linux capabilities: normalization and auditbeat process support #37453
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| 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. | ||
|
|
||
| //go:build linux | ||
|
|
||
| package capabilities | ||
|
|
||
| import ( | ||
| "errors" | ||
| "math/bits" | ||
| "strconv" | ||
| "strings" | ||
|
|
||
| "kernel.org/pub/linux/libs/security/libcap/cap" | ||
| ) | ||
|
|
||
| var ( | ||
| // errInvalidCapability expresses an invalid capability ID: x < 0 || x >= 64. | ||
| errInvalidCapability = errors.New("invalid capability") | ||
| ) | ||
|
|
||
| // 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 | ||
|
|
||
| const ( | ||
| // aka CapEff | ||
| Effective = cap.Effective | ||
| // aka CapPrm | ||
| Permitted = cap.Permitted | ||
| ) | ||
|
|
||
| // 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 | ||
| } | ||
|
|
||
| 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) | ||
| } | ||
|
|
||
| return sl, err | ||
| } | ||
|
|
||
| // 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 | ||
| } | ||
|
|
||
| return sl, nil | ||
| } | ||
|
|
||
| // 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 | ||
| } | ||
|
|
||
| return FromUint64(w) | ||
| } | ||
|
|
||
| // 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 | ||
| } | ||
|
|
||
| return !d.Has(flag), nil | ||
| } | ||
|
|
||
| // 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() | ||
|
|
||
| // 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) | ||
|
|
||
| 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()) | ||
| } | ||
| } | ||
|
|
||
| return func(b int) (string, error) { | ||
| s, ok := ecsNames[b] | ||
| if !ok { | ||
| return "", errInvalidCapability | ||
| } | ||
| return s, nil | ||
| } | ||
| } | ||
|
|
||
| // 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()) | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| 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. | ||
|
|
||
| package capabilities | ||
|
|
||
| import ( | ||
| "os" | ||
| "testing" | ||
|
|
||
| "github.com/stretchr/testify/assert" | ||
| "kernel.org/pub/linux/libs/security/libcap/cap" | ||
| ) | ||
|
|
||
| func TestEmpty(t *testing.T) { | ||
| sl, err := FromString("0", 16) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 0) | ||
|
|
||
| sl, err = FromUint64(0) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 0) | ||
|
|
||
| // 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)) | ||
| } | ||
| } | ||
|
|
||
| func TestOverflow(t *testing.T) { | ||
| sl, err := FromUint64(^uint64(0)) | ||
| assert.Nil(t, err) | ||
| assert.Equal(t, len(sl), 64) | ||
|
|
||
| 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") | ||
| } | ||
| } | ||
|
|
||
| func assertHasCap(t *testing.T, sl []string, s string) { | ||
| var found int | ||
|
|
||
| for _, s2 := range sl { | ||
| if s2 == s { | ||
| found++ | ||
| } | ||
| } | ||
|
|
||
| assert.Equal(t, found, 1, s) | ||
| } | ||
Oops, something went wrong.
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
I don't think it must be true that euid != 0 has no capabilities. If that were to be not true in CI, that could lead to an interesting debugging scenario. Can this be reworked or mock out the os.Geteuid() call?
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
Indeed, you can still have capabilities as a non-root user, I've added the comment to reflect that, I guess it's just rare enough that we could live with it.
I can't think of a good way to mock it, one way would be to drop all capabilities that are "Effective & Permitted", then test Effective for empty and restore the old set, but this is too impure and doesn't sound very appealing to me.
I'd either leave it and improve the comment or just remove it all together, let me know what you think.