authfile.c

OpenSSL Source code for SFTP, SSH, and many others

{
	int i, check1, check2, cipher_type;
	off_t len;
	Buffer buffer, decrypted;
	u_char *cp;
	CipherContext ciphercontext;
	Cipher *cipher;
	Key *prv = NULL;

	len = lseek(fd, (off_t) 0, SEEK_END);
	lseek(fd, (off_t) 0, SEEK_SET);

	buffer_init(&buffer);
	cp = buffer_append_space(&buffer, len);

	if (read(fd, cp, (size_t) len) != (size_t) len) {
		debug("Read from key file %.200s failed: %.100s", filename,
		    strerror(errno));
		buffer_free(&buffer);
		close(fd);
		return NULL;
	}

	/* Check that it is at least big enough to contain the ID string. */
	if (len < sizeof(authfile_id_string)) {
		debug3("Not a RSA1 key file %.200s.", filename);
		buffer_free(&buffer);
		close(fd);
		return NULL;
	}
	/*
	 * Make sure it begins with the id string.  Consume the id string
	 * from the buffer.
	 */
	for (i = 0; i < sizeof(authfile_id_string); i++)
		if (buffer_get_char(&buffer) != authfile_id_string[i]) {
			debug3("Not a RSA1 key file %.200s.", filename);
			buffer_free(&buffer);
			close(fd);
			return NULL;
		}

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

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

	buffer_get_bignum(&buffer, prv->rsa->n);
	buffer_get_bignum(&buffer, prv->rsa->e);
	if (commentp)
		*commentp = buffer_get_string(&buffer, NULL);
	else
		xfree(buffer_get_string(&buffer, NULL));

	/* Check that it is a supported cipher. */
	cipher = cipher_by_number(cipher_type);
	if (cipher == NULL) {
		debug("Unsupported cipher %d used in key file %.200s.",
		    cipher_type, filename);
		buffer_free(&buffer);
		goto fail;
	}
	/* Initialize space for decrypted data. */
	buffer_init(&decrypted);
	cp = buffer_append_space(&decrypted, buffer_len(&buffer));

	/* Rest of the buffer is encrypted.  Decrypt it using the passphrase. */
	cipher_set_key_string(&ciphercontext, cipher, passphrase,
	    CIPHER_DECRYPT);
	cipher_crypt(&ciphercontext, cp,
	    buffer_ptr(&buffer), buffer_len(&buffer));
	cipher_cleanup(&ciphercontext);
	memset(&ciphercontext, 0, sizeof(ciphercontext));
	buffer_free(&buffer);

	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 key file %.200s.",
			    filename);
		/* 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);
	close(fd);
	return prv;

fail:
	if (commentp)
		xfree(*commentp);
	close(fd);
	key_free(prv);
	return NULL;
}

Key *
key_load_private_pem(int fd, int type, const char *passphrase,
    char **commentp)
{
	FILE *fp;
	EVP_PKEY *pk = NULL;
	Key *prv = NULL;
	char *name = "<no key>";

	fp = fdopen(fd, "r");
	if (fp == NULL) {
		error("fdopen failed: %s", strerror(errno));
		close(fd);
		return NULL;
	}
	pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase);
	if (pk == NULL) {
		debug("PEM_read_PrivateKey failed");
		(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
	} 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
	} else {
		error("PEM_read_PrivateKey: mismatch or "
		    "unknown EVP_PKEY save_type %d", pk->save_type);
	}
	fclose(fp);
	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;
}

static 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.",
		    st.st_mode & 0777, filename);
		error("It is recommended that your private key files are NOT accessible by others.");
		error("This private key will be ignored.");
		return 0;
	}
	return 1;
}

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

	fd = open(filename, O_RDONLY);
	if (fd < 0)
		return NULL;
	if (!key_perm_ok(fd, filename)) {
		error("bad permissions: ignore key: %s", filename);
		close(fd);
		return NULL;
	}
	switch (type) {
	case KEY_RSA1:
		return key_load_private_rsa1(fd, filename, passphrase,
		    commentp);
		/* closes fd */
		break;
	case KEY_DSA:
	case KEY_RSA:
	case KEY_UNSPEC:
		return key_load_private_pem(fd, type, passphrase, commentp);
		/* closes fd */
		break;
	default:
		close(fd);
		break;
	}
	return NULL;
}

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

	fd = open(filename, O_RDONLY);
	if (fd < 0)
		return NULL;
	if (!key_perm_ok(fd, filename)) {
		error("bad permissions: ignore key: %s", filename);
		close(fd);
		return NULL;
	}
	pub = key_load_public_rsa1(fd, filename, commentp);
	lseek(fd, (off_t) 0, SEEK_SET);		/* rewind */
	if (pub == NULL) {
		/* closes fd */
		prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL);
		/* use the filename as a comment for PEM */
		if (commentp && prv)
			*commentp = xstrdup(filename);
	} else {
		/* it's a SSH v1 key if the public key part is readable */
		key_free(pub);
		/* closes fd */
		prv = key_load_private_rsa1(fd, filename, passphrase, NULL);
	}
	return prv;
}

static int
key_try_load_public(Key *k, const char *filename, char **commentp)
{
	FILE *f;
	char line[4096];
	char *cp;

	f = fopen(filename, "r");
	if (f != NULL) {
		while (fgets(line, sizeof(line), f)) {
			line[sizeof(line)-1] = '\0';
			cp = line;
			switch (*cp) {
			case '#':
			case '\n':
			case '\0':
				continue;
			}
			/* Skip leading whitespace. */
			for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
				;
			if (*cp) {
				if (key_read(k, &cp) == 1) {
					if (commentp)
						*commentp=xstrdup(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];

	pub = key_load_public_type(KEY_RSA1, filename, commentp);
	if (pub != NULL)
		return pub;
	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;
}