5 files changed, 257 insertions, 2 deletions
diff --git a/pkg/sentry/strace/BUILD b/pkg/sentry/strace/BUILD
index 552e79686..73f1e9814 100644
--- a/pkg/sentry/strace/BUILD
+++ b/pkg/sentry/strace/BUILD
@@ -6,6 +6,7 @@ package(licenses = ["notice"])
 go_library(
     name = "strace",
     srcs = [
+        "capability.go",
         "clone.go",
         "futex.go",
         "linux64.go",
diff --git a/pkg/sentry/strace/capability.go b/pkg/sentry/strace/capability.go
new file mode 100644
index 000000000..9001181e7
--- /dev/null
+++ b/pkg/sentry/strace/capability.go
@@ -0,0 +1,176 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package strace
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi"
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+)
+
+// CapabilityBitset is the set of capabilties in a bitset.
+var CapabilityBitset = abi.FlagSet{
+	{
+		Flag: 1 << uint32(linux.CAP_CHOWN),
+		Name: "CAP_CHOWN",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_DAC_OVERRIDE),
+		Name: "CAP_DAC_OVERRIDE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_DAC_READ_SEARCH),
+		Name: "CAP_DAC_READ_SEARCH",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_FOWNER),
+		Name: "CAP_FOWNER",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_FSETID),
+		Name: "CAP_FSETID",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_KILL),
+		Name: "CAP_KILL",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SETGID),
+		Name: "CAP_SETGID",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SETUID),
+		Name: "CAP_SETUID",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SETPCAP),
+		Name: "CAP_SETPCAP",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_LINUX_IMMUTABLE),
+		Name: "CAP_LINUX_IMMUTABLE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_NET_BIND_SERVICE),
+		Name: "CAP_NET_BIND_SERVICE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_NET_BROADCAST),
+		Name: "CAP_NET_BROADCAST",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_NET_ADMIN),
+		Name: "CAP_NET_ADMIN",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_NET_RAW),
+		Name: "CAP_NET_RAW",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_IPC_LOCK),
+		Name: "CAP_IPC_LOCK",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_IPC_OWNER),
+		Name: "CAP_IPC_OWNER",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_MODULE),
+		Name: "CAP_SYS_MODULE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_RAWIO),
+		Name: "CAP_SYS_RAWIO",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_CHROOT),
+		Name: "CAP_SYS_CHROOT",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_PTRACE),
+		Name: "CAP_SYS_PTRACE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_PACCT),
+		Name: "CAP_SYS_PACCT",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_ADMIN),
+		Name: "CAP_SYS_ADMIN",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_BOOT),
+		Name: "CAP_SYS_BOOT",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_NICE),
+		Name: "CAP_SYS_NICE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_RESOURCE),
+		Name: "CAP_SYS_RESOURCE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_TIME),
+		Name: "CAP_SYS_TIME",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYS_TTY_CONFIG),
+		Name: "CAP_SYS_TTY_CONFIG",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_MKNOD),
+		Name: "CAP_MKNOD",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_LEASE),
+		Name: "CAP_LEASE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_AUDIT_WRITE),
+		Name: "CAP_AUDIT_WRITE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_AUDIT_CONTROL),
+		Name: "CAP_AUDIT_CONTROL",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SETFCAP),
+		Name: "CAP_SETFCAP",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_MAC_OVERRIDE),
+		Name: "CAP_MAC_OVERRIDE",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_MAC_ADMIN),
+		Name: "CAP_MAC_ADMIN",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_SYSLOG),
+		Name: "CAP_SYSLOG",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_WAKE_ALARM),
+		Name: "CAP_WAKE_ALARM",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_BLOCK_SUSPEND),
+		Name: "CAP_BLOCK_SUSPEND",
+	},
+	{
+		Flag: 1 << uint32(linux.CAP_AUDIT_READ),
+		Name: "CAP_AUDIT_READ",
+	},
+}
diff --git a/pkg/sentry/strace/linux64.go b/pkg/sentry/strace/linux64.go
index de2da9369..ca695e80f 100644
--- a/pkg/sentry/strace/linux64.go
+++ b/pkg/sentry/strace/linux64.go
@@ -142,8 +142,8 @@ var linuxAMD64 = SyscallMap{
 	122: makeSyscallInfo("setfsuid", Hex),
 	123: makeSyscallInfo("setfsgid", Hex),
 	124: makeSyscallInfo("getsid", Hex),
-	125: makeSyscallInfo("capget", Hex, Hex),
-	126: makeSyscallInfo("capset", Hex, Hex),
+	125: makeSyscallInfo("capget", CapHeader, PostCapData),
+	126: makeSyscallInfo("capset", CapHeader, CapData),
 	127: makeSyscallInfo("rt_sigpending", Hex),
 	128: makeSyscallInfo("rt_sigtimedwait", SigSet, Hex, Timespec, Hex),
 	129: makeSyscallInfo("rt_sigqueueinfo", Hex, Signal, Hex),
diff --git a/pkg/sentry/strace/strace.go b/pkg/sentry/strace/strace.go
index da27a2ae8..6c93d7de7 100644
--- a/pkg/sentry/strace/strace.go
+++ b/pkg/sentry/strace/strace.go
@@ -271,6 +271,67 @@ func rusage(t *kernel.Task, addr usermem.Addr) string {
 	return fmt.Sprintf("%#x %+v", addr, ru)
 }
 
+func capHeader(t *kernel.Task, addr usermem.Addr) string {
+	if addr == 0 {
+		return "null"
+	}
+
+	var hdr linux.CapUserHeader
+	if _, err := t.CopyIn(addr, &hdr); err != nil {
+		return fmt.Sprintf("%#x (error decoding header: %s)", addr, err)
+	}
+
+	var version string
+	switch hdr.Version {
+	case linux.LINUX_CAPABILITY_VERSION_1:
+		version = "1"
+	case linux.LINUX_CAPABILITY_VERSION_2:
+		version = "2"
+	case linux.LINUX_CAPABILITY_VERSION_3:
+		version = "3"
+	default:
+		version = strconv.FormatUint(uint64(hdr.Version), 16)
+	}
+
+	return fmt.Sprintf("%#x {Version: %s, Pid: %d}", addr, version, hdr.Pid)
+}
+
+func capData(t *kernel.Task, hdrAddr, dataAddr usermem.Addr) string {
+	if dataAddr == 0 {
+		return "null"
+	}
+
+	var hdr linux.CapUserHeader
+	if _, err := t.CopyIn(hdrAddr, &hdr); err != nil {
+		return fmt.Sprintf("%#x (error decoding header: %v)", dataAddr, err)
+	}
+
+	var p, i, e uint64
+
+	switch hdr.Version {
+	case linux.LINUX_CAPABILITY_VERSION_1:
+		var data linux.CapUserData
+		if _, err := t.CopyIn(dataAddr, &data); err != nil {
+			return fmt.Sprintf("%#x (error decoding data: %v)", dataAddr, err)
+		}
+		p = uint64(data.Permitted)
+		i = uint64(data.Inheritable)
+		e = uint64(data.Effective)
+	case linux.LINUX_CAPABILITY_VERSION_2, linux.LINUX_CAPABILITY_VERSION_3:
+		var data [2]linux.CapUserData
+		if _, err := t.CopyIn(dataAddr, &data); err != nil {
+			return fmt.Sprintf("%#x (error decoding data: %v)", dataAddr, err)
+		}
+		p = uint64(data[0].Permitted) | (uint64(data[1].Permitted) << 32)
+		i = uint64(data[0].Inheritable) | (uint64(data[1].Inheritable) << 32)
+		e = uint64(data[0].Effective) | (uint64(data[1].Effective) << 32)
+	default:
+		return fmt.Sprintf("%#x (unknown version %d)", dataAddr, hdr.Version)
+	}
+
+	return fmt.Sprintf("%#x {Permitted: %s, Inheritable: %s, Effective: %s}", dataAddr, CapabilityBitset.Parse(p), CapabilityBitset.Parse(i), CapabilityBitset.Parse(e))
+}
+
 // pre fills in the pre-execution arguments for a system call. If an argument
 // cannot be interpreted before the system call is executed, then a hex value
 // will be used. Note that a full output slice will always be provided, that is
@@ -341,6 +402,10 @@ func (i *SyscallInfo) pre(t *kernel.Task, args arch.SyscallArguments, maximumBlo
 			output = append(output, sigSet(t, args[arg].Pointer()))
 		case SigAction:
 			output = append(output, sigAction(t, args[arg].Pointer()))
+		case CapHeader:
+			output = append(output, capHeader(t, args[arg].Pointer()))
+		case CapData:
+			output = append(output, capData(t, args[arg-1].Pointer(), args[arg].Pointer()))
 		case Oct:
 			output = append(output, "0o"+strconv.FormatUint(args[arg].Uint64(), 8))
 		case Hex:
@@ -403,6 +468,8 @@ func (i *SyscallInfo) post(t *kernel.Task, args arch.SyscallArguments, rval uint
 			output[arg] = sigSet(t, args[arg].Pointer())
 		case PostSigAction:
 			output[arg] = sigAction(t, args[arg].Pointer())
+		case PostCapData:
+			output[arg] = capData(t, args[arg-1].Pointer(), args[arg].Pointer())
 		}
 	}
 }
diff --git a/pkg/sentry/strace/syscalls.go b/pkg/sentry/strace/syscalls.go
index 1ae982354..b2715856e 100644
--- a/pkg/sentry/strace/syscalls.go
+++ b/pkg/sentry/strace/syscalls.go
@@ -188,6 +188,17 @@ const (
 
 	// PostSigAction is a struct sigaction, formatted after syscall execution.
 	PostSigAction
+
+	// CapHeader is a cap_user_header_t.
+	CapHeader
+
+	// CapData is the data argument to capget(2)/capset(2). The previous
+	// argument must be CapHeader.
+	CapData
+
+	// PostCapData is the data argument to capget(2)/capset(2), formatted
+	// after syscall execution. The previous argument must be CapHeader.
+	PostCapData
 )
 
 // defaultFormat is the syscall argument format to use if the actual format is