[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>

1 files changed, 146 insertions, 2 deletions

diff --git a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c
index c802ecfa770e..87563ee58d30 100644
--- a/fs/cifs/smb2transport.c
+++ b/fs/cifs/smb2transport.c
@@ -117,10 +117,154 @@ smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 }
 
 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 */