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

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>

fs/cifs/cifs_ioctl.h

@@ -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)
 
 /*

fs/cifs/ioctl.c

@@ -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 */