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Message-ID: <CAH2r5mutq5vZwKNyZ6nforOierKSH9si+47XoFV7PZSKxuvqHQ@mail.gmail.com>
Date: Sun, 7 Sep 2025 12:59:41 -0500
From: Steve French <smfrench@...il.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-cifs@...r.kernel.org, Steve French <sfrench@...ba.org>,
Paulo Alcantara <pc@...guebit.org>, Namjae Jeon <linkinjeon@...nel.org>,
Ronnie Sahlberg <ronniesahlberg@...il.com>, Shyam Prasad N <sprasad@...rosoft.com>,
Tom Talpey <tom@...pey.com>, Bharath SM <bharathsm@...rosoft.com>,
Sergey Senozhatsky <senozhatsky@...omium.org>, linux-crypto@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] smb: Use arc4 library instead of duplicate arc4 code
Ronnie may have additional context, but it may have been forked due to
unrelated restrictions on the arc4 module (that had nothing to do with
cifs.ko very narrow usage of arc4) breaking cifs.ko.
Ronnie,
Do you remember the context?
On Sat, Sep 6, 2025 at 10:22 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> fs/smb/common/cifs_arc4.c has an implementation of ARC4, but a copy of
> this same code is also present in lib/crypto/arc4.c to serve the other
> users of this legacy algorithm in the kernel. Remove the duplicate
> implementation in fs/smb/, which seems to have been added because of a
> misunderstanding, and just use the lib/crypto/ one.
>
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
> ---
> fs/smb/client/Kconfig | 1 +
> fs/smb/client/cifsencrypt.c | 8 ++--
> fs/smb/common/Makefile | 1 -
> fs/smb/common/arc4.h | 23 ------------
> fs/smb/common/cifs_arc4.c | 75 -------------------------------------
> fs/smb/server/Kconfig | 1 +
> fs/smb/server/auth.c | 9 ++---
> 7 files changed, 10 insertions(+), 108 deletions(-)
> delete mode 100644 fs/smb/common/arc4.h
> delete mode 100644 fs/smb/common/cifs_arc4.c
>
> diff --git a/fs/smb/client/Kconfig b/fs/smb/client/Kconfig
> index 9f05f94e265a6..a4c02199fef48 100644
> --- a/fs/smb/client/Kconfig
> +++ b/fs/smb/client/Kconfig
> @@ -13,10 +13,11 @@ config CIFS
> select CRYPTO_AEAD2
> select CRYPTO_CCM
> select CRYPTO_GCM
> select CRYPTO_ECB
> select CRYPTO_AES
> + select CRYPTO_LIB_ARC4
> select KEYS
> select DNS_RESOLVER
> select ASN1
> select OID_REGISTRY
> select NETFS_SUPPORT
> diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c
> index 3cc6862469087..7b7c8c38fdd08 100644
> --- a/fs/smb/client/cifsencrypt.c
> +++ b/fs/smb/client/cifsencrypt.c
> @@ -20,12 +20,12 @@
> #include <linux/ctype.h>
> #include <linux/random.h>
> #include <linux/highmem.h>
> #include <linux/fips.h>
> #include <linux/iov_iter.h>
> -#include "../common/arc4.h"
> #include <crypto/aead.h>
> +#include <crypto/arc4.h>
>
> static size_t cifs_shash_step(void *iter_base, size_t progress, size_t len,
> void *priv, void *priv2)
> {
> struct shash_desc *shash = priv;
> @@ -723,13 +723,13 @@ calc_seckey(struct cifs_ses *ses)
> if (!ctx_arc4) {
> cifs_dbg(VFS, "Could not allocate arc4 context\n");
> return -ENOMEM;
> }
>
> - cifs_arc4_setkey(ctx_arc4, ses->auth_key.response, CIFS_SESS_KEY_SIZE);
> - cifs_arc4_crypt(ctx_arc4, ses->ntlmssp->ciphertext, sec_key,
> - CIFS_CPHTXT_SIZE);
> + arc4_setkey(ctx_arc4, ses->auth_key.response, CIFS_SESS_KEY_SIZE);
> + arc4_crypt(ctx_arc4, ses->ntlmssp->ciphertext, sec_key,
> + CIFS_CPHTXT_SIZE);
>
> /* make secondary_key/nonce as session key */
> memcpy(ses->auth_key.response, sec_key, CIFS_SESS_KEY_SIZE);
> /* and make len as that of session key only */
> ses->auth_key.len = CIFS_SESS_KEY_SIZE;
> diff --git a/fs/smb/common/Makefile b/fs/smb/common/Makefile
> index c66dbbc1469c3..9e0730a385fb1 100644
> --- a/fs/smb/common/Makefile
> +++ b/fs/smb/common/Makefile
> @@ -1,7 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0-only
> #
> # Makefile for Linux filesystem routines that are shared by client and server.
> #
>
> -obj-$(CONFIG_SMBFS) += cifs_arc4.o
> obj-$(CONFIG_SMBFS) += cifs_md4.o
> diff --git a/fs/smb/common/arc4.h b/fs/smb/common/arc4.h
> deleted file mode 100644
> index 12e71ec033a18..0000000000000
> --- a/fs/smb/common/arc4.h
> +++ /dev/null
> @@ -1,23 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0+ */
> -/*
> - * Common values for ARC4 Cipher Algorithm
> - */
> -
> -#ifndef _CRYPTO_ARC4_H
> -#define _CRYPTO_ARC4_H
> -
> -#include <linux/types.h>
> -
> -#define ARC4_MIN_KEY_SIZE 1
> -#define ARC4_MAX_KEY_SIZE 256
> -#define ARC4_BLOCK_SIZE 1
> -
> -struct arc4_ctx {
> - u32 S[256];
> - u32 x, y;
> -};
> -
> -int cifs_arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len);
> -void cifs_arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len);
> -
> -#endif /* _CRYPTO_ARC4_H */
> diff --git a/fs/smb/common/cifs_arc4.c b/fs/smb/common/cifs_arc4.c
> deleted file mode 100644
> index df360ca47826a..0000000000000
> --- a/fs/smb/common/cifs_arc4.c
> +++ /dev/null
> @@ -1,75 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-or-later
> -/*
> - * Cryptographic API
> - *
> - * ARC4 Cipher Algorithm
> - *
> - * Jon Oberheide <jon@...rheide.org>
> - */
> -
> -#include <linux/module.h>
> -#include "arc4.h"
> -
> -MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
> -MODULE_LICENSE("GPL");
> -
> -int cifs_arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
> -{
> - int i, j = 0, k = 0;
> -
> - ctx->x = 1;
> - ctx->y = 0;
> -
> - for (i = 0; i < 256; i++)
> - ctx->S[i] = i;
> -
> - for (i = 0; i < 256; i++) {
> - u32 a = ctx->S[i];
> -
> - j = (j + in_key[k] + a) & 0xff;
> - ctx->S[i] = ctx->S[j];
> - ctx->S[j] = a;
> - if (++k >= key_len)
> - k = 0;
> - }
> -
> - return 0;
> -}
> -EXPORT_SYMBOL_GPL(cifs_arc4_setkey);
> -
> -void cifs_arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
> -{
> - u32 *const S = ctx->S;
> - u32 x, y, a, b;
> - u32 ty, ta, tb;
> -
> - if (len == 0)
> - return;
> -
> - x = ctx->x;
> - y = ctx->y;
> -
> - a = S[x];
> - y = (y + a) & 0xff;
> - b = S[y];
> -
> - do {
> - S[y] = a;
> - a = (a + b) & 0xff;
> - S[x] = b;
> - x = (x + 1) & 0xff;
> - ta = S[x];
> - ty = (y + ta) & 0xff;
> - tb = S[ty];
> - *out++ = *in++ ^ S[a];
> - if (--len == 0)
> - break;
> - y = ty;
> - a = ta;
> - b = tb;
> - } while (true);
> -
> - ctx->x = x;
> - ctx->y = y;
> -}
> -EXPORT_SYMBOL_GPL(cifs_arc4_crypt);
> diff --git a/fs/smb/server/Kconfig b/fs/smb/server/Kconfig
> index 4a23a5e7e8fec..098cac98d31e6 100644
> --- a/fs/smb/server/Kconfig
> +++ b/fs/smb/server/Kconfig
> @@ -8,10 +8,11 @@ config SMB_SERVER
> select NLS_UCS2_UTILS
> select CRYPTO
> select CRYPTO_MD5
> select CRYPTO_HMAC
> select CRYPTO_ECB
> + select CRYPTO_LIB_ARC4
> select CRYPTO_LIB_DES
> select CRYPTO_LIB_SHA256
> select CRYPTO_SHA256
> select CRYPTO_CMAC
> select CRYPTO_SHA512
> diff --git a/fs/smb/server/auth.c b/fs/smb/server/auth.c
> index d99871c214518..b4020bb55a268 100644
> --- a/fs/smb/server/auth.c
> +++ b/fs/smb/server/auth.c
> @@ -18,20 +18,20 @@
>
> #include "auth.h"
> #include "glob.h"
>
> #include <linux/fips.h>
> +#include <crypto/arc4.h>
> #include <crypto/des.h>
>
> #include "server.h"
> #include "smb_common.h"
> #include "connection.h"
> #include "mgmt/user_session.h"
> #include "mgmt/user_config.h"
> #include "crypto_ctx.h"
> #include "transport_ipc.h"
> -#include "../common/arc4.h"
>
> /*
> * Fixed format data defining GSS header and fixed string
> * "not_defined_in_RFC4178@...ase_ignore".
> * So sec blob data in neg phase could be generated statically.
> @@ -363,14 +363,13 @@ int ksmbd_decode_ntlmssp_auth_blob(struct authenticate_message *authblob,
>
> ctx_arc4 = kmalloc(sizeof(*ctx_arc4), KSMBD_DEFAULT_GFP);
> if (!ctx_arc4)
> return -ENOMEM;
>
> - cifs_arc4_setkey(ctx_arc4, sess->sess_key,
> - SMB2_NTLMV2_SESSKEY_SIZE);
> - cifs_arc4_crypt(ctx_arc4, sess->sess_key,
> - (char *)authblob + sess_key_off, sess_key_len);
> + arc4_setkey(ctx_arc4, sess->sess_key, SMB2_NTLMV2_SESSKEY_SIZE);
> + arc4_crypt(ctx_arc4, sess->sess_key,
> + (char *)authblob + sess_key_off, sess_key_len);
> kfree_sensitive(ctx_arc4);
> }
>
> return ret;
> }
>
> base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0
> --
> 2.50.1
>
>
--
Thanks,
Steve
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