Add syscall capget/capset

docs/src/kernel/linux-compatibility.md

@@ -145,8 +145,8 @@ provided by Linux on x86-64 architecture.
 | 122     | setfsuid         | ✅              |
 | 123     | setfsgid         | ✅              |
 | 124     | getsid           | ✅              |
-| 125     | capget           | ❌              |
+| 125     | capget           | ✅              |
-| 126     | capset           | ❌              |
+| 126     | capset           | ✅              |
 | 127     | rt_sigpending    | ✅              |
 | 128     | rt_sigtimedwait  | ❌              |
 | 129     | rt_sigqueueinfo  | ❌              |

kernel/aster-nix/src/process/credentials/c_types.rs

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: MPL-2.0
+#![allow(non_camel_case_types)]
+
+use crate::{prelude::*, process::Pid};
+
+#[derive(Debug, Clone, Copy, Pod)]
+#[repr(C)]
+pub struct cap_user_header_t {
+    pub version: u32,
+    pub pid: Pid,
+}
+
+#[derive(Debug, Clone, Copy, Pod)]
+#[repr(C)]
+pub struct cap_user_data_t {
+    pub effective: u32,
+    pub permitted: u32,
+    pub inheritable: u32,
+}
+
+pub const LINUX_CAPABILITY_VERSION_3: u32 = 0x20080522;

kernel/aster-nix/src/process/credentials/capabilities.rs

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use core::sync::atomic::{AtomicU64, Ordering};
+
+use bitflags::bitflags;
+
+bitflags! {
+    /// Represents a set of Linux capabilities.
+    pub struct CapSet: u64 {
+        const CHOWN = 1 << 0;
+        const DAC_OVERRIDE = 1 << 1;
+        const DAC_READ_SEARCH = 1 << 2;
+        const FOWNER = 1 << 3;
+        const FSETID = 1 << 4;
+        const KILL = 1 << 5;
+        const SETGID = 1 << 6;
+        const SETUID = 1 << 7;
+        const SETPCAP = 1 << 8;
+        const LINUX_IMMUTABLE = 1 << 9;
+        const NET_BIND_SERVICE = 1 << 10;
+        const NET_BROADCAST = 1 << 11;
+        const NET_ADMIN = 1 << 12;
+        const NET_RAW = 1 << 13;
+        const IPC_LOCK = 1 << 14;
+        const IPC_OWNER = 1 << 15;
+        const SYS_MODULE = 1 << 16;
+        const SYS_RAWIO = 1 << 17;
+        const SYS_CHROOT = 1 << 18;
+        const SYS_PTRACE = 1 << 19;
+        const SYS_PACCT = 1 << 20;
+        const SYS_ADMIN = 1 << 21;
+        const SYS_BOOT = 1 << 22;
+        const SYS_NICE = 1 << 23;
+        const SYS_RESOURCE = 1 << 24;
+        const SYS_TIME = 1 << 25;
+        const SYS_TTY_CONFIG = 1 << 26;
+        const MKNOD = 1 << 27;
+        const LEASE = 1 << 28;
+        const AUDIT_WRITE = 1 << 29;
+        const AUDIT_CONTROL = 1 << 30;
+        const SETFCAP = 1 << 31;
+        const MAC_OVERRIDE = 1 << 32;
+        const MAC_ADMIN = 1 << 33;
+        const SYSLOG = 1 << 34;
+        const WAKE_ALARM = 1 << 35;
+        const BLOCK_SUSPEND = 1 << 36;
+        const AUDIT_READ = 1 << 37;
+        const PERFMON = 1 << 38;
+        const BPF = 1 << 39;
+        const CHECKPOINT_RESTORE = 1u64 << 40;
+        // ... include other capabilities as needed
+    }
+}
+
+impl CapSet {
+    /// Converts the capability set to a `u32`. The higher bits are truncated.
+    pub fn as_u32(&self) -> u32 {
+        self.bits() as u32
+    }
+
+    /// Creates a new `CapSet` with the `SYS_ADMIN` capability set, typically for a root user.
+    pub const fn new_root() -> Self {
+        CapSet::SYS_ADMIN
+    }
+}
+
+#[derive(Debug)]
+pub(super) struct AtomicCapSet(AtomicU64);
+
+impl AtomicCapSet {
+    pub const fn new(capset: CapSet) -> Self {
+        Self(AtomicU64::new(capset.bits))
+    }
+
+    pub fn set(&self, capset: CapSet) {
+        self.0.store(capset.bits(), Ordering::Relaxed);
+    }
+
+    pub fn get(&self) -> CapSet {
+        CapSet::from_bits_truncate(self.0.load(Ordering::Relaxed))
+    }
+}
+
+impl Clone for AtomicCapSet {
+    fn clone(&self) -> Self {
+        Self::new(self.get())
+    }
+}

kernel/aster-nix/src/process/credentials/credentials_.rs

@@ -3,7 +3,10 @@
 use aster_frame::sync::{RwLockReadGuard, RwLockWriteGuard};
 
 use super::{group::AtomicGid, user::AtomicUid, Gid, Uid};
-use crate::prelude::*;
+use crate::{
+    prelude::*,
+    process::credentials::capabilities::{AtomicCapSet, CapSet},
+};
 
 #[derive(Debug)]
 pub(super) struct Credentials_ {
@@ -25,13 +28,27 @@ pub(super) struct Credentials_ {
     /// Group id used for file system checks.
     fsgid: AtomicGid,
 
-    // A set of additional groups to which a process belongs.
+    /// A set of additional groups to which a process belongs.
     supplementary_gids: RwLock<BTreeSet<Gid>>,
+
+    /// The Linux capabilities.
+    /// This is not the capability (in static_cap.rs) enforced on rust objects.
+
+    /// Capability that child processes can inherit
+    inheritable_capset: AtomicCapSet,
+
+    /// Capabilities that a process can potentially be granted.
+    /// It defines the maximum set of privileges that the process could possibly have.
+    /// Even if the process is not currently using these privileges, it has the potential ability to enable them.
+    permitted_capset: AtomicCapSet,
+
+    /// Capability that we can actually use
+    effective_capset: AtomicCapSet,
 }
 
 impl Credentials_ {
     /// Create a new credentials. ruid, euid, suid will be set as the same uid, and gid is the same.
-    pub fn new(uid: Uid, gid: Gid) -> Self {
+    pub fn new(uid: Uid, gid: Gid, capset: CapSet) -> Self {
         let mut supplementary_gids = BTreeSet::new();
         supplementary_gids.insert(gid);
 
@@ -45,6 +62,9 @@ impl Credentials_ {
             sgid: AtomicGid::new(gid),
             fsgid: AtomicGid::new(gid),
             supplementary_gids: RwLock::new(supplementary_gids),
+            inheritable_capset: AtomicCapSet::new(capset),
+            permitted_capset: AtomicCapSet::new(capset),
+            effective_capset: AtomicCapSet::new(capset),
         }
     }
 
@@ -364,6 +384,7 @@ impl Credentials_ {
     }
 
     //  ******* Supplementary groups methods *******
+
     pub(super) fn groups(&self) -> RwLockReadGuard<BTreeSet<Gid>> {
         self.supplementary_gids.read()
     }
@@ -371,6 +392,32 @@ impl Credentials_ {
     pub(super) fn groups_mut(&self) -> RwLockWriteGuard<BTreeSet<Gid>> {
         self.supplementary_gids.write()
     }
+
+    //  ******* Linux Capability methods *******
+
+    pub(super) fn inheritable_capset(&self) -> CapSet {
+        self.inheritable_capset.get()
+    }
+
+    pub(super) fn permitted_capset(&self) -> CapSet {
+        self.permitted_capset.get()
+    }
+
+    pub(super) fn effective_capset(&self) -> CapSet {
+        self.effective_capset.get()
+    }
+
+    pub(super) fn set_inheritable_capset(&self, inheritable_capset: CapSet) {
+        self.inheritable_capset.set(inheritable_capset);
+    }
+
+    pub(super) fn set_permitted_capset(&self, permitted_capset: CapSet) {
+        self.permitted_capset.set(permitted_capset);
+    }
+
+    pub(super) fn set_effective_capset(&self, effective_capset: CapSet) {
+        self.effective_capset.set(effective_capset);
+    }
 }
 
 impl Clone for Credentials_ {
@@ -385,6 +432,9 @@ impl Clone for Credentials_ {
             sgid: self.sgid.clone(),
             fsgid: self.fsgid.clone(),
             supplementary_gids: RwLock::new(self.supplementary_gids.read().clone()),
+            inheritable_capset: self.inheritable_capset.clone(),
+            permitted_capset: self.permitted_capset.clone(),
+            effective_capset: self.effective_capset.clone(),
         }
     }
 }

kernel/aster-nix/src/process/credentials/mod.rs

@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
+pub mod c_types;
+pub mod capabilities;
 mod credentials_;
 mod group;
 mod static_cap;
@@ -20,7 +22,8 @@ use crate::prelude::*;
 /// - effective user ID and group ID;
 /// - saved-set user ID and saved-set group ID;
 /// - file system user ID and group ID (Linux-specific);
-/// - supplementary group IDs.
+/// - supplementary group IDs;
+/// - Linux capabilities.
 pub struct Credentials<R = FullOp>(Arc<Credentials_>, R);
 
 /// Gets read-only credentials of current thread.

kernel/aster-nix/src/process/credentials/static_cap.rs

@@ -6,7 +6,7 @@ use aster_frame::sync::{RwLockReadGuard, RwLockWriteGuard};
 use aster_rights::{Dup, Read, TRights, Write};
 use aster_rights_proc::require;
 
-use super::{credentials_::Credentials_, Credentials, Gid, Uid};
+use super::{capabilities::CapSet, credentials_::Credentials_, Credentials, Gid, Uid};
 use crate::prelude::*;
 
 impl<R: TRights> Credentials<R> {
@@ -14,7 +14,8 @@ impl<R: TRights> Credentials<R> {
     pub fn new_root() -> Self {
         let uid = Uid::new_root();
         let gid = Gid::new_root();
-        let credentials_ = Arc::new(Credentials_::new(uid, gid));
+        let cap = CapSet::new_root();
+        let credentials_ = Arc::new(Credentials_::new(uid, gid, cap));
         Self(credentials_, R::new())
     }
 
@@ -249,4 +250,54 @@ impl<R: TRights> Credentials<R> {
     pub fn groups_mut(&self) -> RwLockWriteGuard<BTreeSet<Gid>> {
         self.0.groups_mut()
     }
+
+    // *********** Linux Capability methods **********
+
+    /// Gets the capabilities that child process can inherit.
+    ///
+    /// This method requies the `Read` right.
+    #[require(R > Read)]
+    pub fn inheritable_capset(&self) -> CapSet {
+        self.0.inheritable_capset()
+    }
+
+    /// Gets the capabilities that are permitted.
+    ///
+    /// This method requies the `Read` right.
+    #[require(R > Read)]
+    pub fn permitted_capset(&self) -> CapSet {
+        self.0.permitted_capset()
+    }
+
+    /// Gets the capabilities that actually use.
+    ///
+    /// This method requies the `Read` right.
+    #[require(R > Read)]
+    pub fn effective_capset(&self) -> CapSet {
+        self.0.effective_capset()
+    }
+
+    /// Sets the capabilities that child process can inherit.
+    ///
+    /// This method requires the `Write` right.
+    #[require(R > Write)]
+    pub fn set_inheritable_capset(&self, inheritable_capset: CapSet) {
+        self.0.set_inheritable_capset(inheritable_capset);
+    }
+
+    /// Sets the capabilities that are permitted.
+    ///
+    /// This method requires the `Write` right.
+    #[require(R > Write)]
+    pub fn set_permitted_capset(&self, permitted_capset: CapSet) {
+        self.0.set_permitted_capset(permitted_capset);
+    }
+
+    /// Sets the capabilities that actually use.
+    ///
+    /// This method requires the `Write` right.
+    #[require(R > Write)]
+    pub fn set_effective_capset(&self, effective_capset: CapSet) {
+        self.0.set_effective_capset(effective_capset);
+    }
 }

kernel/aster-nix/src/process/mod.rs

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
 mod clone;
-mod credentials;
+pub mod credentials;
 mod exit;
 mod kill;
 pub mod posix_thread;

kernel/aster-nix/src/syscall/arch/x86.rs

@@ -7,6 +7,8 @@ use crate::syscall::{
     arch_prctl::sys_arch_prctl,
     bind::sys_bind,
     brk::sys_brk,
+    capget::sys_capget,
+    capset::sys_capset,
     chdir::{sys_chdir, sys_fchdir},
     chmod::{sys_chmod, sys_fchmod, sys_fchmodat},
     chown::{sys_chown, sys_fchown, sys_fchownat, sys_lchown},
@@ -216,6 +218,8 @@ impl_syscall_nums_and_dispatch_fn! {
     SYS_SETFSUID = 122         => sys_setfsuid(args[..1]);
     SYS_SETFSGID = 123         => sys_setfsgid(args[..1]);
     SYS_GETSID = 124           => sys_getsid(args[..1]);
+    SYS_CAPGET = 125           => sys_capget(args[..2]);
+    SYS_CAPSET = 126           => sys_capset(args[..2]);
     SYS_RT_SIGPENDING = 127    => sys_rt_sigpending(args[..2]);
     SYS_RT_SIGSUSPEND = 130    => sys_rt_sigsuspend(args[..2]);
     SYS_SIGALTSTACK = 131      => sys_sigaltstack(args[..2]);

kernel/aster-nix/src/syscall/capget.rs

@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::{
+    prelude::*,
+    process::{
+        credentials,
+        credentials::c_types::{cap_user_data_t, cap_user_header_t, LINUX_CAPABILITY_VERSION_3},
+    },
+    util::{read_val_from_user, write_val_to_user},
+};
+
+pub fn sys_capget(cap_user_header_addr: Vaddr, cap_user_data_addr: Vaddr) -> Result<SyscallReturn> {
+    let cap_user_header: cap_user_header_t =
+        read_val_from_user::<cap_user_header_t>(cap_user_header_addr)?;
+
+    if cap_user_header.version != LINUX_CAPABILITY_VERSION_3 {
+        return_errno_with_message!(Errno::EINVAL, "not supported (capability version is not 3)");
+    };
+
+    // Extract target pid and validate whether it represents the current process.
+    let header_pid = cap_user_header.pid;
+    // Capget only query current process's credential. Namely, it only allows header->pid == 0
+    // or header->pid == getpid(), which are equivalent.
+    // See https://linux.die.net/man/2/capget (Section. With VFS capability support) for details.
+    if header_pid != 0 && header_pid != current!().pid() {
+        return_errno_with_message!(Errno::EINVAL, "invalid pid");
+    }
+
+    let credentials = credentials();
+    let inheritable_capset = credentials.inheritable_capset();
+    let permitted_capset = credentials.permitted_capset();
+    let effective_capset = credentials.effective_capset();
+
+    // Annoying legacy format with 64-bit capabilities exposed as two sets of 32-bit fields,
+    // so we need to split the capability values up.
+    let result = cap_user_data_t {
+        // Note we silently drop the upper capabilities here.
+        // This behavior is considered fail-safe behavior.
+        effective: effective_capset.as_u32(),
+        permitted: permitted_capset.as_u32(),
+        inheritable: inheritable_capset.as_u32(),
+    };
+
+    write_val_to_user(cap_user_data_addr, &result)?;
+    Ok(SyscallReturn::Return(0))
+}

kernel/aster-nix/src/syscall/capset.rs

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::{
+    prelude::*,
+    process::{
+        credentials::{
+            c_types::{cap_user_data_t, cap_user_header_t, LINUX_CAPABILITY_VERSION_3},
+            capabilities::CapSet,
+        },
+        credentials_mut,
+    },
+    util::read_val_from_user,
+};
+
+const CAP_LAST_CAP: u64 = 40; // Number of the last capability (CAP_CHECKPOINT_RESTORE)
+const CAP_VALID_MASK: u64 = (1u64 << (CAP_LAST_CAP + 1)) - 1;
+
+fn make_kernel_cap(low: u32, high: u32) -> u64 {
+    ((low as u64) | ((high as u64) << 32)) & CAP_VALID_MASK
+}
+
+pub fn sys_capset(cap_user_header_addr: Vaddr, cap_user_data_addr: Vaddr) -> Result<SyscallReturn> {
+    let cap_user_header: cap_user_header_t =
+        read_val_from_user::<cap_user_header_t>(cap_user_header_addr)?;
+
+    if cap_user_header.version != LINUX_CAPABILITY_VERSION_3 {
+        return_errno_with_message!(Errno::EINVAL, "not supported (capability version is not 3)");
+    };
+
+    // The ability to set capabilities of any other process has been deprecated.
+    // See: https://elixir.bootlin.com/linux/v6.9.3/source/kernel/capability.c#L209 for more details.
+    let header_pid = cap_user_header.pid;
+    if header_pid != 0 && header_pid != current!().pid() {
+        return_errno_with_message!(Errno::EINVAL, "invalid pid");
+    }
+
+    // Convert the cap(u32) to u64
+    let cap_user_data: cap_user_data_t = read_val_from_user::<cap_user_data_t>(cap_user_data_addr)?;
+    let inheritable = make_kernel_cap(cap_user_data.inheritable, 0);
+    let permitted = make_kernel_cap(cap_user_data.permitted, 0);
+    let effective = make_kernel_cap(cap_user_data.effective, 0);
+
+    let credentials = credentials_mut();
+
+    credentials.set_inheritable_capset(CapSet::from_bits_truncate(inheritable));
+    credentials.set_permitted_capset(CapSet::from_bits_truncate(permitted));
+    credentials.set_effective_capset(CapSet::from_bits_truncate(effective));
+
+    Ok(SyscallReturn::Return(0))
+}

kernel/aster-nix/src/syscall/mod.rs

@@ -14,6 +14,8 @@ mod arch;
 mod arch_prctl;
 mod bind;
 mod brk;
+mod capget;
+mod capset;
 mod chdir;
 mod chmod;
 mod chown;

regression/apps/Makefile

@@ -11,6 +11,7 @@ REGRESSION_BUILD_DIR ?= $(INITRAMFS)/regression
 # These test apps are sorted by name
 TEST_APPS := \
 	alarm \
+	capability \
 	clone3 \
 	cpu_affinity \
 	eventfd2 \

regression/apps/capability/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: MPL-2.0
+
+include ../test_common.mk
+
+EXTRA_C_FLAGS :=

regression/apps/capability/capabilities.c

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <linux/capability.h>
+
+int set_caps(__u32 target_pid, __u32 capabilities)
+{
+	struct __user_cap_header_struct capheader;
+	struct __user_cap_data_struct capdata[2];
+	capheader.version = _LINUX_CAPABILITY_VERSION_3;
+	capheader.pid = target_pid;
+	memset(&capdata, 0, sizeof(capdata));
+
+	// Set specified capabilities
+	capdata[0].effective = capdata[0].permitted = capabilities;
+	capdata[0].inheritable = 0;
+	if (syscall(SYS_capset, &capheader, &capdata) < 0) {
+		perror("capset failed");
+		return 1;
+	}
+	printf("Process capabilities set successfully.\n");
+	return 0;
+}
+
+int check_caps(__u32 target_pid, __u32 capabilities)
+{
+	struct __user_cap_header_struct capheader;
+	struct __user_cap_data_struct capdata[2];
+	memset(&capheader, 0, sizeof(capheader));
+	memset(&capdata, 0, sizeof(capdata));
+	capheader.version = _LINUX_CAPABILITY_VERSION_3;
+	capheader.pid = target_pid;
+	if (syscall(SYS_capget, &capheader, &capdata) == -1) {
+		perror("capget failed");
+		exit(EXIT_FAILURE);
+	}
+	printf("Process capabilities retrieved successfully.\n");
+	return (capdata[0].permitted & capabilities) &&
+	       (capdata[0].effective & capabilities);
+}
+
+int main(void)
+{
+	__u32 target_pid = getpid();
+	printf("Process Pid: %u.\n", target_pid);
+
+	__u32 caps_to_set =
+		(1 << CAP_NET_RAW) |
+		(1 << CAP_NET_ADMIN); // Define the desired capabilities.
+
+	// Try setting the specified capabilities.
+	if (set_caps(target_pid, caps_to_set) != 0) {
+		fprintf(stderr, "Failed to set capabilities.\n");
+		return 1;
+	}
+
+	// Check for CAP_NET_RAW among the process's capabilities.
+	if (check_caps(target_pid, 1 << CAP_NET_RAW)) {
+		printf("Process has CAP_NET_RAW capability.\n");
+	} else {
+		fprintf(stderr,
+			"Process does NOT have CAP_NET_RAW capability.\n");
+		return 1;
+	}
+
+	// Check for CAP_NET_ADMIN among the process's capabilities.
+	if (check_caps(target_pid, 1 << CAP_NET_ADMIN)) {
+		printf("Process has CAP_NET_ADMIN capability.\n");
+	} else {
+		fprintf(stderr,
+			"Process does NOT have CAP_NET_ADMIN capability.\n");
+		return 1;
+	}
+
+	return 0;
+}

regression/syscall_test/blocklists/chroot_test

@@ -1,11 +1 @@
-ChrootTest.Success
+ChrootTest.WithoutCapability
-ChrootTest.PermissionDenied
-ChrootTest.NotDir
-ChrootTest.NotExist
-ChrootTest.WithoutCapability
-ChrootTest.CreatesNewRoot
-ChrootTest.DotDotFromOpenFD
-ChrootTest.ProcFdLinkResolutionInChroot
-ChrootTest.ProcMemSelfFdsNoEscapeProcOpen
-ChrootTest.ProcMemSelfMapsNoEscapeProcOpen
-ChrootTest.ProcMountsMountinfoNoEscape