From: Paulo Alcantara <pc@cjr.nz>

Date: Tue, 7 Dec 2021 22:51:04 -0300

Subject: [PATCH] cifs: fix ntlmssp auth when there is no key exchange

Git-commit: 9de0737d5ba0425c3154d5d83da12a8fa8595c0f

References: bsc#1193629

Patch-mainline: v5.16-rc5

Warn on the lack of key exchange during NTLMSSP authentication rather

than aborting it as there are some servers that do not set it in

CHALLENGE message.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>

Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>

Signed-off-by: Steve French <stfrench@microsoft.com>

Acked-by: Enzo Matsumiya <ematsumiya@suse.de>

---

 fs/cifs/sess.c | 54 +++++++++++++++++++++++++++++++++-----------------

 1 file changed, 36 insertions(+), 18 deletions(-)

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c

index af63548eaf26..035dc3e245dc 100644

--- a/fs/cifs/sess.c

+++ b/fs/cifs/sess.c

@@ -590,8 +590,8 @@ int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,

 {

 	unsigned int tioffset; /* challenge message target info area */

 	unsigned int tilen; /* challenge message target info area length  */

-

 	CHALLENGE_MESSAGE *pblob = (CHALLENGE_MESSAGE *)bcc_ptr;

+	__u32 server_flags;

 	if (blob_len < sizeof(CHALLENGE_MESSAGE)) {

 		cifs_dbg(VFS, "challenge blob len %d too small\n", blob_len);

@@ -609,12 +609,37 @@ int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,

 		return -EINVAL;

 	}

+	server_flags = le32_to_cpu(pblob->NegotiateFlags);

+	cifs_dbg(FYI, "%s: negotiate=0x%08x challenge=0x%08x\n", __func__,

+		 ses->ntlmssp->client_flags, server_flags);

+

+	if ((ses->ntlmssp->client_flags & (NTLMSSP_NEGOTIATE_SEAL | NTLMSSP_NEGOTIATE_SIGN)) &&

+	    (!(server_flags & NTLMSSP_NEGOTIATE_56) && !(server_flags & NTLMSSP_NEGOTIATE_128))) {

+		cifs_dbg(VFS, "%s: requested signing/encryption but server did not return either 56-bit or 128-bit session key size\n",

+			 __func__);

+		return -EINVAL;

+	}

+	if (!(server_flags & NTLMSSP_NEGOTIATE_NTLM) && !(server_flags & NTLMSSP_NEGOTIATE_EXTENDED_SEC)) {

+		cifs_dbg(VFS, "%s: server does not seem to support either NTLMv1 or NTLMv2\n", __func__);

+		return -EINVAL;

+	}

+	if (ses->server->sign && !(server_flags & NTLMSSP_NEGOTIATE_SIGN)) {

+		cifs_dbg(VFS, "%s: forced packet signing but server does not seem to support it\n",

+			 __func__);

+		return -EOPNOTSUPP;

+	}

+	if ((ses->ntlmssp->client_flags & NTLMSSP_NEGOTIATE_KEY_XCH) &&

+	    !(server_flags & NTLMSSP_NEGOTIATE_KEY_XCH))

+		pr_warn_once("%s: authentication has been weakened as server does not support key exchange\n",

+			     __func__);

+

+	ses->ntlmssp->server_flags = server_flags;

+

 	memcpy(ses->ntlmssp->cryptkey, pblob->Challenge, CIFS_CRYPTO_KEY_SIZE);

-	/* BB we could decode pblob->NegotiateFlags; some may be useful */

 	/* In particular we can examine sign flags */

 	/* BB spec says that if AvId field of MsvAvTimestamp is populated then

 		we must set the MIC field of the AUTHENTICATE_MESSAGE */

-	ses->ntlmssp->server_flags = le32_to_cpu(pblob->NegotiateFlags);

+

 	tioffset = le32_to_cpu(pblob->TargetInfoArray.BufferOffset);

 	tilen = le16_to_cpu(pblob->TargetInfoArray.Length);

 	if (tioffset > blob_len || tioffset + tilen > blob_len) {

@@ -721,13 +746,13 @@ int build_ntlmssp_negotiate_blob(unsigned char **pbuffer,

 	flags = NTLMSSP_NEGOTIATE_56 |	NTLMSSP_REQUEST_TARGET |

 		NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |

 		NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC |

-		NTLMSSP_NEGOTIATE_SEAL;

-	if (server->sign)

-		flags |= NTLMSSP_NEGOTIATE_SIGN;

+		NTLMSSP_NEGOTIATE_ALWAYS_SIGN | NTLMSSP_NEGOTIATE_SEAL |

+		NTLMSSP_NEGOTIATE_SIGN;

 	if (!server->session_estab || ses->ntlmssp->sesskey_per_smbsess)

 		flags |= NTLMSSP_NEGOTIATE_KEY_XCH;

 	tmp = *pbuffer + sizeof(NEGOTIATE_MESSAGE);

+	ses->ntlmssp->client_flags = flags;

 	sec_blob->NegotiateFlags = cpu_to_le32(flags);

 	/* these fields should be null in negotiate phase MS-NLMP 3.1.5.1.1 */

@@ -779,15 +804,8 @@ int build_ntlmssp_auth_blob(unsigned char **pbuffer,

 	memcpy(sec_blob->Signature, NTLMSSP_SIGNATURE, 8);

 	sec_blob->MessageType = NtLmAuthenticate;

-	flags = NTLMSSP_NEGOTIATE_56 |

-		NTLMSSP_REQUEST_TARGET | NTLMSSP_NEGOTIATE_TARGET_INFO |

-		NTLMSSP_NEGOTIATE_128 | NTLMSSP_NEGOTIATE_UNICODE |

-		NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_NEGOTIATE_EXTENDED_SEC |

-		NTLMSSP_NEGOTIATE_SEAL | NTLMSSP_NEGOTIATE_WORKSTATION_SUPPLIED;

-	if (ses->server->sign)

-		flags |= NTLMSSP_NEGOTIATE_SIGN;

-	if (!ses->server->session_estab || ses->ntlmssp->sesskey_per_smbsess)

-		flags |= NTLMSSP_NEGOTIATE_KEY_XCH;

+	flags = ses->ntlmssp->server_flags | NTLMSSP_REQUEST_TARGET |

+		NTLMSSP_NEGOTIATE_TARGET_INFO | NTLMSSP_NEGOTIATE_WORKSTATION_SUPPLIED;

 	tmp = *pbuffer + sizeof(AUTHENTICATE_MESSAGE);

 	sec_blob->NegotiateFlags = cpu_to_le32(flags);

@@ -834,9 +852,9 @@ int build_ntlmssp_auth_blob(unsigned char **pbuffer,

 				      *pbuffer, &tmp,

 				      nls_cp);

-	if (((ses->ntlmssp->server_flags & NTLMSSP_NEGOTIATE_KEY_XCH) ||

-		(ses->ntlmssp->server_flags & NTLMSSP_NEGOTIATE_EXTENDED_SEC))

-			&& !calc_seckey(ses)) {

+	if ((ses->ntlmssp->server_flags & NTLMSSP_NEGOTIATE_KEY_XCH) &&

+	    (!ses->server->session_estab || ses->ntlmssp->sesskey_per_smbsess) &&

+	    !calc_seckey(ses)) {

 		memcpy(tmp, ses->ntlmssp->ciphertext, CIFS_CPHTXT_SIZE);

 		sec_blob->SessionKey.BufferOffset = cpu_to_le32(tmp - *pbuffer);

 		sec_blob->SessionKey.Length = cpu_to_le16(CIFS_CPHTXT_SIZE);

-- 

2.34.1