github.com/ttpreport/gvisor-ligolo@v0.0.0-20240123134145-a858404967ba/pkg/sentry/platform/systrap/sysmsg_thread.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package systrap
    16  
    17  import (
    18  	"fmt"
    19  
    20  	"github.com/ttpreport/gvisor-ligolo/pkg/abi/linux"
    21  	"github.com/ttpreport/gvisor-ligolo/pkg/log"
    22  	"github.com/ttpreport/gvisor-ligolo/pkg/seccomp"
    23  	"github.com/ttpreport/gvisor-ligolo/pkg/sentry/arch"
    24  	"github.com/ttpreport/gvisor-ligolo/pkg/sentry/memmap"
    25  	"github.com/ttpreport/gvisor-ligolo/pkg/sentry/platform/systrap/sysmsg"
    26  	"golang.org/x/sys/unix"
    27  )
    28  
    29  // sysmsgThread describes a sysmsg stub thread which isn't traced
    30  // and communicates with the Sentry via the sysmsg protocol.
    31  //
    32  // This type of thread is used to execute user processes.
    33  type sysmsgThread struct {
    34  	// subproc is a link to the subprocess which is used to call native
    35  	// system calls.
    36  	subproc *subprocess
    37  
    38  	// thread is a thread identifier.
    39  	thread *thread
    40  
    41  	// msg is a pointer to a shared sysmsg structure in the Sentry address
    42  	// space which is used to communicate with the thread.
    43  	msg *sysmsg.Msg
    44  
    45  	// context is the last context that ran on this thread.
    46  	context *context
    47  
    48  	// stackRange is a sysmsg stack in the memory file.
    49  	stackRange memmap.FileRange
    50  
    51  	// fpuStateToMsgOffset is the offset of a thread fpu state relative to sysmsg.
    52  	fpuStateToMsgOffset uint64
    53  }
    54  
    55  // sysmsgPerThreadMemAddr returns a sysmsg stack address in the thread address
    56  // space.
    57  func (p *sysmsgThread) sysmsgPerThreadMemAddr() uintptr {
    58  	return stubSysmsgStack + sysmsg.PerThreadMemSize*uintptr(p.thread.sysmsgStackID)
    59  }
    60  
    61  // mapStack maps a sysmsg stack into the thread address space.
    62  func (p *sysmsgThread) mapStack(addr uintptr, readOnly bool) error {
    63  	prot := uintptr(unix.PROT_READ)
    64  	if !readOnly {
    65  		prot |= unix.PROT_WRITE
    66  	}
    67  	_, err := p.thread.syscallIgnoreInterrupt(&p.thread.initRegs, unix.SYS_MMAP,
    68  		arch.SyscallArgument{Value: addr},
    69  		arch.SyscallArgument{Value: uintptr(p.stackRange.Length())},
    70  		arch.SyscallArgument{Value: prot},
    71  		arch.SyscallArgument{Value: unix.MAP_SHARED | unix.MAP_FILE | unix.MAP_FIXED},
    72  		arch.SyscallArgument{Value: uintptr(p.subproc.memoryFile.FD())},
    73  		arch.SyscallArgument{Value: uintptr(p.stackRange.Start)})
    74  	return err
    75  }
    76  
    77  // mapPrivateStack maps a private stack into the thread address space.
    78  func (p *sysmsgThread) mapPrivateStack(addr uintptr, size uintptr) error {
    79  	prot := uintptr(unix.PROT_READ | unix.PROT_WRITE)
    80  	_, err := p.thread.syscallIgnoreInterrupt(&p.thread.initRegs, unix.SYS_MMAP,
    81  		arch.SyscallArgument{Value: addr},
    82  		arch.SyscallArgument{Value: size},
    83  		arch.SyscallArgument{Value: prot},
    84  		arch.SyscallArgument{Value: unix.MAP_PRIVATE | unix.MAP_ANONYMOUS | unix.MAP_FIXED},
    85  		arch.SyscallArgument{Value: 0},
    86  		arch.SyscallArgument{Value: 0})
    87  	return err
    88  }
    89  
    90  func (p *sysmsgThread) Debugf(format string, v ...any) {
    91  	if !log.IsLogging(log.Debug) {
    92  		return
    93  	}
    94  	msg := p.msg
    95  	postfix := fmt.Sprintf(": %s", msg)
    96  	p.thread.Debugf(format+postfix, v...)
    97  }
    98  
    99  func sysmsgThreadRules(stubStart uintptr) []linux.BPFInstruction {
   100  	rules := []seccomp.RuleSet{}
   101  	rules = appendSysThreadArchSeccompRules(rules)
   102  	rules = append(rules, []seccomp.RuleSet{
   103  		// Allow instructions from the sysmsg code stub, which is limited by one page.
   104  		{
   105  			Rules: seccomp.SyscallRules{
   106  				unix.SYS_FUTEX: {
   107  					{
   108  						seccomp.GreaterThan(stubStart),
   109  						seccomp.EqualTo(linux.FUTEX_WAKE),
   110  						seccomp.EqualTo(1),
   111  						seccomp.EqualTo(0),
   112  						seccomp.EqualTo(0),
   113  						seccomp.EqualTo(0),
   114  						seccomp.GreaterThan(stubStart), // rip
   115  					},
   116  					{
   117  						seccomp.GreaterThan(stubStart),
   118  						seccomp.EqualTo(linux.FUTEX_WAIT),
   119  						seccomp.MatchAny{},
   120  						seccomp.EqualTo(0),
   121  						seccomp.EqualTo(0),
   122  						seccomp.EqualTo(0),
   123  						seccomp.GreaterThan(stubStart), // rip
   124  					},
   125  				},
   126  				unix.SYS_RT_SIGRETURN: {
   127  					{
   128  						seccomp.MatchAny{},
   129  						seccomp.MatchAny{},
   130  						seccomp.MatchAny{},
   131  						seccomp.MatchAny{},
   132  						seccomp.MatchAny{},
   133  						seccomp.MatchAny{},
   134  						seccomp.GreaterThan(stubStart), // rip
   135  					},
   136  				},
   137  				unix.SYS_SCHED_YIELD: {
   138  					{
   139  						seccomp.MatchAny{},
   140  						seccomp.MatchAny{},
   141  						seccomp.MatchAny{},
   142  						seccomp.MatchAny{},
   143  						seccomp.MatchAny{},
   144  						seccomp.MatchAny{},
   145  						seccomp.GreaterThan(stubStart), // rip
   146  					},
   147  				},
   148  			},
   149  			Action: linux.SECCOMP_RET_ALLOW,
   150  		},
   151  	}...)
   152  	instrs, err := seccomp.BuildProgram(rules, linux.SECCOMP_RET_TRAP, linux.SECCOMP_RET_TRAP)
   153  	if err != nil {
   154  		panic(fmt.Sprintf("failed to build rules for sysmsg threads: %v", err))
   155  	}
   156  
   157  	return instrs
   158  }