anubis/lib/policy/config/expressionorlist.go
Xe Iaso 865d513e35
feat(checker): add CEL for matching complicated expressions (#421)
* feat(lib/policy): add support for CEL checkers

This adds the ability for administrators to use Common Expression
Language[0] (CEL) for more advanced check logic than Anubis previously
offered.

These can be as simple as:

```yaml
- name: allow-api-routes
  action: ALLOW
  expression:
    and:
    - '!(method == "HEAD" || method == "GET")'
    - path.startsWith("/api/")
```

or get as complicated as:

```yaml
- name: allow-git-clients
  action: ALLOW
  expression:
    and:
    - userAgent.startsWith("git/") || userAgent.contains("libgit") || userAgent.startsWith("go-git") || userAgent.startsWith("JGit/") || userAgent.startsWith("JGit-")
    - >
      "Git-Protocol" in headers && headers["Git-Protocol"] == "version=2"
```

Internally these are compiled and evaluated with cel-go[1]. This also
leaves room for extensibility should that be desired in the future. This
will intersect with #338 and eventually intersect with TLS fingerprints
as in #337.

[0]: https://cel.dev/
[1]: https://github.com/google/cel-go

Signed-off-by: Xe Iaso <me@xeiaso.net>

* feat(data/apps): add API route allow rule for non-HEAD/GET

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: document expression syntax

Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix: fixes in review

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>
2025-05-03 14:26:54 -04:00

63 lines
1.3 KiB
Go

package config
import (
"encoding/json"
"errors"
"slices"
)
var (
ErrExpressionOrListMustBeStringOrObject = errors.New("config: this must be a string or an object")
ErrExpressionEmpty = errors.New("config: this expression is empty")
ErrExpressionCantHaveBoth = errors.New("config: expression block can't contain multiple expression types")
)
type ExpressionOrList struct {
Expression string `json:"-"`
All []string `json:"all"`
Any []string `json:"any"`
}
func (eol ExpressionOrList) Equal(rhs *ExpressionOrList) bool {
if eol.Expression != rhs.Expression {
return false
}
if !slices.Equal(eol.All, rhs.All) {
return false
}
if !slices.Equal(eol.Any, rhs.Any) {
return false
}
return true
}
func (eol *ExpressionOrList) UnmarshalJSON(data []byte) error {
switch string(data[0]) {
case `"`: // string
return json.Unmarshal(data, &eol.Expression)
case "{": // object
type RawExpressionOrList ExpressionOrList
var val RawExpressionOrList
if err := json.Unmarshal(data, &val); err != nil {
return err
}
eol.All = val.All
eol.Any = val.Any
return nil
}
return ErrExpressionOrListMustBeStringOrObject
}
func (eol *ExpressionOrList) Valid() error {
if len(eol.All) != 0 && len(eol.Any) != 0 {
return ErrExpressionCantHaveBoth
}
return nil
}