smb3: allow decryption keys to be dumped by admin for debugging

In order to debug certain problems it is important to be able
to decrypt network traces (e.g. wireshark) but to do this we
need to be able to dump out the encryption/decryption keys.
Dumping them to an ioctl is safer than dumping then to dmesg,
(and better than showing all keys in a pseudofile).

Restrict this to root (CAP_SYS_ADMIN), and only for a mount
that this admin has access to.

Sample smbinfo output:
SMB3.0 encryption
Session Id:   0x82d2ec52
Session Key:  a5 6d 81 d0 e c1 ca e1 d8 13 aa 20 e8 f2 cc 71
Server Encryption Key:  1a c3 be ba 3d fc dc 3c e bc 93 9e 50 9e 19 c1
Server Decryption Key:  e0 d4 d9 43 1b a2 1b e3 d8 76 77 49 56 f7 20 88

Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 76ddd98b6298..1a01e108d75e 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -164,6 +164,7 @@ static long smb_mnt_get_fsinfo(unsigned int xid, struct cifs_tcon *tcon,
 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;
 	int rc = -ENOTTY; /* strange error - but the precedent */
 	unsigned int xid;
 	struct cifsFileInfo *pSMBFile = filep->private_data;
@@ -270,6 +271,34 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 			else
 				rc = -EOPNOTSUPP;
 			break;
+		case CIFS_DUMP_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;
+			}
+			pkey_inf.cipher_type =
+				le16_to_cpu(tcon->ses->server->cipher_type);
+			pkey_inf.Suid = tcon->ses->Suid;
+			memcpy(pkey_inf.auth_key, tcon->ses->auth_key.response,
+					16 /* SMB2_NTLMV2_SESSKEY_SIZE */);
+			memcpy(pkey_inf.smb3decryptionkey,
+			      tcon->ses->smb3decryptionkey, SMB3_SIGN_KEY_SIZE);
+			memcpy(pkey_inf.smb3encryptionkey,
+			      tcon->ses->smb3encryptionkey, SMB3_SIGN_KEY_SIZE);
+			if (copy_to_user((void __user *)arg, &pkey_inf,
+					sizeof(struct smb3_key_debug_info)))
+				rc = -EFAULT;
+			else
+				rc = 0;
+			break;
 		default:
 			cifs_dbg(FYI, "unsupported ioctl\n");
 			break;