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linux capabilities: normalization and auditbeat process support (#37453)
Capabilities normalization and auditbeat process support
This draft implements `process.thread.capabilities.{effective,permitted}` to
auditbeat/system/process and normalizes the other uses of linux capabilities
across beats (only two other cases).
I've tested metricbeat, auditbeat and filebeat+journald.
Co-authored-by: Dan Kortschak <90160302+efd6@users.noreply.github.com>
Co-authored-by: Mattia Meleleo <mattia.meleleo@elastic.co>- Loading branch information
3 people
authored
Feb 6, 2024
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you 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. | ||
|
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| //go:build linux | ||
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| package capabilities | ||
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| import ( | ||
| "errors" | ||
| "math/bits" | ||
| "strconv" | ||
| "strings" | ||
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| "kernel.org/pub/linux/libs/security/libcap/cap" | ||
| ) | ||
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| var ( | ||
| // errInvalidCapability expresses an invalid capability ID: x < 0 || x >= 64. | ||
| errInvalidCapability = errors.New("invalid capability") | ||
| ) | ||
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| // The capability set flag/vector, re-exported from | ||
| // libcap(3). Inherit, Bound & Ambient not exported since we have no | ||
| // use for it yet. | ||
| type Flag = cap.Flag | ||
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||
| const ( | ||
| // aka CapEff | ||
| Effective = cap.Effective | ||
| // aka CapPrm | ||
| Permitted = cap.Permitted | ||
| ) | ||
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||
| // Fetch the capabilities of pid for a given flag/vector and convert | ||
| // it to the representation used in ECS. cap.GetPID() fetches it with | ||
| // SYS_CAPGET. | ||
| // Returns errors.ErrUnsupported on "not linux". | ||
| func FromPid(flag Flag, pid int) ([]string, error) { | ||
| set, err := cap.GetPID(pid) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| empty, err := isEmpty(flag, set) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if empty { | ||
| return []string{}, nil | ||
| } | ||
|
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| sl := make([]string, 0, cap.MaxBits()) | ||
| for i := 0; i < int(cap.MaxBits()); i++ { | ||
| c := cap.Value(i) | ||
| enabled, err := set.GetFlag(flag, c) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if !enabled { | ||
| continue | ||
| } | ||
| s, err := toECS(i) | ||
| // impossible since MaxBits <= 64 | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| sl = append(sl, s) | ||
| } | ||
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|
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| return sl, err | ||
| } | ||
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| // Convert a uint64 to the capabilities representation used in ECS. | ||
| // Returns errors.ErrUnsupported on "not linux". | ||
| func FromUint64(w uint64) ([]string, error) { | ||
| sl := make([]string, 0, bits.OnesCount64(w)) | ||
| for i := 0; w != 0; i++ { | ||
| if w&1 != 0 { | ||
| s, err := toECS(i) | ||
| // impossible since MaxBits <= 64 | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| sl = append(sl, s) | ||
| } | ||
| w >>= 1 | ||
| } | ||
|
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| return sl, nil | ||
| } | ||
|
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| // Convert a string to the capabilities representation used in | ||
| // ECS. Example input: "1ffffffffff", 16. | ||
| // Returns errors.ErrUnsupported on "not linux". | ||
| func FromString(s string, base int) ([]string, error) { | ||
| w, err := strconv.ParseUint(s, 16, 64) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| return FromUint64(w) | ||
| } | ||
|
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| // True if sets are equal for the given flag/vector, errors out in | ||
| // case any of the sets is malformed. | ||
| func isEqual(flag Flag, a *cap.Set, b *cap.Set) (bool, error) { | ||
| d, err := a.Cf(b) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
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| return !d.Has(flag), nil | ||
| } | ||
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| // Convert the capability ID to a string suitable to be used in | ||
| // ECS. | ||
| // If capabiliy ID X is unknown, but valid (0 <= X < 64), "CAP_X" | ||
| // will be returned instead. Fetches from an internal table built at | ||
| // startup. | ||
| var toECS = makeToECS() | ||
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| // Make toECS() which creates a map of every possible valid capability | ||
| // ID on startup. Returns errInvalidCapabilty for an invalid ID. | ||
| func makeToECS() func(int) (string, error) { | ||
| ecsNames := make(map[int]string) | ||
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| for i := 0; i < 64; i++ { | ||
| c := cap.Value(i) | ||
| if i < int(cap.MaxBits()) { | ||
| ecsNames[i] = strings.ToUpper(c.String()) | ||
| } else { | ||
| ecsNames[i] = strings.ToUpper("CAP_" + c.String()) | ||
| } | ||
| } | ||
|
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| return func(b int) (string, error) { | ||
| s, ok := ecsNames[b] | ||
| if !ok { | ||
| return "", errInvalidCapability | ||
| } | ||
| return s, nil | ||
| } | ||
| } | ||
|
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| // Like isAll(), but for the empty set, here for symmetry. | ||
| func isEmpty(flag Flag, set *cap.Set) (bool, error) { | ||
| return isEqual(flag, set, cap.NewSet()) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you 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. | ||
|
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| package capabilities | ||
|
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| import ( | ||
| "os" | ||
| "testing" | ||
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| "github.com/stretchr/testify/assert" | ||
| "kernel.org/pub/linux/libs/security/libcap/cap" | ||
| ) | ||
|
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| func TestEmpty(t *testing.T) { | ||
| sl, err := FromString("0", 16) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 0) | ||
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| sl, err = FromUint64(0) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 0) | ||
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| // assumes non root has no capabilities | ||
| if os.Geteuid() != 0 { | ||
| empty := cap.NewSet() | ||
| self := cap.GetProc() | ||
| d, err := self.Cf(empty) | ||
| assert.Nil(t, err) | ||
| assert.False(t, d.Has(cap.Effective)) | ||
| assert.False(t, d.Has(cap.Permitted)) | ||
| assert.False(t, d.Has(cap.Inheritable)) | ||
| } | ||
| } | ||
|
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| func TestOverflow(t *testing.T) { | ||
| sl, err := FromUint64(^uint64(0)) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 64) | ||
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| for _, cap := range []string{ | ||
| "CAP_CHOWN", | ||
| "CAP_DAC_OVERRIDE", | ||
| "CAP_DAC_READ_SEARCH", | ||
| "CAP_FOWNER", | ||
| "CAP_FSETID", | ||
| "CAP_KILL", | ||
| "CAP_SETGID", | ||
| "CAP_SYS_MODULE", | ||
| "CAP_SYS_RAWIO", | ||
| "CAP_IPC_LOCK", | ||
| "CAP_MAC_OVERRIDE", | ||
| } { | ||
| assertHasCap(t, sl, cap) | ||
| } | ||
| if cap.MaxBits() <= 62 { | ||
| assertHasCap(t, sl, "CAP_62") | ||
| } | ||
| if cap.MaxBits() <= 63 { | ||
| assertHasCap(t, sl, "CAP_63") | ||
| } | ||
| } | ||
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| func assertHasCap(t *testing.T, sl []string, s string) { | ||
| var found int | ||
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| for _, s2 := range sl { | ||
| if s2 == s { | ||
| found++ | ||
| } | ||
| } | ||
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| assert.Equal(t, found, 1, s) | ||
| } |
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