Return to authfile.c CVS log

Up to [local] / src / usr.bin / ssh

Switch to recallocarray() for a few operations.  Both growth and shrinkage
are handled safely, and there also is no need for preallocation dances.
Future changes in this area will be less error prone.
Review and one bug found by markus

/* $OpenBSD: authfile.c,v 1.126 2017/05/31 09:15:42 deraadt Exp $ */
/*
 * Copyright (c) 2000, 2013 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.
 */


#include <sys/types.h>
#include <sys/stat.h>
#include <sys/uio.h>

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>

#include "cipher.h"
#include "ssh.h"
#include "log.h"
#include "authfile.h"
#include "rsa.h"
#include "misc.h"
#include "atomicio.h"
#include "sshkey.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "krl.h"

#define MAX_KEY_FILE_SIZE	(1024 * 1024)

/* Save a key blob to a file */
static int
sshkey_save_private_blob(struct sshbuf *keybuf, const char *filename)
{
	int fd, oerrno;

	if ((fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600)) < 0)
		return SSH_ERR_SYSTEM_ERROR;
	if (atomicio(vwrite, fd, (u_char *)sshbuf_ptr(keybuf),
	    sshbuf_len(keybuf)) != sshbuf_len(keybuf)) {
		oerrno = errno;
		close(fd);
		unlink(filename);
		errno = oerrno;
		return SSH_ERR_SYSTEM_ERROR;
	}
	close(fd);
	return 0;
}

int
sshkey_save_private(struct sshkey *key, const char *filename,
    const char *passphrase, const char *comment,
    int force_new_format, const char *new_format_cipher, int new_format_rounds)
{
	struct sshbuf *keyblob = NULL;
	int r;

	if ((keyblob = sshbuf_new()) == NULL)
		return SSH_ERR_ALLOC_FAIL;
	if ((r = sshkey_private_to_fileblob(key, keyblob, passphrase, comment,
	    force_new_format, new_format_cipher, new_format_rounds)) != 0)
		goto out;
	if ((r = sshkey_save_private_blob(keyblob, filename)) != 0)
		goto out;
	r = 0;
 out:
	sshbuf_free(keyblob);
	return r;
}

/* Load a key from a fd into a buffer */
int
sshkey_load_file(int fd, struct sshbuf *blob)
{
	u_char buf[1024];
	size_t len;
	struct stat st;
	int r;

	if (fstat(fd, &st) < 0)
		return SSH_ERR_SYSTEM_ERROR;
	if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
	    st.st_size > MAX_KEY_FILE_SIZE)
		return SSH_ERR_INVALID_FORMAT;
	for (;;) {
		if ((len = atomicio(read, fd, buf, sizeof(buf))) == 0) {
			if (errno == EPIPE)
				break;
			r = SSH_ERR_SYSTEM_ERROR;
			goto out;
		}
		if ((r = sshbuf_put(blob, buf, len)) != 0)
			goto out;
		if (sshbuf_len(blob) > MAX_KEY_FILE_SIZE) {
			r = SSH_ERR_INVALID_FORMAT;
			goto out;
		}
	}
	if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
	    st.st_size != (off_t)sshbuf_len(blob)) {
		r = SSH_ERR_FILE_CHANGED;
		goto out;
	}
	r = 0;

 out:
	explicit_bzero(buf, sizeof(buf));
	if (r != 0)
		sshbuf_reset(blob);
	return r;
}


/* XXX remove error() calls from here? */
int
sshkey_perm_ok(int fd, const char *filename)
{
	struct stat st;

	if (fstat(fd, &st) < 0)
		return SSH_ERR_SYSTEM_ERROR;
	/*
	 * if a key owned by the user is accessed, then we check the
	 * permissions of the file. if the key owned by a different user,
	 * then we don't care.
	 */
	if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @");
		error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
		error("Permissions 0%3.3o for '%s' are too open.",
		    (u_int)st.st_mode & 0777, filename);
		error("It is required that your private key files are NOT accessible by others.");
		error("This private key will be ignored.");
		return SSH_ERR_KEY_BAD_PERMISSIONS;
	}
	return 0;
}

/* XXX kill perm_ok now that we have SSH_ERR_KEY_BAD_PERMISSIONS? */
int
sshkey_load_private_type(int type, const char *filename, const char *passphrase,
    struct sshkey **keyp, char **commentp, int *perm_ok)
{
	int fd, r;

	if (keyp != NULL)
		*keyp = NULL;
	if (commentp != NULL)
		*commentp = NULL;

	if ((fd = open(filename, O_RDONLY)) < 0) {
		if (perm_ok != NULL)
			*perm_ok = 0;
		return SSH_ERR_SYSTEM_ERROR;
	}
	if (sshkey_perm_ok(fd, filename) != 0) {
		if (perm_ok != NULL)
			*perm_ok = 0;
		r = SSH_ERR_KEY_BAD_PERMISSIONS;
		goto out;
	}
	if (perm_ok != NULL)
		*perm_ok = 1;

	r = sshkey_load_private_type_fd(fd, type, passphrase, keyp, commentp);
 out:
	close(fd);
	return r;
}

int
sshkey_load_private_type_fd(int fd, int type, const char *passphrase,
    struct sshkey **keyp, char **commentp)
{
	struct sshbuf *buffer = NULL;
	int r;

	if (keyp != NULL)
		*keyp = NULL;
	if ((buffer = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshkey_load_file(fd, buffer)) != 0 ||
	    (r = sshkey_parse_private_fileblob_type(buffer, type,
	    passphrase, keyp, commentp)) != 0)
		goto out;

	/* success */
	r = 0;
 out:
	sshbuf_free(buffer);
	return r;
}

/* XXX this is almost identical to sshkey_load_private_type() */
int
sshkey_load_private(const char *filename, const char *passphrase,
    struct sshkey **keyp, char **commentp)
{
	struct sshbuf *buffer = NULL;
	int r, fd;

	if (keyp != NULL)
		*keyp = NULL;
	if (commentp != NULL)
		*commentp = NULL;

	if ((fd = open(filename, O_RDONLY)) < 0)
		return SSH_ERR_SYSTEM_ERROR;
	if (sshkey_perm_ok(fd, filename) != 0) {
		r = SSH_ERR_KEY_BAD_PERMISSIONS;
		goto out;
	}

	if ((buffer = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshkey_load_file(fd, buffer)) != 0 ||
	    (r = sshkey_parse_private_fileblob(buffer, passphrase, keyp,
	    commentp)) != 0)
		goto out;
	r = 0;
 out:
	close(fd);
	sshbuf_free(buffer);
	return r;
}

static int
sshkey_try_load_public(struct sshkey *k, const char *filename, char **commentp)
{
	FILE *f;
	char line[SSH_MAX_PUBKEY_BYTES];
	char *cp;
	u_long linenum = 0;
	int r;

	if (commentp != NULL)
		*commentp = NULL;
	if ((f = fopen(filename, "r")) == NULL)
		return SSH_ERR_SYSTEM_ERROR;
	while (read_keyfile_line(f, filename, line, sizeof(line),
		    &linenum) != -1) {
		cp = line;
		switch (*cp) {
		case '#':
		case '\n':
		case '\0':
			continue;
		}
		/* Abort loading if this looks like a private key */
		if (strncmp(cp, "-----BEGIN", 10) == 0 ||
		    strcmp(cp, "SSH PRIVATE KEY FILE") == 0)
			break;
		/* Skip leading whitespace. */
		for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
			;
		if (*cp) {
			if ((r = sshkey_read(k, &cp)) == 0) {
				cp[strcspn(cp, "\r\n")] = '\0';
				if (commentp) {
					*commentp = strdup(*cp ?
					    cp : filename);
					if (*commentp == NULL)
						r = SSH_ERR_ALLOC_FAIL;
				}
				fclose(f);
				return r;
			}
		}
	}
	fclose(f);
	return SSH_ERR_INVALID_FORMAT;
}

/* load public key from any pubkey file */
int
sshkey_load_public(const char *filename, struct sshkey **keyp, char **commentp)
{
	struct sshkey *pub = NULL;
	char *file = NULL;
	int r;

	if (keyp != NULL)
		*keyp = NULL;
	if (commentp != NULL)
		*commentp = NULL;

	if ((pub = sshkey_new(KEY_UNSPEC)) == NULL)
		return SSH_ERR_ALLOC_FAIL;
	if ((r = sshkey_try_load_public(pub, filename, commentp)) == 0) {
		if (keyp != NULL) {
			*keyp = pub;
			pub = NULL;
		}
		r = 0;
		goto out;
	}
	sshkey_free(pub);

	/* try .pub suffix */
	if (asprintf(&file, "%s.pub", filename) == -1)
		return SSH_ERR_ALLOC_FAIL;
	if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshkey_try_load_public(pub, file, commentp)) == 0) {
		if (keyp != NULL) {
			*keyp = pub;
			pub = NULL;
		}
		r = 0;
	}
 out:
	free(file);
	sshkey_free(pub);
	return r;
}

/* Load the certificate associated with the named private key */
int
sshkey_load_cert(const char *filename, struct sshkey **keyp)
{
	struct sshkey *pub = NULL;
	char *file = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;

	if (keyp != NULL)
		*keyp = NULL;

	if (asprintf(&file, "%s-cert.pub", filename) == -1)
		return SSH_ERR_ALLOC_FAIL;

	if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
		goto out;
	}
	if ((r = sshkey_try_load_public(pub, file, NULL)) != 0)
		goto out;
	/* success */
	if (keyp != NULL) {
		*keyp = pub;
		pub = NULL;
	}
	r = 0;
 out:
	free(file);
	sshkey_free(pub);
	return r;
}

/* Load private key and certificate */
int
sshkey_load_private_cert(int type, const char *filename, const char *passphrase,
    struct sshkey **keyp, int *perm_ok)
{
	struct sshkey *key = NULL, *cert = NULL;
	int r;

	if (keyp != NULL)
		*keyp = NULL;

	switch (type) {
#ifdef WITH_OPENSSL
	case KEY_RSA:
	case KEY_DSA:
	case KEY_ECDSA:
#endif /* WITH_OPENSSL */
	case KEY_ED25519:
	case KEY_UNSPEC:
		break;
	default:
		return SSH_ERR_KEY_TYPE_UNKNOWN;
	}

	if ((r = sshkey_load_private_type(type, filename,
	    passphrase, &key, NULL, perm_ok)) != 0 ||
	    (r = sshkey_load_cert(filename, &cert)) != 0)
		goto out;

	/* Make sure the private key matches the certificate */
	if (sshkey_equal_public(key, cert) == 0) {
		r = SSH_ERR_KEY_CERT_MISMATCH;
		goto out;
	}

	if ((r = sshkey_to_certified(key)) != 0 ||
	    (r = sshkey_cert_copy(cert, key)) != 0)
		goto out;
	r = 0;
	if (keyp != NULL) {
		*keyp = key;
		key = NULL;
	}
 out:
	sshkey_free(key);
	sshkey_free(cert);
	return r;
}

/*
 * Returns success if the specified "key" is listed in the file "filename",
 * SSH_ERR_KEY_NOT_FOUND: if the key is not listed or another error.
 * If "strict_type" is set then the key type must match exactly,
 * otherwise a comparison that ignores certficiate data is performed.
 * If "check_ca" is set and "key" is a certificate, then its CA key is
 * also checked and sshkey_in_file() will return success if either is found.
 */
int
sshkey_in_file(struct sshkey *key, const char *filename, int strict_type,
    int check_ca)
{
	FILE *f;
	char line[SSH_MAX_PUBKEY_BYTES];
	char *cp;
	u_long linenum = 0;
	int r = 0;
	struct sshkey *pub = NULL;
	int (*sshkey_compare)(const struct sshkey *, const struct sshkey *) =
	    strict_type ?  sshkey_equal : sshkey_equal_public;

	if ((f = fopen(filename, "r")) == NULL)
		return SSH_ERR_SYSTEM_ERROR;

	while (read_keyfile_line(f, filename, line, sizeof(line),
	    &linenum) != -1) {
		cp = line;

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

		/* Skip comments and empty lines */
		switch (*cp) {
		case '#':
		case '\n':
		case '\0':
			continue;
		}

		if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
			r = SSH_ERR_ALLOC_FAIL;
			goto out;
		}
		if ((r = sshkey_read(pub, &cp)) != 0)
			goto out;
		if (sshkey_compare(key, pub) ||
		    (check_ca && sshkey_is_cert(key) &&
		    sshkey_compare(key->cert->signature_key, pub))) {
			r = 0;
			goto out;
		}
		sshkey_free(pub);
		pub = NULL;
	}
	r = SSH_ERR_KEY_NOT_FOUND;
 out:
	sshkey_free(pub);
	fclose(f);
	return r;
}

/*
 * Checks whether the specified key is revoked, returning 0 if not,
 * SSH_ERR_KEY_REVOKED if it is or another error code if something
 * unexpected happened.
 * This will check both the key and, if it is a certificate, its CA key too.
 * "revoked_keys_file" may be a KRL or a one-per-line list of public keys.
 */
int
sshkey_check_revoked(struct sshkey *key, const char *revoked_keys_file)
{
	int r;

	r = ssh_krl_file_contains_key(revoked_keys_file, key);
	/* If this was not a KRL to begin with then continue below */
	if (r != SSH_ERR_KRL_BAD_MAGIC)
		return r;

	/*
	 * If the file is not a KRL or we can't handle KRLs then attempt to
	 * parse the file as a flat list of keys.
	 */
	switch ((r = sshkey_in_file(key, revoked_keys_file, 0, 1))) {
	case 0:
		/* Key found => revoked */
		return SSH_ERR_KEY_REVOKED;
	case SSH_ERR_KEY_NOT_FOUND:
		/* Key not found => not revoked */
		return 0;
	default:
		/* Some other error occurred */
		return r;
	}
}