chore: New environment variable obfuscation functionality

Signed-off-by: Matthias Glastra <[email protected]>

attestation/environment/environment.go

@@ -58,7 +58,8 @@ type Attestor struct {
 	Username  string            `json:"username"`
 	Variables map[string]string `json:"variables,omitempty"`
 
-	blockList map[string]struct{}
+	blockList     map[string]struct{}
+	obfuscateList map[string]struct{}
 }
 
 type Option func(*Attestor)
@@ -69,9 +70,18 @@ func WithBlockList(blockList map[string]struct{}) Option {
 	}
 }
 
+func WithObfuscateList(obfuscateList map[string]struct{}) Option {
+	return func(a *Attestor) {
+		for key, value := range obfuscateList {
+			a.obfuscateList[key] = value
+		}
+	}
+}
+
 func New(opts ...Option) *Attestor {
 	attestor := &Attestor{
-		blockList: DefaultBlockList(),
+		blockList:     DefaultBlockList(),
+		obfuscateList: DefaultObfuscateList(),
 	}
 
 	for _, opt := range opts {
@@ -113,6 +123,10 @@ func (a *Attestor) Attest(ctx *attestation.AttestationContext) error {
 		a.Variables[key] = val
 	})
 
+	ObfuscateEnvironmentArray(a.Variables, a.obfuscateList, func(key, val, _ string) {
+		a.Variables[key] = val
+	})
+
 	return nil
 }
 

attestation/environment/environment_test.go

@@ -39,3 +39,35 @@ func TestEnvironment(t *testing.T) {
 		}
 	}
 }
+
+func TestEnvironmentObfuscate(t *testing.T) {
+	attestor := New()
+	ctx, err := attestation.NewContext("test", []attestation.Attestor{attestor})
+	require.NoError(t, err)
+
+	obfuscateEnvs := map[string]struct{}{"API_TOKEN": {}, "SECRET_TEXT": {}}
+	secretVarValue := "secret var"
+	publicVarValue := "public var"
+	for k := range obfuscateEnvs {
+		t.Setenv(k, secretVarValue)
+	}
+
+	notObfuscateEnvs := map[string]struct{}{"VAR_FOO": {}, "VAR_BAR": {}}
+	for k := range notObfuscateEnvs {
+		t.Setenv(k, publicVarValue)
+	}
+
+	origVars := os.Environ()
+	require.NoError(t, attestor.Attest(ctx))
+	for _, env := range origVars {
+		origKey, _ := splitVariable(env)
+		if _, inObfuscateList := obfuscateEnvs[origKey]; inObfuscateList {
+			require.NotEqual(t, attestor.Variables[origKey], secretVarValue)
+			require.Equal(t, attestor.Variables[origKey], "******")
+		}
+
+		if _, inNotObfuscateList := notObfuscateEnvs[origKey]; inNotObfuscateList {
+			require.Equal(t, attestor.Variables[origKey], publicVarValue)
+		}
+	}
+}

attestation/environment/obfuscate.go

@@ -0,0 +1,66 @@
+// Copyright 2021 The Witness Contributors
+//
+// 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 environment
+
+import (
+	"strings"
+
+	"github.com/gobwas/glob"
+	"github.com/in-toto/go-witness/log"
+)
+
+// sourced from https://github.com/Puliczek/awesome-list-of-secrets-in-environment-variables/blob/main/raw_list.txt
+func DefaultObfuscateList() map[string]struct{} {
+	return map[string]struct{}{
+		"*_TOKEN":    {},
+		"SECRET_*":   {},
+		"*_API_KEY":  {},
+		"*_PASSWORD": {},
+		"*_JWT":      {},
+	}
+}
+
+// FilterEnvironmentArray expects an array of strings representing environment variables.  Each element of the array is expected to be in the format of "KEY=VALUE".
+// blockList is the list of elements to filter from variables, and for each element of variables that does not appear in the blockList onAllowed will be called.
+func ObfuscateEnvironmentArray(variables map[string]string, obfuscateList map[string]struct{}, onAllowed func(key, val, orig string)) {
+	obfuscateGlobList := []glob.Glob{}
+
+	for k := range obfuscateList {
+		if strings.Contains(k, "*") {
+			obfuscateGlobCompiled, err := glob.Compile(k)
+			if err != nil {
+				log.Errorf("obfuscate glob pattern could not be interpreted: %w", err)
+			}
+
+			obfuscateGlobList = append(obfuscateGlobList, obfuscateGlobCompiled)
+		}
+	}
+
+	for key, v := range variables {
+		val := v
+
+		if _, inObfuscateList := obfuscateList[key]; inObfuscateList {
+			val = "******"
+		}
+
+		for _, glob := range obfuscateGlobList {
+			if glob.Match(key) {
+				val = "******"
+			}
+		}
+
+		onAllowed(key, val, v)
+	}
+}