Add parse_json function the decode json strings (#2941)

Signed-off-by: Sambhav Kothari <sambhavs.email@gmail.com>

pkg/engine/jmespath/functions.go

@@ -2,6 +2,7 @@ package jmespath
 
 import (
 	"encoding/base64"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"path/filepath"
@@ -57,6 +58,7 @@ var (
 	pathCanonicalize       = "path_canonicalize"
 	truncate               = "truncate"
 	semverCompare          = "semver_compare"
+	parseJson              = "parse_json"
 )
 
 const errorPrefix = "JMESPath function '%s': "
@@ -262,6 +264,13 @@ func getFunctions() []*gojmespath.FunctionEntry {
 			},
 			Handler: jpSemverCompare,
 		},
+		{
+			Name: parseJson,
+			Arguments: []ArgSpec{
+				{Types: []JpType{JpString}},
+			},
+			Handler: jpParseJson,
+		},
 	}
 
 }
@@ -665,6 +674,16 @@ func jpSemverCompare(arguments []interface{}) (interface{}, error) {
 	return false, nil
 }
 
+func jpParseJson(arguments []interface{}) (interface{}, error) {
+	input, err := validateArg(parseJson, arguments, 0, reflect.String)
+	if err != nil {
+		return nil, err
+	}
+	var output interface{}
+	err = json.Unmarshal([]byte(input.String()), &output)
+	return output, err
+}
+
 // InterfaceToString casts an interface to a string type
 func ifaceToString(iface interface{}) (string, error) {
 	switch i := iface.(type) {
@@ -686,7 +705,7 @@ func ifaceToString(iface interface{}) (string, error) {
 func validateArg(f string, arguments []interface{}, index int, expectedType reflect.Kind) (reflect.Value, error) {
 	arg := reflect.ValueOf(arguments[index])
 	if arg.Type().Kind() != expectedType {
-		return reflect.Value{}, fmt.Errorf(invalidArgumentTypeError, equalFold, index+1, expectedType.String())
+		return reflect.Value{}, fmt.Errorf(invalidArgumentTypeError, f, index+1, expectedType.String())
 	}
 
 	return arg, nil

pkg/engine/jmespath/functions_test.go

@@ -43,6 +43,68 @@ func Test_Compare(t *testing.T) {
 	}
 }
 
+func Test_ParseJsonSerde(t *testing.T) {
+	testCases := []string{
+		`{"a":"b"}`,
+		`true`,
+		`[1,2,3,{"a":"b"}]`,
+		`null`,
+		`[]`,
+		`{}`,
+		`0`,
+		`1.2`,
+		`[1.2,true,{"a":{"a":"b"}}]`,
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc, func(t *testing.T) {
+			jp, err := New(fmt.Sprintf(`to_string(parse_json('%s'))`, tc))
+			fmt.Println(err)
+			assert.NilError(t, err)
+
+			result, err := jp.Search("")
+			fmt.Println(err)
+			assert.NilError(t, err)
+
+			assert.Equal(t, result, tc)
+		})
+	}
+}
+
+func Test_ParseJsonComplex(t *testing.T) {
+	testCases := []struct {
+		input          string
+		expectedResult interface{}
+	}{
+		{
+			input:          `parse_json('{"a": "b"}').a`,
+			expectedResult: "b",
+		},
+		{
+			input:          `parse_json('{"a": [1, 2, 3, 4]}').a[0]`,
+			expectedResult: 1.0,
+		},
+		{
+			input:          `parse_json('[1, 2, {"a": {"b": {"c": [1, 2]}}}]')[2].a.b.c[1]`,
+			expectedResult: 2.0,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.input, func(t *testing.T) {
+			jp, err := New(tc.input)
+			fmt.Println(err)
+			assert.NilError(t, err)
+
+			result, err := jp.Search("")
+			fmt.Println(err)
+			assert.NilError(t, err)
+
+			assert.Equal(t, result, tc.expectedResult)
+		})
+	}
+}
+
 func Test_EqualFold(t *testing.T) {
 	testCases := []struct {
 		jmesPath       string

test/cli/test/custom-functions/policy.yaml

@@ -74,3 +74,24 @@ spec:
             - key: "{{ path_canonicalize(element.hostPath.path) }}"
               operator: Equals
               value: "\\var\\run\\containerd\\containerd.sock"
+---
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: test-parse-json
+spec:
+  validationFailureAction: enforce
+  background: false
+  rules:
+  - name: test-json-parsing-jmespath
+    match:
+      resources:
+        kinds:
+         - ConfigMap
+    validate:
+      message: "Test JMESPath"
+      deny:
+        conditions:
+        - key: "{{request.object.metadata.annotations.test | parse_json(@).a }}"
+          operator: NotEquals
+          value: b

test/cli/test/custom-functions/resources.yaml

@@ -51,3 +51,19 @@ spec:
       mountPath: /sock
     - name: test
       mountPath: /test 
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: valid-test
+  annotations:
+    test: |
+      {"a": "b"}
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: invalid-test
+  annotations:
+    test: |
+      {"a": "not-b"}

test/cli/test/custom-functions/test.yaml

@@ -29,3 +29,13 @@ results:
     resource: mount-containerd-sock
     kind: Pod
     status: fail
+  - policy: test-parse-json
+    rule: test-json-parsing-jmespath
+    resource: valid-test
+    kind: ConfigMap
+    result: pass
+  - policy: test-parse-json
+    rule: test-json-parsing-jmespath
+    resource: invalid-test
+    kind: ConfigMap
+    result: fail