de975de39b
* gnu/build/file-system.scm: Change url of LUKS specification. Signed-off-by: Efraim Flashner <efraim@flashner.co.il>
494 lines
18 KiB
Scheme
494 lines
18 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
|
||
;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
|
||
;;;
|
||
;;; This file is part of GNU Guix.
|
||
;;;
|
||
;;; GNU Guix is free software; you can redistribute it and/or modify it
|
||
;;; under the terms of the GNU General Public License as published by
|
||
;;; the Free Software Foundation; either version 3 of the License, or (at
|
||
;;; your option) any later version.
|
||
;;;
|
||
;;; GNU Guix is distributed in the hope that it will be useful, but
|
||
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
;;; GNU General Public License for more details.
|
||
;;;
|
||
;;; You should have received a copy of the GNU General Public License
|
||
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
|
||
|
||
(define-module (gnu build file-systems)
|
||
#:use-module (guix build utils)
|
||
#:use-module (guix build bournish)
|
||
#:use-module (guix build syscalls)
|
||
#:use-module (rnrs io ports)
|
||
#:use-module (rnrs bytevectors)
|
||
#:use-module (ice-9 match)
|
||
#:use-module (ice-9 rdelim)
|
||
#:use-module (ice-9 format)
|
||
#:use-module (ice-9 regex)
|
||
#:use-module (system foreign)
|
||
#:autoload (system repl repl) (start-repl)
|
||
#:use-module (srfi srfi-1)
|
||
#:use-module (srfi srfi-26)
|
||
#:export (disk-partitions
|
||
partition-label-predicate
|
||
partition-uuid-predicate
|
||
partition-luks-uuid-predicate
|
||
find-partition-by-label
|
||
find-partition-by-uuid
|
||
find-partition-by-luks-uuid
|
||
canonicalize-device-spec
|
||
|
||
uuid->string
|
||
string->uuid
|
||
|
||
bind-mount
|
||
|
||
mount-flags->bit-mask
|
||
check-file-system
|
||
mount-file-system)
|
||
#:re-export (mount
|
||
umount
|
||
MS_BIND
|
||
MS_MOVE
|
||
MS_RDONLY))
|
||
|
||
;;; Commentary:
|
||
;;;
|
||
;;; This modules provides tools to deal with disk partitions, and to mount and
|
||
;;; check file systems.
|
||
;;;
|
||
;;; Code:
|
||
|
||
;; 'mount' is already defined in the statically linked Guile used for initial
|
||
;; RAM disks, in which case the bindings in (guix build syscalls) do not work
|
||
;; (the FFI bindings do not work there). Override them in that case.
|
||
(when (module-defined? the-scm-module 'mount)
|
||
(set! mount (@ (guile) mount))
|
||
(set! umount (@ (guile) umount)))
|
||
|
||
(define (bind-mount source target)
|
||
"Bind-mount SOURCE at TARGET."
|
||
(mount source target "" MS_BIND))
|
||
|
||
|
||
;;;
|
||
;;; Ext2 file systems.
|
||
;;;
|
||
|
||
(define-syntax %ext2-endianness
|
||
;; Endianness of ext2 file systems.
|
||
(identifier-syntax (endianness little)))
|
||
|
||
;; Offset in bytes of interesting parts of an ext2 superblock. See
|
||
;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>.
|
||
;; TODO: Use "packed structs" from Guile-OpenGL or similar.
|
||
(define-syntax %ext2-sblock-magic (identifier-syntax 56))
|
||
(define-syntax %ext2-sblock-creator-os (identifier-syntax 72))
|
||
(define-syntax %ext2-sblock-uuid (identifier-syntax 104))
|
||
(define-syntax %ext2-sblock-volume-name (identifier-syntax 120))
|
||
|
||
(define (read-ext2-superblock device)
|
||
"Return the raw contents of DEVICE's ext2 superblock as a bytevector, or #f
|
||
if DEVICE does not contain an ext2 file system."
|
||
(define %ext2-magic
|
||
;; The magic bytes that identify an ext2 file system.
|
||
#xef53)
|
||
|
||
(define superblock-size
|
||
;; Size of the interesting part of an ext2 superblock.
|
||
264)
|
||
|
||
(define block
|
||
;; The superblock contents.
|
||
(make-bytevector superblock-size))
|
||
|
||
(call-with-input-file device
|
||
(lambda (port)
|
||
(seek port 1024 SEEK_SET)
|
||
|
||
;; Note: work around <http://bugs.gnu.org/17466>.
|
||
(and (eqv? superblock-size (get-bytevector-n! port block 0
|
||
superblock-size))
|
||
(let ((magic (bytevector-u16-ref block %ext2-sblock-magic
|
||
%ext2-endianness)))
|
||
(and (= magic %ext2-magic)
|
||
block))))))
|
||
|
||
(define (ext2-superblock-uuid sblock)
|
||
"Return the UUID of ext2 superblock SBLOCK as a 16-byte bytevector."
|
||
(let ((uuid (make-bytevector 16)))
|
||
(bytevector-copy! sblock %ext2-sblock-uuid uuid 0 16)
|
||
uuid))
|
||
|
||
(define (ext2-superblock-volume-name sblock)
|
||
"Return the volume name of SBLOCK as a string of at most 16 characters, or
|
||
#f if SBLOCK has no volume name."
|
||
(let ((bv (make-bytevector 16)))
|
||
(bytevector-copy! sblock %ext2-sblock-volume-name bv 0 16)
|
||
|
||
;; This is a Latin-1, nul-terminated string.
|
||
(let ((bytes (take-while (negate zero?) (bytevector->u8-list bv))))
|
||
(if (null? bytes)
|
||
#f
|
||
(list->string (map integer->char bytes))))))
|
||
|
||
|
||
;;;
|
||
;;; LUKS encrypted devices.
|
||
;;;
|
||
|
||
;; The LUKS header format is described in "LUKS On-Disk Format Specification":
|
||
;; <https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification>. We follow
|
||
;; version 1.2.1 of this document.
|
||
|
||
(define-syntax %luks-endianness
|
||
;; Endianness of LUKS headers.
|
||
(identifier-syntax (endianness big)))
|
||
|
||
(define-syntax %luks-header-size
|
||
;; Size in bytes of the LUKS header, including key slots.
|
||
(identifier-syntax 592))
|
||
|
||
(define %luks-magic
|
||
;; The 'LUKS_MAGIC' constant.
|
||
(u8-list->bytevector (append (map char->integer (string->list "LUKS"))
|
||
(list #xba #xbe))))
|
||
|
||
(define (sub-bytevector bv start size)
|
||
"Return a copy of the SIZE bytes of BV starting from offset START."
|
||
(let ((result (make-bytevector size)))
|
||
(bytevector-copy! bv start result 0 size)
|
||
result))
|
||
|
||
(define (read-luks-header file)
|
||
"Read a LUKS header from FILE. Return the raw header on success, and #f if
|
||
not valid header was found."
|
||
(call-with-input-file file
|
||
(lambda (port)
|
||
(let ((header (make-bytevector %luks-header-size)))
|
||
(match (get-bytevector-n! port header 0 (bytevector-length header))
|
||
((? eof-object?)
|
||
#f)
|
||
((? number? len)
|
||
(and (= len (bytevector-length header))
|
||
(let ((magic (sub-bytevector header 0 6)) ;XXX: inefficient
|
||
(version (bytevector-u16-ref header 6 %luks-endianness)))
|
||
(and (bytevector=? magic %luks-magic)
|
||
(= version 1)
|
||
header)))))))))
|
||
|
||
(define (luks-header-uuid header)
|
||
"Return the LUKS UUID from HEADER, as a 16-byte bytevector."
|
||
;; 40 bytes are reserved for the UUID, but in practice, it contains the 36
|
||
;; bytes of its ASCII representation.
|
||
(let ((uuid (sub-bytevector header 168 36)))
|
||
(string->uuid (utf8->string uuid))))
|
||
|
||
|
||
;;;
|
||
;;; Partition lookup.
|
||
;;;
|
||
|
||
(define (disk-partitions)
|
||
"Return the list of device names corresponding to valid disk partitions."
|
||
(define (last-character str)
|
||
(string-ref str (- (string-length str) 1)))
|
||
|
||
(define (partition? name major minor)
|
||
;; Select device names that end in a digit, like libblkid's 'probe_all'
|
||
;; function does. Checking for "/sys/dev/block/MAJOR:MINOR/partition"
|
||
;; doesn't work for partitions coming from mapped devices.
|
||
(and (char-set-contains? char-set:digit (last-character name))
|
||
(> major 2))) ;ignore RAM disks and floppy disks
|
||
|
||
(call-with-input-file "/proc/partitions"
|
||
(lambda (port)
|
||
;; Skip the two header lines.
|
||
(read-line port)
|
||
(read-line port)
|
||
|
||
;; Read each subsequent line, and extract the last space-separated
|
||
;; field.
|
||
(let loop ((parts '()))
|
||
(let ((line (read-line port)))
|
||
(if (eof-object? line)
|
||
(reverse parts)
|
||
(match (string-tokenize line)
|
||
(((= string->number major) (= string->number minor)
|
||
blocks name)
|
||
(if (partition? name major minor)
|
||
(loop (cons name parts))
|
||
(loop parts))))))))))
|
||
|
||
(define (ENOENT-safe proc)
|
||
"Wrap the one-argument PROC such that ENOENT errors are caught and lead to a
|
||
warning and #f as the result."
|
||
(lambda (device)
|
||
(catch 'system-error
|
||
(lambda ()
|
||
(proc device))
|
||
(lambda args
|
||
;; When running on the hand-made /dev,
|
||
;; 'disk-partitions' could return partitions for which
|
||
;; we have no /dev node. Handle that gracefully.
|
||
(let ((errno (system-error-errno args)))
|
||
(cond ((= ENOENT errno)
|
||
(format (current-error-port)
|
||
"warning: device '~a' not found~%" device)
|
||
#f)
|
||
((= ENOMEDIUM errno) ;for removable media
|
||
#f)
|
||
(else
|
||
(apply throw args))))))))
|
||
|
||
(define (partition-predicate read field =)
|
||
"Return a predicate that returns true if the FIELD of partition header that
|
||
was READ is = to the given value."
|
||
(let ((read (ENOENT-safe read)))
|
||
(lambda (expected)
|
||
"Return a procedure that, when applied to a partition name such as \"sda1\",
|
||
returns #t if that partition's volume name is LABEL."
|
||
(lambda (part)
|
||
(let* ((device (string-append "/dev/" part))
|
||
(sblock (read device)))
|
||
(and sblock
|
||
(let ((actual (field sblock)))
|
||
(and actual
|
||
(= actual expected)))))))))
|
||
|
||
(define partition-label-predicate
|
||
(partition-predicate read-ext2-superblock
|
||
ext2-superblock-volume-name
|
||
string=?))
|
||
|
||
(define partition-uuid-predicate
|
||
(partition-predicate read-ext2-superblock
|
||
ext2-superblock-uuid
|
||
bytevector=?))
|
||
|
||
(define partition-luks-uuid-predicate
|
||
(partition-predicate read-luks-header
|
||
luks-header-uuid
|
||
bytevector=?))
|
||
|
||
(define (find-partition-by-label label)
|
||
"Return the first partition found whose volume name is LABEL, or #f if none
|
||
were found."
|
||
(and=> (find (partition-label-predicate label)
|
||
(disk-partitions))
|
||
(cut string-append "/dev/" <>)))
|
||
|
||
(define (find-partition-by-uuid uuid)
|
||
"Return the first partition whose unique identifier is UUID (a bytevector),
|
||
or #f if none was found."
|
||
(and=> (find (partition-uuid-predicate uuid)
|
||
(disk-partitions))
|
||
(cut string-append "/dev/" <>)))
|
||
|
||
(define (find-partition-by-luks-uuid uuid)
|
||
"Return the first LUKS partition whose unique identifier is UUID (a bytevector),
|
||
or #f if none was found."
|
||
(and=> (find (partition-luks-uuid-predicate uuid)
|
||
(disk-partitions))
|
||
(cut string-append "/dev/" <>)))
|
||
|
||
|
||
;;;
|
||
;;; UUIDs.
|
||
;;;
|
||
|
||
(define-syntax %network-byte-order
|
||
(identifier-syntax (endianness big)))
|
||
|
||
(define (uuid->string uuid)
|
||
"Convert UUID, a 16-byte bytevector, to its string representation, something
|
||
like \"6b700d61-5550-48a1-874c-a3d86998990e\"."
|
||
;; See <https://tools.ietf.org/html/rfc4122>.
|
||
(let ((time-low (bytevector-uint-ref uuid 0 %network-byte-order 4))
|
||
(time-mid (bytevector-uint-ref uuid 4 %network-byte-order 2))
|
||
(time-hi (bytevector-uint-ref uuid 6 %network-byte-order 2))
|
||
(clock-seq (bytevector-uint-ref uuid 8 %network-byte-order 2))
|
||
(node (bytevector-uint-ref uuid 10 %network-byte-order 6)))
|
||
(format #f "~8,'0x-~4,'0x-~4,'0x-~4,'0x-~12,'0x"
|
||
time-low time-mid time-hi clock-seq node)))
|
||
|
||
(define %uuid-rx
|
||
;; The regexp of a UUID.
|
||
(make-regexp "^([[:xdigit:]]{8})-([[:xdigit:]]{4})-([[:xdigit:]]{4})-([[:xdigit:]]{4})-([[:xdigit:]]{12})$"))
|
||
|
||
(define (string->uuid str)
|
||
"Parse STR as a DCE UUID (see <https://tools.ietf.org/html/rfc4122>) and
|
||
return its contents as a 16-byte bytevector. Return #f if STR is not a valid
|
||
UUID representation."
|
||
(and=> (regexp-exec %uuid-rx str)
|
||
(lambda (match)
|
||
(letrec-syntax ((hex->number
|
||
(syntax-rules ()
|
||
((_ index)
|
||
(string->number (match:substring match index)
|
||
16))))
|
||
(put!
|
||
(syntax-rules ()
|
||
((_ bv index (number len) rest ...)
|
||
(begin
|
||
(bytevector-uint-set! bv index number
|
||
(endianness big) len)
|
||
(put! bv (+ index len) rest ...)))
|
||
((_ bv index)
|
||
bv))))
|
||
(let ((time-low (hex->number 1))
|
||
(time-mid (hex->number 2))
|
||
(time-hi (hex->number 3))
|
||
(clock-seq (hex->number 4))
|
||
(node (hex->number 5))
|
||
(uuid (make-bytevector 16)))
|
||
(put! uuid 0
|
||
(time-low 4) (time-mid 2) (time-hi 2)
|
||
(clock-seq 2) (node 6)))))))
|
||
|
||
|
||
(define* (canonicalize-device-spec spec #:optional (title 'any))
|
||
"Return the device name corresponding to SPEC. TITLE is a symbol, one of
|
||
the following:
|
||
|
||
• 'device', in which case SPEC is known to designate a device node--e.g.,
|
||
\"/dev/sda1\";
|
||
• 'label', in which case SPEC is known to designate a partition label--e.g.,
|
||
\"my-root-part\";
|
||
• 'uuid', in which case SPEC must be a UUID (a 16-byte bytevector)
|
||
designating a partition;
|
||
• 'any', in which case SPEC can be anything.
|
||
"
|
||
(define max-trials
|
||
;; Number of times we retry partition label resolution, 1 second per
|
||
;; trial. Note: somebody reported a delay of 16 seconds (!) before their
|
||
;; USB key would be detected by the kernel, so we must wait for at least
|
||
;; this long.
|
||
20)
|
||
|
||
(define canonical-title
|
||
;; The realm of canonicalization.
|
||
(if (eq? title 'any)
|
||
(if (string? spec)
|
||
;; The "--root=SPEC" kernel command-line option always provides a
|
||
;; string, but the string can represent a device, a UUID, or a
|
||
;; label. So check for all three.
|
||
(cond ((string-prefix? "/" spec) 'device)
|
||
((string->uuid spec) 'uuid)
|
||
(else 'label))
|
||
'uuid)
|
||
title))
|
||
|
||
(define (resolve find-partition spec fmt)
|
||
(let loop ((count 0))
|
||
(let ((device (find-partition spec)))
|
||
(or device
|
||
;; Some devices take a bit of time to appear, most notably USB
|
||
;; storage devices. Thus, wait for the device to appear.
|
||
(if (> count max-trials)
|
||
(error "failed to resolve partition" (fmt spec))
|
||
(begin
|
||
(format #t "waiting for partition '~a' to appear...~%"
|
||
(fmt spec))
|
||
(sleep 1)
|
||
(loop (+ 1 count))))))))
|
||
|
||
(case canonical-title
|
||
((device)
|
||
;; Nothing to do.
|
||
spec)
|
||
((label)
|
||
;; Resolve the label.
|
||
(resolve find-partition-by-label spec identity))
|
||
((uuid)
|
||
(resolve find-partition-by-uuid
|
||
(if (string? spec)
|
||
(string->uuid spec)
|
||
spec)
|
||
uuid->string))
|
||
(else
|
||
(error "unknown device title" title))))
|
||
|
||
(define (check-file-system device type)
|
||
"Run a file system check of TYPE on DEVICE."
|
||
(define fsck
|
||
(string-append "fsck." type))
|
||
|
||
(let ((status (system* fsck "-v" "-p" "-C" "0" device)))
|
||
(match (status:exit-val status)
|
||
(0
|
||
#t)
|
||
(1
|
||
(format (current-error-port) "'~a' corrected errors on ~a; continuing~%"
|
||
fsck device))
|
||
(2
|
||
(format (current-error-port) "'~a' corrected errors on ~a; rebooting~%"
|
||
fsck device)
|
||
(sleep 3)
|
||
(reboot))
|
||
(code
|
||
(format (current-error-port) "'~a' exited with code ~a on ~a; \
|
||
spawning Bourne-like REPL~%"
|
||
fsck code device)
|
||
(start-repl %bournish-language)))))
|
||
|
||
(define (mount-flags->bit-mask flags)
|
||
"Return the number suitable for the 'flags' argument of 'mount' that
|
||
corresponds to the symbols listed in FLAGS."
|
||
(let loop ((flags flags))
|
||
(match flags
|
||
(('read-only rest ...)
|
||
(logior MS_RDONLY (loop rest)))
|
||
(('bind-mount rest ...)
|
||
(logior MS_BIND (loop rest)))
|
||
(('no-suid rest ...)
|
||
(logior MS_NOSUID (loop rest)))
|
||
(('no-dev rest ...)
|
||
(logior MS_NODEV (loop rest)))
|
||
(('no-exec rest ...)
|
||
(logior MS_NOEXEC (loop rest)))
|
||
(()
|
||
0))))
|
||
|
||
(define (regular-file? file-name)
|
||
"Return #t if FILE-NAME is a regular file."
|
||
(eq? (stat:type (stat file-name)) 'regular))
|
||
|
||
(define* (mount-file-system spec #:key (root "/root"))
|
||
"Mount the file system described by SPEC under ROOT. SPEC must have the
|
||
form:
|
||
|
||
(DEVICE TITLE MOUNT-POINT TYPE (FLAGS ...) OPTIONS CHECK?)
|
||
|
||
DEVICE, MOUNT-POINT, and TYPE must be strings; OPTIONS can be a string or #f;
|
||
FLAGS must be a list of symbols. CHECK? is a Boolean indicating whether to
|
||
run a file system check."
|
||
(match spec
|
||
((source title mount-point type (flags ...) options check?)
|
||
(let ((source (canonicalize-device-spec source title))
|
||
(mount-point (string-append root "/" mount-point))
|
||
(flags (mount-flags->bit-mask flags)))
|
||
(when check?
|
||
(check-file-system source type))
|
||
|
||
;; Create the mount point. Most of the time this is a directory, but
|
||
;; in the case of a bind mount, a regular file may be needed.
|
||
(if (and (= MS_BIND (logand flags MS_BIND))
|
||
(regular-file? source))
|
||
(unless (file-exists? mount-point)
|
||
(mkdir-p (dirname mount-point))
|
||
(call-with-output-file mount-point (const #t)))
|
||
(mkdir-p mount-point))
|
||
|
||
(mount source mount-point type flags options)
|
||
|
||
;; For read-only bind mounts, an extra remount is needed, as per
|
||
;; <http://lwn.net/Articles/281157/>, which still applies to Linux 4.0.
|
||
(when (and (= MS_BIND (logand flags MS_BIND))
|
||
(= MS_RDONLY (logand flags MS_RDONLY)))
|
||
(let ((flags (logior MS_BIND MS_REMOUNT MS_RDONLY)))
|
||
(mount source mount-point type flags #f)))))))
|
||
|
||
;;; file-systems.scm ends here
|