[SMB3] dump encryption keys to allow wireshark debugging of encrypted
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Message ID CAH2r5mvcRuSihH58GgrzXTAHuXnQ9a0N-d8AkLLOigQrqincKg@mail.gmail.com
State New
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  • [SMB3] dump encryption keys to allow wireshark debugging of encrypted
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Commit Message

Steve French Sept. 20, 2019, 7:07 a.m. UTC
kernel patch updated to check if encryption is enabled

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

Comments

Steve French Sept. 20, 2019, 7:20 a.m. UTC | #1
And updated patch for cifs-utils ("smbinfo keys <filename>")


On Fri, Sep 20, 2019 at 2:07 AM Steve French <smfrench@gmail.com> wrote:
>
> kernel patch updated to check if encryption is enabled
>
> 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
>
>
> --
> Thanks,
>
> Steve
Pavel Shilovsky Sept. 20, 2019, 5:14 p.m. UTC | #2
Thanks, this is very useful functionality! A couple comments below.

kernel patch:

+ cifs_dbg(VFS, "ioctl dumpkey\n"); /* BB REMOVEME */

please remove this or change to FYI.

user space patch:

+ if (keys_info.cipher_type == 1)
+ printf("CCM encryption");
+ else if (keys_info.cipher_type == 2)
+ printf("GCM encryption");
+ else if (keys_info.cipher_type == 0)
+ printf("SMB3.0 encryption");
^^^
SMB3.0 encryption is CCM, so, let's not confuse users and print "CCM
encryption" for both cipher_type values of 0 and 1.


Best regards,
Pavel Shilovskiy

пт, 20 сент. 2019 г. в 00:20, Steve French via samba-technical
<samba-technical@lists.samba.org>:
>
> And updated patch for cifs-utils ("smbinfo keys <filename>")
>
>
> On Fri, Sep 20, 2019 at 2:07 AM Steve French <smfrench@gmail.com> wrote:
> >
> > kernel patch updated to check if encryption is enabled
> >
> > 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
> >
> >
> > --
> > Thanks,
> >
> > Steve
>
>
>
> --
> Thanks,
>
> Steve
Steve French Sept. 21, 2019, 11:04 a.m. UTC | #3
On Fri, Sep 20, 2019 at 12:14 PM Pavel Shilovsky
<pavel.shilovsky@gmail.com> wrote:
>
> Thanks, this is very useful functionality! A couple comments below.
>
> kernel patch:
>
> + cifs_dbg(VFS, "ioctl dumpkey\n"); /* BB REMOVEME */
>
> please remove this or change to FYI.

Good catch - removed and repushed

Patch
diff mbox series

From 3cee2eec9c2849bf1148b5d51b5e7147e97b0b55 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 19 Sep 2019 04:00:55 -0500
Subject: [PATCH] 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>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifs_ioctl.h |  9 +++++++++
 fs/cifs/ioctl.c      | 29 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/fs/cifs/cifs_ioctl.h b/fs/cifs/cifs_ioctl.h
index 6c3bd07868d7..0f0dc1c1fe41 100644
--- a/fs/cifs/cifs_ioctl.h
+++ b/fs/cifs/cifs_ioctl.h
@@ -57,9 +57,18 @@  struct smb_query_info {
 	/* char buffer[]; */
 } __packed;
 
+struct smb3_key_debug_info {
+	__u64	Suid;
+	__u16	cipher_type;
+	__u8	auth_key[16]; /* SMB2_NTLMV2_SESSKEY_SIZE */
+	__u8	smb3encryptionkey[SMB3_SIGN_KEY_SIZE];
+	__u8	smb3decryptionkey[SMB3_SIGN_KEY_SIZE];
+} __packed;
+
 #define CIFS_IOCTL_MAGIC	0xCF
 #define CIFS_IOC_COPYCHUNK_FILE	_IOW(CIFS_IOCTL_MAGIC, 3, int)
 #define CIFS_IOC_SET_INTEGRITY  _IO(CIFS_IOCTL_MAGIC, 4)
 #define CIFS_IOC_GET_MNT_INFO _IOR(CIFS_IOCTL_MAGIC, 5, struct smb_mnt_fs_info)
 #define CIFS_ENUMERATE_SNAPSHOTS _IOR(CIFS_IOCTL_MAGIC, 6, struct smb_snapshot_array)
 #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)
diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 76ddd98b6298..48c23929350c 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:
+			cifs_dbg(VFS, "ioctl dumpkey\n"); /* BB REMOVEME */
+			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;
-- 
2.20.1