Commit 29e27923 authored by Steve French's avatar Steve French
Browse files

smb3.1.1: add new module load parm enable_gcm_256 



Add new module load parameter enable_gcm_256. If set, then add
AES-256-GCM (strongest encryption type) to the list of encryption
types requested. Put it in the list as the second choice (since
AES-128-GCM is faster and much more broadly supported by
SMB3 servers).  To make this stronger encryption type, GCM-256,
required (the first and only choice, you would use module parameter
"require_gcm_256."

Reviewed-by: default avatarRonnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent fbfd0b46

fs/cifs/cifsfs.c

+4 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ bool enable_oplocks = true; 
bool linuxExtEnabled = true;

bool lookupCacheEnabled = true;

bool disable_legacy_dialects; /* false by default */

bool enable_gcm_256;  /* false by default, change when more servers support it */

bool require_gcm_256; /* false by default */

unsigned int global_secflags = CIFSSEC_DEF;

/* unsigned int ntlmv2_support = 0; */
@@ -105,6 +106,9 @@ MODULE_PARM_DESC(slow_rsp_threshold, "Amount of time (in seconds) to wait " 
module_param(enable_oplocks, bool, 0644);

MODULE_PARM_DESC(enable_oplocks, "Enable or disable oplocks. Default: y/Y/1");



module_param(enable_gcm_256, bool, 0644);

MODULE_PARM_DESC(enable_gcm_256, "Enable requesting strongest (256 bit) GCM encryption. Default: n/N/0");



module_param(require_gcm_256, bool, 0644);

MODULE_PARM_DESC(require_gcm_256, "Require strongest (256 bit) GCM encryption. Default: n/N/0");

fs/cifs/cifsglob.h

+1 −0
Original line number Diff line number Diff line
@@ -1956,6 +1956,7 @@ extern bool lookupCacheEnabled; 
extern unsigned int global_secflags;	/* if on, session setup sent

				with more secure ntlmssp2 challenge/resp */

extern unsigned int sign_CIFS_PDUs;  /* enable smb packet signing */

extern bool enable_gcm_256; /* allow optional negotiate of strongest signing (aes-gcm-256) */

extern bool require_gcm_256; /* require use of strongest signing (aes-gcm-256) */

extern bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/

extern unsigned int CIFSMaxBufSize;  /* max size not including hdr */

fs/cifs/smb2pdu.c

+6 −0
Original line number Diff line number Diff line
@@ -453,6 +453,12 @@ build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt) 
		pneg_ctxt->DataLength = cpu_to_le16(4); /* Cipher Count + 1 cipher */

		pneg_ctxt->CipherCount = cpu_to_le16(1);

		pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES256_GCM;

	} else if (enable_gcm_256) {

		pneg_ctxt->DataLength = cpu_to_le16(8); /* Cipher Count + 3 ciphers */

		pneg_ctxt->CipherCount = cpu_to_le16(3);

		pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES128_GCM;

		pneg_ctxt->Ciphers[1] = SMB2_ENCRYPTION_AES256_GCM;

		pneg_ctxt->Ciphers[2] = SMB2_ENCRYPTION_AES128_CCM;

	} else {

		pneg_ctxt->DataLength = cpu_to_le16(6); /* Cipher Count + 2 ciphers */

		pneg_ctxt->CipherCount = cpu_to_le16(2);

fs/cifs/smb2pdu.h

+3 −2
Original line number Diff line number Diff line
@@ -361,8 +361,9 @@ struct smb2_encryption_neg_context { 
	__le16	ContextType; /* 2 */

	__le16	DataLength;

	__le32	Reserved;

	__le16	CipherCount; /* AES-128-GCM and AES-128-CCM */

	__le16	Ciphers[2];

	/* CipherCount usally 2, but can be 3 when AES256-GCM enabled */

	__le16	CipherCount; /* AES128-GCM and AES128-CCM by default */

	__le16	Ciphers[3];

} __packed;



/* See MS-SMB2 2.2.3.1.3 */

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