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Code Issues Releases Wiki Activity

smb3.1.1: allow dumping GCM256 keys to improve debugging of encrypted shares

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Previously we were only able to dump CCM or GCM-128 keys (see "smbinfo keys" e.g.)
to allow network debugging (e.g. wireshark) of mounts to SMB3.1.1 encrypted
shares.  But with the addition of GCM-256 support, we have to be able to dump
32 byte instead of 16 byte keys which requires adding an additional ioctl
for that.

Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Steve French 2021-04-30 17:14:45 -05:00
parent 087f757b01
commit aa22ebc382
2 changed files with 52 additions and 0 deletions
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19
fs/cifs/cifs_ioctl.h
View file

@ -57,6 +57,12 @@ struct smb_query_info {
/* char buffer[]; */
} __packed;
/*
* Dumping the commonly used 16 byte (e.g. CCM and GCM128) keys still supported
* for backlevel compatibility, but is not sufficient for dumping the less
* frequently used GCM256 (32 byte) keys (see the newer "CIFS_DUMP_FULL_KEY"
* ioctl for dumping decryption info for GCM256 mounts)
*/
struct smb3_key_debug_info {
__u64 Suid;
__u16 cipher_type;
@ -65,6 +71,18 @@ struct smb3_key_debug_info {
__u8 smb3decryptionkey[SMB3_SIGN_KEY_SIZE];
} __packed;
/*
* Dump full key (32 byte encrypt/decrypt keys instead of 16 bytes)
* is needed if GCM256 (stronger encryption) negotiated
*/
struct smb3_full_key_debug_info {
__u64 Suid;
__u16 cipher_type;
__u8 auth_key[16]; /* SMB2_NTLMV2_SESSKEY_SIZE */
__u8 smb3encryptionkey[32]; /* SMB3_ENC_DEC_KEY_SIZE */
__u8 smb3decryptionkey[32]; /* SMB3_ENC_DEC_KEY_SIZE */
} __packed;
struct smb3_notify {
__u32 completion_filter;
bool watch_tree;
@ -78,6 +96,7 @@ struct smb3_notify {
#define CIFS_QUERY_INFO _IOWR(CIFS_IOCTL_MAGIC, 7, struct smb_query_info)
#define CIFS_DUMP_KEY _IOWR(CIFS_IOCTL_MAGIC, 8, struct smb3_key_debug_info)
#define CIFS_IOC_NOTIFY _IOW(CIFS_IOCTL_MAGIC, 9, struct smb3_notify)
#define CIFS_DUMP_FULL_KEY _IOWR(CIFS_IOCTL_MAGIC, 10, struct smb3_full_key_debug_info)
#define CIFS_IOC_SHUTDOWN _IOR ('X', 125, __u32)
/*

33
fs/cifs/ioctl.c
View file

@ -218,6 +218,7 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
{
struct inode *inode = file_inode(filep);
struct smb3_key_debug_info pkey_inf;
struct smb3_full_key_debug_info pfull_key_inf;
int rc = -ENOTTY; /* strange error - but the precedent */
unsigned int xid;
struct cifsFileInfo *pSMBFile = filep->private_data;
@ -354,6 +355,38 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
else
rc = 0;
break;
/*
* Dump full key (32 bytes instead of 16 bytes) is
* needed if GCM256 (stronger encryption) negotiated
*/
case CIFS_DUMP_FULL_KEY:
if (pSMBFile == NULL)
break;
if (!capable(CAP_SYS_ADMIN)) {
rc = -EACCES;
break;
}
tcon = tlink_tcon(pSMBFile->tlink);
if (!smb3_encryption_required(tcon)) {
rc = -EOPNOTSUPP;
break;
}
pfull_key_inf.cipher_type =
le16_to_cpu(tcon->ses->server->cipher_type);
pfull_key_inf.Suid = tcon->ses->Suid;
memcpy(pfull_key_inf.auth_key, tcon->ses->auth_key.response,
16 /* SMB2_NTLMV2_SESSKEY_SIZE */);
memcpy(pfull_key_inf.smb3decryptionkey,
tcon->ses->smb3decryptionkey, 32 /* SMB3_ENC_DEC_KEY_SIZE */);
memcpy(pfull_key_inf.smb3encryptionkey,
tcon->ses->smb3encryptionkey, 32 /* SMB3_ENC_DEC_KEY_SIZE */);
if (copy_to_user((void __user *)arg, &pfull_key_inf,
sizeof(struct smb3_full_key_debug_info)))
rc = -EFAULT;
else
rc = 0;
break;
case CIFS_IOC_NOTIFY:
if (!S_ISDIR(inode->i_mode)) {
/* Notify can only be done on directories */