starnix_uapi/
auth.rs

1// Copyright 2023 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#![allow(dead_code)]
6
7use crate::errors::{Errno, error};
8use crate::{gid_t, uapi, uid_t};
9use bitflags::bitflags;
10use std::ops;
11use std::sync::{Arc, LazyLock};
12
13// We don't use bitflags for this because capability sets can have bits set that don't have defined
14// meaning as capabilities. init has all 64 bits set, even though only 40 of them are valid.
15#[derive(Clone, Copy, Eq, PartialEq)]
16pub struct Capabilities {
17    mask: u64,
18}
19
20impl Capabilities {
21    pub fn empty() -> Self {
22        Self { mask: 0 }
23    }
24
25    pub fn all() -> Self {
26        Self { mask: u64::MAX }
27    }
28
29    pub fn union(&self, caps: Capabilities) -> Self {
30        let mut new_caps = *self;
31        new_caps.insert(caps);
32        new_caps
33    }
34
35    pub fn difference(&self, caps: Capabilities) -> Self {
36        let mut new_caps = *self;
37        new_caps.remove(caps);
38        new_caps
39    }
40
41    pub fn contains(self, caps: Capabilities) -> bool {
42        (self & caps) == caps
43    }
44
45    pub fn insert(&mut self, caps: Capabilities) {
46        *self |= caps;
47    }
48
49    pub fn remove(&mut self, caps: Capabilities) {
50        *self &= !caps;
51    }
52
53    pub fn as_abi_v1(self) -> u32 {
54        self.mask as u32
55    }
56
57    pub fn from_abi_v1(bits: u32) -> Self {
58        Self { mask: bits as u64 }
59    }
60
61    pub fn as_abi_v3(self) -> (u32, u32) {
62        (self.mask as u32, (self.mask >> 32) as u32)
63    }
64
65    pub fn from_abi_v3(u32s: (u32, u32)) -> Self {
66        Self { mask: u32s.0 as u64 | ((u32s.1 as u64) << 32) }
67    }
68}
69
70impl std::convert::TryFrom<u64> for Capabilities {
71    type Error = Errno;
72
73    fn try_from(capability_num: u64) -> Result<Self, Self::Error> {
74        match 1u64.checked_shl(capability_num as u32) {
75            Some(mask) => Ok(Self { mask }),
76            _ => error!(EINVAL),
77        }
78    }
79}
80
81impl ops::BitAnd for Capabilities {
82    type Output = Self;
83
84    // rhs is the "right-hand side" of the expression `a & b`
85    fn bitand(self, rhs: Self) -> Self::Output {
86        Self { mask: self.mask & rhs.mask }
87    }
88}
89
90impl ops::BitAndAssign for Capabilities {
91    // rhs is the "right-hand side" of the expression `a & b`
92    fn bitand_assign(&mut self, rhs: Self) {
93        self.mask &= rhs.mask;
94    }
95}
96
97impl ops::BitOr for Capabilities {
98    type Output = Self;
99
100    fn bitor(self, rhs: Self) -> Self::Output {
101        Self { mask: self.mask | rhs.mask }
102    }
103}
104
105impl ops::BitOrAssign for Capabilities {
106    fn bitor_assign(&mut self, rhs: Self) {
107        self.mask |= rhs.mask;
108    }
109}
110
111impl ops::Not for Capabilities {
112    type Output = Self;
113
114    fn not(self) -> Self::Output {
115        Self { mask: !self.mask }
116    }
117}
118
119impl std::fmt::Debug for Capabilities {
120    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
121        write!(f, "Capabilities({:#x})", self.mask)
122    }
123}
124
125impl std::str::FromStr for Capabilities {
126    type Err = Errno;
127    fn from_str(s: &str) -> Result<Self, Self::Err> {
128        Ok(match s {
129            "CHOWN" => CAP_CHOWN,
130            "DAC_OVERRIDE" => CAP_DAC_OVERRIDE,
131            "DAC_READ_SEARCH" => CAP_DAC_READ_SEARCH,
132            "FOWNER" => CAP_FOWNER,
133            "FSETID" => CAP_FSETID,
134            "KILL" => CAP_KILL,
135            "SETGID" => CAP_SETGID,
136            "SETUID" => CAP_SETUID,
137            "SETPCAP" => CAP_SETPCAP,
138            "LINUX_IMMUTABLE" => CAP_LINUX_IMMUTABLE,
139            "NET_BIND_SERVICE" => CAP_NET_BIND_SERVICE,
140            "NET_BROADCAST" => CAP_NET_BROADCAST,
141            "NET_ADMIN" => CAP_NET_ADMIN,
142            "NET_RAW" => CAP_NET_RAW,
143            "IPC_LOCK" => CAP_IPC_LOCK,
144            "IPC_OWNER" => CAP_IPC_OWNER,
145            "SYS_MODULE" => CAP_SYS_MODULE,
146            "SYS_RAWIO" => CAP_SYS_RAWIO,
147            "SYS_CHROOT" => CAP_SYS_CHROOT,
148            "SYS_PTRACE" => CAP_SYS_PTRACE,
149            "SYS_PACCT" => CAP_SYS_PACCT,
150            "SYS_ADMIN" => CAP_SYS_ADMIN,
151            "SYS_BOOT" => CAP_SYS_BOOT,
152            "SYS_NICE" => CAP_SYS_NICE,
153            "SYS_RESOURCE" => CAP_SYS_RESOURCE,
154            "SYS_TIME" => CAP_SYS_TIME,
155            "SYS_TTY_CONFIG" => CAP_SYS_TTY_CONFIG,
156            "MKNOD" => CAP_MKNOD,
157            "LEASE" => CAP_LEASE,
158            "AUDIT_WRITE" => CAP_AUDIT_WRITE,
159            "AUDIT_CONTROL" => CAP_AUDIT_CONTROL,
160            "SETFCAP" => CAP_SETFCAP,
161            "MAC_OVERRIDE" => CAP_MAC_OVERRIDE,
162            "MAC_ADMIN" => CAP_MAC_ADMIN,
163            "SYSLOG" => CAP_SYSLOG,
164            "WAKE_ALARM" => CAP_WAKE_ALARM,
165            "BLOCK_SUSPEND" => CAP_BLOCK_SUSPEND,
166            "AUDIT_READ" => CAP_AUDIT_READ,
167            "PERFMON" => CAP_PERFMON,
168            "BPF" => CAP_BPF,
169            "CHECKPOINT_RESTORE" => CAP_CHECKPOINT_RESTORE,
170            _ => return error!(EINVAL),
171        })
172    }
173}
174
175pub const CAP_CHOWN: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_CHOWN };
176pub const CAP_DAC_OVERRIDE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_DAC_OVERRIDE };
177pub const CAP_DAC_READ_SEARCH: Capabilities =
178    Capabilities { mask: 1u64 << uapi::CAP_DAC_READ_SEARCH };
179pub const CAP_FOWNER: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_FOWNER };
180pub const CAP_FSETID: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_FSETID };
181pub const CAP_KILL: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_KILL };
182pub const CAP_SETGID: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SETGID };
183pub const CAP_SETUID: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SETUID };
184pub const CAP_SETPCAP: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SETPCAP };
185pub const CAP_LINUX_IMMUTABLE: Capabilities =
186    Capabilities { mask: 1u64 << uapi::CAP_LINUX_IMMUTABLE };
187pub const CAP_NET_BIND_SERVICE: Capabilities =
188    Capabilities { mask: 1u64 << uapi::CAP_NET_BIND_SERVICE };
189pub const CAP_NET_BROADCAST: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_NET_BROADCAST };
190pub const CAP_NET_ADMIN: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_NET_ADMIN };
191pub const CAP_NET_RAW: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_NET_RAW };
192pub const CAP_IPC_LOCK: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_IPC_LOCK };
193pub const CAP_IPC_OWNER: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_IPC_OWNER };
194pub const CAP_SYS_MODULE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_MODULE };
195pub const CAP_SYS_RAWIO: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_RAWIO };
196pub const CAP_SYS_CHROOT: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_CHROOT };
197pub const CAP_SYS_PTRACE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_PTRACE };
198pub const CAP_SYS_PACCT: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_PACCT };
199pub const CAP_SYS_ADMIN: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_ADMIN };
200pub const CAP_SYS_BOOT: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_BOOT };
201pub const CAP_SYS_NICE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_NICE };
202pub const CAP_SYS_RESOURCE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_RESOURCE };
203pub const CAP_SYS_TIME: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYS_TIME };
204pub const CAP_SYS_TTY_CONFIG: Capabilities =
205    Capabilities { mask: 1u64 << uapi::CAP_SYS_TTY_CONFIG };
206pub const CAP_MKNOD: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_MKNOD };
207pub const CAP_LEASE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_LEASE };
208pub const CAP_AUDIT_WRITE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_AUDIT_WRITE };
209pub const CAP_AUDIT_CONTROL: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_AUDIT_CONTROL };
210pub const CAP_SETFCAP: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SETFCAP };
211pub const CAP_MAC_OVERRIDE: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_MAC_OVERRIDE };
212pub const CAP_MAC_ADMIN: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_MAC_ADMIN };
213pub const CAP_SYSLOG: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_SYSLOG };
214pub const CAP_WAKE_ALARM: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_WAKE_ALARM };
215pub const CAP_BLOCK_SUSPEND: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_BLOCK_SUSPEND };
216pub const CAP_AUDIT_READ: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_AUDIT_READ };
217pub const CAP_PERFMON: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_PERFMON };
218pub const CAP_BPF: Capabilities = Capabilities { mask: 1u64 << uapi::CAP_BPF };
219pub const CAP_CHECKPOINT_RESTORE: Capabilities =
220    Capabilities { mask: 1u64 << uapi::CAP_CHECKPOINT_RESTORE };
221pub const CAP_LAST_CAP: u32 = uapi::CAP_LAST_CAP;
222
223bitflags! {
224    #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
225    pub struct PtraceAccessMode: u32 {
226        const READ      = 1 << 0;
227        const ATTACH    = 1 << 1;
228        const FSCREDS   = 1 << 2;
229        const REALCREDS = 1 << 3;
230        const NOAUDIT   = 1 << 4;
231    }
232}
233
234pub const PTRACE_MODE_READ: PtraceAccessMode = PtraceAccessMode::READ;
235pub const PTRACE_MODE_ATTACH: PtraceAccessMode = PtraceAccessMode::ATTACH;
236pub const PTRACE_MODE_FSCREDS: PtraceAccessMode = PtraceAccessMode::FSCREDS;
237pub const PTRACE_MODE_REALCREDS: PtraceAccessMode = PtraceAccessMode::REALCREDS;
238pub const PTRACE_MODE_READ_FSCREDS: PtraceAccessMode = PtraceAccessMode::from_bits_truncate(
239    PtraceAccessMode::READ.bits() | PtraceAccessMode::FSCREDS.bits(),
240);
241pub const PTRACE_MODE_READ_REALCREDS: PtraceAccessMode = PtraceAccessMode::from_bits_truncate(
242    PtraceAccessMode::READ.bits() | PtraceAccessMode::REALCREDS.bits(),
243);
244pub const PTRACE_MODE_ATTACH_FSCREDS: PtraceAccessMode = PtraceAccessMode::from_bits_truncate(
245    PtraceAccessMode::ATTACH.bits() | PtraceAccessMode::FSCREDS.bits(),
246);
247pub const PTRACE_MODE_ATTACH_REALCREDS: PtraceAccessMode = PtraceAccessMode::from_bits_truncate(
248    PtraceAccessMode::ATTACH.bits() | PtraceAccessMode::REALCREDS.bits(),
249);
250pub const PTRACE_MODE_NOAUDIT: PtraceAccessMode = PtraceAccessMode::NOAUDIT;
251
252#[derive(Debug, Clone)]
253pub struct Credentials {
254    pub uid: uid_t,
255    pub gid: gid_t,
256    pub euid: uid_t,
257    pub egid: gid_t,
258    pub saved_uid: uid_t,
259    pub saved_gid: gid_t,
260    pub groups: Vec<gid_t>,
261
262    /// See https://man7.org/linux/man-pages/man2/setfsuid.2.html
263    pub fsuid: uid_t,
264
265    /// See https://man7.org/linux/man-pages/man2/setfsgid.2.html
266    pub fsgid: gid_t,
267
268    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
269    ///
270    /// > This is a limiting superset for the effective capabilities that the thread may assume. It
271    /// > is also a limiting superset for the capabilities that may be added to the inheritable set
272    /// > by a thread that does not have the CAP_SETPCAP capability in its effective set.
273    ///
274    /// > If a thread drops a capability from its permitted set, it can never reacquire that
275    /// > capability (unless it execve(2)s either a set-user-ID-root program, or a program whose
276    /// > associated file capabilities grant that capability).
277    pub cap_permitted: Capabilities,
278
279    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
280    ///
281    /// > This is the set of capabilities used by the kernel to perform permission checks for the
282    /// > thread.
283    pub cap_effective: Capabilities,
284
285    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
286    ///
287    /// > This is a set of capabilities preserved across an execve(2).  Inheritable capabilities
288    /// > remain inheritable when executing any program, and inheritable capabilities are added to
289    /// > the permitted set when executing a program that has the corresponding bits set in the file
290    /// > inheritable set.
291    ///
292    /// > Because inheritable capabilities are not generally preserved across execve(2) when running
293    /// > as a non-root user, applications that wish to run helper programs with elevated
294    /// > capabilities should consider using ambient capabilities, described below.
295    pub cap_inheritable: Capabilities,
296
297    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
298    ///
299    /// > The capability bounding set is a mechanism that can be used to limit the capabilities that
300    /// > are gained during execve(2).
301    ///
302    /// > Since Linux 2.6.25, this is a per-thread capability set. In older kernels, the capability
303    /// > bounding set was a system wide attribute shared by all threads on the system.
304    pub cap_bounding: Capabilities,
305
306    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
307    ///
308    /// > This is a set of capabilities that are preserved across an execve(2) of a program that is
309    /// > not privileged.  The ambient capability set obeys the invariant that no capability can
310    /// > ever be ambient if it is not both permitted and inheritable.
311    ///
312    /// > Executing a program that changes UID or GID due to the set-user-ID or set-group-ID bits
313    /// > or executing a program that has any file capabilities set will clear the ambient set.
314    pub cap_ambient: Capabilities,
315
316    /// From https://man7.org/linux/man-pages/man7/capabilities.7.html
317    ///
318    /// > Starting with kernel 2.6.26, and with a kernel in which file capabilities are enabled,
319    /// > Linux implements a set of per-thread securebits flags that can be used to disable special
320    /// > handling of capabilities for UID 0 (root).
321    ///
322    /// > The securebits flags can be modified and retrieved using the prctl(2)
323    /// > PR_SET_SECUREBITS and PR_GET_SECUREBITS operations.  The CAP_SETPCAP capability is
324    /// > required to modify the flags.
325    pub securebits: SecureBits,
326}
327
328bitflags! {
329    #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
330    pub struct SecureBits: u32 {
331        const KEEP_CAPS = 1 << uapi::SECURE_KEEP_CAPS;
332        const KEEP_CAPS_LOCKED = 1 <<  uapi::SECURE_KEEP_CAPS_LOCKED;
333        const NO_SETUID_FIXUP = 1 << uapi::SECURE_NO_SETUID_FIXUP;
334        const NO_SETUID_FIXUP_LOCKED = 1 << uapi::SECURE_NO_SETUID_FIXUP_LOCKED;
335        const NOROOT = 1 << uapi::SECURE_NOROOT;
336        const NOROOT_LOCKED = 1 << uapi::SECURE_NOROOT_LOCKED;
337        const NO_CAP_AMBIENT_RAISE = 1 << uapi::SECURE_NO_CAP_AMBIENT_RAISE;
338        const NO_CAP_AMBIENT_RAISE_LOCKED = 1 << uapi::SECURE_NO_CAP_AMBIENT_RAISE_LOCKED;
339    }
340}
341
342static ROOT_CREDENTIALS: LazyLock<Arc<Credentials>> =
343    LazyLock::new(|| Arc::new(Credentials::with_ids(0, 0)));
344
345impl Credentials {
346    /// Creates a set of credentials with all possible permissions and capabilities.
347    pub fn root() -> Arc<Self> {
348        ROOT_CREDENTIALS.clone()
349    }
350
351    /// Creates a set of credentials with the given uid and gid. If the uid is 0, the credentials
352    /// will grant superuser access.
353    pub fn with_ids(uid: uid_t, gid: gid_t) -> Credentials {
354        let caps = if uid == 0 { Capabilities::all() } else { Capabilities::empty() };
355        Credentials {
356            uid,
357            gid,
358            euid: uid,
359            egid: gid,
360            saved_uid: uid,
361            saved_gid: gid,
362            groups: vec![],
363            fsuid: uid,
364            fsgid: gid,
365            cap_permitted: caps,
366            cap_effective: caps,
367            cap_inheritable: Capabilities::empty(),
368            cap_bounding: Capabilities::all(),
369            cap_ambient: Capabilities::empty(),
370            securebits: SecureBits::empty(),
371        }
372    }
373
374    pub fn is_superuser(&self) -> bool {
375        self.euid == 0
376    }
377
378    pub fn is_in_group(&self, gid: gid_t) -> bool {
379        self.egid == gid || self.groups.contains(&gid)
380    }
381
382    /// Returns whether or not the task has the given `capability`.
383    pub fn has_capability(&self, capability: Capabilities) -> bool {
384        self.cap_effective.contains(capability)
385    }
386
387    fn apply_suid_and_sgid(&mut self, maybe_set: UserAndOrGroupId) {
388        if maybe_set.is_none() {
389            return;
390        }
391
392        let prev = self.copy_user_credentials();
393
394        if let Some(uid) = maybe_set.uid {
395            self.euid = uid;
396            self.fsuid = uid;
397        }
398
399        if let Some(gid) = maybe_set.gid {
400            self.egid = gid;
401            self.fsgid = gid;
402        }
403
404        self.update_capabilities(prev);
405    }
406
407    pub fn exec(&mut self, maybe_set: UserAndOrGroupId) {
408        let is_suid_or_sgid = maybe_set.is_some();
409        // From <https://man7.org/linux/man-pages/man2/execve.2.html>:
410        //
411        //   If the set-user-ID bit is set on the program file referred to by
412        //   pathname, then the effective user ID of the calling process is
413        //   changed to that of the owner of the program file.  Similarly, if
414        //   the set-group-ID bit is set on the program file, then the
415        //   effective group ID of the calling process is set to the group of
416        //   the program file.
417        self.apply_suid_and_sgid(maybe_set);
418
419        // From <https://man7.org/linux/man-pages/man2/execve.2.html>:
420        //
421        //   The effective user ID of the process is copied to the saved set-
422        //   user-ID; similarly, the effective group ID is copied to the saved
423        //   set-group-ID.  This copying takes place after any effective ID
424        //   changes that occur because of the set-user-ID and set-group-ID
425        //   mode bits.
426        self.saved_uid = self.euid;
427        self.saved_gid = self.egid;
428
429        // From <https://man7.org/linux/man-pages/man7/capabilities.7.html>:
430        //
431        //   During an execve(2), the kernel calculates the new capabilities
432        //   of the process using the following algorithm:
433        //   P'(ambient)     = (file is privileged) ? 0 : P(ambient)
434        //   P'(permitted)   = (P(inheritable) & F(inheritable)) |
435        //                     (F(permitted) & P(bounding)) | P'(ambient)
436        //   P'(effective)   = F(effective) ? P'(permitted) : P'(ambient)
437        //   P'(inheritable) = P(inheritable)    [i.e., unchanged]
438        //   P'(bounding)    = P(bounding)       [i.e., unchanged]
439        // where:
440        //   P()    denotes the value of a thread capability set before
441        //          the execve(2)
442        //   P'()   denotes the value of a thread capability set after the
443        //          execve(2)
444        //   F()    denotes a file capability set
445
446        // a privileged file is one that has capabilities or
447        // has the set-user-ID or set-group-ID bit set.
448        // TODO(https://fxbug.dev/328629782): Add support for file capabilities.
449        let file_is_privileged = is_suid_or_sgid;
450
451        // After having performed any changes to the process effective ID
452        // that were triggered by the set-user-ID mode bit of the binary—
453        // e.g., switching the effective user ID to 0 (root) because a set-
454        // user-ID-root program was executed—the kernel calculates the file
455        // capability sets as follows:
456
457        // (1)  If the real or effective user ID of the process is 0 (root),
458        //  then the file inheritable and permitted sets are ignored;
459        //  instead they are notionally considered to be all ones (i.e.,
460        //  all capabilities enabled).
461        let (file_permitted, file_inheritable) = if self.uid == 0 || self.euid == 0 {
462            (Capabilities::all(), Capabilities::all())
463        } else {
464            (Capabilities::empty(), Capabilities::empty())
465        };
466
467        // (2)  If the effective user ID of the process is 0 (root) or the
468        //  file effective bit is in fact enabled, then the file
469        //  effective bit is notionally defined to be one (enabled).
470        let file_effective = self.euid == 0;
471
472        // TODO(https://fxbug.dev/328629782): File capabilities are honored for set-user-ID-root
473        // binaries with capabilities executed by non-root users. See "Set-user-ID-root programs
474        // that have file capabilities" in the man page.
475
476        //   P'(ambient)     = (file is privileged) ? 0 : P(ambient)
477        self.cap_ambient =
478            if file_is_privileged { Capabilities::empty() } else { self.cap_ambient };
479
480        //   P'(permitted)   = (P(inheritable) & F(inheritable)) |
481        //                     (F(permitted) & P(bounding)) | P'(ambient)
482        self.cap_permitted = (self.cap_inheritable & file_inheritable)
483            | (file_permitted & self.cap_bounding)
484            | self.cap_ambient;
485
486        //   P'(effective)   = F(effective) ? P'(permitted) : P'(ambient)
487        self.cap_effective = if file_effective { self.cap_permitted } else { self.cap_ambient };
488
489        self.securebits.remove(SecureBits::KEEP_CAPS);
490    }
491
492    pub fn as_fscred(&self) -> FsCred {
493        FsCred { uid: self.fsuid, gid: self.fsgid }
494    }
495
496    pub fn euid_as_fscred(&self) -> FsCred {
497        FsCred { uid: self.euid, gid: self.egid }
498    }
499
500    pub fn uid_as_fscred(&self) -> FsCred {
501        FsCred { uid: self.uid, gid: self.gid }
502    }
503
504    pub fn copy_user_credentials(&self) -> UserCredentials {
505        UserCredentials {
506            uid: self.uid,
507            euid: self.euid,
508            fsuid: self.fsuid,
509            saved_uid: self.saved_uid,
510        }
511    }
512
513    pub fn update_capabilities(&mut self, prev: UserCredentials) {
514        // https://man7.org/linux/man-pages/man7/capabilities.7.html
515        // If one or more of the real, effective, or saved set user IDs
516        // was previously 0, and as a result of the UID changes all of
517        // these IDs have a nonzero value, then all capabilities are
518        // cleared from the permitted, effective, and ambient capability
519        // sets.
520        //
521        // SECBIT_KEEP_CAPS: Setting this flag allows a thread that has one or more 0
522        // UIDs to retain capabilities in its permitted set when it
523        // switches all of its UIDs to nonzero values.
524        // The setting of the SECBIT_KEEP_CAPS flag is ignored if the
525        // SECBIT_NO_SETUID_FIXUP flag is set.  (The latter flag
526        // provides a superset of the effect of the former flag.)
527        // SECBIT_NO_SETUID_FIXUP: Setting  this  flag  stops  the  kernel from adjusting
528        // the process's permitted, effective, and ambient capability sets when the thread's
529        // effective and filesystem UIDs are switched between zero and nonzero values.
530        if self.securebits.contains(SecureBits::NO_SETUID_FIXUP) {
531            return;
532        }
533        if !self.securebits.contains(SecureBits::KEEP_CAPS)
534            && (prev.uid == 0 || prev.euid == 0 || prev.saved_uid == 0)
535            && (self.uid != 0 && self.euid != 0 && self.saved_uid != 0)
536        {
537            self.cap_permitted = Capabilities::empty();
538            self.cap_effective = Capabilities::empty();
539            self.cap_ambient = Capabilities::empty();
540        }
541        // If the effective user ID is changed from 0 to nonzero, then
542        // all capabilities are cleared from the effective set.
543        if prev.euid == 0 && self.euid != 0 {
544            self.cap_effective = Capabilities::empty();
545        } else if prev.euid != 0 && self.euid == 0 {
546            // If the effective user ID is changed from nonzero to 0, then
547            // the permitted set is copied to the effective set.
548            self.cap_effective = self.cap_permitted;
549        }
550
551        // If the filesystem user ID is changed from 0 to nonzero (see
552        // setfsuid(2)), then the following capabilities are cleared from
553        // the effective set: CAP_CHOWN, CAP_DAC_OVERRIDE,
554        // CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID,
555        // CAP_LINUX_IMMUTABLE (since Linux 2.6.30), CAP_MAC_OVERRIDE,
556        // and CAP_MKNOD (since Linux 2.6.30).
557        let fs_capabilities = CAP_CHOWN
558            | CAP_DAC_OVERRIDE
559            | CAP_DAC_READ_SEARCH
560            | CAP_FOWNER
561            | CAP_FSETID
562            | CAP_LINUX_IMMUTABLE
563            | CAP_MAC_OVERRIDE
564            | CAP_MKNOD;
565        if prev.fsuid == 0 && self.fsuid != 0 {
566            self.cap_effective &= !fs_capabilities;
567        } else if prev.fsuid != 0 && self.fsuid == 0 {
568            // If the filesystem UID is changed from nonzero to 0, then any
569            // of these capabilities that are enabled in the permitted set
570            // are enabled in the effective set.
571            self.cap_effective |= self.cap_permitted & fs_capabilities;
572        }
573    }
574}
575
576/// The owner and group of a file. Used as a parameter for functions that create files.
577#[derive(Debug, Clone, Copy)]
578pub struct FsCred {
579    pub uid: uid_t,
580    pub gid: gid_t,
581}
582
583impl FsCred {
584    pub const fn root() -> Self {
585        Self { uid: 0, gid: 0 }
586    }
587}
588
589impl From<Credentials> for FsCred {
590    fn from(c: Credentials) -> Self {
591        c.as_fscred()
592    }
593}
594
595#[derive(Debug, Clone, Copy)]
596pub struct UserCredentials {
597    pub uid: uid_t,
598    pub euid: uid_t,
599    pub saved_uid: uid_t,
600    pub fsuid: uid_t,
601}
602
603#[derive(Debug, Default, Clone)]
604pub struct UserAndOrGroupId {
605    pub uid: Option<uid_t>,
606    pub gid: Option<gid_t>,
607}
608
609impl UserAndOrGroupId {
610    pub fn is_none(&self) -> bool {
611        self.uid.is_none() && self.gid.is_none()
612    }
613
614    pub fn is_some(&self) -> bool {
615        !self.is_none()
616    }
617
618    pub fn clear(&mut self) {
619        self.uid = None;
620        self.gid = None;
621    }
622}
623
624#[cfg(test)]
625mod tests {
626    use super::*;
627
628    #[::fuchsia::test]
629    fn test_empty() {
630        assert_eq!(Capabilities::empty().mask, 0);
631    }
632
633    #[::fuchsia::test]
634    fn test_all() {
635        // all() should be every bit set, not just all the CAP_* constants.
636        assert_eq!(Capabilities::all().mask, u64::MAX);
637    }
638
639    #[::fuchsia::test]
640    fn test_union() {
641        let expected = Capabilities { mask: CAP_BLOCK_SUSPEND.mask | CAP_AUDIT_READ.mask };
642        assert_eq!(CAP_BLOCK_SUSPEND.union(CAP_AUDIT_READ), expected);
643        assert_eq!(CAP_BLOCK_SUSPEND.union(CAP_BLOCK_SUSPEND), CAP_BLOCK_SUSPEND);
644    }
645
646    #[::fuchsia::test]
647    fn test_difference() {
648        let base = CAP_BPF | CAP_AUDIT_WRITE;
649        let expected = CAP_BPF;
650        assert_eq!(base.difference(CAP_AUDIT_WRITE), expected);
651        assert_eq!(base.difference(CAP_AUDIT_WRITE | CAP_BPF), Capabilities::empty());
652    }
653
654    #[::fuchsia::test]
655    fn test_contains() {
656        let base = CAP_BPF | CAP_AUDIT_WRITE;
657        assert!(base.contains(CAP_AUDIT_WRITE));
658        assert!(base.contains(CAP_BPF));
659        assert!(base.contains(CAP_AUDIT_WRITE | CAP_BPF));
660
661        assert!(!base.contains(CAP_AUDIT_CONTROL));
662        assert!(!base.contains(CAP_AUDIT_WRITE | CAP_BPF | CAP_AUDIT_CONTROL));
663    }
664
665    #[::fuchsia::test]
666    fn test_insert() {
667        let mut capabilities = CAP_BLOCK_SUSPEND;
668        capabilities.insert(CAP_BLOCK_SUSPEND);
669        assert_eq!(capabilities, CAP_BLOCK_SUSPEND);
670
671        capabilities.insert(CAP_AUDIT_READ);
672        let expected = Capabilities { mask: CAP_BLOCK_SUSPEND.mask | CAP_AUDIT_READ.mask };
673        assert_eq!(capabilities, expected);
674    }
675
676    #[::fuchsia::test]
677    fn test_remove() {
678        let mut capabilities = CAP_BLOCK_SUSPEND;
679        capabilities.remove(CAP_BLOCK_SUSPEND);
680        assert_eq!(capabilities, Capabilities::empty());
681
682        let mut capabilities = CAP_BLOCK_SUSPEND | CAP_AUDIT_READ;
683        capabilities.remove(CAP_AUDIT_READ);
684        assert_eq!(capabilities, CAP_BLOCK_SUSPEND);
685    }
686
687    #[::fuchsia::test]
688    fn test_try_from() {
689        let capabilities = CAP_BLOCK_SUSPEND;
690        assert_eq!(Capabilities::try_from(uapi::CAP_BLOCK_SUSPEND as u64), Ok(capabilities));
691
692        assert_eq!(Capabilities::try_from(200000), error!(EINVAL));
693    }
694}
starnix_uapi/auth.rs

starnix_uapi/
auth.rs
