openssh/6.6p1/authfile.c

/* $OpenBSD: authfile.c,v 1.103 2014/02/02 03:44:31 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * This file contains functions for reading and writing identity files, and
 * for reading the passphrase from the user.
 *
 * 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, 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 "includes.h"

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

#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/pem.h>

/* compatibility with old or broken OpenSSL versions */
#include "openbsd-compat/openssl-compat.h"

#include "crypto_api.h"

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

#ifdef HAVE_UTIL_H
#include <util.h>
#endif

#include "xmalloc.h"
#include "cipher.h"
#include "buffer.h"
#include "key.h"
#include "ssh.h"
#include "log.h"
#include "authfile.h"
#include "rsa.h"
#include "misc.h"
#include "atomicio.h"
#include "uuencode.h"

/* openssh private key file format */
#define MARK_BEGIN              "-----BEGIN OPENSSH PRIVATE KEY-----\n"
#define MARK_END                "-----END OPENSSH PRIVATE KEY-----\n"
#define KDFNAME                 "bcrypt"
#define AUTH_MAGIC              "openssh-key-v1"
#define SALT_LEN                16
#define DEFAULT_CIPHERNAME      "aes256-cbc"
#define DEFAULT_ROUNDS          16

#define MAX_KEY_FILE_SIZE       (1024 * 1024)

/* Version identification string for SSH v1 identity files. */
static const char authfile_id_string[] =
    "SSH PRIVATE KEY FILE FORMAT 1.1\n";

static int
key_private_to_blob2(Key *prv, Buffer *blob, const char *passphrase,
    const char *comment, const char *ciphername, int rounds)
{
        u_char *key, *cp, salt[SALT_LEN];
        size_t keylen, ivlen, blocksize, authlen;
        u_int len, check;
        int i, n;
        const Cipher *c;
        Buffer encoded, b, kdf;
        CipherContext ctx;
        const char *kdfname = KDFNAME;

        if (rounds <= 0)
                rounds = DEFAULT_ROUNDS;
        if (passphrase == NULL || !strlen(passphrase)) {
                ciphername = "none";
                kdfname = "none";
        } else if (ciphername == NULL)
                ciphername = DEFAULT_CIPHERNAME;
        else if (cipher_number(ciphername) != SSH_CIPHER_SSH2)
                fatal("invalid cipher");

        if ((c = cipher_by_name(ciphername)) == NULL)
                fatal("unknown cipher name");
        buffer_init(&kdf);
        blocksize = cipher_blocksize(c);
        keylen = cipher_keylen(c);
        ivlen = cipher_ivlen(c);
        authlen = cipher_authlen(c);
        key = xcalloc(1, keylen + ivlen);
        if (strcmp(kdfname, "none") != 0) {
                arc4random_buf(salt, SALT_LEN);
                if (bcrypt_pbkdf(passphrase, strlen(passphrase),
                    salt, SALT_LEN, key, keylen + ivlen, rounds) < 0)
                        fatal("bcrypt_pbkdf failed");
                buffer_put_string(&kdf, salt, SALT_LEN);
                buffer_put_int(&kdf, rounds);
        }
        cipher_init(&ctx, c, key, keylen, key + keylen , ivlen, 1);
        explicit_bzero(key, keylen + ivlen);
        free(key);

        buffer_init(&encoded);
        buffer_append(&encoded, AUTH_MAGIC, sizeof(AUTH_MAGIC));
        buffer_put_cstring(&encoded, ciphername);
        buffer_put_cstring(&encoded, kdfname);
        buffer_put_string(&encoded, buffer_ptr(&kdf), buffer_len(&kdf));
        buffer_put_int(&encoded, 1);                    /* number of keys */
        key_to_blob(prv, &cp, &len);                    /* public key */
        buffer_put_string(&encoded, cp, len);

        explicit_bzero(cp, len);
        free(cp);

        buffer_free(&kdf);

        /* set up the buffer that will be encrypted */
        buffer_init(&b);

        /* Random check bytes */
        check = arc4random();
        buffer_put_int(&b, check);
        buffer_put_int(&b, check);

        /* append private key and comment*/
        key_private_serialize(prv, &b);
        buffer_put_cstring(&b, comment);

        /* padding */
        i = 0;
        while (buffer_len(&b) % blocksize)
                buffer_put_char(&b, ++i & 0xff);

        /* length */
        buffer_put_int(&encoded, buffer_len(&b));

        /* encrypt */
        cp = buffer_append_space(&encoded, buffer_len(&b) + authlen);
        if (cipher_crypt(&ctx, 0, cp, buffer_ptr(&b), buffer_len(&b), 0,
            authlen) != 0)
                fatal("%s: cipher_crypt failed", __func__);
        buffer_free(&b);
        cipher_cleanup(&ctx);

        /* uuencode */
        len = 2 * buffer_len(&encoded);
        cp = xmalloc(len);
        n = uuencode(buffer_ptr(&encoded), buffer_len(&encoded),
            (char *)cp, len);
        if (n < 0)
                fatal("%s: uuencode", __func__);

        buffer_clear(blob);
        buffer_append(blob, MARK_BEGIN, sizeof(MARK_BEGIN) - 1);
        for (i = 0; i < n; i++) {
                buffer_put_char(blob, cp[i]);
                if (i % 70 == 69)
                        buffer_put_char(blob, '\n');
        }
        if (i % 70 != 69)
                buffer_put_char(blob, '\n');
        buffer_append(blob, MARK_END, sizeof(MARK_END) - 1);
        free(cp);

        return buffer_len(blob);
}

static Key *
key_parse_private2(Buffer *blob, int type, const char *passphrase,
    char **commentp)
{
        u_char *key = NULL, *cp, *salt = NULL, pad, last;
        char *comment = NULL, *ciphername = NULL, *kdfname = NULL, *kdfp;
        u_int keylen = 0, ivlen, blocksize, slen, klen, len, rounds, nkeys;
        u_int check1, check2, m1len, m2len;
        size_t authlen;
        const Cipher *c;
        Buffer b, encoded, copy, kdf;
        CipherContext ctx;
        Key *k = NULL;
        int dlen, ret, i;

        buffer_init(&b);
        buffer_init(&kdf);
        buffer_init(&encoded);
        buffer_init(&copy);

        /* uudecode */
        m1len = sizeof(MARK_BEGIN) - 1;
        m2len = sizeof(MARK_END) - 1;
        cp = buffer_ptr(blob);
        len = buffer_len(blob);
        if (len < m1len || memcmp(cp, MARK_BEGIN, m1len)) {
                debug("%s: missing begin marker", __func__);
                goto out;
        }
        cp += m1len;
        len -= m1len;
        while (len) {
                if (*cp != '\n' && *cp != '\r')
                        buffer_put_char(&encoded, *cp);
                last = *cp;
                len--;
                cp++;
                if (last == '\n') {
                        if (len >= m2len && !memcmp(cp, MARK_END, m2len)) {
                                buffer_put_char(&encoded, '\0');
                                break;
                        }
                }
        }
        if (!len) {
                debug("%s: no end marker", __func__);
                goto out;
        }
        len = buffer_len(&encoded);
        if ((cp = buffer_append_space(&copy, len)) == NULL) {
                error("%s: buffer_append_space", __func__);
                goto out;
        }
        if ((dlen = uudecode(buffer_ptr(&encoded), cp, len)) < 0) {
                error("%s: uudecode failed", __func__);
                goto out;
        }
        if ((u_int)dlen > len) {
                error("%s: crazy uudecode length %d > %u", __func__, dlen, len);
                goto out;
        }
        buffer_consume_end(&copy, len - dlen);
        if (buffer_len(&copy) < sizeof(AUTH_MAGIC) ||
            memcmp(buffer_ptr(&copy), AUTH_MAGIC, sizeof(AUTH_MAGIC))) {
                error("%s: bad magic", __func__);
                goto out;
        }
        buffer_consume(&copy, sizeof(AUTH_MAGIC));

        ciphername = buffer_get_cstring_ret(&copy, NULL);
        if (ciphername == NULL ||
            (c = cipher_by_name(ciphername)) == NULL) {
                error("%s: unknown cipher name", __func__);
                goto out;
        }
        if ((passphrase == NULL || !strlen(passphrase)) &&
            strcmp(ciphername, "none") != 0) {
                /* passphrase required */
                goto out;
        }
        kdfname = buffer_get_cstring_ret(&copy, NULL);
        if (kdfname == NULL ||
            (!strcmp(kdfname, "none") && !strcmp(kdfname, "bcrypt"))) {
                error("%s: unknown kdf name", __func__);
                goto out;
        }
        if (!strcmp(kdfname, "none") && strcmp(ciphername, "none") != 0) {
                error("%s: cipher %s requires kdf", __func__, ciphername);
                goto out;
        }
        /* kdf options */
        kdfp = buffer_get_string_ptr_ret(&copy, &klen);
        if (kdfp == NULL) {
                error("%s: kdf options not set", __func__);
                goto out;
        }
        if (klen > 0) {
                if ((cp = buffer_append_space(&kdf, klen)) == NULL) {
                        error("%s: kdf alloc failed", __func__);
                        goto out;
                }
                memcpy(cp, kdfp, klen);
        }
        /* number of keys */
        if (buffer_get_int_ret(&nkeys, &copy) < 0) {
                error("%s: key counter missing", __func__);
                goto out;
        }
        if (nkeys != 1) {
                error("%s: only one key supported", __func__);
                goto out;
        }
        /* pubkey */
        if ((cp = buffer_get_string_ret(&copy, &len)) == NULL) {
                error("%s: pubkey not found", __func__);
                goto out;
        }
        free(cp); /* XXX check pubkey against decrypted private key */

        /* size of encrypted key blob */
        len = buffer_get_int(&copy);
        blocksize = cipher_blocksize(c);
        authlen = cipher_authlen(c);
        if (len < blocksize) {
                error("%s: encrypted data too small", __func__);
                goto out;
        }
        if (len % blocksize) {
                error("%s: length not multiple of blocksize", __func__);
                goto out;
        }

        /* setup key */
        keylen = cipher_keylen(c);
        ivlen = cipher_ivlen(c);
        key = xcalloc(1, keylen + ivlen);
        if (!strcmp(kdfname, "bcrypt")) {
                if ((salt = buffer_get_string_ret(&kdf, &slen)) == NULL) {
                        error("%s: salt not set", __func__);
                        goto out;
                }
                if (buffer_get_int_ret(&rounds, &kdf) < 0) {
                        error("%s: rounds not set", __func__);
                        goto out;
                }
                if (bcrypt_pbkdf(passphrase, strlen(passphrase), salt, slen,
                    key, keylen + ivlen, rounds) < 0) {
                        error("%s: bcrypt_pbkdf failed", __func__);
                        goto out;
                }
        }

        cp = buffer_append_space(&b, len);
        cipher_init(&ctx, c, key, keylen, key + keylen, ivlen, 0);
        ret = cipher_crypt(&ctx, 0, cp, buffer_ptr(&copy), len, 0, authlen);
        cipher_cleanup(&ctx);
        buffer_consume(&copy, len);

        /* fail silently on decryption errors */
        if (ret != 0) {
                debug("%s: decrypt failed", __func__);
                goto out;
        }

        if (buffer_len(&copy) != 0) {
                error("%s: key blob has trailing data (len = %u)", __func__,
                    buffer_len(&copy));
                goto out;
        }

        /* check bytes */
        if (buffer_get_int_ret(&check1, &b) < 0 ||
            buffer_get_int_ret(&check2, &b) < 0) {
                error("check bytes missing");
                goto out;
        }
        if (check1 != check2) {
                debug("%s: decrypt failed: 0x%08x != 0x%08x", __func__,
                    check1, check2);
                goto out;
        }

        k = key_private_deserialize(&b);

        /* comment */
        comment = buffer_get_cstring_ret(&b, NULL);

        i = 0;
        while (buffer_len(&b)) {
                if (buffer_get_char_ret(&pad, &b) == -1 ||
                    pad != (++i & 0xff)) {
                        error("%s: bad padding", __func__);
                        key_free(k);
                        k = NULL;
                        goto out;
                }
        }

        if (k && commentp) {
                *commentp = comment;
                comment = NULL;
        }

        /* XXX decode pubkey and check against private */
 out:
        free(ciphername);
        free(kdfname);
        free(salt);
        free(comment);
        if (key)
                explicit_bzero(key, keylen + ivlen);
        free(key);
        buffer_free(&encoded);
        buffer_free(&copy);
        buffer_free(&kdf);
        buffer_free(&b);
        return k;
}

/*
 * Serialises the authentication (private) key to a blob, encrypting it with
 * passphrase.  The identification of the blob (lowest 64 bits of n) will
 * precede the key to provide identification of the key without needing a
 * passphrase.
 */
static int
key_private_rsa1_to_blob(Key *key, Buffer *blob, const char *passphrase,
    const char *comment)
{
        Buffer buffer, encrypted;
        u_char buf[100], *cp;
        int i, cipher_num;
        CipherContext ciphercontext;
        const Cipher *cipher;
        u_int32_t rnd;

        /*
         * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
         * to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
         */
        cipher_num = (strcmp(passphrase, "") == 0) ?
            SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER;
        if ((cipher = cipher_by_number(cipher_num)) == NULL)
                fatal("save_private_key_rsa: bad cipher");

        /* This buffer is used to built the secret part of the private key. */
        buffer_init(&buffer);

        /* Put checkbytes for checking passphrase validity. */
        rnd = arc4random();
        buf[0] = rnd & 0xff;
        buf[1] = (rnd >> 8) & 0xff;
        buf[2] = buf[0];
        buf[3] = buf[1];
        buffer_append(&buffer, buf, 4);

        /*
         * Store the private key (n and e will not be stored because they
         * will be stored in plain text, and storing them also in encrypted
         * format would just give known plaintext).
         */
        buffer_put_bignum(&buffer, key->rsa->d);
        buffer_put_bignum(&buffer, key->rsa->iqmp);
        buffer_put_bignum(&buffer, key->rsa->q);        /* reverse from SSL p */
        buffer_put_bignum(&buffer, key->rsa->p);        /* reverse from SSL q */

        /* Pad the part to be encrypted until its size is a multiple of 8. */
        while (buffer_len(&buffer) % 8 != 0)
                buffer_put_char(&buffer, 0);

        /* This buffer will be used to contain the data in the file. */
        buffer_init(&encrypted);

        /* First store keyfile id string. */
        for (i = 0; authfile_id_string[i]; i++)
                buffer_put_char(&encrypted, authfile_id_string[i]);
        buffer_put_char(&encrypted, 0);

        /* Store cipher type. */
        buffer_put_char(&encrypted, cipher_num);
        buffer_put_int(&encrypted, 0);  /* For future extension */

        /* Store public key.  This will be in plain text. */
        buffer_put_int(&encrypted, BN_num_bits(key->rsa->n));
        buffer_put_bignum(&encrypted, key->rsa->n);
        buffer_put_bignum(&encrypted, key->rsa->e);
        buffer_put_cstring(&encrypted, comment);

        /* Allocate space for the private part of the key in the buffer. */
        cp = buffer_append_space(&encrypted, buffer_len(&buffer));

        cipher_set_key_string(&ciphercontext, cipher, passphrase,
            CIPHER_ENCRYPT);
        if (cipher_crypt(&ciphercontext, 0, cp,
            buffer_ptr(&buffer), buffer_len(&buffer), 0, 0) != 0)
                fatal("%s: cipher_crypt failed", __func__);
        cipher_cleanup(&ciphercontext);
        explicit_bzero(&ciphercontext, sizeof(ciphercontext));

        /* Destroy temporary data. */
        explicit_bzero(buf, sizeof(buf));
        buffer_free(&buffer);

        buffer_append(blob, buffer_ptr(&encrypted), buffer_len(&encrypted));
        buffer_free(&encrypted);

        return 1;
}

/* convert SSH v2 key in OpenSSL PEM format */
static int
key_private_pem_to_blob(Key *key, Buffer *blob, const char *_passphrase,
    const char *comment)
{
        int success = 0;
        int blen, len = strlen(_passphrase);
        u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL;
#if (OPENSSL_VERSION_NUMBER < 0x00907000L)
        const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL;
#else
        const EVP_CIPHER *cipher = (len > 0) ? EVP_aes_128_cbc() : NULL;
#endif
        const u_char *bptr;
        BIO *bio;

        if (len > 0 && len <= 4) {
                error("passphrase too short: have %d bytes, need > 4", len);
                return 0;
        }
        if ((bio = BIO_new(BIO_s_mem())) == NULL) {
                error("%s: BIO_new failed", __func__);
                return 0;
        }
        switch (key->type) {
        case KEY_DSA:
                success = PEM_write_bio_DSAPrivateKey(bio, key->dsa,
                    cipher, passphrase, len, NULL, NULL);
                break;
#ifdef OPENSSL_HAS_ECC
        case KEY_ECDSA:
                success = PEM_write_bio_ECPrivateKey(bio, key->ecdsa,
                    cipher, passphrase, len, NULL, NULL);
                break;
#endif
        case KEY_RSA:
                success = PEM_write_bio_RSAPrivateKey(bio, key->rsa,
                    cipher, passphrase, len, NULL, NULL);
                break;
        }
        if (success) {
                if ((blen = BIO_get_mem_data(bio, &bptr)) <= 0)
                        success = 0;
                else
                        buffer_append(blob, bptr, blen);
        }
        BIO_free(bio);
        return success;
}

/* Save a key blob to a file */
static int
key_save_private_blob(Buffer *keybuf, const char *filename)
{
        int fd;

        if ((fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600)) < 0) {
                error("open %s failed: %s.", filename, strerror(errno));
                return 0;
        }
        if (atomicio(vwrite, fd, buffer_ptr(keybuf),
            buffer_len(keybuf)) != buffer_len(keybuf)) {
                error("write to key file %s failed: %s", filename,
                    strerror(errno));
                close(fd);
                unlink(filename);
                return 0;
        }
        close(fd);
        return 1;
}

/* Serialise "key" to buffer "blob" */
static int
key_private_to_blob(Key *key, Buffer *blob, const char *passphrase,
    const char *comment, int force_new_format, const char *new_format_cipher,
    int new_format_rounds)
{
        switch (key->type) {
        case KEY_RSA1:
                return key_private_rsa1_to_blob(key, blob, passphrase, comment);
        case KEY_DSA:
        case KEY_ECDSA:
        case KEY_RSA:
                if (force_new_format) {
                        return key_private_to_blob2(key, blob, passphrase,
                            comment, new_format_cipher, new_format_rounds);
                }
                return key_private_pem_to_blob(key, blob, passphrase, comment);
        case KEY_ED25519:
                return key_private_to_blob2(key, blob, passphrase,
                    comment, new_format_cipher, new_format_rounds);
        default:
                error("%s: cannot save key type %d", __func__, key->type);
                return 0;
        }
}

int
key_save_private(Key *key, const char *filename, const char *passphrase,
    const char *comment, int force_new_format, const char *new_format_cipher,
    int new_format_rounds)
{
        Buffer keyblob;
        int success = 0;

        buffer_init(&keyblob);
        if (!key_private_to_blob(key, &keyblob, passphrase, comment,
            force_new_format, new_format_cipher, new_format_rounds))
                goto out;
        if (!key_save_private_blob(&keyblob, filename))
                goto out;
        success = 1;
 out:
        buffer_free(&keyblob);
        return success;
}

/*
 * Parse the public, unencrypted portion of a RSA1 key.
 */
static Key *
key_parse_public_rsa1(Buffer *blob, char **commentp)
{
        Key *pub;
        Buffer copy;

        /* Check that it is at least big enough to contain the ID string. */
        if (buffer_len(blob) < sizeof(authfile_id_string)) {
                debug3("Truncated RSA1 identifier");
                return NULL;
        }

        /*
         * Make sure it begins with the id string.  Consume the id string
         * from the buffer.
         */
        if (memcmp(buffer_ptr(blob), authfile_id_string,
            sizeof(authfile_id_string)) != 0) {
                debug3("Incorrect RSA1 identifier");
                return NULL;
        }
        buffer_init(&copy);
        buffer_append(&copy, buffer_ptr(blob), buffer_len(blob));
        buffer_consume(&copy, sizeof(authfile_id_string));

        /* Skip cipher type and reserved data. */
        (void) buffer_get_char(&copy);          /* cipher type */
        (void) buffer_get_int(&copy);           /* reserved */

        /* Read the public key from the buffer. */
        (void) buffer_get_int(&copy);
        pub = key_new(KEY_RSA1);
        buffer_get_bignum(&copy, pub->rsa->n);
        buffer_get_bignum(&copy, pub->rsa->e);
        if (commentp)
                *commentp = buffer_get_string(&copy, NULL);
        /* The encrypted private part is not parsed by this function. */
        buffer_free(&copy);

        return pub;
}

/* Load a key from a fd into a buffer */
int
key_load_file(int fd, const char *filename, Buffer *blob)
{
        u_char buf[1024];
        size_t len;
        struct stat st;

        if (fstat(fd, &st) < 0) {
                error("%s: fstat of key file %.200s%sfailed: %.100s", __func__,
                    filename == NULL ? "" : filename,
                    filename == NULL ? "" : " ",
                    strerror(errno));
                return 0;
        }
        if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
            st.st_size > MAX_KEY_FILE_SIZE) {
 toobig:
                error("%s: key file %.200s%stoo large", __func__,
                    filename == NULL ? "" : filename,
                    filename == NULL ? "" : " ");
                return 0;
        }
        buffer_clear(blob);
        for (;;) {
                if ((len = atomicio(read, fd, buf, sizeof(buf))) == 0) {
                        if (errno == EPIPE)
                                break;
                        debug("%s: read from key file %.200s%sfailed: %.100s",
                            __func__, filename == NULL ? "" : filename,
                            filename == NULL ? "" : " ", strerror(errno));
                        buffer_clear(blob);
                        explicit_bzero(buf, sizeof(buf));
                        return 0;
                }
                buffer_append(blob, buf, len);
                if (buffer_len(blob) > MAX_KEY_FILE_SIZE) {
                        buffer_clear(blob);
                        explicit_bzero(buf, sizeof(buf));
                        goto toobig;
                }
        }
        explicit_bzero(buf, sizeof(buf));
        if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
            st.st_size != buffer_len(blob)) {
                debug("%s: key file %.200s%schanged size while reading",
                    __func__, filename == NULL ? "" : filename,
                    filename == NULL ? "" : " ");
                buffer_clear(blob);
                return 0;
        }

        return 1;
}

/*
 * Loads the public part of the ssh v1 key file.  Returns NULL if an error was
 * encountered (the file does not exist or is not readable), and the key
 * otherwise.
 */
static Key *
key_load_public_rsa1(int fd, const char *filename, char **commentp)
{
        Buffer buffer;
        Key *pub;

        buffer_init(&buffer);
        if (!key_load_file(fd, filename, &buffer)) {
                buffer_free(&buffer);
                return NULL;
        }

        pub = key_parse_public_rsa1(&buffer, commentp);
        if (pub == NULL)
                debug3("Could not load \"%s\" as a RSA1 public key", filename);
        buffer_free(&buffer);
        return pub;
}

/* load public key from private-key file, works only for SSH v1 */
Key *
key_load_public_type(int type, const char *filename, char **commentp)
{
        Key *pub;
        int fd;

        if (type == KEY_RSA1) {
                fd = open(filename, O_RDONLY);
                if (fd < 0)
                        return NULL;
                pub = key_load_public_rsa1(fd, filename, commentp);
                close(fd);
                return pub;
        }
        return NULL;
}

static Key *
key_parse_private_rsa1(Buffer *blob, const char *passphrase, char **commentp)
{
        int check1, check2, cipher_type;
        Buffer decrypted;
        u_char *cp;
        CipherContext ciphercontext;
        const Cipher *cipher;
        Key *prv = NULL;
        Buffer copy;

        /* Check that it is at least big enough to contain the ID string. */
        if (buffer_len(blob) < sizeof(authfile_id_string)) {
                debug3("Truncated RSA1 identifier");
                return NULL;
        }

        /*
         * Make sure it begins with the id string.  Consume the id string
         * from the buffer.
         */
        if (memcmp(buffer_ptr(blob), authfile_id_string,
            sizeof(authfile_id_string)) != 0) {
                debug3("Incorrect RSA1 identifier");
                return NULL;
        }
        buffer_init(&copy);
        buffer_append(&copy, buffer_ptr(blob), buffer_len(blob));
        buffer_consume(&copy, sizeof(authfile_id_string));

        /* Read cipher type. */
        cipher_type = buffer_get_char(&copy);
        (void) buffer_get_int(&copy);   /* Reserved data. */

        /* Read the public key from the buffer. */
        (void) buffer_get_int(&copy);
        prv = key_new_private(KEY_RSA1);

        buffer_get_bignum(&copy, prv->rsa->n);
        buffer_get_bignum(&copy, prv->rsa->e);
        if (commentp)
                *commentp = buffer_get_string(&copy, NULL);
        else
                (void)buffer_get_string_ptr(&copy, NULL);

        /* Check that it is a supported cipher. */
        cipher = cipher_by_number(cipher_type);
        if (cipher == NULL) {
                debug("Unsupported RSA1 cipher %d", cipher_type);
                buffer_free(&copy);
                goto fail;
        }
        /* Initialize space for decrypted data. */
        buffer_init(&decrypted);
        cp = buffer_append_space(&decrypted, buffer_len(&copy));

        /* Rest of the buffer is encrypted.  Decrypt it using the passphrase. */
        cipher_set_key_string(&ciphercontext, cipher, passphrase,
            CIPHER_DECRYPT);
        if (cipher_crypt(&ciphercontext, 0, cp,
            buffer_ptr(&copy), buffer_len(&copy), 0, 0) != 0)
                fatal("%s: cipher_crypt failed", __func__);
        cipher_cleanup(&ciphercontext);
        explicit_bzero(&ciphercontext, sizeof(ciphercontext));
        buffer_free(&copy);

        check1 = buffer_get_char(&decrypted);
        check2 = buffer_get_char(&decrypted);
        if (check1 != buffer_get_char(&decrypted) ||
            check2 != buffer_get_char(&decrypted)) {
                if (strcmp(passphrase, "") != 0)
                        debug("Bad passphrase supplied for RSA1 key");
                /* Bad passphrase. */
                buffer_free(&decrypted);
                goto fail;
        }
        /* Read the rest of the private key. */
        buffer_get_bignum(&decrypted, prv->rsa->d);
        buffer_get_bignum(&decrypted, prv->rsa->iqmp);          /* u */
        /* in SSL and SSH v1 p and q are exchanged */
        buffer_get_bignum(&decrypted, prv->rsa->q);             /* p */
        buffer_get_bignum(&decrypted, prv->rsa->p);             /* q */

        /* calculate p-1 and q-1 */
        rsa_generate_additional_parameters(prv->rsa);

        buffer_free(&decrypted);

        /* enable blinding */
        if (RSA_blinding_on(prv->rsa, NULL) != 1) {
                error("%s: RSA_blinding_on failed", __func__);
                goto fail;
        }
        return prv;

fail:
        if (commentp != NULL)
                free(*commentp);
        key_free(prv);
        return NULL;
}

static Key *
key_parse_private_pem(Buffer *blob, int type, const char *passphrase,
    char **commentp)
{
        EVP_PKEY *pk = NULL;
        Key *prv = NULL;
        char *name = "<no key>";
        BIO *bio;

        if ((bio = BIO_new_mem_buf(buffer_ptr(blob),
            buffer_len(blob))) == NULL) {
                error("%s: BIO_new_mem_buf failed", __func__);
                return NULL;
        }
        
        pk = PEM_read_bio_PrivateKey(bio, NULL, NULL, (char *)passphrase);
        BIO_free(bio);
        if (pk == NULL) {
                debug("%s: PEM_read_PrivateKey failed", __func__);
                (void)ERR_get_error();
        } else if (pk->type == EVP_PKEY_RSA &&
            (type == KEY_UNSPEC||type==KEY_RSA)) {
                prv = key_new(KEY_UNSPEC);
                prv->rsa = EVP_PKEY_get1_RSA(pk);
                prv->type = KEY_RSA;
                name = "rsa w/o comment";
#ifdef DEBUG_PK
                RSA_print_fp(stderr, prv->rsa, 8);
#endif
                if (RSA_blinding_on(prv->rsa, NULL) != 1) {
                        error("%s: RSA_blinding_on failed", __func__);
                        key_free(prv);
                        prv = NULL;
                }
        } else if (pk->type == EVP_PKEY_DSA &&
            (type == KEY_UNSPEC||type==KEY_DSA)) {
                prv = key_new(KEY_UNSPEC);
                prv->dsa = EVP_PKEY_get1_DSA(pk);
                prv->type = KEY_DSA;
                name = "dsa w/o comment";
#ifdef DEBUG_PK
                DSA_print_fp(stderr, prv->dsa, 8);
#endif
#ifdef OPENSSL_HAS_ECC
        } else if (pk->type == EVP_PKEY_EC &&
            (type == KEY_UNSPEC||type==KEY_ECDSA)) {
                prv = key_new(KEY_UNSPEC);
                prv->ecdsa = EVP_PKEY_get1_EC_KEY(pk);
                prv->type = KEY_ECDSA;
                if ((prv->ecdsa_nid = key_ecdsa_key_to_nid(prv->ecdsa)) == -1 ||
                    key_curve_nid_to_name(prv->ecdsa_nid) == NULL ||
                    key_ec_validate_public(EC_KEY_get0_group(prv->ecdsa),
                    EC_KEY_get0_public_key(prv->ecdsa)) != 0 ||
                    key_ec_validate_private(prv->ecdsa) != 0) {
                        error("%s: bad ECDSA key", __func__);
                        key_free(prv);
                        prv = NULL;
                }
                name = "ecdsa w/o comment";
#ifdef DEBUG_PK
                if (prv != NULL && prv->ecdsa != NULL)
                        key_dump_ec_key(prv->ecdsa);
#endif
#endif /* OPENSSL_HAS_ECC */
        } else {
                error("%s: PEM_read_PrivateKey: mismatch or "
                    "unknown EVP_PKEY save_type %d", __func__, pk->save_type);
        }
        if (pk != NULL)
                EVP_PKEY_free(pk);
        if (prv != NULL && commentp)
                *commentp = xstrdup(name);
        debug("read PEM private key done: type %s",
            prv ? key_type(prv) : "<unknown>");
        return prv;
}

Key *
key_load_private_pem(int fd, int type, const char *passphrase,
    char **commentp)
{
        Buffer buffer;
        Key *prv;

        buffer_init(&buffer);
        if (!key_load_file(fd, NULL, &buffer)) {
                buffer_free(&buffer);
                return NULL;
        }
        prv = key_parse_private_pem(&buffer, type, passphrase, commentp);
        buffer_free(&buffer);
        return prv;
}

int
key_perm_ok(int fd, const char *filename)
{
        struct stat st;

        if (fstat(fd, &st) < 0)
                return 0;
        /*
         * 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.
         */
#ifdef HAVE_CYGWIN
        if (check_ntsec(filename))
#endif
        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 0;
        }
        return 1;
}

static Key *
key_parse_private_type(Buffer *blob, int type, const char *passphrase,
    char **commentp)
{
        Key *k;

        switch (type) {
        case KEY_RSA1:
                return key_parse_private_rsa1(blob, passphrase, commentp);
        case KEY_DSA:
        case KEY_ECDSA:
        case KEY_RSA:
                return key_parse_private_pem(blob, type, passphrase, commentp);
        case KEY_ED25519:
                return key_parse_private2(blob, type, passphrase, commentp);
        case KEY_UNSPEC:
                if ((k = key_parse_private2(blob, type, passphrase, commentp)))
                        return k;
                return key_parse_private_pem(blob, type, passphrase, commentp);
        default:
                error("%s: cannot parse key type %d", __func__, type);
                break;
        }
        return NULL;
}

Key *
key_load_private_type(int type, const char *filename, const char *passphrase,
    char **commentp, int *perm_ok)
{
        int fd;
        Key *ret;
        Buffer buffer;

        fd = open(filename, O_RDONLY);
        if (fd < 0) {
                debug("could not open key file '%s': %s", filename,
                    strerror(errno));
                if (perm_ok != NULL)
                        *perm_ok = 0;
                return NULL;
        }
        if (!key_perm_ok(fd, filename)) {
                if (perm_ok != NULL)
                        *perm_ok = 0;
                error("bad permissions: ignore key: %s", filename);
                close(fd);
                return NULL;
        }
        if (perm_ok != NULL)
                *perm_ok = 1;

        buffer_init(&buffer);
        if (!key_load_file(fd, filename, &buffer)) {
                buffer_free(&buffer);
                close(fd);
                return NULL;
        }
        close(fd);
        ret = key_parse_private_type(&buffer, type, passphrase, commentp);
        buffer_free(&buffer);
        return ret;
}

Key *
key_parse_private(Buffer *buffer, const char *filename,
    const char *passphrase, char **commentp)
{
        Key *pub, *prv;

        /* it's a SSH v1 key if the public key part is readable */
        pub = key_parse_public_rsa1(buffer, commentp);
        if (pub == NULL) {
                prv = key_parse_private_type(buffer, KEY_UNSPEC,
                    passphrase, NULL);
                /* use the filename as a comment for PEM */
                if (commentp && prv)
                        *commentp = xstrdup(filename);
        } else {
                key_free(pub);
                /* key_parse_public_rsa1() has already loaded the comment */
                prv = key_parse_private_type(buffer, KEY_RSA1, passphrase,
                    NULL);
        }
        return prv;
}

Key *
key_load_private(const char *filename, const char *passphrase,
    char **commentp)
{
        Key *prv;
        Buffer buffer;
        int fd;

        fd = open(filename, O_RDONLY);
        if (fd < 0) {
                debug("could not open key file '%s': %s", filename,
                    strerror(errno));
                return NULL;
        }
        if (!key_perm_ok(fd, filename)) {
                error("bad permissions: ignore key: %s", filename);
                close(fd);
                return NULL;
        }

        buffer_init(&buffer);
        if (!key_load_file(fd, filename, &buffer)) {
                buffer_free(&buffer);
                close(fd);
                return NULL;
        }
        close(fd);

        prv = key_parse_private(&buffer, filename, passphrase, commentp);
        buffer_free(&buffer);
        return prv;
}

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

        f = fopen(filename, "r");
        if (f != NULL) {
                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)
                                break;
                        /* Skip leading whitespace. */
                        for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
                                ;
                        if (*cp) {
                                if (key_read(k, &cp) == 1) {
                                        cp[strcspn(cp, "\r\n")] = '\0';
                                        if (commentp) {
                                                *commentp = xstrdup(*cp ?
                                                    cp : filename);
                                        }
                                        fclose(f);
                                        return 1;
                                }
                        }
                }
                fclose(f);
        }
        return 0;
}

/* load public key from ssh v1 private or any pubkey file */
Key *
key_load_public(const char *filename, char **commentp)
{
        Key *pub;
        char file[MAXPATHLEN];

        /* try rsa1 private key */
        pub = key_load_public_type(KEY_RSA1, filename, commentp);
        if (pub != NULL)
                return pub;

        /* try rsa1 public key */
        pub = key_new(KEY_RSA1);
        if (key_try_load_public(pub, filename, commentp) == 1)
                return pub;
        key_free(pub);

        /* try ssh2 public key */
        pub = key_new(KEY_UNSPEC);
        if (key_try_load_public(pub, filename, commentp) == 1)
                return pub;
        if ((strlcpy(file, filename, sizeof file) < sizeof(file)) &&
            (strlcat(file, ".pub", sizeof file) < sizeof(file)) &&
            (key_try_load_public(pub, file, commentp) == 1))
                return pub;
        key_free(pub);
        return NULL;
}

/* Load the certificate associated with the named private key */
Key *
key_load_cert(const char *filename)
{
        Key *pub;
        char *file;

        pub = key_new(KEY_UNSPEC);
        xasprintf(&file, "%s-cert.pub", filename);
        if (key_try_load_public(pub, file, NULL) == 1) {
                free(file);
                return pub;
        }
        free(file);
        key_free(pub);
        return NULL;
}

/* Load private key and certificate */
Key *
key_load_private_cert(int type, const char *filename, const char *passphrase,
    int *perm_ok)
{
        Key *key, *pub;

        switch (type) {
        case KEY_RSA:
        case KEY_DSA:
        case KEY_ECDSA:
        case KEY_ED25519:
                break;
        default:
                error("%s: unsupported key type", __func__);
                return NULL;
        }

        if ((key = key_load_private_type(type, filename, 
            passphrase, NULL, perm_ok)) == NULL)
                return NULL;

        if ((pub = key_load_cert(filename)) == NULL) {
                key_free(key);
                return NULL;
        }

        /* Make sure the private key matches the certificate */
        if (key_equal_public(key, pub) == 0) {
                error("%s: certificate does not match private key %s",
                    __func__, filename);
        } else if (key_to_certified(key, key_cert_is_legacy(pub)) != 0) {
                error("%s: key_to_certified failed", __func__);
        } else {
                key_cert_copy(pub, key);
                key_free(pub);
                return key;
        }

        key_free(key);
        key_free(pub);
        return NULL;
}

/*
 * Returns 1 if the specified "key" is listed in the file "filename",
 * 0 if the key is not listed or -1 on error.
 * If strict_type is set then the key type must match exactly,
 * otherwise a comparison that ignores certficiate data is performed.
 */
int
key_in_file(Key *key, const char *filename, int strict_type)
{
        FILE *f;
        char line[SSH_MAX_PUBKEY_BYTES];
        char *cp;
        u_long linenum = 0;
        int ret = 0;
        Key *pub;
        int (*key_compare)(const Key *, const Key *) = strict_type ?
            key_equal : key_equal_public;

        if ((f = fopen(filename, "r")) == NULL) {
                if (errno == ENOENT) {
                        debug("%s: keyfile \"%s\" missing", __func__, filename);
                        return 0;
                } else {
                        error("%s: could not open keyfile \"%s\": %s", __func__,
                            filename, strerror(errno));
                        return -1;
                }
        }

        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;
                }

                pub = key_new(KEY_UNSPEC);
                if (key_read(pub, &cp) != 1) {
                        key_free(pub);
                        continue;
                }
                if (key_compare(key, pub)) {
                        ret = 1;
                        key_free(pub);
                        break;
                }
                key_free(pub);
        }
        fclose(f);
        return ret;
}
Revision:	6864
Committed:	Sat Oct 11 16:33:42 2014 UTC (9 years, 6 months ago) by laffer1
Content type:	text/plain
File size:	34352 byte(s)
Log Message:	tag openssh 6.6p1