Re: [PATCH v2 7/8] xfs_io/encrypt: add 'rm_enckey' command

[Eric Sandeen <sandeen@sandeen.net>]

On 9/19/19 7:18 PM, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a 'rm_enckey' command to xfs_io, to provide a command-line interface
> to the FS_IOC_REMOVE_ENCRYPTION_KEY and
> FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS ioctls.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  io/encrypt.c      | 75 +++++++++++++++++++++++++++++++++++++++++++++++
>  man/man8/xfs_io.8 | 15 ++++++++++
>  2 files changed, 90 insertions(+)
> 
> diff --git a/io/encrypt.c b/io/encrypt.c
> index d38ac595..7531c4ad 100644
> --- a/io/encrypt.c
> +++ b/io/encrypt.c
> @@ -139,6 +139,7 @@ struct fscrypt_get_key_status_arg {
>  static cmdinfo_t get_encpolicy_cmd;
>  static cmdinfo_t set_encpolicy_cmd;
>  static cmdinfo_t add_enckey_cmd;
> +static cmdinfo_t rm_enckey_cmd;
>  
>  static void
>  get_encpolicy_help(void)
> @@ -200,6 +201,21 @@ add_enckey_help(void)
>  "\n"));
>  }
>  
> +static void
> +rm_enckey_help(void)
> +{
> +	printf(_(
> +"\n"
> +" remove an encryption key from the filesystem\n"
> +"\n"
> +" Examples:\n"
> +" 'rm_enckey 0000111122223333' - remove key for v1 policies w/ given descriptor\n"
> +" 'rm_enckey 00001111222233334444555566667777' - remove key for v2 policies w/ given identifier\n"
> +"\n"
> +" -a -- remove key for all users who have added it (privileged operation)\n"
> +"\n"));
> +}
> +
>  static const struct {
>  	__u8 mode;
>  	const char *name;
> @@ -693,6 +709,54 @@ out:
>  	return 0;
>  }
>  
> +static int
> +rm_enckey_f(int argc, char **argv)
> +{
> +	int c;
> +	struct fscrypt_remove_key_arg arg;
> +	int ioc = FS_IOC_REMOVE_ENCRYPTION_KEY;
> +
> +	memset(&arg, 0, sizeof(arg));
> +
> +	while ((c = getopt(argc, argv, "a")) != EOF) {
> +		switch (c) {
> +		case 'a':
> +			ioc = FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS;
> +			break;
> +		default:
> +			return command_usage(&rm_enckey_cmd);
> +		}
> +	}
> +	argc -= optind;
> +	argv += optind;
> +
> +	if (argc != 1)
> +		return command_usage(&rm_enckey_cmd);
> +
> +	if (str2keyspec(argv[0], -1, &arg.key_spec) < 0)
> +		return 0;
> +
> +	if (ioctl(file->fd, ioc, &arg) != 0) {
> +		fprintf(stderr, "Error removing encryption key: %s\n",
> +			strerror(errno));
> +		exitcode = 1;
> +		return 0;
> +	}
> +	if (arg.removal_status_flags &
> +	    FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS) {
> +		printf("Removed user's claim to encryption key with %s %s\n",
> +		       keyspectype(&arg.key_spec), keyspec2str(&arg.key_spec));
> +	} else if (arg.removal_status_flags &
> +		   FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY) {
> +		printf("Removed encryption key with %s %s, but files still busy\n",
> +		       keyspectype(&arg.key_spec), keyspec2str(&arg.key_spec));
> +	} else {
> +		printf("Removed encryption key with %s %s\n",
> +		       keyspectype(&arg.key_spec), keyspec2str(&arg.key_spec));
> +	}
> +	return 0;
> +}
> +
>  void
>  encrypt_init(void)
>  {
> @@ -726,7 +790,18 @@ encrypt_init(void)
>  	add_enckey_cmd.oneline = _("add an encryption key to the filesystem");
>  	add_enckey_cmd.help = add_enckey_help;
>  
> +	rm_enckey_cmd.name = "rm_enckey";
> +	rm_enckey_cmd.cfunc = rm_enckey_f;
> +	rm_enckey_cmd.args = _("keyspec");

can you add "-a" to the args for the shorthelp/args here please?

I don't know anything about this stuff.  :(  Is it to be used as:

rm_enckey -a <keyspec> ?

> +	rm_enckey_cmd.argmin = 0;
> +	rm_enckey_cmd.argmax = -1;

I wonder if min/max should be 1/2 but eh, I think you catch wrong counts
in the function itself, just without the explicit message the built-in
checkers would give.

> +	rm_enckey_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
> +	rm_enckey_cmd.oneline =
> +		_("remove an encryption key from the filesystem");
> +	rm_enckey_cmd.help = rm_enckey_help;
> +
>  	add_command(&get_encpolicy_cmd);
>  	add_command(&set_encpolicy_cmd);
>  	add_command(&add_enckey_cmd);
> +	add_command(&rm_enckey_cmd);
>  }
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index 7d6a23fe..a6894778 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -764,6 +764,21 @@ Otherwise, the key is added as a v2 policy key, and on success the resulting
>  .RE
>  .PD
>  .TP
> +.BI "rm_enckey " keyspec

show [-a] here as well?

> +On filesystems that support encryption, remove an encryption key from the
> +filesystem containing the currently open file.
> +.I keyspec
> +is a hex string specifying the key to remove, as a 16-character "key descriptor"
> +or a 32-character "key identifier".
> +.RS 1.0i
> +.PD 0
> +.TP 0.4i
> +.BI \-a
> +Remove the key for all users who have added it, not just the current user.  This
> +is a privileged operation.
> +.RE
> +.PD
> +.TP
>  .BR lsattr " [ " \-R " | " \-D " | " \-a " | " \-v " ]"
>  List extended inode flags on the currently open file. If the
>  .B \-R
>