[CIFS] SMB3 Signing enablement

SMB3 uses a much faster method of signing (which is also better in other ways),
AES-CMAC.  With the kernel now supporting AES-CMAC since last release, we
are overdue to allow SMB3 signing (today only CIFS and SMB2 and SMB2.1,
but not SMB3 and SMB3.1 can sign) - and we need this also for checking
secure negotation and also per-share encryption (two other new SMB3 features
which we need to implement).

This patch needs some work in a few areas - for example we need to
move signing for SMB2/SMB3 from per-socket to per-user (we may be able to
use the "nosharesock" mount option in the interim for the multiuser case),
and Shirish found a bug in the earlier authentication overhaul
(setting signing flags properly) - but those can be done in followon
patches.

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/Kconfig

@@ -10,6 +10,7 @@ config CIFS
 	select CRYPTO_ECB
 	select CRYPTO_DES
 	select CRYPTO_SHA256
+	select CRYPTO_CMAC
 	help
 	  This is the client VFS module for the Common Internet File System
 	  (CIFS) protocol which is the successor to the Server Message Block

fs/cifs/cifsencrypt.c

@@ -705,6 +705,9 @@ calc_seckey(struct cifs_ses *ses)
 void
 cifs_crypto_shash_release(struct TCP_Server_Info *server)
 {
+	if (server->secmech.cmacaes)
+		crypto_free_shash(server->secmech.cmacaes);
+
 	if (server->secmech.hmacsha256)
 		crypto_free_shash(server->secmech.hmacsha256);
 
@@ -714,6 +717,8 @@ cifs_crypto_shash_release(struct TCP_Server_Info *server)
 	if (server->secmech.hmacmd5)
 		crypto_free_shash(server->secmech.hmacmd5);
 
+	kfree(server->secmech.sdesccmacaes);
+
 	kfree(server->secmech.sdeschmacsha256);
 
 	kfree(server->secmech.sdeschmacmd5);
@@ -747,6 +752,13 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
 		goto crypto_allocate_hmacsha256_fail;
 	}
 
+	server->secmech.cmacaes = crypto_alloc_shash("cmac(aes)", 0, 0);
+	if (IS_ERR(server->secmech.cmacaes)) {
+		cifs_dbg(VFS, "could not allocate crypto cmac-aes");
+		rc = PTR_ERR(server->secmech.cmacaes);
+		goto crypto_allocate_cmacaes_fail;
+	}
+
 	size = sizeof(struct shash_desc) +
 			crypto_shash_descsize(server->secmech.hmacmd5);
 	server->secmech.sdeschmacmd5 = kmalloc(size, GFP_KERNEL);
@@ -777,8 +789,22 @@ cifs_crypto_shash_allocate(struct TCP_Server_Info *server)
 	server->secmech.sdeschmacsha256->shash.tfm = server->secmech.hmacsha256;
 	server->secmech.sdeschmacsha256->shash.flags = 0x0;
 
+	size = sizeof(struct shash_desc) +
+			crypto_shash_descsize(server->secmech.cmacaes);
+	server->secmech.sdesccmacaes = kmalloc(size, GFP_KERNEL);
+	if (!server->secmech.sdesccmacaes) {
+		cifs_dbg(VFS, "%s: Can't alloc cmacaes\n", __func__);
+		rc = -ENOMEM;
+		goto crypto_allocate_cmacaes_sdesc_fail;
+	}
+	server->secmech.sdesccmacaes->shash.tfm = server->secmech.cmacaes;
+	server->secmech.sdesccmacaes->shash.flags = 0x0;
+
 	return 0;
 
+crypto_allocate_cmacaes_sdesc_fail:
+	kfree(server->secmech.sdeschmacsha256);
+
 crypto_allocate_hmacsha256_sdesc_fail:
 	kfree(server->secmech.sdescmd5);
 
@@ -786,6 +812,9 @@ crypto_allocate_md5_sdesc_fail:
 	kfree(server->secmech.sdeschmacmd5);
 
 crypto_allocate_hmacmd5_sdesc_fail:
+	crypto_free_shash(server->secmech.cmacaes);
+
+crypto_allocate_cmacaes_fail:
 	crypto_free_shash(server->secmech.hmacsha256);
 
 crypto_allocate_hmacsha256_fail:

fs/cifs/cifsglob.h

@@ -125,9 +125,11 @@ struct cifs_secmech {
 	struct crypto_shash *hmacmd5; /* hmac-md5 hash function */
 	struct crypto_shash *md5; /* md5 hash function */
 	struct crypto_shash *hmacsha256; /* hmac-sha256 hash function */
+	struct crypto_shash *cmacaes; /* block-cipher based MAC function */
 	struct sdesc *sdeschmacmd5;  /* ctxt to generate ntlmv2 hash, CR1 */
 	struct sdesc *sdescmd5; /* ctxt to generate cifs/smb signature */
 	struct sdesc *sdeschmacsha256;  /* ctxt to generate smb2 signature */
+	struct sdesc *sdesccmacaes;  /* ctxt to generate smb3 signature */
 };
 
 /* per smb session structure/fields */
@@ -538,6 +540,7 @@ struct TCP_Server_Info {
 	int timeAdj;  /* Adjust for difference in server time zone in sec */
 	__u64 CurrentMid;         /* multiplex id - rotating counter */
 	char cryptkey[CIFS_CRYPTO_KEY_SIZE]; /* used by ntlm, ntlmv2 etc */
+	char smb3signingkey[SMB3_SIGN_KEY_SIZE]; /* for signing smb3 packets */
 	/* 16th byte of RFC1001 workstation name is always null */
 	char workstation_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
 	__u32 sequence_number; /* for signing, protected by srv_mutex */

fs/cifs/cifspdu.h

@@ -142,6 +142,11 @@
  */
 #define CIFS_SESS_KEY_SIZE (16)
 
+/*
+ * Size of the smb3 signing key
+ */
+#define SMB3_SIGN_KEY_SIZE (16)
+
 #define CIFS_CLIENT_CHALLENGE_SIZE (8)
 #define CIFS_SERVER_CHALLENGE_SIZE (8)
 #define CIFS_HMAC_MD5_HASH_SIZE (16)

fs/cifs/cifsproto.h

@@ -436,6 +436,7 @@ extern int setup_ntlmv2_rsp(struct cifs_ses *, const struct nls_table *);
 extern int cifs_crypto_shash_allocate(struct TCP_Server_Info *);
 extern void cifs_crypto_shash_release(struct TCP_Server_Info *);
 extern int calc_seckey(struct cifs_ses *);
+extern int generate_smb3signingkey(struct TCP_Server_Info *);
 
 #ifdef CONFIG_CIFS_WEAK_PW_HASH
 extern int calc_lanman_hash(const char *password, const char *cryptkey,

fs/cifs/connect.c

@@ -3841,6 +3841,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 			server->sequence_number = 0x2;
 			server->session_estab = true;
 			ses->auth_key.response = NULL;
+			generate_smb3signingkey(server);
 		}
 		mutex_unlock(&server->srv_mutex);
 

fs/cifs/smb2glob.h

@@ -54,5 +54,7 @@
 #define SMB2_SIGNATURE_SIZE (16)
 #define SMB2_NTLMV2_SESSKEY_SIZE (16)
 #define SMB2_HMACSHA256_SIZE (32)
+#define SMB2_CMACAES_SIZE (16)
+#define SMB3_SIGNKEY_SIZE (16)
 
 #endif	/* _SMB2_GLOB_H */

fs/cifs/smb2transport.c

@@ -116,11 +116,155 @@ smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 	return rc;
 }
 
+int
+generate_smb3signingkey(struct TCP_Server_Info *server)
+{
+	unsigned char zero = 0x0;
+	__u8 i[4] = {0, 0, 0, 1};
+	__u8 L[4] = {0, 0, 0, 128};
+	int rc = 0;
+	unsigned char prfhash[SMB2_HMACSHA256_SIZE];
+	unsigned char *hashptr = prfhash;
+
+	memset(prfhash, 0x0, SMB2_HMACSHA256_SIZE);
+	memset(server->smb3signingkey, 0x0, SMB3_SIGNKEY_SIZE);
+
+	rc = crypto_shash_setkey(server->secmech.hmacsha256,
+		server->session_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not set with session key\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_init(&server->secmech.sdeschmacsha256->shash);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not init sign hmac\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+				i, 4);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update with n\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+				"SMB2AESCMAC", 12);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update with label\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+				&zero, 1);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update with zero\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+				"SmbSign", 8);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update with context\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_update(&server->secmech.sdeschmacsha256->shash,
+				L, 4);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update with L\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	rc = crypto_shash_final(&server->secmech.sdeschmacsha256->shash,
+				hashptr);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not generate sha256 hash\n", __func__);
+		goto smb3signkey_ret;
+	}
+
+	memcpy(server->smb3signingkey, hashptr, SMB3_SIGNKEY_SIZE);
+
+smb3signkey_ret:
+	return rc;
+}
+
 int
 smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
-	cifs_dbg(FYI, "smb3 signatures not supported yet\n");
-	return -EOPNOTSUPP;
+	int i, rc;
+	unsigned char smb3_signature[SMB2_CMACAES_SIZE];
+	unsigned char *sigptr = smb3_signature;
+	struct kvec *iov = rqst->rq_iov;
+	int n_vec = rqst->rq_nvec;
+	struct smb2_hdr *smb2_pdu = (struct smb2_hdr *)iov[0].iov_base;
+
+	memset(smb3_signature, 0x0, SMB2_CMACAES_SIZE);
+	memset(smb2_pdu->Signature, 0x0, SMB2_SIGNATURE_SIZE);
+
+	rc = crypto_shash_setkey(server->secmech.cmacaes,
+		server->smb3signingkey, SMB2_CMACAES_SIZE);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not set key for cmac aes\n", __func__);
+		return rc;
+	}
+
+	rc = crypto_shash_init(&server->secmech.sdesccmacaes->shash);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not init cmac aes\n", __func__);
+		return rc;
+	}
+
+	for (i = 0; i < n_vec; i++) {
+		if (iov[i].iov_len == 0)
+			continue;
+		if (iov[i].iov_base == NULL) {
+			cifs_dbg(VFS, "null iovec entry");
+			return -EIO;
+		}
+		/*
+		 * The first entry includes a length field (which does not get
+		 * signed that occupies the first 4 bytes before the header).
+		 */
+		if (i == 0) {
+			if (iov[0].iov_len <= 8) /* cmd field at offset 9 */
+				break; /* nothing to sign or corrupt header */
+			rc =
+			crypto_shash_update(
+				&server->secmech.sdesccmacaes->shash,
+				iov[i].iov_base + 4, iov[i].iov_len - 4);
+		} else {
+			rc =
+			crypto_shash_update(
+				&server->secmech.sdesccmacaes->shash,
+				iov[i].iov_base, iov[i].iov_len);
+		}
+		if (rc) {
+			cifs_dbg(VFS, "%s: Couldn't update cmac aes with payload\n",
+							__func__);
+			return rc;
+		}
+	}
+
+	/* now hash over the rq_pages array */
+	for (i = 0; i < rqst->rq_npages; i++) {
+		struct kvec p_iov;
+
+		cifs_rqst_page_to_kvec(rqst, i, &p_iov);
+		crypto_shash_update(&server->secmech.sdesccmacaes->shash,
+					p_iov.iov_base, p_iov.iov_len);
+		kunmap(rqst->rq_pages[i]);
+	}
+
+	rc = crypto_shash_final(&server->secmech.sdesccmacaes->shash,
+						sigptr);
+	if (rc)
+		cifs_dbg(VFS, "%s: Could not generate cmac aes\n", __func__);
+
+	memcpy(smb2_pdu->Signature, sigptr, SMB2_SIGNATURE_SIZE);
+
+	return rc;
 }
 
 /* must be called with server->srv_mutex held */