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

[Steve French]

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.

Signed-off-by: Steve French <stfrench at microsoft.com>
---
 fs/cifs/cifs_ioctl.h | 19 +++++++++++++++++++
 fs/cifs/ioctl.c      | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/fs/cifs/cifs_ioctl.h b/fs/cifs/cifs_ioctl.h
index f262c64516bc..9f2ed9cccb08 100644
--- a/fs/cifs/cifs_ioctl.h
+++ b/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[SMB3_ENC_DEC_KEY_SIZE];
+ __u8 smb3decryptionkey[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)

 /*
diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index ef41fa878793..e4321e2a27d2 100644
--- a/fs/cifs/ioctl.c
+++ b/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, SMB3_ENC_DEC_KEY_SIZE);
+ memcpy(pfull_key_inf.smb3encryptionkey,
+       tcon->ses->smb3encryptionkey, 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 */

-- 
Thanks,

Steve
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