Support for faster packet signing (using GMAC instead of CMAC) can now be negotiated to some newer servers, including Windows. See MS-SMB2 section 2.2.3.17. This patch adds support for sending the new negotiate context with the first of three supported signing algorithms (AES-CMAC) and decoding the response. A followon patch will add support for sending the other two (including AES-GMAC, which is fastest) and changing the signing algorithm used based on what was negotiated. To allow the client to request GMAC signing set module parameter "enable_negotiate_signing" to 1. Reviewed-by: Ronnie Sahlberg Signed-off-by: Steve French --- fs/cifs/cifsfs.c | 4 +++ fs/cifs/cifsglob.h | 3 ++ fs/cifs/smb2pdu.c | 83 ++++++++++++++++++++++++++++++++++++++++------ fs/cifs/smb2pdu.h | 5 ++- 4 files changed, 84 insertions(+), 11 deletions(-) diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 9fb874dd8d24..476b07213fcd 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -65,6 +65,7 @@ bool lookupCacheEnabled = true; bool disable_legacy_dialects; /* false by default */ bool enable_gcm_256 = true; bool require_gcm_256; /* false by default */ +bool enable_negotiate_signing; /* false by default */ unsigned int global_secflags = CIFSSEC_DEF; /* unsigned int ntlmv2_support = 0; */ unsigned int sign_CIFS_PDUs = 1; @@ -104,6 +105,9 @@ MODULE_PARM_DESC(enable_gcm_256, "Enable requesting strongest (256 bit) GCM encr module_param(require_gcm_256, bool, 0644); MODULE_PARM_DESC(require_gcm_256, "Require strongest (256 bit) GCM encryption. Default: n/N/0"); +module_param(enable_negotiate_signing, bool, 0644); +MODULE_PARM_DESC(enable_GMAC_signing, "Enable requesting faster (GMAC) packet signing. Default: n/N/0"); + module_param(disable_legacy_dialects, bool, 0644); MODULE_PARM_DESC(disable_legacy_dialects, "To improve security it may be " "helpful to restrict the ability to " diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 921680fb7931..3c2e117bb926 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -667,9 +667,11 @@ struct TCP_Server_Info { unsigned int max_write; unsigned int min_offload; __le16 compress_algorithm; + __u16 signing_algorithm; __le16 cipher_type; /* save initital negprot hash */ __u8 preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE]; + bool signing_negotiated; /* true if valid signing context rcvd from server */ bool posix_ext_supported; struct delayed_work reconnect; /* reconnect workqueue job */ struct mutex reconnect_mutex; /* prevent simultaneous reconnects */ @@ -1869,6 +1871,7 @@ extern unsigned int global_secflags; /* if on, session setup sent 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 enable_negotiate_signing; /* request use of faster (GMAC) signing if available */ extern bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/ extern unsigned int CIFSMaxBufSize; /* max size not including hdr */ extern unsigned int cifs_min_rcv; /* min size of big ntwrk buf pool */ diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index 962826dc3316..757f145e70e5 100644 --- a/fs/cifs/smb2pdu.c +++ b/fs/cifs/smb2pdu.c @@ -433,6 +433,23 @@ build_compression_ctxt(struct smb2_compression_capabilities_context *pneg_ctxt) pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1; } +static void +build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt) +{ + pneg_ctxt->ContextType = SMB2_SIGNING_CAPABILITIES; + /* + * Data length must be increased here if more than 3 signing algorithms + * sent but currently only 3 are defined. And context Data length must + * be rounded to multiple of 8 for some servers. + */ + pneg_ctxt->DataLength = + cpu_to_le16(DIV_ROUND_UP(sizeof(struct smb2_signing_capabilities) - + sizeof(struct smb2_neg_context), 8) * 8); + pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(1); + pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC); + /* TBD add SIGNING_ALG_AES_GMAC and/or SIGNING_ALG_HMAC_SHA256 */ +} + static void build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt) { @@ -498,7 +515,7 @@ assemble_neg_contexts(struct smb2_negotiate_req *req, struct TCP_Server_Info *server, unsigned int *total_len) { char *pneg_ctxt; - unsigned int ctxt_len; + unsigned int ctxt_len, neg_context_count; if (*total_len > 200) { /* In case length corrupted don't want to overrun smb buffer */ @@ -525,6 +542,17 @@ assemble_neg_contexts(struct smb2_negotiate_req *req, *total_len += ctxt_len; pneg_ctxt += ctxt_len; + ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt, + server->hostname); + *total_len += ctxt_len; + pneg_ctxt += ctxt_len; + + build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt); + *total_len += sizeof(struct smb2_posix_neg_context); + pneg_ctxt += sizeof(struct smb2_posix_neg_context); + + neg_context_count = 4; + if (server->compress_algorithm) { build_compression_ctxt((struct smb2_compression_capabilities_context *) pneg_ctxt); @@ -533,17 +561,24 @@ assemble_neg_contexts(struct smb2_negotiate_req *req, 8) * 8; *total_len += ctxt_len; pneg_ctxt += ctxt_len; - req->NegotiateContextCount = cpu_to_le16(5); - } else - req->NegotiateContextCount = cpu_to_le16(4); + neg_context_count++; + } - ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt, - server->hostname); - *total_len += ctxt_len; - pneg_ctxt += ctxt_len; + if (enable_negotiate_signing) { + pr_warn_once("requesting GMAC signing is experimental\n"); + build_signing_ctxt((struct smb2_signing_capabilities *) + pneg_ctxt); + ctxt_len = DIV_ROUND_UP( + sizeof(struct smb2_signing_capabilities), + 8) * 8; + *total_len += ctxt_len; + pneg_ctxt += ctxt_len; + neg_context_count++; + } + + /* check for and add transport_capabilities and signing capabilities */ + req->NegotiateContextCount = cpu_to_le16(neg_context_count); - build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt); - *total_len += sizeof(struct smb2_posix_neg_context); } static void decode_preauth_context(struct smb2_preauth_neg_context *ctxt) @@ -632,6 +667,31 @@ static int decode_encrypt_ctx(struct TCP_Server_Info *server, return 0; } +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"); + return; + } + if (le16_to_cpu(pctxt->SigningAlgorithmCount) != 1) { + pr_warn_once("Invalid signing algorithm count\n"); + return; + } + if (le16_to_cpu(pctxt->SigningAlgorithms[0]) > 2) { + pr_warn_once("unknown signing algorithm\n"); + 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); +} + + static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp, struct TCP_Server_Info *server, unsigned int len_of_smb) @@ -675,6 +735,9 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp, (struct smb2_compression_capabilities_context *)pctx); else if (pctx->ContextType == SMB2_POSIX_EXTENSIONS_AVAILABLE) server->posix_ext_supported = true; + else if (pctx->ContextType == SMB2_SIGNING_CAPABILITIES) + decode_signing_ctx(server, + (struct smb2_signing_capabilities *)pctx); else cifs_server_dbg(VFS, "unknown negcontext of type %d ignored\n", le16_to_cpu(pctx->ContextType)); diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h index ba75e65924ac..4b27cb9105fd 100644 --- a/fs/cifs/smb2pdu.h +++ b/fs/cifs/smb2pdu.h @@ -329,7 +329,7 @@ struct smb2_neg_context { __le16 ContextType; __le16 DataLength; __le32 Reserved; - /* Followed by array of data */ + /* Followed by array of data. NOTE: some servers require padding to 8 byte boundary */ } __packed; #define SMB311_LINUX_CLIENT_SALT_SIZE 32 @@ -394,6 +394,7 @@ struct smb2_compression_capabilities_context { __u16 Padding; __u32 Flags; __le16 CompressionAlgorithms[3]; + /* Check if pad needed */ } __packed; /* @@ -420,6 +421,7 @@ struct smb2_transport_capabilities_context { __le16 DataLength; __u32 Reserved; __le32 Flags; + __u32 Pad; } __packed; /* @@ -458,6 +460,7 @@ struct smb2_signing_capabilities { __u32 Reserved; __le16 SigningAlgorithmCount; __le16 SigningAlgorithms[]; + /* Followed by padding to 8 byte boundary (required by some servers) */ } __packed; #define POSIX_CTXT_DATA_LEN 16 -- Thanks, Steve