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net/rxrpc: Reimplement DES-PCBC using DES library

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Since the use of "pcbc(des)" in rxkad_decrypt_ticket() is the only
remaining user of the crypto API "pcbc" template, just implement
DES-PCBC by locally implementing PCBC mode on top of the DES library.
Note that only the decryption direction is needed.

This will allow support for the obsolete PCBC mode to be removed from
the crypto API.

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
Link: https://patch.msgid.link/20260522050740.84561-4-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Biggers
2026-05-22 00:07:34 -05:00
committed by Jakub Kicinski
parent 97b768514a
commit 432042e25e
6 changed files with 79 additions and 40 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
net/rxrpc/Kconfig
View File

@@ -7,6 +7,7 @@ config AF_RXRPC
tristate "RxRPC session sockets"
depends on INET
select CRYPTO
select CRYPTO_LIB_DES if RXKAD
select KEYS
select NET_UDP_TUNNEL
help
@@ -56,10 +57,6 @@ config AF_RXRPC_DEBUG
config RXKAD
bool "RxRPC Kerberos security"
select CRYPTO
select CRYPTO_MANAGER
select CRYPTO_SKCIPHER
select CRYPTO_PCBC
help
Provide kerberos 4 and AFS kaserver security handling for AF_RXRPC
through the use of the key retention service.

5
net/rxrpc/ar-internal.h
View File

@@ -36,6 +36,11 @@ void fcrypt_pcbc_encrypt(const struct fcrypt_key *key,
void fcrypt_pcbc_decrypt(const struct fcrypt_key *key,
const u8 iv[FCRYPT_BSIZE], const void *src, void *dst,
size_t nblocks);
#if IS_ENABLED(CONFIG_KUNIT)
struct des_ctx;
void des_pcbc_decrypt_inplace(const struct des_ctx *key, __le64 iv, u8 *data,
size_t len);
#endif
#define rxrpc_queue_work(WS) queue_work(rxrpc_workqueue, (WS))
#define rxrpc_queue_delayed_work(WS,D) \

1
net/rxrpc/key.c
View File

@@ -10,7 +10,6 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <crypto/skcipher.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/overflow.h>

76
net/rxrpc/rxkad.c
View File

@@ -7,16 +7,18 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <crypto/skcipher.h>
#include <crypto/des.h>
#include <kunit/visibility.h>
#include <linux/export.h>
#include <linux/fips.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/udp.h>
#include <linux/scatterlist.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/key-type.h>
#include <linux/unaligned.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <keys/rxrpc-type.h>
@@ -52,40 +54,41 @@ static void rxkad_prime_packet_security(struct rxrpc_connection *conn,
*/
static int rxkad_preparse_server_key(struct key_preparsed_payload *prep)
{
struct crypto_skcipher *ci;
struct des_ctx *des_key;
int err;
if (prep->datalen != 8)
return -EINVAL;
memcpy(&prep->payload.data[2], prep->data, 8);
ci = crypto_alloc_skcipher("pcbc(des)", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(ci)) {
_leave(" = %ld", PTR_ERR(ci));
return PTR_ERR(ci);
des_key = kmalloc_obj(*des_key);
if (!des_key) {
_leave(" = -ENOMEM");
return -ENOMEM;
}
if (crypto_skcipher_setkey(ci, prep->data, 8) < 0)
BUG();
err = des_expand_key(des_key, prep->data, 8);
if (err) {
kfree_sensitive(des_key);
_leave(" = %d", err);
return err;
}
prep->payload.data[0] = ci;
prep->payload.data[0] = des_key;
_leave(" = 0");
return 0;
}
static void rxkad_free_preparse_server_key(struct key_preparsed_payload *prep)
{
if (prep->payload.data[0])
crypto_free_skcipher(prep->payload.data[0]);
kfree_sensitive(prep->payload.data[0]);
}
static void rxkad_destroy_server_key(struct key *key)
{
if (key->payload.data[0]) {
crypto_free_skcipher(key->payload.data[0]);
key->payload.data[0] = NULL;
}
kfree_sensitive(key->payload.data[0]);
key->payload.data[0] = NULL;
}
/*
@@ -771,6 +774,22 @@ int rxkad_kernel_respond_to_challenge(struct sk_buff *challenge)
}
EXPORT_SYMBOL(rxkad_kernel_respond_to_challenge);
/* Decrypt data in-place using DES-PCBC. @len must be a multiple of 8. */
VISIBLE_IF_KUNIT void des_pcbc_decrypt_inplace(const struct des_ctx *key,
__le64 iv, u8 *data, size_t len)
{
for (size_t i = 0; i < len; i += DES_BLOCK_SIZE) {
__le64 ctext, ptext;
ctext = get_unaligned((const __le64 *)&data[i]);
des_decrypt(key, (u8 *)&ptext, (const u8 *)&ctext);
ptext ^= iv;
put_unaligned(ptext, (__le64 *)&data[i]);
iv = ptext ^ ctext;
}
}
EXPORT_SYMBOL_IF_KUNIT(des_pcbc_decrypt_inplace);
/*
* decrypt the kerberos IV ticket in the response
*/
@@ -781,13 +800,10 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
struct rxrpc_crypt *_session_key,
time64_t *_expiry)
{
struct skcipher_request *req;
struct rxrpc_crypt iv, key;
struct scatterlist sg[1];
struct rxrpc_crypt key;
struct in_addr addr;
unsigned int life;
time64_t issue, now;
int ret;
bool little_endian;
u8 *p, *q, *name, *end;
@@ -797,21 +813,13 @@ static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
ASSERT(server_key->payload.data[0] != NULL);
memcpy(&iv, &server_key->payload.data[2], sizeof(iv));
req = skcipher_request_alloc(server_key->payload.data[0], GFP_NOFS);
if (!req)
return -ENOMEM;
sg_init_one(&sg[0], ticket, ticket_len);
skcipher_request_set_callback(req, 0, NULL, NULL);
skcipher_request_set_crypt(req, sg, sg, ticket_len, iv.x);
ret = crypto_skcipher_decrypt(req);
skcipher_request_free(req);
if (ret < 0)
if (ticket_len % DES_BLOCK_SIZE != 0)
return rxrpc_abort_conn(conn, skb, RXKADBADTICKET, -EPROTO,
rxkad_abort_resp_tkt_short);
des_pcbc_decrypt_inplace(
server_key->payload.data[0],
get_unaligned((const __le64 *)&server_key->payload.data[2]),
ticket, ticket_len);
p = ticket;
end = p + ticket_len;

1
net/rxrpc/server_key.c
View File

@@ -10,7 +10,6 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <crypto/skcipher.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>

31
net/rxrpc/tests/rxrpc_kunit.c
View File

@@ -5,6 +5,7 @@
* Copyright 2026 Google LLC
*/
#include "../ar-internal.h"
#include <crypto/des.h>
#include <kunit/test.h>
struct fcrypt_pcbc_testvec {
@@ -93,8 +94,38 @@ static void test_fcrypt_pcbc(struct kunit *test)
}
}
static void test_des_pcbc(struct kunit *test)
{
/* This was generated from the original pcbc(des) crypto API code. */
static const u8 expected_ptext[24] =
"\xc8\xe2\x3c\xdf\x80\x61\x8a\xad\xa5\x52\xb4\x20"
"\x74\x32\x1f\xe4\x2c\x15\x7d\x21\x57\xda\x3f\x31";
u8 key[8];
union {
__le64 w;
u8 b[8];
} iv;
u8 data[24];
struct des_ctx ctx;
int err;
for (int i = 0; i < 8; i++) {
key[i] = i;
iv.b[i] = 255 - i;
}
for (int i = 0; i < sizeof(data); i++)
data[i] = i;
err = des_expand_key(&ctx, key, sizeof(key));
KUNIT_ASSERT_EQ(test, 0, err);
des_pcbc_decrypt_inplace(&ctx, iv.w, data, sizeof(data));
KUNIT_ASSERT_MEMEQ(test, expected_ptext, data, sizeof(data));
}
static struct kunit_case rxrpc_test_cases[] = {
KUNIT_CASE(test_fcrypt_pcbc),
KUNIT_CASE(test_des_pcbc),
{},
};