From patchwork Mon Aug 29 21:33:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Enzo Matsumiya X-Patchwork-Id: 12958464 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66A1CECAAD4 for ; Mon, 29 Aug 2022 21:34:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229567AbiH2VeP (ORCPT ); Mon, 29 Aug 2022 17:34:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229512AbiH2VeO (ORCPT ); Mon, 29 Aug 2022 17:34:14 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 758F5175B9 for ; Mon, 29 Aug 2022 14:34:11 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 2210621C92; Mon, 29 Aug 2022 21:34:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1661808850; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ODuODS6qZlP3pDQFfvTvOQ7MqZxEWEXJmyr/IMmDlGE=; b=GZo5wcYdXJCaYe3gh3gtvk9xMQHoaEBs08e2es7wtv5PCX0P9PiG2pcok6pELao+Cb/Opi fc0QVr8eGFg5DH/WXoQYcWu5OXr3VPQ4VC9uKxLBANfC8MpHzfLWBNXeNj7Va73v+9lJGI pefu9235Zousj+LqnpGYA2DkOUNSRQk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1661808850; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ODuODS6qZlP3pDQFfvTvOQ7MqZxEWEXJmyr/IMmDlGE=; b=1TV9WA+iyl/2thuFwBI1VpcguWjYNJMeGTlP+n9XNohkbBrO7edyN/DbX89KWQF9Ttp4IJ JlZFo3xWAf7iUQAQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 56AB3133A6; Mon, 29 Aug 2022 21:34:09 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id BDJaBtEwDWM2CAAAMHmgww (envelope-from ); Mon, 29 Aug 2022 21:34:09 +0000 From: Enzo Matsumiya To: linux-cifs@vger.kernel.org Cc: smfrench@gmail.com, pc@cjr.nz, ronniesahlberg@gmail.com, nspmangalore@gmail.com Subject: [RFC PATCH v2 1/3] cifs: introduce AES-GMAC signing support for SMB 3.1.1 Date: Mon, 29 Aug 2022 18:33:52 -0300 Message-Id: <20220829213354.2714-2-ematsumiya@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220829213354.2714-1-ematsumiya@suse.de> References: <20220829213354.2714-1-ematsumiya@suse.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org This patch implements the support for AES-GMAC message signing, as specified in MS-SMB2 3.1.4.1 "Signing An Outgoing Message". The core function is smb311_calc_aes_gmac(), which is to be used as the ->calc_signature op when a signing negotiate context (SMB2_SIGNING_CAPABILITIES) has been sent ("enable_negotiate_signing" module parameter) to the server and replied to with SIGNING_ALG_AES_GMAC (i.e. the server supports it). If "enable_negotiate_signing" is false (default) or if the server reply with SIGNING_ALG_AES_CMAC, ->calc_signature will point to smb3_calc_aes_cmac() (this was renamed from smb3_calc_signature() to better identify which functions are dealing with which algorithms). Since, in the crypto API context, AES-GMAC is not a hashing algorithm, but rather AES-128-GCM with an empty plaintext buffer, the following modifications were made: - Introduce smb311_crypt_sign() to accommodate the common code for encrypt/decrypt and signing operations that deals with the crypto API - crypt_message() has been modified to adopt smb311_crypt_sign() usage; no change of behaviour whatsoever - init_sg() now takes a bool argument 'crypt' to indicate when it's initializing an SG list for crypt operations, or set to false when it's for initializing it for AES-GMAC signing. This is needed because crypt operations use a transform header, and it needs to skip the first 20 bytes of the first iov. For AES-GMAC signing this is not needed because iov[0] is already the beginning of the message - Introduce smb311_aes_gmac_alloc() to allocate the secmech. This is called only once in smb311_update_preauth_hash(). The TFM has the lifetime of the TCP session, so it's only free when the TCP session is put() (via cifs_crypto_secmech_release()) - Introduce smb311_aes_gmac_nonce() to produce the nonce for AES-GMAC signing (as per MS-SMB2 3.1.4.1, item 2) More implementation-specific information can be found in the kernel-doc comments for the introduced functions. Other smaller modifications: - Check if the request is encrypted in smb2_setup_request(), as we must not sign a message if it is (MS-SMB2 3.2.4.1.1) -- AES-GCM and AES-CCM will generate their signatures based on the ciphertext (AES-GCM) or the plaintext (AES-CCM) - smb2_verify_signature(): - Remove extra call to memset to zero the header signature as this is already done in the beginning ->calc_signature() implementations - Remove useless call to check for "BSRSPYL" signature as it's SMB1 only - Add checks for if command is 0xFFFFFFFFFFFFFFFF or if status is STATUS_PENDING (MS-SMB2 3.2.5.1.3) - Remove useless variable from smb2_sign_rqst() - smb2_get_sign_key() is no longer static as it's now used by smb311_calc_aes_gmac() - Use sizeof u16/__le16 in build_signing_ctxt() instead of hardcoded values Signed-off-by: Enzo Matsumiya --- fs/cifs/cifsencrypt.c | 5 + fs/cifs/cifsglob.h | 9 +- fs/cifs/sess.c | 2 + fs/cifs/smb2misc.c | 6 + fs/cifs/smb2ops.c | 484 +++++++++++++++++++++++++++++++++------- fs/cifs/smb2pdu.c | 93 ++++++-- fs/cifs/smb2proto.h | 7 +- fs/cifs/smb2transport.c | 87 ++++++-- 8 files changed, 571 insertions(+), 122 deletions(-) diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c index 46f5718754f9..39e934277dfc 100644 --- a/fs/cifs/cifsencrypt.c +++ b/fs/cifs/cifsencrypt.c @@ -743,6 +743,11 @@ cifs_crypto_secmech_release(struct TCP_Server_Info *server) server->secmech.hmacmd5 = NULL; } + if (server->secmech.aes_gmac) { + crypto_free_aead(server->secmech.aes_gmac); + server->secmech.aes_gmac = NULL; + } + if (server->secmech.ccmaesencrypt) { crypto_free_aead(server->secmech.ccmaesencrypt); server->secmech.ccmaesencrypt = NULL; diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index ae7f571a7dba..0ce2ceaf039e 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -171,6 +171,7 @@ struct cifs_secmech { struct sdesc *sdeschmacsha256; /* ctxt to generate smb2 signature */ struct sdesc *sdesccmacaes; /* ctxt to generate smb3 signature */ struct sdesc *sdescsha512; /* ctxt to generate smb3.11 signing key */ + struct crypto_aead *aes_gmac; /* to generate SMB3.1.1 signature */ struct crypto_aead *ccmaesencrypt; /* smb3 encryption aead */ struct crypto_aead *ccmaesdecrypt; /* smb3 decryption aead */ }; @@ -704,7 +705,13 @@ struct TCP_Server_Info { unsigned int max_write; unsigned int min_offload; __le16 compress_algorithm; - __u16 signing_algorithm; + /* + * algorithm to be used to sign messages: + * SMB 2.x - HMAC-SHA256 (unsupported in SMB 3.1.1) + * SMB 3.0.x - AES-CMAC + * SMB 3.1.1 - AES-GMAC, if server negotiated it, or AES-CMAC otherwise + */ + __u16 signing_algorithm; __le16 cipher_type; /* save initital negprot hash */ __u8 preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE]; diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c index 3af3b05b6c74..9708a531d604 100644 --- a/fs/cifs/sess.c +++ b/fs/cifs/sess.c @@ -458,6 +458,8 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses, * We need to allocate the server crypto now as we will need * to sign packets before we generate the channel signing key * (we sign with the session key) + * + * AES-GMAC secmech is allocated in smb311_update_preauth_hash() call. */ rc = smb311_crypto_shash_allocate(chan->server); if (rc) { diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c index d73e5672aac4..950f601fca7a 100644 --- a/fs/cifs/smb2misc.c +++ b/fs/cifs/smb2misc.c @@ -854,6 +854,8 @@ smb2_handle_cancelled_mid(struct mid_q_entry *mid, struct TCP_Server_Info *serve return rc; } +extern int smb311_aes_gmac_alloc(struct crypto_aead **); + /** * smb311_update_preauth_hash - update @ses hash with the packet data in @iov * @@ -897,6 +899,10 @@ smb311_update_preauth_hash(struct cifs_ses *ses, struct TCP_Server_Info *server, return 0; ok: + rc = smb311_aes_gmac_alloc(&server->secmech.aes_gmac); + if (rc) + return rc; + rc = smb311_crypto_shash_allocate(server); if (rc) return rc; diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 5b5ddc1b4638..d93c385314dd 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include "cifsfs.h" @@ -4221,21 +4222,52 @@ static inline void smb2_sg_set_buf(struct scatterlist *sg, const void *buf, sg_set_page(sg, addr, buflen, offset_in_page(buf)); } -/* Assumes the first rqst has a transform header as the first iov. - * I.e. - * rqst[0].rq_iov[0] is transform header - * rqst[0].rq_iov[1+] data to be encrypted/decrypted - * rqst[1+].rq_iov[0+] data to be encrypted/decrypted +/* + * Initialize a scatterlist for encrypt/decrypt/sign (AES-GMAC) operations + * + * @num_rqst: Number of requests that will be transformed. Note that this is always 1 for AES-GMAC + * signing. + * @rqst: Points to the first request to be transformed. Note that this is always a single request + * for AES-GMAC signing, that might contain 1 or more iovs. + * @sig: Points to a caller-allocated buffer that will hold the computed signature. + * @crypt: If true, indicates that this SG list is for a encryption/decryption transform. If false, + * this is an AES-GMAC signing operation. See 'skip' variable. + * + * General notes for callers: + * + * - The crypto API fully supports using the same SG list for encrypt/decrypt operations,i.e. it + * encrypts/decrypts the plain/cipher text in src SG and then copies the result into dst SG, + * where src == dst. The AAD buffer are should not be modified + * - If it's desired to use 2 different SGs, one for src, another for dst, make sure they have the + * same layout, and same AAD/text/signature sizes + * - It's ok to have a hole/pad in the SG, if required, but make sure to account for its size when + * setting crypt len/AAD len. Also, there should be no NULL buffers. init_sg() checks for that + * when looping through the iovs, and will return ERR_PTR(-EIO) in case a NULL iov is found. + * + * Notes for encrypt/decrypt: + * - Assumes the first rqst has a transform header as the first iov, i.e.: + * - rqst[0].rq_iov[0]: Transform header. The first 20 bytes of the transform header are not + * part of the encrypted blob (see 'skip' variable) + * - rqst[0].rq_iov[1+]: Data to be encrypted/decrypted + * - rqst[1+].rq_iov[0+]: Data to be encrypted/decrypted + * + * Notes for AES-GMAC signing: + * - @num_rqst is always 1 + * - 'skip' variable must be 0 (rqst[0].rq_iov[0] is smb2_hdr already) + * - The memory layout is slightly different from encrypt/decrypt: + * crypt: [ AAD (20 bytes) | plain/cipher text (iovs, variable length) | signature buffer (16 bytes) ] + * sign: [ AAD (iovs, variable length) | empty plaintext (0 bytes, not NULL) | signature buffer (16 bytes) ] + * + * Return: On success, returns an SG filled with the iovs from @rqst. On + * failure, returns ERR_PTR(errno). */ -static struct scatterlist * -init_sg(int num_rqst, struct smb_rqst *rqst, u8 *sign) +static struct scatterlist *init_sg(int num_rqst, struct smb_rqst *rqst, + u8 *sig, bool crypt) { unsigned int sg_len; struct scatterlist *sg; - unsigned int i; - unsigned int j; - unsigned int idx = 0; - int skip; + unsigned int i, j, idx = 0; + int skip = 0; sg_len = 1; for (i = 0; i < num_rqst; i++) @@ -4243,20 +4275,26 @@ init_sg(int num_rqst, struct smb_rqst *rqst, u8 *sign) sg = kmalloc_array(sg_len, sizeof(struct scatterlist), GFP_KERNEL); if (!sg) - return NULL; + return ERR_PTR(-ENOMEM); sg_init_table(sg, sg_len); + + /* + * initializes the plain/cipher text buffers for encrypt/decrypt, or + * the AAD area for signing + */ for (i = 0; i < num_rqst; i++) { for (j = 0; j < rqst[i].rq_nvec; j++) { - /* - * The first rqst has a transform header where the - * first 20 bytes are not part of the encrypted blob - */ - skip = (i == 0) && (j == 0) ? 20 : 0; + if (unlikely(!rqst[i].rq_iov[j].iov_base)) + return ERR_PTR(-EIO); + + if (crypt) + skip = (i == 0) && (j == 0) ? 20 : 0; + smb2_sg_set_buf(&sg[idx++], rqst[i].rq_iov[j].iov_base + skip, rqst[i].rq_iov[j].iov_len - skip); - } + } for (j = 0; j < rqst[i].rq_npages; j++) { unsigned int len, offset; @@ -4265,7 +4303,10 @@ init_sg(int num_rqst, struct smb_rqst *rqst, u8 *sign) sg_set_page(&sg[idx++], rqst[i].rq_pages[j], len, offset); } } - smb2_sg_set_buf(&sg[idx], sign, SMB2_SIGNATURE_SIZE); + + /* initialize signature buffer */ + smb2_sg_set_buf(&sg[idx], sig, SMB2_SIGNATURE_SIZE); + return sg; } @@ -4293,6 +4334,178 @@ smb2_get_enc_key(struct TCP_Server_Info *server, __u64 ses_id, int enc, u8 *key) return -EAGAIN; } + +/** + * smb311_crypt_sign() - Encrypts, decrypts, or sign an SMB2 message using AES-GCM algorithm. + * @rqst: SMB2 request to transform. + * @num_rqst: Number of requests to transform. Must be 1 if @sign_only is true. + * @enc: True for an encryption operation, false for decryption. If both @enc and @sign_only are + * true, assumes an encryption operation and set @sign_only to false. + * @sign_only: True if the request must only have the signature computed. + * @tfm: AES-GCM crypto transformation object. Must be allocated and freed by the caller. + * @key: The private key to be used for the operation. Must be allocated and freed by the caller. + * @keylen: The size of @key. Must be 16 for AES-128-GCM crypt ops and AES-GMAC, or 32 for + * AES-256-GCM. + * @iv: The Initialization Vector, a.k.a. nonce. Must be allocated and freed by the caller. + * @assoclen: Size of the Additional Authenticated Data (AAD) (or Associated Data (AD)). Must be + * size of smb2_transform_hdr - 20 for encryption/decryption, and the size of the whole + * SMB2 message for signing (e.g gotten from smb_rqst_len()). + * @cryptlen: Size of the plain/cipher text buffer. Must be 0 if @sign_only is true. + * + * This function is shared between the SMB 3.1.1 AES-GCM encryption/decryption operations + * (crypt_message()), and AES-GMAC signing operation (smb311_calc_aes_gmac()). + * + * This function will perform the core operations (encrypt and decrypt) using the parameters passed + * by the callers, which is what differ encrypt/decrypt ops from signing ops. + * + * Note that signing functionality (@sign_only == true) must only be used when the request must NOT + * be encrypted, as encrypted requests will have their own signatures, but computed differently. + * + * References: + * MS-SMB2 3.2.4.1.1 "Signing the Message" + * + * Return: 0 on success, negative errno otherwise. + */ +static int smb311_crypt_sign(struct smb_rqst *rqst, int num_rqst, int enc, + bool sign_only, struct crypto_aead *tfm, u8 *key, + unsigned int keylen, u8 *iv, unsigned int assoclen, + unsigned int cryptlen) +{ + struct smb2_hdr *shdr = (struct smb2_hdr *)rqst[0].rq_iov[0].iov_base; + struct smb2_transform_hdr *tr_hdr = + (struct smb2_transform_hdr *)rqst[0].rq_iov[0].iov_base; + u8 sig[SMB2_SIGNATURE_SIZE] = { 0 }; + struct aead_request *aead_req; + DECLARE_CRYPTO_WAIT(wait); + struct scatterlist *sg; + int rc = 0; + + /* basic checks */ + if (!rqst || !tfm || !key || !iv) + return -EINVAL; + + if (unlikely(!rqst)) + return -ENODATA; + + /* signing checks */ + if (sign_only) { + /* + * !enc && !sign_only == decrypt, but enc && sign_only is + * invalid. + * + * Warn the user, but continue normally assuming this is an + * encryption operation. + * + * (this is probably a bug from the caller) + */ + if (unlikely(enc)) { + pr_warn_once("%s: cannot have enc == true and sign_only == true, assuming " + "encrypt\n", __func__); + sign_only = false; + goto check_key; + } + + /* signing is done on single requests only */ + if (num_rqst > 1) { + cifs_dbg(VFS, "%s: invalid number of requests to sign '%u', expected 1\n", + __func__, num_rqst); + return -EINVAL; + } + + if (unlikely(assoclen == 0)) { + cifs_dbg(FYI, "%s: assoclen is 0 for signing operation\n", __func__); + return -ENODATA; + } + + if (unlikely(cryptlen > 0)) { + cifs_dbg(FYI, "%s: AES-GMAC signing must have cryptlen 0, got '%u'\n", + __func__, cryptlen); + return -EINVAL; + } + } else { + /* crypt checks */ + if (unlikely(assoclen != sizeof(struct smb2_transform_hdr) - 20)) { + cifs_dbg(FYI, "%s: invalid assoclen '%u' for %scrypt operation\n", + __func__, assoclen, enc ? "en" : "de"); + return -EINVAL; + } + + if (unlikely(cryptlen == 0)) { + cifs_dbg(FYI, "%s: empty cryptlen for %scrypt operation\n", __func__, + enc ? "en" : "de"); + return -ENODATA; + } + } + +check_key: + if (keylen != SMB3_GCM128_CRYPTKEY_SIZE && /* 16 bytes, for AES-GMAC too */ + keylen != SMB3_GCM256_CRYPTKEY_SIZE) { /* 32 bytes */ + cifs_dbg(FYI, "%s: invalid key size '%u'\n", __func__, keylen); + return -EINVAL; + } + + rc = crypto_aead_setkey(tfm, key, keylen); + if (rc) { + cifs_dbg(VFS, "%s: Failed to set AEAD key, rc=%d\n", __func__, rc); + return rc; + } + + rc = crypto_aead_setauthsize(tfm, SMB2_SIGNATURE_SIZE); + if (rc) { + cifs_dbg(VFS, "%s: Failed to set AEAD authsize, rc=%d\n", + __func__, rc); + return rc; + } + + aead_req = aead_request_alloc(tfm, GFP_KERNEL); + if (!aead_req) { + cifs_dbg(VFS, "%s: Failed to alloc AEAD request\n", __func__); + return -ENOMEM; + } + + /* decrypting */ + if (!enc && !sign_only) { + memcpy(sig, &tr_hdr->Signature, SMB2_SIGNATURE_SIZE); + cryptlen += SMB2_SIGNATURE_SIZE; + } + + sg = init_sg(num_rqst, rqst, sig, !sign_only); + if (IS_ERR(sg)) { + rc = PTR_ERR(sg); + cifs_dbg(VFS, "%s: Failed to init SG, rc=%d\n", __func__, rc); + goto out_free_req; + } + + aead_request_set_crypt(aead_req, sg, sg, cryptlen, iv); + aead_request_set_ad(aead_req, assoclen); + aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_BACKLOG, + crypto_req_done, &wait); + + /* + * Note for AES-GMAC (@sign_only): whether signing or verifying a signature, we must + * always use the encrypt function, as AES-GCM decrypt will internally try to match the + * authentication codes, which were computed based on the ciphertext, and fail (-EBADMSG), + * as expected. + */ + if (enc || sign_only) + rc = crypto_wait_req(crypto_aead_encrypt(aead_req), &wait); + else + rc = crypto_wait_req(crypto_aead_decrypt(aead_req), &wait); + + if (!rc) { + if (enc) + memcpy(&tr_hdr->Signature, sig, SMB2_SIGNATURE_SIZE); + else if (sign_only) + memcpy(&shdr->Signature, sig, SMB2_SIGNATURE_SIZE); + } + + kfree(sg); +out_free_req: + kfree(aead_req); + + return rc; +} + /* * Encrypt or decrypt @rqst message. @rqst[0] has the following format: * iov[0] - transform header (associate data), @@ -4306,17 +4519,16 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst, { struct smb2_transform_hdr *tr_hdr = (struct smb2_transform_hdr *)rqst[0].rq_iov[0].iov_base; - unsigned int assoc_data_len = sizeof(struct smb2_transform_hdr) - 20; - int rc = 0; - struct scatterlist *sg; - u8 sign[SMB2_SIGNATURE_SIZE] = {}; + unsigned int assoclen, cryptlen; u8 key[SMB3_ENC_DEC_KEY_SIZE]; - struct aead_request *req; - char *iv; - unsigned int iv_len; - DECLARE_CRYPTO_WAIT(wait); struct crypto_aead *tfm; - unsigned int crypt_len = le32_to_cpu(tr_hdr->OriginalMessageSize); + unsigned int iv_len; + unsigned int keylen; + char *iv; + int rc = 0; + + assoclen = sizeof(struct smb2_transform_hdr) - 20; + cryptlen = le32_to_cpu(tr_hdr->OriginalMessageSize); rc = smb2_get_enc_key(server, le64_to_cpu(tr_hdr->SessionId), enc, key); if (rc) { @@ -4332,49 +4544,24 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst, } tfm = enc ? server->secmech.ccmaesencrypt : - server->secmech.ccmaesdecrypt; - - if ((server->cipher_type == SMB2_ENCRYPTION_AES256_CCM) || - (server->cipher_type == SMB2_ENCRYPTION_AES256_GCM)) - rc = crypto_aead_setkey(tfm, key, SMB3_GCM256_CRYPTKEY_SIZE); - else - rc = crypto_aead_setkey(tfm, key, SMB3_GCM128_CRYPTKEY_SIZE); - - if (rc) { - cifs_server_dbg(VFS, "%s: Failed to set aead key %d\n", __func__, rc); - return rc; - } - - rc = crypto_aead_setauthsize(tfm, SMB2_SIGNATURE_SIZE); - if (rc) { - cifs_server_dbg(VFS, "%s: Failed to set authsize %d\n", __func__, rc); - return rc; - } - - req = aead_request_alloc(tfm, GFP_KERNEL); - if (!req) { - cifs_server_dbg(VFS, "%s: Failed to alloc aead request\n", __func__); - return -ENOMEM; - } - - if (!enc) { - memcpy(sign, &tr_hdr->Signature, SMB2_SIGNATURE_SIZE); - crypt_len += SMB2_SIGNATURE_SIZE; + server->secmech.ccmaesdecrypt; + /* sanity check -- shouldn't happen */ + if (unlikely(!tfm)) { + cifs_server_dbg(FYI, "%s: AEAD TFM is NULL\n", __func__); + return -EIO; } - sg = init_sg(num_rqst, rqst, sign); - if (!sg) { - cifs_server_dbg(VFS, "%s: Failed to init sg\n", __func__); - rc = -ENOMEM; - goto free_req; - } + if (server->cipher_type == SMB2_ENCRYPTION_AES256_CCM || + server->cipher_type == SMB2_ENCRYPTION_AES256_GCM) + keylen = SMB3_GCM256_CRYPTKEY_SIZE; + else + keylen = SMB3_GCM128_CRYPTKEY_SIZE; iv_len = crypto_aead_ivsize(tfm); iv = kzalloc(iv_len, GFP_KERNEL); if (!iv) { cifs_server_dbg(VFS, "%s: Failed to alloc iv\n", __func__); - rc = -ENOMEM; - goto free_sg; + return -ENOMEM; } if ((server->cipher_type == SMB2_ENCRYPTION_AES128_GCM) || @@ -4385,23 +4572,158 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst, memcpy(iv + 1, (char *)tr_hdr->Nonce, SMB3_AES_CCM_NONCE); } - aead_request_set_crypt(req, sg, sg, crypt_len, iv); - aead_request_set_ad(req, assoc_data_len); + rc = smb311_crypt_sign(rqst, num_rqst, enc, false, tfm, key, keylen, + iv, assoclen, cryptlen); + if (rc) + cifs_server_dbg(VFS, "%s: Failed to %scrypt request, rc=%d\n", + __func__, enc ? "en" : "de", rc); - aead_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, - crypto_req_done, &wait); + kfree(iv); + return rc; +} - rc = crypto_wait_req(enc ? crypto_aead_encrypt(req) - : crypto_aead_decrypt(req), &wait); +/** + * smb311_aes_gmac_nonce() - Setup AES-GMAC nonce. + * @shdr: SMB2 header containing the MessageId and the Command of the request. + * @is_server: True if the request came from the server (i.e. we're verifying a signature), false + * if the request is being sent from the client (i.e. we're signing a request to be + * sent). + * @out_nonce: Output buffer to put the computed nonce. Must be allocated and freed by the caller. + * @*out_nonce will be allocated here, and, on success, must be freed by the caller. + * + * Allocates @*out_nonce and fill it with the nonce computed. + * + * MS-SMB2 3.1.4.1 "Signing An Outgoing Message", item 2: + * + * If Connection.SigningAlgorithmId is AES-GMAC, Nonce specified in [RFC4543], MUST be initialized + * to 12 bytes with the following syntax: + * - First 8 bytes are set to MessageId. + * - Following 4 bytes are set as follows: If the sender is a client, least significant bit is + * set to zero, otherwise set to 1. If the message is SMB2 CANCEL request, the penultimate bit + * is set to 1, otherwise set to zero. Remaining 30 bits are set to zero. + * + * References: + * MS-SMB2 3.1.4.1 "Signing An Outgoing Message" + * RFC 4543 "GMAC in IPsec ESP and AH", section 3.2 "Nonce Format" + * https://www.ietf.org/rfc/rfc4543.txt + * + * Return: 0 on success, negative errno otherwise. + */ +static int smb311_aes_gmac_nonce(struct smb2_hdr *shdr, bool is_server, + u8 **out_nonce) +{ + struct { + /* for MessageId (8 bytes) */ + __le64 mid; + /* for role (client or server) and if SMB2 CANCEL (4 bytes) */ + __le32 role; + } __packed nonce; + + if (!shdr || !out_nonce) + return -EINVAL; - if (!rc && enc) - memcpy(&tr_hdr->Signature, sign, SMB2_SIGNATURE_SIZE); + *out_nonce = kzalloc(SMB3_AES_GCM_NONCE, GFP_KERNEL); + if (!*out_nonce) + return -ENOMEM; - kfree(iv); -free_sg: - kfree(sg); -free_req: - kfree(req); + memset(&nonce, 0, SMB3_AES_GCM_NONCE); + + /* note that nonce must always be little endian */ + nonce.mid = shdr->MessageId; + + /* request is coming from the server */ + if (is_server) + set_bit(0, (unsigned long *)&nonce.role); + + /* set penultimate bit if SMB2_CANCEL command */ + if (shdr->Command == SMB2_CANCEL) + set_bit(1, (unsigned long *)&nonce.role); + + memcpy(*out_nonce, (u8 *)&nonce, SMB3_AES_GCM_NONCE); + + return 0; +} + +extern int smb2_get_sign_key(__u64, struct TCP_Server_Info *, u8 *); + +/** + * smb311_calc_aes_gmac() - Calculate the signature for a request using AES-GMAC algorithm. + * @rqst: SMB2 request to be signed. + * @server: Server pointer that holds the secmech to be used. + * @verify: If true, compute the nonce considering it came from the server. + * + * This function implements AES-GMAC signing for SMB2 messages as described in MS-SMB2 + * specification. This algorithm is only supported on SMB 3.1.1. + * + * For our purposes, AES-GMAC is AES-128-GCM, but without encrypting anything. IOW, this is what's + * done: + * - set an Additional Authenticated Data (AAD) buffer, with the contents of the SMB2 request, + * starting from the SMB2 header, and the length of rq_nvec + rq_npages + * - set plaintext buffer to have a 0 length, so AES-GCM will not encrypt anything + * - set a signature buffer, where AES-GCM will place the signature computed from the AAD buffer + * + * Most of that is done in smb311_crypt_sign(). + * + * Note: even though Microsoft mentions RFC4543 in MS-SMB2, the mechanism used _must_ be the "raw" + * AES-128-GCM. RFC4543 is designed for IPsec Encapsulating Security Payload (ESP) and + * Authentication Header (AH). Trying to use "rfc(gcm(aes)))" as the AEAD algorithm will fail the + * signature calculation. + * + * References: + * MS-SMB2 3.1.4.1 "Signing An Outgoing Message" + * + * Return: 0 on success, negative errno otherwise. + */ +int smb311_calc_aes_gmac(struct smb_rqst *rqst, struct TCP_Server_Info *server, + bool verify) +{ + u8 key[SMB3_SIGN_KEY_SIZE] = { 0 }; + struct crypto_aead *tfm = NULL; + struct smb2_hdr *shdr; + unsigned int assoclen; + u8 *nonce = NULL; + int rc = 0; + + /* allocated in smb311_update_preauth_hash() */ + tfm = server->secmech.aes_gmac; + /* sanity check -- shouldn't happen */ + if (unlikely(!tfm)) { + cifs_server_dbg(FYI, "%s: AES-GMAC TFM is NULL\n", __func__); + return -EIO; + } + + shdr = (struct smb2_hdr *)rqst->rq_iov[0].iov_base; + memset(shdr->Signature, 0, SMB2_SIGNATURE_SIZE); + + rc = smb2_get_sign_key(le64_to_cpu(shdr->SessionId), server, key); + if (rc) { + cifs_server_dbg(VFS, "%s: Could not get AES-GMAC signing key, rc=%d\n", __func__, + rc); + goto out; + } + + rc = smb311_aes_gmac_nonce(shdr, verify, &nonce); + if (rc) { + cifs_server_dbg(VFS, "%s: Could not get AES-GMAC nonce, rc=%d\n", __func__, rc); + goto out; + } + + /* + * Set the Additional Authenticated Data (AAD)/Associated Data (AD) length to the SMB + * request length, which corresponds to the part of the buffer we want to sign/authenticate. + */ + assoclen = smb_rqst_len(server, rqst); + + /* + * Use 0 for cryptlen because we're not interested in encrypting, but only computing the + * authentication tag (signature) of the AAD buffer. + */ + rc = smb311_crypt_sign(rqst, 1, false, true, tfm, key, SMB3_SIGN_KEY_SIZE, nonce, assoclen, 0); + if (rc) + cifs_server_dbg(VFS, "%s: Failed to compute AES-GMAC signature for request, rc=%d\n", + __func__, rc); + kfree(nonce); +out: return rc; } @@ -5458,7 +5780,7 @@ struct smb_version_operations smb30_operations = { .set_lease_key = smb2_set_lease_key, .new_lease_key = smb2_new_lease_key, .generate_signingkey = generate_smb30signingkey, - .calc_signature = smb3_calc_signature, + .calc_signature = smb3_calc_aes_cmac, .set_integrity = smb3_set_integrity, .is_read_op = smb21_is_read_op, .set_oplock_level = smb3_set_oplock_level, @@ -5572,7 +5894,11 @@ struct smb_version_operations smb311_operations = { .set_lease_key = smb2_set_lease_key, .new_lease_key = smb2_new_lease_key, .generate_signingkey = generate_smb311signingkey, - .calc_signature = smb3_calc_signature, + /* + * .calc_signature is replaced by smb311_calc_aes_gmac if AES-GMAC + * gets negotiated with the server. + */ + .calc_signature = smb3_calc_aes_cmac, .set_integrity = smb3_set_integrity, .is_read_op = smb21_is_read_op, .set_oplock_level = smb3_set_oplock_level, diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 128e44e57528..45215e4e6f37 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -460,7 +460,7 @@ static unsigned int build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt) { unsigned int ctxt_len = sizeof(struct smb2_signing_capabilities); - unsigned short num_algs = 1; /* number of signing algorithms sent */ + unsigned short num_algs = 2; /* number of signing algorithms sent */ pneg_ctxt->ContextType = SMB2_SIGNING_CAPABILITIES; /* @@ -469,14 +469,25 @@ build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt) pneg_ctxt->DataLength = cpu_to_le16(DIV_ROUND_UP( sizeof(struct smb2_signing_capabilities) - sizeof(struct smb2_neg_context) + - (num_algs * 2 /* sizeof u16 */), 8) * 8); + (num_algs * sizeof(u16)), 8) * 8); pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(num_algs); - pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC); - ctxt_len += 2 /* sizeof le16 */ * num_algs; + /* + * MS-SMB2 2.2.3.1.7: + * These IDs MUST be in an order such that the most preferred + * signing algorithm MUST be at the beginning of the array and least + * preferred signing algorithm at the end of the array. + * + * Hint the server that we prefer AES-GMAC, but there's no guarantee + * it'll be used, e.g. server might not support it. + */ + pneg_ctxt->SigningAlgorithms[0] = SIGNING_ALG_AES_GMAC_LE; + pneg_ctxt->SigningAlgorithms[1] = SIGNING_ALG_AES_CMAC_LE; + /* SMB 3.1.1 doesn't accept HMAC-SHA256, so no need to send it */ + + ctxt_len += sizeof(__le16) * num_algs; ctxt_len = DIV_ROUND_UP(ctxt_len, 8) * 8; return ctxt_len; - /* TBD add SIGNING_ALG_AES_GMAC and/or SIGNING_ALG_HMAC_SHA256 */ } static void @@ -613,7 +624,6 @@ assemble_neg_contexts(struct smb2_negotiate_req *req, /* check for and add transport_capabilities and signing capabilities */ req->NegotiateContextCount = cpu_to_le16(neg_context_count); - } static void decode_preauth_context(struct smb2_preauth_neg_context *ctxt) @@ -702,30 +712,49 @@ static int decode_encrypt_ctx(struct TCP_Server_Info *server, return 0; } +/* XXX: maybe move this somewhere else? */ +static const char *smb3_signing_algo_str(u16 algo) +{ + switch (algo) { + case SIGNING_ALG_AES_CMAC: return "AES-CMAC"; + case SIGNING_ALG_AES_GMAC: return "AES-GMAC"; + /* HMAC-SHA256 is unused in SMB3+ context */ + default: return "unknown"; + } +} + static void decode_signing_ctx(struct TCP_Server_Info *server, struct smb2_signing_capabilities *pctxt) { unsigned int len = le16_to_cpu(pctxt->DataLength); if ((len < 4) || (len > 16)) { - pr_warn_once("server sent bad signing negcontext\n"); + pr_warn_once("server sent bad signing negcontext, len=%u\n", len); return; } + if (le16_to_cpu(pctxt->SigningAlgorithmCount) != 1) { - pr_warn_once("Invalid signing algorithm count\n"); + pr_warn_once("invalid signing algorithm count '%u'\n", + le16_to_cpu(pctxt->SigningAlgorithmCount)); return; } - if (le16_to_cpu(pctxt->SigningAlgorithms[0]) > 2) { - pr_warn_once("unknown signing algorithm\n"); + + if (le16_to_cpu(pctxt->SigningAlgorithms[0]) > SIGNING_ALG_AES_GMAC) { + pr_warn_once("unknown signing algorithm '%u'\n", + le16_to_cpu(pctxt->SigningAlgorithms[0])); return; } server->signing_negotiated = true; server->signing_algorithm = le16_to_cpu(pctxt->SigningAlgorithms[0]); - cifs_dbg(FYI, "signing algorithm %d chosen\n", - server->signing_algorithm); -} + if (server->signing_algorithm == SIGNING_ALG_AES_GMAC) + server->ops->calc_signature = smb311_calc_aes_gmac; + /* AES-CMAC is already the default, in case AES-GMAC wasn't negotiated */ + + cifs_dbg(FYI, "negotiated signing algorithm '%s'\n", + smb3_signing_algo_str(server->signing_algorithm)); +} static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp, struct TCP_Server_Info *server, @@ -745,6 +774,9 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp, len_of_ctxts = len_of_smb - offset; + /* ensure this is false before decoding */ + server->signing_negotiated = false; + for (i = 0; i < ctxt_cnt; i++) { int clen; /* check that offset is not beyond end of SMB */ @@ -784,6 +816,21 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp, offset += clen + sizeof(struct smb2_neg_context); len_of_ctxts -= clen; } + + /* + * Throw a warning if user requested signing to be negotiated, but it + * wasn't. + * + * Some servers will not send a SMB2_SIGNING_CAPABILITIES context (*), + * so we use AES-CMAC (default in smb311 ops) as it is expected to be + * accepted (e.g. only Windows Server 2022 supports AES-GMAC) + * + * (*) see note "<125> Section 3.2.4.2.2.2" in MS-SMB2 + */ + if (!server->signing_negotiated && enable_negotiate_signing) + cifs_dbg(VFS, "signing capabilities were not negotiated, using " + "AES-CMAC for message signing\n"); + return rc; } @@ -931,6 +978,15 @@ SMB2_negotiate(const unsigned int xid, if (ses->chan_max > 1) req->Capabilities |= cpu_to_le32(SMB2_GLOBAL_CAP_MULTI_CHANNEL); + /* set default settings for signing */ + if (server->vals->protocol_id >= SMB30_PROT_ID) { + server->signing_algorithm = SIGNING_ALG_AES_CMAC; + server->ops->calc_signature = smb3_calc_aes_cmac; + } else if (server->vals->protocol_id >= SMB20_PROT_ID) { + server->signing_algorithm = SIGNING_ALG_HMAC_SHA256; + /* ->calc_signature is already set to smb2_calc_signature */ + } + /* ClientGUID must be zero for SMB2.02 dialect */ if (server->vals->protocol_id == SMB20_PROT_ID) memset(req->ClientGUID, 0, SMB2_CLIENT_GUID_SIZE); @@ -1078,11 +1134,15 @@ SMB2_negotiate(const unsigned int xid, } if (rsp->DialectRevision == cpu_to_le16(SMB311_PROT_ID)) { - if (rsp->NegotiateContextCount) + if (rsp->NegotiateContextCount) { rc = smb311_decode_neg_context(rsp, server, rsp_iov.iov_len); - else + } else { cifs_server_dbg(VFS, "Missing expected negotiate contexts\n"); + cifs_server_dbg(VFS, "Using default signing algorithm (AES-CMAC)\n"); + server->signing_algorithm = SIGNING_ALG_AES_CMAC; + server->ops->calc_signature = smb3_calc_aes_cmac; + } } neg_exit: free_rsp_buf(resp_buftype, rsp); @@ -1387,8 +1447,7 @@ SMB2_sess_establish_session(struct SMB2_sess_data *sess_data) if (server->ops->generate_signingkey) { rc = server->ops->generate_signingkey(ses, server); if (rc) { - cifs_dbg(FYI, - "SMB3 session key generation failed\n"); + cifs_dbg(FYI, "SMB3 session key generation failed\n"); cifs_server_unlock(server); return rc; } diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h index 3f740f24b96a..3ed03417007b 100644 --- a/fs/cifs/smb2proto.h +++ b/fs/cifs/smb2proto.h @@ -44,9 +44,12 @@ extern struct cifs_tcon *smb2_find_smb_tcon(struct TCP_Server_Info *server, extern int smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server, bool allocate_crypto); -extern int smb3_calc_signature(struct smb_rqst *rqst, +extern int smb3_calc_aes_cmac(struct smb_rqst *rqst, + struct TCP_Server_Info *server, + bool allocate_crypto); +extern int smb311_calc_aes_gmac(struct smb_rqst *rqst, struct TCP_Server_Info *server, - bool allocate_crypto); + bool alloc); extern void smb2_echo_request(struct work_struct *work); extern __le32 smb2_get_lease_state(struct cifsInodeInfo *cinode); extern bool smb2_is_valid_oplock_break(char *buffer, diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c index 1a5fc3314dbf..bffdf8f4f8d2 100644 --- a/fs/cifs/smb2transport.c +++ b/fs/cifs/smb2transport.c @@ -76,8 +76,6 @@ smb311_crypto_shash_allocate(struct TCP_Server_Info *server) return rc; } - -static int smb2_get_sign_key(__u64 ses_id, struct TCP_Server_Info *server, u8 *key) { struct cifs_chan *chan; @@ -542,8 +540,8 @@ generate_smb311signingkey(struct cifs_ses *ses, } int -smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server, - bool allocate_crypto) +smb3_calc_aes_cmac(struct smb_rqst *rqst, struct TCP_Server_Info *server, + bool allocate_crypto) { int rc; unsigned char smb3_signature[SMB2_CMACAES_SIZE]; @@ -625,7 +623,6 @@ smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server, static int smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server) { - int rc = 0; struct smb2_hdr *shdr; struct smb2_sess_setup_req *ssr; bool is_binding; @@ -652,9 +649,7 @@ smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server) return 0; } - rc = server->ops->calc_signature(rqst, server, false); - - return rc; + return server->ops->calc_signature(rqst, server, false); } int @@ -668,6 +663,8 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server) if ((shdr->Command == SMB2_NEGOTIATE) || (shdr->Command == SMB2_SESSION_SETUP) || (shdr->Command == SMB2_OPLOCK_BREAK) || + (shdr->Command == 0xFFFFFFFFFFFFFFFF) || /* MS-SMB2 3.2.5.1.3 */ + (shdr->Status == STATUS_PENDING) || /* MS-SMB2 3.2.5.1.3 */ server->ignore_signature || (!server->session_estab)) return 0; @@ -677,21 +674,17 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server) * server does not send one? BB */ - /* Do not need to verify session setups with signature "BSRSPYL " */ - if (memcmp(shdr->Signature, "BSRSPYL ", 8) == 0) - cifs_dbg(FYI, "dummy signature received for smb command 0x%x\n", - shdr->Command); - /* * Save off the origiginal signature so we can modify the smb and check * our calculated signature against what the server sent. */ memcpy(server_response_sig, shdr->Signature, SMB2_SIGNATURE_SIZE); - memset(shdr->Signature, 0, SMB2_SIGNATURE_SIZE); - + /* + * all implementations of ->calc_signature() will zero shdr->Signature + * before computing it + */ rc = server->ops->calc_signature(rqst, server, true); - if (rc) return rc; @@ -699,8 +692,9 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server) cifs_dbg(VFS, "sign fail cmd 0x%x message id 0x%llx\n", shdr->Command, shdr->MessageId); return -EACCES; - } else - return 0; + } + + return 0; } /* @@ -843,7 +837,23 @@ smb2_setup_request(struct cifs_ses *ses, struct TCP_Server_Info *server, int rc; struct smb2_hdr *shdr = (struct smb2_hdr *)rqst->rq_iov[0].iov_base; + struct smb2_transform_hdr *trhdr = + (struct smb2_transform_hdr *)rqst->rq_iov[0].iov_base; struct mid_q_entry *mid; + bool is_encrypted; + + /* + * Client must not sign the request is encrypted. + * + * Note: we can't rely on SMB2_SESSION_FLAG_ENCRYPT_DATA or + * SMB2_GLOBAL_CAP_ENCRYPTION here because they might be set, but not + * being actively used (e.g. not mounted with "seal"). So we just check + * if the request header is a transform header. + * + * References: + * MS-SMB2 3.2.4.1.1 + */ + is_encrypted = (trhdr->ProtocolId == SMB2_TRANSFORM_PROTO_NUM); smb2_seq_num_into_buf(server, shdr); @@ -853,11 +863,13 @@ smb2_setup_request(struct cifs_ses *ses, struct TCP_Server_Info *server, return ERR_PTR(rc); } - rc = smb2_sign_rqst(rqst, server); - if (rc) { - revert_current_mid_from_hdr(server, shdr); - delete_mid(mid); - return ERR_PTR(rc); + if (!is_encrypted) { + rc = smb2_sign_rqst(rqst, server); + if (rc) { + revert_current_mid_from_hdr(server, shdr); + delete_mid(mid); + return ERR_PTR(rc); + } } return mid; @@ -897,6 +909,35 @@ smb2_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst) return mid; } +int smb311_aes_gmac_alloc(struct crypto_aead **tfm) +{ + int rc = 0; + + if (!tfm) + return -EIO; + + /* + * This is unlikely as we only call this once per TCP session in + * smb311_update_preauth_hash(). If *tfm is already allocated, this + * is probably a bug. + * + * XXX: rc == 0 here, maybe return an error here instead? + */ + if (unlikely(*tfm)) + return rc; + + *tfm = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(*tfm)) { + rc = PTR_ERR(*tfm); + + cifs_dbg(VFS, "%s: Failed to alloc AES-GMAC AEAD, rc=%d\n", + __func__, rc); + *tfm = NULL; + } + + return rc; +} + int smb3_crypto_aead_allocate(struct TCP_Server_Info *server) {