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Author SHA1 Message Date
Reepca Russelstein
05a669efa5
daemon: Gracefully handle target mount point already existing.
Fixes guix/guix#903.

* nix/libutil/spawn.cc (bindMount): in the "regular file" case, only create a
  placeholder file if one doesn't already exist.

Change-Id: Ie46b2fef2cea5b2a052c4ec48d00e97bfc1ee506
Reported-by: Hilton Chain <hako@ultrarare.space>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-07-04 18:41:43 +02:00
Reepca Russelstein
b79100ef61
daemon: Conditionally disable seccomp filter on ‘socketcall’ systems.
glibc currently will insist on using 'socketcall' on i686-linux unless built
with '--enable-kernel=4.3.0' or above, even on systems that have dedicated
system calls available for all the socket-related functionality.  This
behavior breaks the assumption that socketcall can be safely blocked without
impacting functionality in slirp4netns, rendering the seccomp filter unusable
with those glibcs.

This change makes the slirp4netns seccomp filter opt-in on systems with a
'socketcall' system call.  It can either be opted-into at compile-time or at
runtime using the NO_SOCKETCALL_LIBC preprocessor define or the
GUIX_FORCE_SECCOMP environment variable, respectively.

The seccomp filter being disabled on these systems means that it is possible
for a compromised slirp4netns to access abstract unix domain sockets in the
root network namespace.  It does not affect any of the other mechanisms used
to isolate slirp4netns (e.g. chroot, namespaces, etc).

Fixes guix/guix#808.

* nix/libstore/build.cc (spawnSlirp4netns) [__NR_socketcall]: Do not add
seccomp filter, unless ‘GUIX_FORCE_SECCOMP’ is set.

Change-Id: Ibfe8becc9431f5aff11a21f06858b20496f9cb4a
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-06-30 19:36:41 +02:00
Reepca Russelstein
1ee291139f
daemon: Fix build of spawn.cc for non-Linux and newer GCC.
* nix/libutil/spawn.cc: Include <fcntl.h> and <cstdint>.
(cloneChild): Wrap body in #if CLONE_ENABLED.

Change-Id: I0be7e6dbe80ac2f7022793149472270a4e49d23c
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-06-26 15:41:57 +02:00
Andreas Enge
3eb03534e6
daemon: Fix build with gcc-14.
* nix/libutil/seccomp.hh: Include cstdint.

Change-Id: I454c7abd56abbe4cf03a5bc8ebc402678e07a0f0
2025-06-25 14:33:26 +02:00
Ludovic Courtès
0e79d5b655
daemon: Protect ‘copyFileRecursively’ from race conditions.
Previously, if an attacker managed to introduce a hard link or a symlink
on one of the destination file names before it is opened,
‘copyFileRecursively’ would overwrite the symlink’s target or the hard
link’s content.

This kind of attack could be carried out while guix-daemon is copying
the output or the chroot directory of a failed fixed-output derivation
build, possibly allowing the attacker to escalate to the privileges of
the build user.

* nix/libutil/util.cc (copyFileRecursively): In the ‘S_ISREG’ case, open
‘destination’ with O_NOFOLLOW | O_EXCL.  In the ‘S_ISDIR’ case, open
‘destination’ with O_NOFOLLOW.

Reported-by: Reepca Russelstein <reepca@russelstein.xyz>
Change-Id: I94273efe4e92c1a4270a98c5ec47bd098e9227c9
Signed-off-by: John Kehayias <john.kehayias@protonmail.com>
2025-06-24 10:07:59 -04:00
Reepca Russelstein
c659f977bb
daemon: add seccomp filter for slirp4netns.
The container that slirp4netns runs in should already be quite difficult to do
anything malicious in beyond basic denial of service or sending of network
traffic.  There is, however, one hole remaining in the case in which there is
an adversary able to run code locally: abstract unix sockets.  Because these
are governed by network namespaces, not IPC namespaces, and slirp4netns is in
the root network namespace, any process in the root network namespace can
cooperate with the slirp4netns process to take over its user.

To close this, we use seccomp to block the creation of unix-domain sockets by
slirp4netns.  This requires some finesse, since slirp4netns absolutely needs
to be able to create other types of sockets - at minimum AF_INET and AF_INET6

Seccomp has many, many pitfalls.  To name a few:

1. Seccomp provides you with an "arch" field, but this does not uniquely
   determine the ABI being used; the actual meaning of a system call number
   depends on both the number (which is often the result of ORing a related
   system call with a flag for an alternate ABI) and the architecture.

2. Seccomp provides no direct way of knowing what the native value for the
   arch field should be; the user must do configure/compile-time testing for
   every architecture+ABI combination they want to support.  Amusingly enough,
   the linux-internal header files have this exact information
   (SECCOMP_ARCH_NATIVE), but they aren't sharing it.

3. The only system call numbers we naturally have are the native ones in
   asm/unistd.h.  __NR_socket will always refer to the system call number for
   the target system's ABI.

4. Seccomp can only manipulate 32-bit words, but represents every system call
   argument as a uint64.

5. New system call numbers with as-yet-unknown semantics can be added to the
   kernel at any time.

6. Based on this comment in arch/x86/entry/syscalls/syscall_32.tbl:

   # 251 is available for reuse (was briefly sys_set_zone_reclaim)

   previously-invalid system call numbers may later be reused for new system
   calls.

7. Most architecture+ABI combinations have system call tables with many gaps
   in them.  arm-eabi, for example, has 35 such gaps (note: this is just the
   number of distinct gaps, not the number of system call numbers contained in
   those gaps).

8. Seccomp's BPF filters require a fully-acyclic control flow graph.
   Any operation on a data structure must therefore first be fully
   unrolled before it can be run.

9. Seccomp cannot dereference pointers.  Only the raw bits provided to the
   system calls can be inspected.

10. Some architecture+ABI combos have multiplexer system calls.  For example,
    socketcall can perform any socket-related system call.  The arguments to
    the multiplexed system call are passed indirectly, via a pointer to user
    memory.  They therefore cannot be inspected by seccomp.

11. Some valid system calls are not listed in any table in the kernel source.
    For example, __ARM_NR_cacheflush is an "ARM private" system call.  It does
    not appear in any *.tbl file.

12. Conditional branches are limited to relative jumps of at most 256
    instructions forward.

13. Prior to Linux 4.8, any process able to spawn another process and call
    ptrace could bypass seccomp restrictions.

To address (1), (2), and (3), we include preprocessor checks to identify the
native architecture value, and reject all system calls that don't use the
native architecture.

To address (4), we use the AC_C_BIGENDIAN autoconf check to conditionally
define WORDS_BIGENDIAN, and match up the proper portions of any uint64 we test
for with the value in the accumulator being tested against.

To address (5) and (6), we use system call pinning.  That is, we hardcode a
snapshot of all the valid system call numbers at the time of writing, and
reject any system call numbers not in the recorded set.  A set is recorded for
every architecture+ABI combo, and the native one is chosen at compile-time.
This ensures that not only are non-native architectures rejected, but so are
non-native ABIs.  For the sake of conciseness, we represent these sets as sets
of disjoint ranges.  Due to (7), checking each range in turn could add a lot
of overhead to each system call, so we instead binary search through the
ranges.  Due to (8), this binary search has to be fully unrolled, so we do
that too.

It can be tedious and error-prone to manually produce the syscall ranges by
looking at linux's *.tbl files, since the gaps are often small and
uncommented.  To address this, a script, build-aux/extract-syscall-ranges.sh,
is added that will produce them given a *.tbl filename and an ABI regex (some
tables seem to abuse the ABI field with strange values like "memfd_secret").
Note that producing the final values still requires looking at the proper
asm/unistd.h file to find any private numbers and to identify any offsets and
ABI variants used.

(10) used to have no good solution, but in the past decade most architectures
have gained dedicated system call alternatives to at least socketcall, so we
can (hopefully) just block it entirely.

To address (13), we block ptrace also.

* build-aux/extract-syscall-ranges.sh: new script.
* Makefile.am (EXTRA_DIST): register it.
* config-daemon.ac: use AC_C_BIGENDIAN.
* nix/libutil/spawn.cc (setNoNewPrivsAction, addSeccompFilterAction): new
  functions.
* nix/libutil/spawn.hh (setNoNewPrivsAction, addSeccompFilterAction): new
  declarations.
  (SpawnContext)[setNoNewPrivs, addSeccompFilter]: new fields.
* nix/libutil/seccomp.hh: new header file.
* nix/libutil/seccomp.cc: new file.
* nix/local.mk (libutil_a_SOURCES, libutil_headers): register them.
* nix/libstore/build.cc (slirpSeccompFilter, writeSeccompFilterDot):
  new functions.
  (spawnSlirp4netns): use them, set seccomp filter for slirp4netns.

Change-Id: Ic92c7f564ab12596b87ed0801b22f88fbb543b95
Signed-off-by: John Kehayias <john.kehayias@protonmail.com>
2025-06-24 10:07:58 -04:00
Reepca Russelstein
fb42611b8f
daemon: Use slirp4netns to provide networking to fixed-output derivations.
Previously, the builder of a fixed-output derivation could communicate with an
external process via an abstract Unix-domain socket.  In particular, it could
send an open file descriptor to the store, granting write access to some of
its output files in the store provided the derivation build fails—the fix for
CVE-2024-27297 did not address this specific case.  It could also send an open
file descriptor to a setuid program, which could then be executed using
execveat to gain the privileges of the build user.

With this change, fixed-output derivations other than “builtin:download”
and “builtin:git-download” always run in a separate network namespace
and have network access provided by a TAP device backed by slirp4netns,
thereby closing the abstract Unix-domain socket channel.

* nix/libstore/globals.hh (Settings)[useHostLoopback, slirp4netns]: new
fields.
* config-daemon.ac (SLIRP4NETNS): new C preprocessor definition.
* nix/libstore/globals.cc (Settings::Settings): initialize them to defaults.
* nix/nix-daemon/guix-daemon.cc (options): add --isolate-host-loopback option.
* doc/guix.texi: document it.
* nix/libstore/build.cc (DerivationGoal)[slirp]: New field.
(setupTap, setupTapAction, waitForSlirpReadyAction, enableRouteLocalnetAction,
 prepareSlirpChrootAction, spawnSlirp4netns, haveGlobalIPv6Address,
 remapIdsTo0Action): New functions.
(initializeUserNamespace): allow the guest UID and GID to be specified.
(DerivationGoal::killChild): When ‘slirp’ is not -1, call ‘kill’.
(DerivationGoal::startBuilder): Unconditionally add CLONE_NEWNET to FLAGS.
When ‘fixedOutput’ is true, spawn ‘slirp4netns’.
When ‘fixedOutput’ and ‘useChroot’ are true, add setupTapAction,
waitForSlirpReadyAction, and enableRouteLocalnetAction to builder setup
phases.
Create a /etc/resolv.conf for fixed-output derivations that directs them to
slirp4netns's dns address.
When settings.useHostLoopback is true, supply fixed-output derivations with a
/etc/hosts that resolves "localhost" to slirp4netns's address for accessing
the host loopback.
* nix/libutil/util.cc (keepOnExec, decodeOctalEscaped, sendFD, receiveFD,
  findProgram): New functions.
* nix/libutil/util.hh (keepOnExec, decodeOctalEscaped, sendFD, receiveFD,
  findProgram): New declarations.
* gnu/packages/package-management.scm (guix): add slirp4netns input for linux
  targets.
* tests/derivations.scm (builder-network-isolated?): new variable.
  ("fixed-output derivation, network access, localhost", "fixed-output
  derivation, network access, external host"):
  skip test case if fixed output derivations are isolated from the network.

Change-Id: Ia3fea2ab7add56df66800071cf15cdafe7bfab96
Signed-off-by: John Kehayias <john.kehayias@protonmail.com>
2025-06-24 10:07:57 -04:00
Reepca Russelstein
be8aca0651
daemon: add and use spawn.cc and spawn.hh.
This adds a mechanism for manipulating and running "spawn phases" similarly to
how builder-side code manipulates "build phases".  The main difference is that
spawn phases take a (reference to a) single structure that they can both read
from and write to, with their writes being visible to subsequent phases.  The
base structure type for this is SpawnContext.

It also adds some predefined phase sequences, namely basicSpawnPhases and
cloneSpawnPhases, and exposes each of the actions performed by these phases.

Finally, it modifies build.cc to replace runChild() with use of this new code.

* nix/libutil/util.cc (keepOnExec, waitForMessage): new functions.
* nix/libutil.util.hh (keepOnExec, waitForMessage): add prototypes.
* nix/libutil/spawn.cc, nix/libutil/spawn.hh: new files.
  (addPhaseAfter, addPhaseBefore, prependPhase, appendPhase, deletePhase,
  replacePhase, reset_writeToStderrAction, restoreAffinityAction,
  setsidAction, earlyIOSetupAction, dropAmbientCapabilitiesAction,
  chrootAction, chdirAction, closeMostFDsAction, setPersonalityAction,
  oomSacrificeAction, setIDsAction, restoreSIGPIPEAction, setupSuccessAction,
  execAction, getBasicSpawnPhases, usernsInitSyncAction, usernsSetIDsAction,
  initLoopbackAction, setHostAndDomainAction, makeFilesystemsPrivateAction,
  makeChrootSeparateFilesystemAction, statfsToMountFlags, bindMount,
  mountIntoChroot, mountIntoChrootAction, mountProcAction, mountDevshmAction,
  mountDevptsAction, pivotRootAction, lockMountsAction, getCloneSpawnPhases,
  runChildSetup, runChildSetupEntry, cloneChild, idMapToIdentityMap,
  unshareAndInitUserns): new procedures.
* nix/local.mk (libutil_a_SOURCES): add spawn.cc.
  (libutil_headers): add spawn.hh.
* nix/libstore/build.cc (restoreSIGPIPE, DerivationGoal::runChild,
  childEntry): removed procedures.
  (DerivationGoal::{dirsInChroot,env,readiness}): removed.
  (execBuilderOrBuiltin, execBuilderOrBuiltinAction,
  clearRootWritePermsAction): new procedures.
  (DerivationGoal::startBuilder): modified to use a CloneSpawnContext if
  chroot builds are available, otherwise a SpawnContext.

Change-Id: Ifd50110de077378ee151502eda62b99973d083bf

Change-Id: I76e10d3f928cc30566e1e6ca79077196972349f8

spawn.cc, util.cc, util.hh changes

Change-Id: I287320e63197cb4f65665ee5b3fdb3a0e125ebac
Signed-off-by: John Kehayias <john.kehayias@protonmail.com>
2025-06-24 10:07:56 -04:00
Reepca Russelstein
7173c2c0ca
daemon: Implement ‘deletePath’ in terms of the *at functions.
deletePath needs to be able to operate securely in unfriendly environments,
where adversaries may be concurrently modifying the files being operated on.
For example, directories that we are currently recursing through may be
replaced with symbolic links.

We err on the side of early failure here: if a file or directory is
concurrently modified in a way that causes one of the system calls to fail, we
throw an exception immediately instead of trying to adapt to the change.

Note that we use fstat instead of fstatat for verifying the directory's
st_mode field because AT_EMPTY_PATH is linux-specific.

* nix/libutil/util.cc (_deletePathAt): new procedure.
(_deletePath): use it.

Change-Id: I7ccfe6f1f74dbab95617b24034494e0f63030582
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
Signed-off-by: John Kehayias <john.kehayias@protonmail.com>
2025-06-24 10:07:55 -04:00
Congcong Kuo
3721eb1d6a
daemon: Remove ‘foreach’ and ‘foreach_reverse’
‘foreach_reverse’ is not used anywhere

* nix/libutil/util.hh (foreach, foreach_reverse): Remove.
* nix/libstore/build.cc (addToWeakGoals): Use ‘std::none_of’ instead of macro ‘foreach’.
(Goal::waiteeDone, Goal::amDone, UserLock::acquire, rewriteHashes,
DerivationGoal::addWantedOutputs, DerivationGoal::haveDerivation,
DerivationGoal::outputsSubstituted, DerivationGoal::repairClosure,
DerivationGoal::inputsRealised, DerivationGoal::tryToBuild,
DerivationGoal::buildDone, DerivationGoal::tryBuildHook,
DerivationGoal::startBuilder, DerivationGoal::runChild,
parseReferenceSpecifiers, DerivationGoal::registerOutputs,
DerivationGoal::checkPathValidity, SubstitutionGoal::tryNext,
SubstitutionGoal::referencesValid, Worker::removeGoal,
Worker::childTerminated, Worker::run, Worker::waitForInput): Use range-based
‘for’ instead of macro ‘foreach’.
* nix/libstore/derivations.cc (writeDerivation, unparseDerivation,
hashDerivationModulo): Likewise.
* nix/libstore/gc.cc (addAdditionalRoots, LocalStore::deletePathRecursive,
LocalStore::canReachRoot, LocalStore::collectGarbage): Likewise.
* nix/libstore/globals.cc (Settings::pack): Likewise.
* nix/libstore/local-store.cc (checkDerivationOutputs, queryValidPaths,
querySubstitutablePaths, querySubstitutablePathInfos, registerValidPaths, verifyStore,
verifyPath): Likewise.
* nix/libstore/misc.cc (computeFSClosure, dfsVisit, topoSortPaths): Likewise.
* nix/libstore/optimise-store.cc (LocalStore::optimisePath_, LocalStore::optimiseStore): Likewise.
* nix/libstore/pathlocks.cc (PathLocks::lockPaths, PathLocks::~PathLocks): Likewise.
* nix/libstore/references.cc (search, scanForReferences): Likewise.
* nix/libstore/store-api.cc (checkStoreName, computeStorePathForText,
StoreAPI::makeValidityRegistration, showPaths, readStorePaths): Likewise.
* nix/libutil/serialise.cc (writeStrings): Likewise.
* nix/libutil/util.cc (concatStringsSep): Likewise.
* nix/nix-daemon/nix-daemon.cc (performOp): Likewise.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-06-09 22:05:13 +02:00
Congcong Kuo
4b9d14378f
daemon: Remove ‘singleton’ and replace ‘typedef’ with ‘using’ in ‘types.hh’
* nix/libutil/util.hh (singleton): Remove.
* nix/libstore/build.cc (DerivationGoal::startBuilder)
(SubstitutionGoal::tryNext, SubstitutionGoal::tryToRun)
(LocalStore::ensurePath, LocalStore::repairPath): Use normal
construction function instead of ‘singleton’.
* nix/libstore/local-store.cc (LocalStore::addToStoreFromDump)
(LocalStore::addTextToStore, LocalStore::importPath): Likewise.
* nix/nix-daemon/nix-daemon.cc (performOp): Likewise.

Change-Id: If0d929407c09482f3b506a1c51dfda70e29696dd
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-06-03 15:09:55 +02:00
wrobell
7b66b41ce5
daemon: Fix build failure with gcc@15.
* nix/libstore/build.cc (CompareGoalPtrs::operator): Add const keyword.
* nix/libstore/store-api.hh: Add missing include for uint64_t.

Change-Id: I56368da9eb10dc376f7e6eeae6a61746bb36c9cf
Signed-off-by: Andreas Enge <andreas@enge.fr>
2025-06-01 16:01:03 +02:00
Congcong Kuo
583e0688e3
daemon: Remove ‘AutoDeleteArray’.
* libutil/util.hh (AutoDeleteArray): Remove.
* libutil/util.cc (readString, readStrings): Use ‘std::vector’ instead
of ‘AutoDeleteArray’.
* libutil/serialise.cc (readFile): Likewise.

Change-Id: I45362998dbb8226874f66b77cd19f071f7bb2ab3
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-05-28 19:31:45 +02:00
Congcong Kuo
e3bd9a65cc
daemon: Remove ‘defined’ in macro definition.
Closes #6.

* nix/libstore/build.cc (CHROOT_ENABLED, CLONE_ENABLED): Wrap in #ifdefs.

Change-Id: I217e46fc2cac579a199fcd7c28ef5a8155a12750
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-05-25 17:47:03 +02:00
Ludovic Courtès
b47eed5ea7
build: Fix substitutions for .service files.
Fixes <https://issues.guix.gnu.org/78318>.

This is a followup to 107eb8ee8f.

* nix/local.mk (etc/guix-%.service): Add ‘g’ for ‘@localstatedir@’
substitution.  Substitute ‘@storedir@’.

Reported-by: Ido Yariv <yarivido@gmail.com>
Change-Id: I9b53d3a6d713a000bc0a7a57f667badc00d2dff8
2025-05-14 22:39:03 +02:00
Congcong Kuo
5f3518ca83
daemon: Replace ‘random_shuffle’ with ‘shuffle’.
‘std::random_shuffle’ was removed in C++14.

* nix/libstore/gc.cc (LocalStore::collectGarbage): Use ‘std::random’ and
‘std::shuffle’.

Change-Id: If91ed3ec3596a419ae7c87d7ce677e0970853e9f
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2025-05-12 10:40:02 +02:00
Ludovic Courtès
0d3bc50b0c
daemon: Use the guest GID in /etc/group.
Partly fixes <https://issues.guix.gnu.org/77862>.

Fixes a bug whereby, when running guix-daemon unprivileged, /etc/group
would contain the wrong GID for the “nixbld” group.  This inconsistency
would lead to failures in the Coreutils test suite, for instance.

* nix/libstore/build.cc (DerivationGoal::startBuilder): Use ‘guestGID’
when writing /etc/group.
* tests/store.scm ("/etc/passwd and /etc/group"): New test.

Reported-by: keinflue <keinflue@posteo.net>
Change-Id: I739bc96c4c935fd9015a45e2bfe5b3e3f90554a9
2025-04-25 20:25:54 +02:00
Ludovic Courtès
dd94798552
daemon: Catch SIGINT, SIGTERM, and SIGHUP for proper termination.
Previously the daemon would not install handlers for these signals.  It
would thus terminate abruptly when receiving them, without properly
closing the SQLite database.

Consequently, the database’s WAL file, which is normally deleted by the
last client closing the database (via ‘sqlite3_close’), would not be
deleted when the guix-daemon process is terminated; instead, it would
persist and possibly keep growing beyond reason.

This patch fixes that.

* nix/nix-daemon/nix-daemon.cc (handleSignal, setTerminationSignalHandler):
New functions.
(processConnection): Call it.

Reported-by: Christopher Baines <mail@cbaines.net>
Change-Id: I07e510a1242e92b6a629d60eb840e029c0f921be
2025-04-14 17:33:11 +02:00
Ludovic Courtès
ff5181e27e
daemon: Do not make chroot root directory read-only.
Fixes <https://issues.guix.gnu.org/77570>.

Commit 40f69b586a made chroot root
directory read-only; as a consequence, build processes attempting to
write to the root directory would now get EROFS instead of EACCES.

It turns out that a number of test suites (Go, Ruby, SCons, Shepherd)
would fail because of this observable difference.

To restore previous behavior in build environments while still
preventing build processes from exposing their root directory to outside
processes, this patch (1) keeps the root writable but #o555 by default,
thereby restoring the EACCES behavior, and (2) ensures that the parent
of the chroot root directory is itself user-accessible only.

* nix/libstore/build.cc (class DerivationGoal)[chrootRootTop]: New
field.
(DerivationGoal::startBuilder): Initialize ‘chrootRootTop’ and make it
‘AutoDelete’.  Replace ‘mount’ call that made the root directory
read-only by a mere ‘chmod_’ call.
* tests/store.scm ("build root cannot be made world-readable"): Remove.
("writing to build root leads to EACCES"): New test.

Reported-by: Ada Stevenson <adanskana@gmail.com>
Reported-by: keinflue <keinflue@posteo.net>
Suggested-by: Reepca Russelstein <reepca@russelstein.xyz>
Change-Id: I5912e8b3b293f8242a010cfc79255fc981314445
2025-04-11 12:18:01 +02:00
Ludovic Courtès
bdd7b9a45d
daemon: Move comments where they belong.
* nix/libstore/build.cc (DerivationGoal::startBuilder): Shuffle
comments for clarity.

Change-Id: I6557c103ade4a3ab046354548ea193c68f8c9c05
2025-03-26 17:57:44 +01:00
Ludovic Courtès
0163c732a1
daemon: Drop Linux ambient capabilities before executing builder.
* config-daemon.ac: Check for <sys/prctl.h>.
* nix/libstore/build.cc (DerivationGoal::runChild): When ‘useChroot’ is
true, call ‘prctl’ to drop all ambient capabilities.

Change-Id: If34637fc508e5fb6d278167f5df7802fc595284f
2025-03-26 17:57:44 +01:00
Ludovic Courtès
a3d6f5ae70
daemon: Create /var/guix/profiles/per-user unconditionally.
* nix/libstore/local-store.cc (LocalStore::LocalStore): Create
‘perUserDir’ unconditionally.

Change-Id: I5188320f9630a81d16f79212d0fffabd55d94abe
2025-03-26 17:57:44 +01:00
Ludovic Courtès
ae18b3d9e6
daemon: Allow running as non-root with unprivileged user namespaces.
Many thanks to Reepca Russelstein for their review and guidance on these
changes.

* nix/libstore/build.cc (guestUID, guestGID): New variables.
(DerivationGoal)[readiness]: New field.
(initializeUserNamespace): New function.
(DerivationGoal::runChild): When ‘readiness.readSide’ is positive, read
from it.
(DerivationGoal::startBuilder): Call ‘chown’
only when ‘buildUser.enabled()’ is true.  Pass CLONE_NEWUSER to ‘clone’
when ‘buildUser.enabled()’ is false or not running as root.  Retry
‘clone’ without CLONE_NEWUSER upon EPERM.
(DerivationGoal::registerOutputs): Make ‘actualPath’ writable before
‘rename’.
(DerivationGoal::deleteTmpDir): Catch ‘SysError’ around ‘_chown’ call.
* nix/libstore/local-store.cc (LocalStore::createUser): Do nothing if
‘dirs’ already exists.  Warn instead of failing when failing to chown
‘dir’.
* guix/substitutes.scm (%narinfo-cache-directory): Check for
‘_NIX_OPTIONS’ rather than getuid() == 0 to determine the cache
location.
* doc/guix.texi (Build Environment Setup): Reorganize a bit.  Add
section headings “Daemon Running as Root” and “The Isolated Build
Environment”.  Add “Daemon Running Without Privileges” subsection.
Remove paragraph about ‘--disable-chroot’.
(Invoking guix-daemon): Warn against ‘--disable-chroot’ and explain why.
* tests/derivations.scm ("builder is outside the store"): New test.

Reviewed-by: Reepca Russelstein <reepca@russelstein.xyz>
2025-03-26 17:57:43 +01:00
Ludovic Courtès
40f69b586a
daemon: Remount root directory as read-only.
* nix/libstore/build.cc (DerivationGoal::runChild): Bind-mount the store
and /tmp under ‘chrootRootDir’ to themselves as read-write.
Remount / as read-only.

Change-Id: I79565094c8ec8448401897c720aad75304fd1948
2025-03-26 17:57:43 +01:00
Ludovic Courtès
93474f9288
daemon: Remount inputs as read-only.
* nix/libstore/build.cc (DerivationGoal::runChild): Remount ‘target’ as
read-only.

Reported-by: Reepca Russelstein <reepca@russelstein.xyz>
Change-Id: Ib7201bcf4363be566f205d23d17fe2f55d3ad666
2025-03-26 17:57:43 +01:00
Ludovic Courtès
550ca89744
daemon: Bind-mount all the inputs, not just directories.
* nix/libstore/build.cc (DerivationGoal::startBuilder): Add all of
‘inputPaths’ to ‘dirsInChroot’ instead of hard-linking regular files.
Special-case symlinks.
(DerivationGoal)[regularInputPaths]: Remove.

Reported-by: Reepca Russelstein <reepca@russelstein.xyz>
Change-Id: I070987f92d73f187f7826a975bee9ee309d67f56
2025-03-26 17:57:43 +01:00
Ludovic Courtès
5c0b93b244
daemon: Bind-mount /etc/nsswitch.conf & co. only if it exists.
Those files may be missing in some contexts, for instance within the
build environment.

* nix/libstore/build.cc (DerivationGoal::runChild): Add /etc/resolv.conf
and related files to ‘ss’ only if they exist.

Change-Id: Ie19664a86c8101a1dc82cf39ad4b7abb10f8250a
2025-03-26 17:57:43 +01:00
Ludovic Courtès
7bad04fac0
daemon: Close the read end of the logging pipe.
* nix/libutil/util.cc (commonChildInit): Close ‘logPipe.readSide’.

Reported-by: Reepca Russelstein <reepca@russelstein.xyz>
Change-Id: Ia9e48d1afb85d7af52770e016f2b6832792044dd
2025-03-26 17:57:43 +01:00
Ludovic Courtès
f03e6eff2f
daemon: Use ‘close_range’ where available.
* nix/libutil/util.cc (closeMostFDs) [HAVE_CLOSE_RANGE]: Use
‘close_range’ when ‘exceptions’ is empty.
* config-daemon.ac: Check for <linux/close_range.h> and the
‘close_range’ symbol.

Change-Id: I12fa3bde58b003fcce5ea5a1fee1dcf9a92c0359
2025-03-26 17:57:42 +01:00
Efraim Flashner
61ca5bdbce
nix: Install guix-gc systemd timer.
* nix/local.mk (nodist_systemdservice_DATA): Add etc/guix-gc.timer.
(etc/guix-gc.timer): Add rule to generate file.
(EXTRA_DIST): Add guix-gc.timer.in, remove guix-gc.timer.
* gitignore: Add etc/guix-gc.timer.

Change-Id: I361aef660fe7d9803f58f4e31e16d8db595d1853
2025-03-02 14:21:59 +02:00
Efraim Flashner
7b091cefa4
Revert "nix: Install guix-gc systemd timer."
This reverts commit 3355de608c.

This commit does the opposite of what it was supposed to do.
2025-03-02 13:58:25 +02:00
Efraim Flashner
3355de608c
nix: Install guix-gc systemd timer.
* nix/local.mk (nodist_systemdservice_DATA): Add etc/guix-gc.timer.

Change-Id: I6f71d68f77ff07976f9ec16c37dba99ebedd9b9d
2025-02-26 10:01:00 +02:00
Reepca Russelstein
78da695178
daemon: Explicitly unlock output path in the has-become-valid case.
Fixes <https://issues.guix.gnu.org/31785>.

Similar to <https://github.com/NixOS/nix/issues/178>, fixed in
<29cde917fe>.

We can't rely on Goal deletion to release our locks in a timely manner.  In
the case in which multiple guix-daemon processes simultaneously try producing
an output path path1, the one that gets there first (P1) will get the lock,
and the second one (P2) will continue trying to acquire the lock until it is
released.  Once it has acquired the lock, it checks to see whether the path
has already become valid in the meantime, and if so it reports success to
those Goals waiting on its completion and finishes.  Unfortunately, it fails
to release the locks it holds first, so those stay held until that Goal gets
deleted.

Suppose we have the following store path dependency graph:

          path4
      /     |     \
   path1   path2   path3

P2 is now sitting on path1's lock, and will continue to do so until path4 is
completed.  Suppose there is also a P3, and it has been blocked while P1
builds path2.  Now P3 is sitting on path2's lock, and can't acquire path1's
lock to determine that it has been completed.  Likewise P2 is sitting on
path1's lock, and now can't acquire path2's lock to determine that it has been
completed.  Finally, P3 completes path3 while P2 is blocked.

Now:

- P1 knows that path1 and path2 are complete, and holds no locks, but can't
  determine that path3 is complete
- P2 knows that path1 and path3 are complete, and holds locks on path1 and
  path3, but can't determine that path2 is complete
- P3 knows that path2 and path3 are complete, and holds a lock on path2, but
  can't determine that path1 is complete

And none of these locks will be released until path4 is complete.  Thus, we
have a deadlock.

To resolve this, we should explicitly release these locks as soon as they
should be released.

* nix/libstore/build.cc
  (DerivationGoal::tryToBuild, SubstitutionGoal::tryToRun):
  Explicitly release locks in the has-become-valid case.
* tests/store-deadlock.scm: New file.
* Makefile.am (SCM_TESTS): Add it.

Change-Id: Ie510f84828892315fe6776c830db33d0f70bcef8
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2024-12-30 00:51:57 +01:00
Doğan Çeçen
dcaccc8b72
daemon: Fix linking gcrypt when --as-needed linker arg is used
This is a followup to 8a7bd211d2.

As it is mentioned in autoconf manual that library names should be
specified in LIBS, not LDFLAGS. See:

https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.72/html_node/Preset-Output-Variables.html#index-LDFLAGS-2

This change also brings back the save_* vars trick that was there
before. I missed in my earlier change that nix/local.mk was referring
LIBGCRYPT_* vars directly.

And, instead of CXXFLAGS, CPPFLAGS is used since the latter is probably
more correct as this is used for include dirs, therefore using
preprocessor flags.

Tested with ./configure LDFLAGS="-Wl,--as-needed" --with-libgcrypt-prefix=... combinations.

* config-daemon.ac: Set ‘LIBGCRYPT_CPPFLAGS’ instead of
‘LIBGCRYPT_CXXFLAGS’.  Set ‘LIBGCRYPT_LIBS’ in addition to
‘LIBGCRYPT_LDFLAGS’.  Save and restore ‘CPPFLAGS’, ‘LDFLAGS’, and ‘LIBS’
around test.
* nix/local.mk (libutil_a_CPPFLAGS): Add $(LIBGCRYPT_CPPFLAGS).
(libstore_a_CXXFLAGS): Remove $(LIBGCRYPT_CFLAGS).
(guix_daemon_LDFLAGS): New variable.

Change-Id: Iadb10e1994c9a78e2927847af2cfe5e096fbb2a8
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2024-12-09 23:15:45 +01:00
Brennan Vincent
cf10268a77
daemon: Improve error message in ‘checkStoreName’.
* nix/libstore/store-api.cc (checkStoreName): Clarify message when NAME
starts with a dot.

Change-Id: I045a663bc6cd9844677c65b38a31d3941cf212b5
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2024-11-17 23:15:49 +01:00
Reepca Russelstein
5ab3c4c1e4
daemon: Sanitize successful build outputs prior to exposing them.
There is currently a window of time between when the build outputs are exposed
and when their metadata is canonicalized.

* nix/libstore/build.cc (DerivationGoal::registerOutputs): wait until after
  metadata canonicalization to move successful build outputs to the store.

Change-Id: Ia995136f3f965eaf7b0e1d92af964b816f3fb276
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2024-10-21 00:09:24 +02:00
Reepca Russelstein
558224140d
daemon: Sanitize failed build outputs prior to exposing them.
The only thing keeping a rogue builder and a local user from collaborating to
usurp control over the builder's user during the build is the fact that
whatever files the builder may produce are not accessible to any other users
yet.  If we're going to make them accessible, we should probably do some
sanity checking to ensure that sort of collaborating can't happen.

Currently this isn't happening when failed build outputs are moved from the
chroot as an aid to debugging.

* nix/libstore/build.cc (secureFilePerms): new function.
  (DerivationGoal::buildDone): use it.

Change-Id: I9dce1e3d8813b31cabd87a0e3219bf9830d8be96
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2024-10-21 00:09:10 +02:00
Ludovic Courtès
d11b96eb54
etc: Add explicit ‘--substitute-urls’ in guix-daemon service files.
Having substitute URLs explicitly listed in the service startup file
makes it clearer what should be modified to permanently change the list
of substitute URLs.

* config-daemon.ac: Rename ‘guix_substitute_urls’ to
‘GUIX_SUBSTITUTE_URLS’ and substitute it.
* nix/local.mk (etc/guix-%.service, etc/init.d/guix-daemon)
(etc/guix-%.conf): Substitute it.
* etc/guix-daemon.conf.in, etc/guix-daemon.service.in,
etc/init.d/guix-daemon.in: Add an explicit ‘--substitute-urls’ option.

Change-Id: Ie491b7fab5c42e54dca582801c03805a85de2bf9
2024-06-26 22:59:55 +02:00
Ludovic Courtès
7757fdd491
daemon: Loop over ‘copy_file_range’ upon short writes.
Fixes <https://issues.guix.gnu.org/70877>.

* nix/libutil/util.cc (copyFile): Loop over ‘copy_file_range’ instead of
throwing upon short write.

Reported-by: Ricardo Wurmus <rekado@elephly.net>
Change-Id: Id7b8a65ea59006c2d91bc23732309a68665b9ca0
2024-05-13 16:31:34 +02:00
Ludovic Courtès
ff1251de0b
daemon: Address shortcoming in previous security fix for CVE-2024-27297.
This is a followup to 8f4ffb3fae.

Commit 8f4ffb3fae fell short in two
ways: (1) it didn’t have any effet for fixed-output derivations
performed in a chroot, which is the case for all of them except those
using “builtin:download” and “builtin:git-download”, and (2) it did not
preserve ownership when copying, leading to “suspicious ownership or
permission […] rejecting this build output” errors.

* nix/libstore/build.cc (DerivationGoal::buildDone): Account for
‘chrootRootDir’ when copying ‘drv.outputs’.
* nix/libutil/util.cc (copyFileRecursively): Add ‘fchown’ and ‘fchownat’
calls to preserve file ownership; this is necessary for chrooted
fixed-output derivation builds.
* nix/libutil/util.hh: Update comment.

Change-Id: Ib59f040e98fed59d1af81d724b874b592cbef156
2024-03-12 14:07:28 +01:00
Ludovic Courtès
8f4ffb3fae
daemon: Protect against FD escape when building fixed-output derivations (CVE-2024-27297).
This fixes a security issue (CVE-2024-27297) whereby a fixed-output
derivation build process could open a writable file descriptor to its
output, send it to some outside process for instance over an abstract
AF_UNIX socket, which would then allow said process to modify the file
in the store after it has been marked as “valid”.

Vulnerability discovered by puck <https://github.com/puckipedia>.

Nix security advisory:
https://github.com/NixOS/nix/security/advisories/GHSA-2ffj-w4mj-pg37

Nix fix:
244f3eee0b

* nix/libutil/util.cc (readDirectory): Add variants that take a DIR* and
a file descriptor.  Rewrite the ‘Path’ variant accordingly.
(copyFile, copyFileRecursively): New functions.
* nix/libutil/util.hh (copyFileRecursively): New declaration.
* nix/libstore/build.cc (DerivationGoal::buildDone): When ‘fixedOutput’
is true, call ‘copyFileRecursively’ followed by ‘rename’ on each output.

Change-Id: I7952d41093eed26e123e38c14a4c1424be1ce1c4

Reported-by: Picnoir <picnoir@alternativebit.fr>, Théophane Hufschmitt <theophane.hufschmitt@tweag.io>
Change-Id: Idb5f2757f35af86b032a9851cecb19b70227bd88
2024-03-11 22:12:34 +01:00
Ludovic Courtès
d5724111ea
daemon: Change default ‘timeout’ and ‘max-silent-time’ values.
Having a timeout seems generally preferable as it makes sure build slots
are not kept busy for no good reason (few package builds, if any, are
expected to exceed these values).

* nix/libstore/globals.cc (Settings::Settings): Change ‘maxSilentTime’
and ‘buildTimeout’.
* gnu/services/base.scm (<guix-configuration>)[max-silent-time]
[timeout]: Change default values.
* doc/guix.texi (Invoking guix-daemon, Base Services): Adjust
accordingly.

Change-Id: I25c50893f3f7fcca451b8f093d9d4d1a15fa58d8
2024-01-05 17:27:21 +01:00
Tobias Geerinckx-Rice
892ec53b7e
daemon: Fix my own whitespace errors.
This follows up on commit d993ed43b2 and
was entirely predictable.  The noise, sorry for it.

Change-Id: I8ddb8cfe33db3864949f6589cc091616a90ebc5b
2023-12-17 01:00:00 +01:00
Tobias Geerinckx-Rice
d993ed43b2
daemon: Sacrifice builders on OOM.
* nix/libstore/build.cc (DerivationGoal::runChild):
Maximise our OOM score adjustment.

Change-Id: I418c763b499ca16e1ffe3c6033319112b9744f51
2023-12-10 01:00:00 +01:00
Ludovic Courtès
1e47148f46
daemon: Implement ‘substitute-urls’ RPC.
* nix/libstore/worker-protocol.hh (PROTOCOL_VERSION): Bump.
(WorkerOp): Add ‘wopSubstituteURLs’.
* nix/nix-daemon/nix-daemon.cc (performOp): Implement it.
* guix/store.scm (%protocol-version): Bump.
(operation-id): Add ‘substitute-urls’.
(substitute-urls): New procedure.
* tests/store.scm ("substitute-urls, default")
("substitute-urls, client-specified URLs")
("substitute-urls, disabled"): New tests.

Change-Id: I2c0119500c3a1eecfa5ebf32463ffb0f173161de
2023-12-11 23:18:53 +01:00
Ludovic Courtès
d83d4488da
daemon: Simplify “empty status” substitute error message.
* nix/libstore/build.cc (SubstitutionGoal::finished): Don’t show what
the empty status looks like.

Change-Id: Ie898432aeb047aff3d59024de6ed6d18f68903c4
2023-12-04 22:26:36 +01:00
Tobias Geerinckx-Rice
0500af5556
Revert "build: Add missing guix-gc.timer file to binary tarball."
This reverts commit 69f6edc1a8.

The intention is good, but nodist_systemdservice_DATA are meant to be
disposable artefacts generated from corresponding ‘.in’ files.

etc/guix-gc.timer doesn't fit that description, breaking builds:

  $ make clean && make
  …
  make[2]: *** No rule to make target 'etc/guix-gc.timer', needed by 'all-am'.  Stop.
2023-09-24 02:00:00 +02:00
Ludovic Courtès
95f2123135
daemon: Add “git-download” built-in builder.
The new builder makes it possible to break cycles that occurs when the
fixed-output derivation for the source of a dependency of ‘git’ would
itself depend on ‘git’.

* guix/scripts/perform-download.scm (perform-git-download): New
procedure.
(perform-download): Move fixed-output derivation check to…
(guix-perform-download): … here.  Invoke ‘perform-download’ or
‘perform-git-download’ depending on what ‘derivation-builder’ returns.
* nix/libstore/builtins.cc (builtins): Add “git-download”.
* tests/derivations.scm ("built-in-builders"): Update.
("'git-download' built-in builder")
("'git-download' built-in builder, invalid hash")
("'git-download' built-in builder, invalid commit")
("'git-download' built-in builder, not found"): New tests.
2023-09-26 17:36:58 +02:00
Sören Tempel
cd46993275
daemon: Fix build with GCC 13.
The sqlite.hh file uses fixed-width integer types from stdint.h. As
such, it needs to include <cstdint>. Without this include, the file
doesn't compile successfully with GCC13.

See: https://gcc.gnu.org/gcc-13/porting_to.html#header-dep-changes

* nix/libstore/sqlite.hh: include <cstdint>

Signed-off-by: Sören Tempel <soeren@soeren-tempel.net>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
2023-09-09 18:47:35 +02:00
Maxim Cournoyer
69f6edc1a8
build: Add missing guix-gc.timer file to binary tarball.
Partially fixes <https://issues.guix.gnu.org/65117>.

* nix/local.mk (nodist_systemdservice_DATA): Add etc/guix-gc.timer.
2023-08-31 23:31:49 -04:00