feat: enable loading config fragments (#321)

* feat(config): support importing bot policy snippets

This changes the grammar of the Anubis bot policy config to allow
importing from internal shared rules or external rules on the
filesystem.

This lets you create a file at `/data/policies/block-evilbot.yaml` and
then import it with:

```yaml
bots:
- import: /data/policies/block-evilbot.yaml
```

This also explodes the default policy file into a bunch of composable
snippets.

Thank you @Aibrew for your example gitea Atom / RSS feed rules!

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

* fix(data): update botPolicies.json to use imports

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

* fix(cmd/anubis): extract bot policies with --extract-resources

This allows a user that doesn't have anything but the Anubis binary to
figure out what the default configuration does.

* docs(data/botPolices.yaml): document import syntax in-line

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

* fix(lib/policy): better test importing from JSON snippets

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

* docs(admin): Add import syntax documentation

This documents the import syntax and is based on the block comment at
the top of the default bot policy file.

* docs(changelog): add note about importing snippets

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

* style(lib/policy/config): use an error value instead of an inline error

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

---------

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

15 files changed, 348 insertions, 16 deletions

diff --git a/lib/policy/config/config.go b/lib/policy/config/config.go
index b3d5cac..627e9cf 100644
--- a/lib/policy/config/config.go
+++ b/lib/policy/config/config.go
@@ -3,8 +3,15 @@ package config
 import (
 	"errors"
 	"fmt"
+	"io"
+	"io/fs"
 	"net"
+	"os"
 	"regexp"
+	"strings"
+
+	"github.com/TecharoHQ/anubis/data"
+	"k8s.io/apimachinery/pkg/util/yaml"
 )
 
 var (
@@ -17,6 +24,9 @@ var (
 	ErrInvalidPathRegex                  = errors.New("config.Bot: invalid path regex")
 	ErrInvalidHeadersRegex               = errors.New("config.Bot: invalid headers regex")
 	ErrInvalidCIDR                       = errors.New("config.Bot: invalid CIDR")
+	ErrInvalidImportStatement            = errors.New("config.ImportStatement: invalid source file")
+	ErrCantSetBotAndImportValuesAtOnce   = errors.New("config.BotOrImport: can't set bot rules and import values at the same time")
+	ErrMustSetBotOrImportRules           = errors.New("config.BotOrImport: rule definition is invalid, you must set either bot rules or an import statement, not both")
 )
 
 type Rule string
@@ -47,6 +57,24 @@ type BotConfig struct {
 	Challenge      *ChallengeRules   `json:"challenge,omitempty"`
 }
 
+func (b BotConfig) Zero() bool {
+	for _, cond := range []bool{
+		b.Name != "",
+		b.UserAgentRegex != nil,
+		b.PathRegex != nil,
+		len(b.HeadersRegex) != 0,
+		b.Action != "",
+		len(b.RemoteAddr) != 0,
+		b.Challenge != nil,
+	} {
+		if cond {
+			return false
+		}
+	}
+
+	return true
+}
+
 func (b BotConfig) Valid() error {
 	var errs []error
 
@@ -151,9 +179,147 @@ func (cr ChallengeRules) Valid() error {
 	return nil
 }
 
+type ImportStatement struct {
+	Import string `json:"import"`
+	Bots   []BotConfig
+}
+
+func (is *ImportStatement) open() (fs.File, error) {
+	if strings.HasPrefix(is.Import, "(data)/") {
+		fname := strings.TrimPrefix(is.Import, "(data)/")
+		fin, err := data.BotPolicies.Open(fname)
+		return fin, err
+	}
+
+	return os.Open(is.Import)
+}
+
+func (is *ImportStatement) load() error {
+	fin, err := is.open()
+	if err != nil {
+		return fmt.Errorf("can't open %s: %w", is.Import, err)
+	}
+	defer fin.Close()
+
+	var result []BotConfig
+
+	if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&result); err != nil {
+		return fmt.Errorf("can't parse %s: %w", is.Import, err)
+	}
+
+	var errs []error
+
+	for _, b := range result {
+		if err := b.Valid(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) != 0 {
+		return fmt.Errorf("config %s is not valid:\n%w", is.Import, errors.Join(errs...))
+	}
+
+	is.Bots = result
+
+	return nil
+}
+
+func (is *ImportStatement) Valid() error {
+	return is.load()
+}
+
+type BotOrImport struct {
+	*BotConfig       `json:",inline"`
+	*ImportStatement `json:",inline"`
+}
+
+func (boi *BotOrImport) Valid() error {
+	if boi.BotConfig != nil && boi.ImportStatement != nil {
+		return ErrCantSetBotAndImportValuesAtOnce
+	}
+
+	if boi.BotConfig != nil {
+		return boi.BotConfig.Valid()
+	}
+
+	if boi.ImportStatement != nil {
+		return boi.ImportStatement.Valid()
+	}
+
+	return ErrMustSetBotOrImportRules
+}
+
+type fileConfig struct {
+	Bots  []BotOrImport `json:"bots"`
+	DNSBL bool          `json:"dnsbl"`
+}
+
+func (c fileConfig) Valid() error {
+	var errs []error
+
+	if len(c.Bots) == 0 {
+		errs = append(errs, ErrNoBotRulesDefined)
+	}
+
+	for _, b := range c.Bots {
+		if err := b.Valid(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) != 0 {
+		return fmt.Errorf("config is not valid:\n%w", errors.Join(errs...))
+	}
+
+	return nil
+}
+
+func Load(fin io.Reader, fname string) (*Config, error) {
+	var c fileConfig
+	if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&c); err != nil {
+		return nil, fmt.Errorf("can't parse policy config YAML %s: %w", fname, err)
+	}
+
+	if err := c.Valid(); err != nil {
+		return nil, err
+	}
+
+	result := &Config{
+		DNSBL: c.DNSBL,
+	}
+
+	var validationErrs []error
+
+	for _, boi := range c.Bots {
+		if boi.ImportStatement != nil {
+			if err := boi.load(); err != nil {
+				validationErrs = append(validationErrs, err)
+				continue
+			}
+
+			result.Bots = append(result.Bots, boi.ImportStatement.Bots...)
+		}
+
+		if boi.BotConfig != nil {
+			if err := boi.BotConfig.Valid(); err != nil {
+				validationErrs = append(validationErrs, err)
+				continue
+			}
+
+			result.Bots = append(result.Bots, *boi.BotConfig)
+		}
+	}
+
+	if len(validationErrs) > 0 {
+		return nil, fmt.Errorf("errors validating policy config %s: %w", fname, errors.Join(validationErrs...))
+	}
+
+	return result, nil
+}
+
 type Config struct {
-	Bots  []BotConfig `json:"bots"`
-	DNSBL bool        `json:"dnsbl"`
+	Bots  []BotConfig
+	DNSBL bool
 }
 
 func (c Config) Valid() error {
diff --git a/lib/policy/config/config_test.go b/lib/policy/config/config_test.go
index 4176126..86c490e 100644
--- a/lib/policy/config/config_test.go
+++ b/lib/policy/config/config_test.go
@@ -2,10 +2,12 @@ package config
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"testing"
 
+	"github.com/TecharoHQ/anubis/data"
 	"k8s.io/apimachinery/pkg/util/yaml"
 )
 
@@ -219,13 +221,69 @@ func TestConfigValidKnownGood(t *testing.T) {
 			}
 			defer fin.Close()
 
-			var c Config
-			if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&c); err != nil {
-				t.Fatalf("can't decode file: %v", err)
+			c, err := Load(fin, st.Name())
+			if err != nil {
+				t.Fatal(err)
 			}
 
 			if err := c.Valid(); err != nil {
-				t.Fatal(err)
+				t.Error(err)
+			}
+
+			if len(c.Bots) == 0 {
+				t.Error("wanted more than 0 bots, got zero")
+			}
+		})
+	}
+}
+
+func TestImportStatement(t *testing.T) {
+	type testCase struct {
+		name       string
+		importPath string
+		err        error
+	}
+
+	var tests []testCase
+
+	for _, folderName := range []string{
+		"apps",
+		"bots",
+		"common",
+		"crawlers",
+	} {
+		if err := fs.WalkDir(data.BotPolicies, folderName, func(path string, d fs.DirEntry, err error) error {
+			if err != nil {
+				return err
+			}
+			if d.IsDir() {
+				return nil
+			}
+
+			tests = append(tests, testCase{
+				name:       "(data)/" + path,
+				importPath: "(data)/" + path,
+				err:        nil,
+			})
+
+			return nil
+		}); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			is := &ImportStatement{
+				Import: tt.importPath,
+			}
+
+			if err := is.Valid(); err != nil {
+				t.Errorf("validation error: %v", err)
+			}
+
+			if len(is.Bots) == 0 {
+				t.Error("wanted bot definitions, but got none")
 			}
 		})
 	}
@@ -246,7 +304,7 @@ func TestConfigValidBad(t *testing.T) {
 			}
 			defer fin.Close()
 
-			var c Config
+			var c fileConfig
 			if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&c); err != nil {
 				t.Fatalf("can't decode file: %v", err)
 			}
@@ -259,3 +317,49 @@ func TestConfigValidBad(t *testing.T) {
 		})
 	}
 }
+
+func TestBotConfigZero(t *testing.T) {
+	var b BotConfig
+	if !b.Zero() {
+		t.Error("zero value BotConfig is not zero value")
+	}
+
+	b.Name = "hi"
+	if b.Zero() {
+		t.Error("BotConfig with name is zero value")
+	}
+
+	b.UserAgentRegex = p(".*")
+	if b.Zero() {
+		t.Error("BotConfig with user agent regex is zero value")
+	}
+
+	b.PathRegex = p(".*")
+	if b.Zero() {
+		t.Error("BotConfig with path regex is zero value")
+	}
+
+	b.HeadersRegex = map[string]string{"hi": "there"}
+	if b.Zero() {
+		t.Error("BotConfig with headers regex is zero value")
+	}
+
+	b.Action = RuleAllow
+	if b.Zero() {
+		t.Error("BotConfig with action is zero value")
+	}
+
+	b.RemoteAddr = []string{"::/0"}
+	if b.Zero() {
+		t.Error("BotConfig with remote addresses is zero value")
+	}
+
+	b.Challenge = &ChallengeRules{
+		Difficulty: 4,
+		ReportAs:   4,
+		Algorithm:  AlgorithmFast,
+	}
+	if b.Zero() {
+		t.Error("BotConfig with challenge rules is zero value")
+	}
+}
diff --git a/lib/policy/config/testdata/bad/import_and_bot.json b/lib/policy/config/testdata/bad/import_and_bot.json
new file mode 100644
index 0000000..7fa4255
--- /dev/null
+++ b/lib/policy/config/testdata/bad/import_and_bot.json
@@ -0,0 +1,10 @@
+{
+  "bots": [
+    {
+      "import": "(data)/bots/ai-robots-txt.yaml",
+      "name": "generic-browser",
+      "user_agent_regex": "Mozilla|Opera\n",
+      "action": "CHALLENGE"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/lib/policy/config/testdata/bad/import_and_bot.yaml b/lib/policy/config/testdata/bad/import_and_bot.yaml
new file mode 100644
index 0000000..0080b10
--- /dev/null
+++ b/lib/policy/config/testdata/bad/import_and_bot.yaml
@@ -0,0 +1,6 @@
+bots:
+- import: (data)/bots/ai-robots-txt.yaml
+  name: generic-browser
+  user_agent_regex: >
+    Mozilla|Opera
+  action: CHALLENGE
\ No newline at end of file
diff --git a/lib/policy/config/testdata/bad/import_invalid_file.json b/lib/policy/config/testdata/bad/import_invalid_file.json
new file mode 100644
index 0000000..c7546c0
--- /dev/null
+++ b/lib/policy/config/testdata/bad/import_invalid_file.json
@@ -0,0 +1,7 @@
+{
+  "bots": [
+    {
+      "import": "(data)/does-not-exist-fake-file.yaml"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/lib/policy/config/testdata/bad/import_invalid_file.yaml b/lib/policy/config/testdata/bad/import_invalid_file.yaml
new file mode 100644
index 0000000..df78c06
--- /dev/null
+++ b/lib/policy/config/testdata/bad/import_invalid_file.yaml
@@ -0,0 +1,2 @@
+bots:
+- import: (data)/does-not-exist-fake-file.yaml
\ No newline at end of file
diff --git a/lib/policy/config/testdata/good/import_filesystem.json b/lib/policy/config/testdata/good/import_filesystem.json
new file mode 100644
index 0000000..23480c9
--- /dev/null
+++ b/lib/policy/config/testdata/good/import_filesystem.json
@@ -0,0 +1,7 @@
+{
+  "bots": [
+    {
+      "import": "./testdata/hack-test.json"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/lib/policy/config/testdata/good/import_filesystem.yaml b/lib/policy/config/testdata/good/import_filesystem.yaml
new file mode 100644
index 0000000..422ccc4
--- /dev/null
+++ b/lib/policy/config/testdata/good/import_filesystem.yaml
@@ -0,0 +1,2 @@
+bots:
+- import: ./testdata/hack-test.yaml
\ No newline at end of file
diff --git a/lib/policy/config/testdata/good/import_keep_internet_working.json b/lib/policy/config/testdata/good/import_keep_internet_working.json
new file mode 100644
index 0000000..68ff2db
--- /dev/null
+++ b/lib/policy/config/testdata/good/import_keep_internet_working.json
@@ -0,0 +1,7 @@
+{
+  "bots": [
+    {
+      "import": "(data)/common/keep-internet-working.yaml"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/lib/policy/config/testdata/good/import_keep_internet_working.yaml b/lib/policy/config/testdata/good/import_keep_internet_working.yaml
new file mode 100644
index 0000000..923ffe3
--- /dev/null
+++ b/lib/policy/config/testdata/good/import_keep_internet_working.yaml
@@ -0,0 +1,2 @@
+bots:
+- import: (data)/common/keep-internet-working.yaml
\ No newline at end of file
diff --git a/lib/policy/config/testdata/hack-test.json b/lib/policy/config/testdata/hack-test.json
new file mode 100644
index 0000000..652dcd8
--- /dev/null
+++ b/lib/policy/config/testdata/hack-test.json
@@ -0,0 +1,9 @@
+[
+  {
+    "name": "ipv6-ula",
+    "action": "ALLOW",
+    "remote_addresses": [
+      "fc00::/7"
+    ]
+  }
+]
\ No newline at end of file
diff --git a/lib/policy/config/testdata/hack-test.yaml b/lib/policy/config/testdata/hack-test.yaml
new file mode 100644
index 0000000..cd4d7d0
--- /dev/null
+++ b/lib/policy/config/testdata/hack-test.yaml
@@ -0,0 +1,3 @@
+- name: well-known
+  path_regex: ^/.well-known/.*$
+  action: ALLOW
\ No newline at end of file
diff --git a/lib/policy/policy.go b/lib/policy/policy.go
index 368768b..7c45ff6 100644
--- a/lib/policy/policy.go
+++ b/lib/policy/policy.go
@@ -7,7 +7,6 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
-	"k8s.io/apimachinery/pkg/util/yaml"
 
 	"github.com/TecharoHQ/anubis/lib/policy/config"
 )
@@ -20,26 +19,22 @@ var (
 )
 
 type ParsedConfig struct {
-	orig config.Config
+	orig *config.Config
 
 	Bots              []Bot
 	DNSBL             bool
 	DefaultDifficulty int
 }
 
-func NewParsedConfig(orig config.Config) *ParsedConfig {
+func NewParsedConfig(orig *config.Config) *ParsedConfig {
 	return &ParsedConfig{
 		orig: orig,
 	}
 }
 
 func ParseConfig(fin io.Reader, fname string, defaultDifficulty int) (*ParsedConfig, error) {
-	var c config.Config
-	if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&c); err != nil {
-		return nil, fmt.Errorf("can't parse policy config YAML %s: %w", fname, err)
-	}
-
-	if err := c.Valid(); err != nil {
+	c, err := config.Load(fin, fname)
+	if err != nil {
 		return nil, err
 	}
 
diff --git a/lib/policy/testdata/hack-test.json b/lib/policy/testdata/hack-test.json
new file mode 100644
index 0000000..652dcd8
--- /dev/null
+++ b/lib/policy/testdata/hack-test.json
@@ -0,0 +1,9 @@
+[
+  {
+    "name": "ipv6-ula",
+    "action": "ALLOW",
+    "remote_addresses": [
+      "fc00::/7"
+    ]
+  }
+]
\ No newline at end of file
diff --git a/lib/policy/testdata/hack-test.yaml b/lib/policy/testdata/hack-test.yaml
new file mode 100644
index 0000000..cd4d7d0
--- /dev/null
+++ b/lib/policy/testdata/hack-test.yaml
@@ -0,0 +1,3 @@
+- name: well-known
+  path_regex: ^/.well-known/.*$
+  action: ALLOW
\ No newline at end of file