywhere it goes.
 * Movement is taken from dgst_raw 2bit-wise.  Bumping into walls
 * makes the respective movement vector be ignored for this turn.
 * Graphs are not unambiguous, because circles in graphs can be
 * walked in either direction.
 */

/*
 * Field sizes for the random art.  Have to be odd, so the starting point
 * can be in the exact middle of the picture, and FLDBASE should be >=8 .
 * Else pictures would be too dense, and drawing the frame would
 * fail, too, because the key type would not fit in anymore.
 */
#define	FLDBASE		8
#define	FLDSIZE_Y	(FLDBASE + 1)
#define	FLDSIZE_X	(FLDBASE * 2 + 1)
static char *
key_fingerprint_randomart(u_char *dgst_raw, u_int dgst_raw_len, const Key *k)
{
	/*
	 * Chars to be used after each other every time the worm
	 * intersects with itself.  Matter of taste.
	 */
	char	*augmentation_string = " .o+=*BOX@%&#/^SE";
	char	*retval, *p;
	u_char	 field[FLDSIZE_X][FLDSIZE_Y];
	u_int	 i, b;
	int	 x, y;
	size_t	 len = strlen(augmentation_string) - 1;

	retval = xcalloc(1, (FLDSIZE_X + 3) * (FLDSIZE_Y + 2));

	/* initialize field */
	memset(field, 0, FLDSIZE_X * FLDSIZE_Y * sizeof(char));
	x = FLDSIZE_X / 2;
	y = FLDSIZE_Y / 2;

	/* process raw key */
	for (i = 0; i < dgst_raw_len; i++) {
		int input;
		/* each byte conveys four 2-bit move commands */
		input = dgst_raw[i];
		for (b = 0; b < 4; b++) {
			/* evaluate 2 bit, rest is shifted later */
			x += (input & 0x1) ? 1 : -1;
			y += (input & 0x2) ? 1 : -1;

			/* assure we are still in bounds */
			x = MAX(x, 0);
			y = MAX(y, 0);
			x = MIN(x, FLDSIZE_X - 1);
			y = MIN(y, FLDSIZE_Y - 1);

			/* augment the field */
			if (field[x][y] < len - 2)
				field[x][y]++;
			input = input >> 2;
		}
	}

	/* mark starting point and end point*/
	field[FLDSIZE_X / 2][FLDSIZE_Y / 2] = len - 1;
	field[x][y] = len;

	/* fill in retval */
	snprintf(retval, FLDSIZE_X, "+--[%4s %4u]", key_type(k), key_size(k));
	p = strchr(retval, '\0');

	/* output upper border */
	for (i = p - retval - 1; i < FLDSIZE_X; i++)
		*p++ = '-';
	*p++ = '+';
	*p++ = '\n';

	/* output content */
	for (y = 0; y < FLDSIZE_Y; y++) {
		*p++ = '|';
		for (x = 0; x < FLDSIZE_X; x++)
			*p++ = augmentation_string[MIN(field[x][y], len)];
		*p++ = '|';
		*p++ = '\n';
	}

	/* output lower border */
	*p++ = '+';
	for (i = 0; i < FLDSIZE_X; i++)
		*p++ = '-';
	*p++ = '+';

	return retval;
}

char *
key_fingerprint(Key *k, enum fp_type dgst_type, enum fp_rep dgst_rep)
{
	char *retval = NULL;
	u_char *dgst_raw;
	u_int dgst_raw_len;

	dgst_raw = key_fingerprint_raw(k, dgst_type, &dgst_raw_len);
	if (!dgst_raw)
		fatal("key_fingerprint: null from key_fingerprint_raw()");
	switch (dgst_rep) {
	case SSH_FP_HEX:
		retval = key_fingerprint_hex(dgst_raw, dgst_raw_len);
		break;
	case SSH_FP_BUBBLEBABBLE:
		retval = key_fingerprint_bubblebabble(dgst_raw, dgst_raw_len);
		break;
	case SSH_FP_RANDOMART:
		retval = key_fingerprint_randomart(dgst_raw, dgst_raw_len, k);
		break;
	default:
		fatal("key_fingerprint: bad digest representation %d",
		    dgst_rep);
		break;
	}
	memset(dgst_raw, 0, dgst_raw_len);
	xfree(dgst_raw);
	return retval;
}

/*
 * Reads a multiple-precision integer in decimal from the buffer, and advances
 * the pointer.  The integer must already be initialized.  This function is
 * permitted to modify the buffer.  This leaves *cpp to point just beyond the
 * last processed (and maybe modified) character.  Note that this may modify
 * the buffer containing the number.
 */
static int
read_bignum(char **cpp, BIGNUM * value)
{
	char *cp = *cpp;
	int old;

	/* Skip any leading whitespace. */
	for (; *cp == ' ' || *cp == '\t'; cp++)
		;

	/* Check that it begins with a decimal digit. */
	if (*cp < '0' || *cp > '9')
		return 0;

	/* Save starting position. */
	*cpp = cp;

	/* Move forward until all decimal digits skipped. */
	for (; *cp >= '0' && *cp <= '9'; cp++)
		;

	/* Save the old terminating character, and replace it by \0. */
	old = *cp;
	*cp = 0;

	/* Parse the number. */
	if (BN_dec2bn(&value, *cpp) == 0)
		return 0;

	/* Restore old terminating character. */
	*cp = old;

	/* Move beyond the number and return success. */
	*cpp = cp;
	return 1;
}

static int
write_bignum(FILE *f, BIGNUM *num)
{
	char *buf = BN_bn2dec(num);
	if (buf == NULL) {
		error("write_bignum: BN_bn2dec() failed");
		return 0;
	}
	fprintf(f, " %s", buf);
	OPENSSL_free(buf);
	return 1;
}

/* returns 1 ok, -1 error */
int
key_read(Key *ret, char **cpp)
{
	Key *k;
	int success = -1;
	char *cp, *space;
	int len, n, type;
	u_int bits;
	u_char *blob;

	cp = *cpp;

	switch (ret->type) {
	case KEY_RSA1:
		/* Get number of bits. */
		if (*cp < '0' || *cp > '9')
			return -1;	/* Bad bit count... */
		for (bits = 0; *cp >= '0' && *cp <= '9'; cp++)
			bits = 10 * bits + *cp - '0';
		if (bits == 0)
			return -1;
		*cpp = cp;
		/* Get public exponent, public modulus. */
		if (!read_bignum(cpp, ret->rsa->e))
			return -1;
		if (!read_bignum(cpp, ret->rsa->n))
			return -1;
		/* validate the claimed number of bits */
		if ((u_int)BN_num_bits(ret->rsa->n) != bits) {
			verbose("key_read: claimed key size %d does not match "
			   "actual %d", bits, BN_num_bits(ret->rsa->n));
			return -1;
		}
		success = 1;
		break;
	case KEY_UNSPEC:
	case KEY_RSA:
	case KEY_DSA:
	case KEY_DSA_CERT:
	case KEY_RSA_CERT:
		space = strchr(cp, ' ');
		if (space == NULL) {
			debug3("key_read: missing whitespace");
			return -1;
		}
		*space = '\0';
		type = key_type_from_name(cp);
		*space = ' ';
		if (type == KEY_UNSPEC) {
			debug3("key_read: missing keytype");
			return -1;
		}
		cp = space+1;
		if (*cp == '\0') {
			debug3("key_read: short string");
			return -1;
		}
		if (ret->type == KEY_UNSPEC) {
			ret->type = type;
		} else if (ret->type != type) {
			/* is a key, but different type */
			debug3("key_read: type mismatch");
			return -1;
		}
		len = 2*strlen(cp);
		blob = xmalloc(len);
		n = uudecode(cp, blob, len);
		if (n < 0) {
			error("key_read: uudecode %s failed", cp);
			xfree(blob);
			return -1;
		}
		k = key_from_blob(blob, (u_int)n);
		xfree(blob);
		if (k == NULL) {
			error("key_read: key_from_blob %s failed", cp);
			return -1;
		}
		if (k->type != type) {
			error("key_read: type mismatch: encoding error");
			key_free(k);
			return -1;
		}
/*XXXX*/
		if (key_is_cert(ret)) {
			if (!key_is_cert(k)) {
				error("key_read: loaded key is not a cert");
				key_free(k);
				return -1;
			}
			if (ret->cert != NULL)
				cert_free(ret->cert);
			ret->cert = k->cert;
			k->cert = NULL;
		}
		if (key_type_plain(ret->type) == KEY_RSA) {
			if (ret->rsa != NULL)
				RSA_free(ret->rsa);
			ret->rsa = k->rsa;
			k->rsa = NULL;
#ifdef DEBUG_PK
			RSA_print_fp(stderr, ret->rsa, 8);
#endif
		}
		if (key_type_plain(ret->type) == KEY_DSA) {
			if (ret->dsa != NULL)
				DSA_free(ret->dsa);
			ret->dsa = k->dsa;
			k->dsa = NULL;
#ifdef DEBUG_PK
			DSA_print_fp(stderr, ret->dsa, 8);
#endif
		}
		success = 1;
/*XXXX*/
		key_free(k);
		if (success != 1)
			break;
		/* advance cp: skip whitespace and data */
		while (*cp == ' ' || *cp == '\t')
			cp++;
		while (*cp != '\0' && *cp != ' ' && *cp != '\t')
			cp++;
		*cpp = cp;
		break;
	default:
		fatal("key_read: bad key type: %d", ret->type);
		break;
	}
	return success;
}

int
key_write(const Key *key, FILE *f)
{
	int n, success = 0;
	u_int len, bits = 0;
	u_char *blob;
	char *uu;

	if (key_is_cert(key)) {
		if (key->cert == NULL) {
			error("%s: no cert data", __func__);
			return 0;
		}
		if (buffer_len(&key->cert->certblob) == 0) {
			error("%s: no signed certificate blob", __func__);
			return 0;
		}
	}

	switch (key->type) {
	case KEY_RSA1:
		if (key->rsa == NULL)
			return 0;
		/* size of modulus 'n' */
		bits = BN_num_bits(key->rsa->n);
		fprintf(f, "%u", bits);
		if (write_bignum(f, key->rsa->e) &&
		    write_bignum(f, key->rsa->n))
			return 1;
		error("key_write: failed for RSA key");
		return 0;
	case KEY_DSA:
	case KEY_DSA_CERT:
		if (key->dsa == NULL)
			return 0;
		break;
	case KEY_RSA:
	case KEY_RSA_CERT:
		if (key->rsa == NULL)
			return 0;
		break;
	default:
		return 0;
	}

	key_to_blob(key, &blob, &len);
	uu = xmalloc(2*len);
	n = uuencode(blob, len, uu, 2*len);
	if (n > 0) {
		fprintf(f, "%s %s", key_ssh_name(key), uu);
		success = 1;
	}
	xfree(blob);
	xfree(uu);

	return success;
}

const char *
key_type(const Key *k)
{
	switch (k->type) {
	case KEY_RSA1:
		return "RSA1";
	case KEY_RSA:
		return "RSA";
	case KEY_DSA:
		return "DSA";
	case KEY_RSA_CERT:
		return "RSA-CERT";
	case KEY_DSA_CERT:
		return "DSA-CERT";
	}
	return "unknown";
}

const char *
key_ssh_name(const Key *k)
{
	switch (k->type) {
	case KEY_RSA:
		return "ssh-rsa";
	case KEY_DSA:
		return "ssh-dss";
	case KEY_RSA_CERT:
		return "ssh-rsa-cert-v00@openssh.com";
	case KEY_DSA_CERT:
		return "ssh-dss-cert-v00@openssh.com";
	}
	return "ssh-unknown";
}

u_int
key_size(const Key *k)
{
	switch (k->type) {
	case KEY_RSA1:
	case KEY_RSA:
	case KEY_RSA_CERT:
		return BN_num_bits(k->rsa->n);
	case KEY_DSA:
	case KEY_DSA_CERT:
		return BN_num_bits(k->dsa->p);
	}
	return 0;
}

static RSA *
rsa_generate_private_key(u_int bits)
{
	RSA *private;

	private = RSA_generate_key(bits, RSA_F4, NULL, NULL);
	if (private == NULL)
		fatal("rsa_generate_private_key: key generation failed.");
	return private;
}

static DSA*
dsa_generate_private_key(u_int bits)
{
	DSA *private = DSA_generate_parameters(bits, NULL, 0, NULL, NULL, NULL, NULL);

	if (private == NULL)
		fatal("dsa_generate_private_key: DSA_generate_parameters failed");
	if (!DSA_generate_key(private))
		fatal("dsa_generate_private_key: DSA_generate_key failed.");
	if (private == NULL)
		fatal("dsa_generate_private_key: NULL.");
	return private;
}

Key *
key_generate(int type, u_int bits)
{
	Key *k = key_new(KEY_UNSPEC);
	switch (type) {
	case KEY_DSA:
		k->dsa = dsa_generate_private_key(bits);
		break;
	case KEY_RSA:
	case KEY_RSA1:
		k->rsa = rsa_generate_private_key(bits);
		break;
	case KEY_RSA_CERT:
	case KEY_DSA_CERT:
		fatal("key_generate: cert keys cannot be generated directly");
	default:
		fatal("key_generate: unknown type %d", type);
	}
	k->type = type;
	return k;
}

void
key_cert_copy(const Key *from_key, struct Key *to_key)
{
	u_int i;
	const struct KeyCert *from;
	struct KeyCert *to;

	if (to_key->cert != NULL) {
		cert_free(to_key->cert);
		to_key->cert = NULL;
	}

	if ((from = from_key->cert) == NULL)
		return;

	to = to_key->cert = cert_new();

	buffer_append(&to->certblob, buffer_ptr(&from->certblob),
	    buffer_len(&from->certblob));

	buffer_append(&to->constraints, buffer_ptr(&from->constraints),
	    buffer_len(&from->constraints));

	to->type = from->type;
	to->key_id = from->key_id == NULL ? NULL : xstrdup(from->key_id);
	to->valid_after = from->valid_after;
	to->valid_before = from->valid_before;
	to->signature_key = from->signature_key == NULL ?
	    NULL : key_from_private(from->signature_key);

	to->nprincipals = from->nprincipals;
	if (to->nprincipals > CERT_MAX_PRINCIPALS)
		fatal("%s: nprincipals (%u) > CERT_MAX_PRINCIPALS (%u)",
		    __func__, to->nprincipals, CERT_MAX_PRINCIPALS);
	if (to->nprincipals > 0) {
		to->principals = xcalloc(from->nprincipals,
		    sizeof(*to->principals));
		for (i = 0; i < to->nprincipals; i++)
			to->principals[i] = xstrdup(from->principals[i]);
	}
}

Key *
key_from_private(const Key *k)
{
	Key *n = NULL;
	switch (k->type) {
	case KEY_DSA:
	case KEY_DSA_CERT:
		n = key_new(k->type);
		if ((BN_copy(n->dsa->p, k->dsa->p) == NULL) ||
		    (BN_copy(n->dsa->q, k->dsa->q) == NULL) ||
		    (BN_copy(n->dsa->g, k->dsa->g) == NULL) ||
		    (BN_copy(n->dsa->pub_key, k->dsa->pub_key) == NULL))
			fatal("key_from_private: BN_copy failed");
		break;
	case KEY_RSA:
	case KEY_RSA1:
	case KEY_RSA_CERT:
		n = key_new(k->type);
		if ((BN_copy(n->rsa->n, k->rsa->n) == NULL) ||
		    (BN_copy(n->rsa->e, k->rsa->e) == NULL))
			fatal("key_from_private: BN_copy failed");
		break;
	default:
		fatal("key_from_private: unknown type %d", k->type);
		break;
	}
	if (key_is_cert(k))
		key_cert_copy(k, n);
	return n;
}

int
key_type_from_name(char *name)
{
	if (strcmp(name, "rsa1") == 0) {
		return KEY_RSA1;
	} else if (strcmp(name, "rsa") == 0) {
		return KEY_RSA;
	} else if (strcmp(name, "dsa") == 0) {
		return KEY_DSA;
	} else if (strcmp(name, "ssh-rsa") == 0) {
		return KEY_RSA;
	} else if (strcmp(name, "ssh-dss") == 0) {
		return KEY_DSA;
	} else if (strcmp(name, "ssh-rsa-cert-v00@openssh.com") == 0) {
		return KEY_RSA_CERT;
	} else if (strcmp(name, "ssh-dss-cert-v00@openssh.com") == 0) {
		return KEY_DSA_CERT;
	}
	debug2("key_type_from_name: unknown key type '%s'", name);
	return KEY_UNSPEC;
}

int
key_names_valid2(const char *names)
{
	char *s, *cp, *p;

	if (names == NULL || strcmp(names, "") == 0)
		return 0;
	s = cp = xstrdup(names);
	for ((p = strsep(&cp, ",")); p && *p != '\0';
	    (p = strsep(&cp, ","))) {
		switch (key_type_from_name(p)) {
		case KEY_RSA1:
		case KEY_UNSPEC:
			xfree(s);
			return 0;
		}
	}
	debug3("key names ok: [%s]", names);
	xfree(s);
	return 1;
}

static int
cert_parse(Buffer *b, Key *key, const u_char *blob, u_int blen)
{
	u_char *principals, *constraints, *sig_key, *sig;
	u_int signed_len, plen, clen, sklen, slen;
	Buffer tmp;
	char *principal;
	int ret = -1;

	buffer_init(&tmp);

	/* Copy the entire key blob for verification and later serialisation */
	buffer_append(&key->cert->certblob, blob, blen);

	principals = constraints = sig_key = sig = NULL;
	if (buffer_get_int_ret(&key->cert->type, b) != 0 ||
	    (key->cert->key_id = buffer_get_string_ret(b, NULL)) == NULL ||
	    (principals = buffer_get_string_ret(b, &plen)) == NULL ||
	    buffer_get_int64_ret(&key->cert->valid_after, b) != 0 ||
	    buffer_get_int64_ret(&key->cert->valid_before, b) != 0 ||
	    (constraints = buffer_get_string_ret(b, &clen)) == NULL ||
	    /* skip nonce */ buffer_get_string_ptr_ret(b, NULL) == NULL ||
	    /* skip reserved */ buffer_get_string_ptr_ret(b, NULL) == NULL ||
	    (sig_key = buffer_get_string_ret(b, &sklen)) == NULL) {
		error("%s: parse error", __func__);
		goto out;
	}

	/* Signature is left in the buffer so we can calculate this length */
	signed_len = buffer_len(&key->cert->certblob) - buffer_len(b);

	if ((sig = buffer_get_string_ret(b, &slen)) == NULL) {
		error("%s: parse error", __func__);
		goto out;
	}

	if (key->cert->type != SSH2_CERT_TYPE_USER &&
	    key->cert->type != SSH2_CERT_TYPE_HOST) {
		error("Unknown certificate type %u", key->cert->type);
		goto out;
	}

	buffer_append(&tmp, principals, plen);
	while (buffer_len(&tmp) > 0) {
		if (key->cert->nprincipals >= CERT_MAX_PRINCIPALS) {
			error("Too many principals");
			goto out;
		}
		if ((principal = buffer_get_string_ret(&tmp, NULL)) == NULL) {
			error("Principals data invalid");
			goto out;
		}
		key->cert->principals = xrealloc(key->cert->principals,
		    key->cert->nprincipals + 1, sizeof(*key->cert->principals));
		key->cert->principals[key->cert->nprincipals++] = principal;
	}

	buffer_clear(&tmp);

	buffer_append(&key->cert->constraints, constraints, clen);
	buffer_append(&tmp, constraints, clen);
	/* validate structure */
	while (buffer_len(&tmp) != 0) {
		if (buffer_get_string_ptr(&tmp, NULL) == NULL ||
		    buffer_get_string_ptr(&tmp, NULL) == NULL) {
			error("Constraints data invalid");
			goto out;
		}
	}
	buffer_clear(&tmp);

	if ((key->cert->signature_key = key_from_blob(sig_key,
	    sklen)) == NULL) {
		error("Signature key invalid");
		goto out;
	}
	if (key->cert->signature_key->type != KEY_RSA &&
	    key->cert->signature_key->type != KEY_DSA) {
		error("Invalid signature key type %s (%d)",
		    key_type(key->cert->signature_key),
		    key->cert->signature_key->type);
		goto out;
	}

	switch (key_verify(key->cert->signature_key, sig, slen, 
	    buffer_ptr(&key->cert->certblob), signed_len)) {
	case 1:
		break; /* Good signature */
	case 0:
		error("Invalid signature on certificate");
		goto out;
	case -1:
		error("Certificate signature verification failed");
		goto out;
	}

	ret = 0;

 out:
	buffer_free(&tmp);
	if (principals != NULL)
		xfree(principals);
	if (constraints != NULL)
		xfree(constraints);
	if (sig_key != NULL)
		xfree(sig_key);
	if (sig != NULL)
		xfree(sig);
	return ret;
}

Key *
key_from_blob(const u_char *blob, u_int blen)
{
	Buffer b;
	int rlen, type;
	char *ktype = NULL;
	Key *key = NULL;

#ifdef DEBUG_PK
	dump_base64(stderr, blob, blen);
#endif
	buffer_init(&b);
	buffer_append(&b, blob, blen);
	if ((ktype = buffer_get_string_ret(&b, NULL)) == NULL) {
		error("key_from_blob: can't read key type");
		goto out;
	}

	type = key_type_from_name(ktype);

	switch (type) {
	case KEY_RSA:
	case KEY_RSA_CERT:
		key = key_new(type);
		if (buffer_get_bignum2_ret(&b, key->rsa->e) == -1 ||
		    buffer_get_bignum2_ret(&b, key->rsa->n) == -1) {
			error("key_from_blob: can't read rsa key");
 badkey:
			key_free(key);
			key = NULL;
			goto out;
		}
#ifdef DEBUG_PK
		RSA_print_fp(stderr, key->rsa, 8);
#endif
		break;
	case KEY_DSA:
	case KEY_DSA_CERT:
		key = key_new(type);
		if (buffer_get_bignum2_ret(&b, key->dsa->p) == -1 ||
		    buffer_get_bignum2_ret(&b, key->dsa->q) == -1 ||
		    buffer_get_bignum2_ret(&b, key->dsa->g) == -1 ||
		    buffer_get_bignum2_ret(&b, key->dsa->pub_key) == -1) {
			error("key_from_blob: can't read dsa key");
			goto badkey;
		}
#ifdef DEBUG_PK
		DSA_print_fp(stderr, key->dsa, 8);
#endif
		break;
	case KEY_UNSPEC:
		key = key_new(type);
		break;
	default:
		error("key_from_blob: cannot handle type %s", ktype);
		goto out;
	}
	if (key_is_cert(key) && cert_parse(&b, key, blob, blen) == -1) {
		error("key_from_blob: can't parse cert data");
		goto badkey;
	}
	rlen = buffer_len(&b);
	if (key != NULL && rlen != 0)
		error("key_from_blob: remaining bytes in key blob %d", rlen);
 out:
	if (ktype != NULL)
		xfree(ktype);
	buffer_free(&b);
	return key;
}

int
key_to_blob(const Key *key, u_char **blobp, u_int *lenp)
{
	Buffer b;
	int len;

	if (key == NULL) {
		error("key_to_blob: key == NULL");
		return 0;
	}
	buffer_init(&b);
	switch (key->type) {
	case KEY_DSA_CERT:
	case KEY_RSA_CERT:
		/* Use the existing blob */
		buffer_append(&b, buffer_ptr(&key->cert->certblob),
		    buffer_len(&key->cert->certblob));
		break;
	case KEY_DSA:
		buffer_put_cstring(&b, key_ssh_name(key));
		buffer_put_bignum2(&b, key->dsa->p);
		buffer_put_bignum2(&b, key->dsa->q);
		buffer_put_bignum2(&b, key->dsa->g);
		buffer_put_bignum2(&b, key->dsa->pub_key);
		break;
	case KEY_RSA:
		buffer_put_cstring(&b, key_ssh_name(key));
		buffer_put_bignum2(&b, key->rsa->e);
		buffer_put_bignum2(&b, key->rsa->n);
		break;
	default:
		error("key_to_blob: unsupported key type %d", key->type);
		buffer_free(&b);
		return 0;
	}
	len = buffer_len(&b);
	if (lenp != NULL)
		*lenp = len;
	if (blobp != NULL) {
		*blobp = xmalloc(len);
		memcpy(*blobp, buffer_ptr(&b), len);
	}
	memset(buffer_ptr(&b), 0, len);
	buffer_free(&b);
	return len;
}

int
key_sign(
    const Key *key,
    u_char **sigp, u_int *lenp,
    const u_char *data, u_int datalen)
{
	switch (key->type) {
	case KEY_DSA_CERT:
	case KEY_DSA:
		return ssh_dss_sign(key, sigp, lenp, data, datalen);
	case KEY_RSA_CERT:
	case KEY_RSA:
		return ssh_rsa_sign(key, sigp, lenp, data, datalen);
	default:
		error("key_sign: invalid key type %d", key->type);
		return -1;
	}
}

/*
 * key_verify returns 1 for a correct signature, 0 for an incorrect signature
 * and -1 on error.
 */
int
key_verify(
    const Key *key,
    const u_char *signature, u_int signaturelen,
    const u_char *data, u_int datalen)
{
	if (signaturelen == 0)
		return -1;

	switch (key->type) {
	case KEY_DSA_CERT:
	case KEY_DSA:
		return ssh_dss_verify(key, signature, signaturelen, data, datalen);
	case KEY_RSA_CERT:
	case KEY_RSA:
		return ssh_rsa_verify(key, signature, signaturelen, data, datalen);
	default:
		error("key_verify: invalid key type %d", key->type);
		return -1;
	}
}

/* Converts a private to a public key */
Key *
key_demote(const Key *k)
{
	Key *pk;

	pk = xcalloc(1, sizeof(*pk));
	pk->type = k->type;
	pk->flags = k->flags;
	pk->dsa = NULL;
	pk->rsa = NULL;

	switch (k->type) {
	case KEY_RSA_CERT:
		key_cert_copy(k, pk);
		/* FALLTHROUGH */
	case KEY_RSA1:
	case KEY_RSA:
		if ((pk->rsa = RSA_new()) == NULL)
			fatal("key_demote: RSA_new failed");
		if ((pk->rsa->e = BN_dup(k->rsa->e)) == NULL)
			fatal("key_demote: BN_dup failed");
		if ((pk->rsa->n = BN_dup(k->rsa->n)) == NULL)
			fatal("key_demote: BN_dup failed");
		break;
	case KEY_DSA_CERT:
		key_cert_copy(k, pk);
		/* FALLTHROUGH */
	case KEY_DSA:
		if ((pk->dsa = DSA_new()) == NULL)
			fatal("key_demote: DSA_new failed");
		if ((pk->dsa->p = BN_dup(k->dsa->p)) == NULL)
			fatal("key_demote: BN_dup failed");
		if ((pk->dsa->q = BN_dup(k->dsa->q)) == NULL)
			fatal("key_demote: BN_dup failed");
		if ((pk->dsa->g = BN_dup(k->dsa->g)) == NULL)
			fatal("key_demote: BN_dup failed");
		if ((pk->dsa->pub_key = BN_dup(k->dsa->pub_key)) == NULL)
			fatal("key_demote: BN_dup failed");
		break;
	default:
		fatal("key_free: bad key type %d", k->type);
		break;
	}

	return (pk);
}

int
key_is_cert(const Key *k)
{
	return k != NULL &&
	    (k->type == KEY_RSA_CERT || k->type == KEY_DSA_CERT);
}

/* Return the cert-less equivalent to a certified key type */
int
key_type_plain(int type)
{
	switch (type) {
	case KEY_RSA_CERT:
		return KEY_RSA;
	case KEY_DSA_CERT:
		return KEY_DSA;
	default:
		return type;
	}
}

/* Convert a KEY_RSA or KEY_DSA to their _CERT equivalent */
int
key_to_certified(Key *k)
{
	switch (k->type) {
	case KEY_RSA:
		k->cert = cert_new();
		k->type = KEY_RSA_CERT;
		return 0;
	case KEY_DSA:
		k->cert = cert_new();
		k->type = KEY_DSA_CERT;
		return 0;
	default:
		error("%s: key has incorrect type %s", __func__, key_type(k));
		return -1;
	}
}

/* Convert a KEY_RSA_CERT or KEY_DSA_CERT to their raw key equivalent */
int
key_drop_cert(Key *k)
{
	switch (k->type) {
	case KEY_RSA_CERT:
		cert_free(k->cert);
		k->type = KEY_RSA;
		return 0;
	case KEY_DSA_CERT:
		cert_free(k->cert);
		k->type = KEY_DSA;
		return 0;
	default:
		error("%s: key has incorrect type %s", __func__, key_type(k));
		return -1;
	}
}

/* Sign a KEY_RSA_CERT or KEY_DSA_CERT, (re-)generating the signed certblob */
int
key_certify(Key *k, Key *ca)
{
	Buffer principals;
	u_char *ca_blob, *sig_blob, nonce[32];
	u_int i, ca_len, sig_len;

	if (k->cert == NULL) {
		error("%s: key lacks cert info", __func__);
		return -1;
	}

	if (!key_is_cert(k)) {
		error("%s: certificate has unknown type %d", __func__,
		    k->cert->type);
		return -1;
	}

	if (ca->type != KEY_RSA && ca->type != KEY_DSA) {
		error("%s: CA key has unsupported type %s", __func__,
		    key_type(ca));
		return -1;
	}

	key_to_blob(ca, &ca_blob, &ca_len);

	buffer_clear(&k->cert->certblob);
	buffer_put_cstring(&k->cert->certblob, key_ssh_name(k));

	switch (k->type) {
	case KEY_DSA_CERT:
		buffer_put_bignum2(&k->cert->certblob, k->dsa->p);
		buffer_put_bignum2(&k->cert->certblob, k->dsa->q);
		buffer_put_bignum2(&k->cert->certblob, k->dsa->g);
		buffer_put_bignum2(&k->cert->certblob, k->dsa->pub_key);
		break;
	case KEY_RSA_CERT:
		buffer_put_bignum2(&k->cert->certblob, k->rsa->e);
		buffer_put_bignum2(&k->cert->certblob, k->rsa->n);
		break;
	default:
		error("%s: key has incorrect type %s", __func__, key_type(k));
		buffer_clear(&k->cert->certblob);
		xfree(ca_blob);
		return -1;
	}

	buffer_put_int(&k->cert->certblob, k->cert->type);
	buffer_put_cstring(&k->cert->certblob, k->cert->key_id);

	buffer_init(&principals);
	for (i = 0; i < k->cert->nprincipals; i++)
		buffer_put_cstring(&principals, k->cert->principals[i]);
	buffer_put_string(&k->cert->certblob, buffer_ptr(&principals),
	    buffer_len(&principals));
	buffer_free(&principals);

	buffer_put_int64(&k->cert->certblob, k->cert->valid_after);
	buffer_put_int64(&k->cert->certblob, k->cert->valid_before);
	buffer_put_string(&k->cert->certblob,
	    buffer_ptr(&k->cert->constraints),
	    buffer_len(&k->cert->constraints));

	arc4random_buf(&nonce, sizeof(nonce));
	buffer_put_string(&k->cert->certblob, nonce, sizeof(nonce));
	buffer_put_string(&k->cert->certblob, NULL, 0); /* reserved */
	buffer_put_string(&k->cert->certblob, ca_blob, ca_len);
	xfree(ca_blob);

	/* Sign the whole mess */
	if (key_sign(ca, &sig_blob, &sig_len, buffer_ptr(&k->cert->certblob),
	    buffer_len(&k->cert->certblob)) != 0) {
		error("%s: signature operation failed", __func__);
		buffer_clear(&k->cert->certblob);
		return -1;
	}
	/* Append signature and we are done */
	buffer_put_string(&k->cert->certblob, sig_blob, sig_len);
	xfree(sig_blob);

	return 0;
}

int
key_cert_check_authority(const Key *k, int want_host, int require_principal,
    const char *name, const char **reason)
{
	u_int i, principal_matches;
	time_t now = time(NULL);

	if (want_host) {
		if (k->cert->type != SSH2_CERT_TYPE_HOST) {
			*reason = "Certificate invalid: not a host certificate";
			return -1;
		}
	} else {
		if (k->cert->type != SSH2_CERT_TYPE_USER) {
			*reason = "Certificate invalid: not a user certificate";
			return -1;
		}
	}
	if (now < 0) {
		error("%s: system clock lies before epoch", __func__);
		*reason = "Certificate invalid: not yet valid";
		return -1;
	}
	if ((u_int64_t)now < k->cert->valid_after) {
		*reason = "Certificate invalid: not yet valid";
		return -1;
	}
	if ((u_int64_t)now >= k->cert->valid_before) {
		*reason = "Certificate invalid: expired";
		return -1;
	}
	if (k->cert->nprincipals == 0) {
		if (require_principal) {
			*reason = "Certificate lacks principal list";
			return -1;
		}
	} else {
		principal_matches = 0;
		for (i = 0; i < k->cert->nprincipals; i++) {
			if (strcmp(name, k->cert->principals[i]) == 0) {
				principal_matches = 1;
				break;
			}
		}
		if (!principal_matches) {
			*reason = "Certificate invalid: name is not a listed "
			    "principal";
			return -1;
		}
	}
	return 0;
}