rxkad.c

linux 内核源代码

/* Kerberos-based RxRPC security
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/udp.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/ctype.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#define rxrpc_debug rxkad_debug
#include "ar-internal.h"

#define RXKAD_VERSION			2
#define MAXKRB5TICKETLEN		1024
#define RXKAD_TKT_TYPE_KERBEROS_V5	256
#define ANAME_SZ			40	/* size of authentication name */
#define INST_SZ				40	/* size of principal's instance */
#define REALM_SZ			40	/* size of principal's auth domain */
#define SNAME_SZ			40	/* size of service name */

unsigned rxrpc_debug;
module_param_named(debug, rxrpc_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(rxrpc_debug, "rxkad debugging mask");

struct rxkad_level1_hdr {
	__be32	data_size;	/* true data size (excluding padding) */
};

struct rxkad_level2_hdr {
	__be32	data_size;	/* true data size (excluding padding) */
	__be32	checksum;	/* decrypted data checksum */
};

MODULE_DESCRIPTION("RxRPC network protocol type-2 security (Kerberos)");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");

/*
 * this holds a pinned cipher so that keventd doesn't get called by the cipher
 * alloc routine, but since we have it to hand, we use it to decrypt RESPONSE
 * packets
 */
static struct crypto_blkcipher *rxkad_ci;
static DEFINE_MUTEX(rxkad_ci_mutex);

/*
 * initialise connection security
 */
static int rxkad_init_connection_security(struct rxrpc_connection *conn)
{
	struct rxrpc_key_payload *payload;
	struct crypto_blkcipher *ci;
	int ret;

	_enter("{%d},{%x}", conn->debug_id, key_serial(conn->key));

	payload = conn->key->payload.data;
	conn->security_ix = payload->k.security_index;

	ci = crypto_alloc_blkcipher("pcbc(fcrypt)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(ci)) {
		_debug("no cipher");
		ret = PTR_ERR(ci);
		goto error;
	}

	if (crypto_blkcipher_setkey(ci, payload->k.session_key,
				    sizeof(payload->k.session_key)) < 0)
		BUG();

	switch (conn->security_level) {
	case RXRPC_SECURITY_PLAIN:
		break;
	case RXRPC_SECURITY_AUTH:
		conn->size_align = 8;
		conn->security_size = sizeof(struct rxkad_level1_hdr);
		conn->header_size += sizeof(struct rxkad_level1_hdr);
		break;
	case RXRPC_SECURITY_ENCRYPT:
		conn->size_align = 8;
		conn->security_size = sizeof(struct rxkad_level2_hdr);
		conn->header_size += sizeof(struct rxkad_level2_hdr);
		break;
	default:
		ret = -EKEYREJECTED;
		goto error;
	}

	conn->cipher = ci;
	ret = 0;
error:
	_leave(" = %d", ret);
	return ret;
}

/*
 * prime the encryption state with the invariant parts of a connection's
 * description
 */
static void rxkad_prime_packet_security(struct rxrpc_connection *conn)
{
	struct rxrpc_key_payload *payload;
	struct blkcipher_desc desc;
	struct scatterlist sg[2];
	struct rxrpc_crypt iv;
	struct {
		__be32 x[4];
	} tmpbuf __attribute__((aligned(16))); /* must all be in same page */

	_enter("");

	if (!conn->key)
		return;

	payload = conn->key->payload.data;
	memcpy(&iv, payload->k.session_key, sizeof(iv));

	desc.tfm = conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	tmpbuf.x[0] = conn->epoch;
	tmpbuf.x[1] = conn->cid;
	tmpbuf.x[2] = 0;
	tmpbuf.x[3] = htonl(conn->security_ix);

	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));

	memcpy(&conn->csum_iv, &tmpbuf.x[2], sizeof(conn->csum_iv));
	ASSERTCMP(conn->csum_iv.n[0], ==, tmpbuf.x[2]);

	_leave("");
}

/*
 * partially encrypt a packet (level 1 security)
 */
static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
				    struct sk_buff *skb,
				    u32 data_size,
				    void *sechdr)
{
	struct rxrpc_skb_priv *sp;
	struct blkcipher_desc desc;
	struct rxrpc_crypt iv;
	struct scatterlist sg[2];
	struct {
		struct rxkad_level1_hdr hdr;
		__be32	first;	/* first four bytes of data and padding */
	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
	u16 check;

	sp = rxrpc_skb(skb);

	_enter("");

	check = ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
	data_size |= (u32) check << 16;

	tmpbuf.hdr.data_size = htonl(data_size);
	memcpy(&tmpbuf.first, sechdr + 4, sizeof(tmpbuf.first));

	/* start the encryption afresh */
	memset(&iv, 0, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));

	memcpy(sechdr, &tmpbuf, sizeof(tmpbuf));

	_leave(" = 0");
	return 0;
}

/*
 * wholly encrypt a packet (level 2 security)
 */
static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
					struct sk_buff *skb,
					u32 data_size,
					void *sechdr)
{
	const struct rxrpc_key_payload *payload;
	struct rxkad_level2_hdr rxkhdr
		__attribute__((aligned(8))); /* must be all on one page */
	struct rxrpc_skb_priv *sp;
	struct blkcipher_desc desc;
	struct rxrpc_crypt iv;
	struct scatterlist sg[16];
	struct sk_buff *trailer;
	unsigned len;
	u16 check;
	int nsg;

	sp = rxrpc_skb(skb);

	_enter("");

	check = ntohl(sp->hdr.seq ^ sp->hdr.callNumber);

	rxkhdr.data_size = htonl(data_size | (u32) check << 16);
	rxkhdr.checksum = 0;

	/* encrypt from the session key */
	payload = call->conn->key->payload.data;
	memcpy(&iv, payload->k.session_key, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	sg_init_one(&sg[0], sechdr, sizeof(rxkhdr));
	sg_init_one(&sg[1], &rxkhdr, sizeof(rxkhdr));
	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(rxkhdr));

	/* we want to encrypt the skbuff in-place */
	nsg = skb_cow_data(skb, 0, &trailer);
	if (nsg < 0 || nsg > 16)
		return -ENOMEM;

	len = data_size + call->conn->size_align - 1;
	len &= ~(call->conn->size_align - 1);

	sg_init_table(sg, nsg);
	skb_to_sgvec(skb, sg, 0, len);
	crypto_blkcipher_encrypt_iv(&desc, sg, sg, len);

	_leave(" = 0");
	return 0;
}

/*
 * checksum an RxRPC packet header
 */
static int rxkad_secure_packet(const struct rxrpc_call *call,
				struct sk_buff *skb,
				size_t data_size,
				void *sechdr)
{
	struct rxrpc_skb_priv *sp;
	struct blkcipher_desc desc;
	struct rxrpc_crypt iv;
	struct scatterlist sg[2];
	struct {
		__be32 x[2];
	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
	__be32 x;
	int ret;

	sp = rxrpc_skb(skb);

	_enter("{%d{%x}},{#%u},%zu,",
	       call->debug_id, key_serial(call->conn->key), ntohl(sp->hdr.seq),
	       data_size);

	if (!call->conn->cipher)
		return 0;

	ret = key_validate(call->conn->key);
	if (ret < 0)
		return ret;

	/* continue encrypting from where we left off */
	memcpy(&iv, call->conn->csum_iv.x, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	/* calculate the security checksum */
	x = htonl(call->channel << (32 - RXRPC_CIDSHIFT));
	x |= sp->hdr.seq & __constant_cpu_to_be32(0x3fffffff);
	tmpbuf.x[0] = sp->hdr.callNumber;
	tmpbuf.x[1] = x;

	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));

	x = ntohl(tmpbuf.x[1]);
	x = (x >> 16) & 0xffff;
	if (x == 0)
		x = 1; /* zero checksums are not permitted */
	sp->hdr.cksum = htons(x);

	switch (call->conn->security_level) {
	case RXRPC_SECURITY_PLAIN:
		ret = 0;
		break;
	case RXRPC_SECURITY_AUTH:
		ret = rxkad_secure_packet_auth(call, skb, data_size, sechdr);
		break;
	case RXRPC_SECURITY_ENCRYPT:
		ret = rxkad_secure_packet_encrypt(call, skb, data_size,
						  sechdr);
		break;
	default:
		ret = -EPERM;
		break;
	}

	_leave(" = %d [set %hx]", ret, x);
	return ret;
}

/*
 * decrypt partial encryption on a packet (level 1 security)
 */
static int rxkad_verify_packet_auth(const struct rxrpc_call *call,
				    struct sk_buff *skb,
				    u32 *_abort_code)
{
	struct rxkad_level1_hdr sechdr;
	struct rxrpc_skb_priv *sp;
	struct blkcipher_desc desc;
	struct rxrpc_crypt iv;
	struct scatterlist sg[16];
	struct sk_buff *trailer;
	u32 data_size, buf;
	u16 check;
	int nsg;

	_enter("");

	sp = rxrpc_skb(skb);

	/* we want to decrypt the skbuff in-place */
	nsg = skb_cow_data(skb, 0, &trailer);
	if (nsg < 0 || nsg > 16)
		goto nomem;

	sg_init_table(sg, nsg);
	skb_to_sgvec(skb, sg, 0, 8);

	/* start the decryption afresh */
	memset(&iv, 0, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	crypto_blkcipher_decrypt_iv(&desc, sg, sg, 8);

	/* remove the decrypted packet length */
	if (skb_copy_bits(skb, 0, &sechdr, sizeof(sechdr)) < 0)
		goto datalen_error;
	if (!skb_pull(skb, sizeof(sechdr)))
		BUG();

	buf = ntohl(sechdr.data_size);
	data_size = buf & 0xffff;

	check = buf >> 16;
	check ^= ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
	check &= 0xffff;
	if (check != 0) {
		*_abort_code = RXKADSEALEDINCON;
		goto protocol_error;
	}

	/* shorten the packet to remove the padding */
	if (data_size > skb->len)
		goto datalen_error;
	else if (data_size < skb->len)
		skb->len = data_size;

	_leave(" = 0 [dlen=%x]", data_size);
	return 0;

datalen_error:
	*_abort_code = RXKADDATALEN;
protocol_error:
	_leave(" = -EPROTO");
	return -EPROTO;

nomem:
	_leave(" = -ENOMEM");
	return -ENOMEM;
}

/*
 * wholly decrypt a packet (level 2 security)
 */
static int rxkad_verify_packet_encrypt(const struct rxrpc_call *call,
				       struct sk_buff *skb,
				       u32 *_abort_code)
{
	const struct rxrpc_key_payload *payload;
	struct rxkad_level2_hdr sechdr;
	struct rxrpc_skb_priv *sp;
	struct blkcipher_desc desc;
	struct rxrpc_crypt iv;
	struct scatterlist _sg[4], *sg;
	struct sk_buff *trailer;
	u32 data_size, buf;
	u16 check;
	int nsg;

	_enter(",{%d}", skb->len);

	sp = rxrpc_skb(skb);

	/* we want to decrypt the skbuff in-place */
	nsg = skb_cow_data(skb, 0, &trailer);
	if (nsg < 0)
		goto nomem;

	sg = _sg;
	if (unlikely(nsg > 4)) {
		sg = kmalloc(sizeof(*sg) * nsg, GFP_NOIO);
		if (!sg)
			goto nomem;
	}

	sg_init_table(sg, nsg);
	skb_to_sgvec(skb, sg, 0, skb->len);

	/* decrypt from the session key */
	payload = call->conn->key->payload.data;
	memcpy(&iv, payload->k.session_key, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	crypto_blkcipher_decrypt_iv(&desc, sg, sg, skb->len);
	if (sg != _sg)
		kfree(sg);

	/* remove the decrypted packet length */
	if (skb_copy_bits(skb, 0, &sechdr, sizeof(sechdr)) < 0)
		goto datalen_error;
	if (!skb_pull(skb, sizeof(sechdr)))
		BUG();

	buf = ntohl(sechdr.data_size);
	data_size = buf & 0xffff;

	check = buf >> 16;
	check ^= ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
	check &= 0xffff;
	if (check != 0) {
		*_abort_code = RXKADSEALEDINCON;
		goto protocol_error;
	}

	/* shorten the packet to remove the padding */
	if (data_size > skb->len)
		goto datalen_error;
	else if (data_size < skb->len)
		skb->len = data_size;

	_leave(" = 0 [dlen=%x]", data_size);
	return 0;

datalen_error:
	*_abort_code = RXKADDATALEN;
protocol_error:
	_leave(" = -EPROTO");
	return -EPROTO;

nomem:
	_leave(" = -ENOMEM");
	return -ENOMEM;
}

/*
 * verify the security on a received packet
 */
static int rxkad_verify_packet(const struct rxrpc_call *call,
			       struct sk_buff *skb,
			       u32 *_abort_code)
{
	struct blkcipher_desc desc;
	struct rxrpc_skb_priv *sp;
	struct rxrpc_crypt iv;
	struct scatterlist sg[2];
	struct {
		__be32 x[2];
	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
	__be32 x;
	__be16 cksum;
	int ret;

	sp = rxrpc_skb(skb);

	_enter("{%d{%x}},{#%u}",
	       call->debug_id, key_serial(call->conn->key),
	       ntohl(sp->hdr.seq));

	if (!call->conn->cipher)
		return 0;

	if (sp->hdr.securityIndex != 2) {
		*_abort_code = RXKADINCONSISTENCY;
		_leave(" = -EPROTO [not rxkad]");
		return -EPROTO;
	}

	/* continue encrypting from where we left off */
	memcpy(&iv, call->conn->csum_iv.x, sizeof(iv));
	desc.tfm = call->conn->cipher;
	desc.info = iv.x;
	desc.flags = 0;

	/* validate the security checksum */
	x = htonl(call->channel << (32 - RXRPC_CIDSHIFT));
	x |= sp->hdr.seq & __constant_cpu_to_be32(0x3fffffff);
	tmpbuf.x[0] = call->call_id;
	tmpbuf.x[1] = x;

	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));

	x = ntohl(tmpbuf.x[1]);
	x = (x >> 16) & 0xffff;
	if (x == 0)
		x = 1; /* zero checksums are not permitted */

	cksum = htons(x);
	if (sp->hdr.cksum != cksum) {
		*_abort_code = RXKADSEALEDINCON;
		_leave(" = -EPROTO [csum failed]");
		return -EPROTO;
	}

	switch (call->conn->security_level) {
	case RXRPC_SECURITY_PLAIN:
		ret = 0;
		break;
	case RXRPC_SECURITY_AUTH:
		ret = rxkad_verify_packet_auth(call, skb, _abort_code);
		break;
	case RXRPC_SECURITY_ENCRYPT:
		ret = rxkad_verify_packet_encrypt(call, skb, _abort_code);
		break;
	default:
		ret = -ENOANO;
		break;
	}

	_leave(" = %d", ret);
	return ret;
}

/*
 * issue a challenge
 */
static int rxkad_issue_challenge(struct rxrpc_connection *conn)
{
	struct rxkad_challenge challenge;
	struct rxrpc_header hdr;
	struct msghdr msg;
	struct kvec iov[2];
	size_t len;
	int ret;

	_enter("{%d,%x}", conn->debug_id, key_serial(conn->key));

	ret = key_validate(conn->key);
	if (ret < 0)
		return ret;

	get_random_bytes(&conn->security_nonce, sizeof(conn->security_nonce));