Track sensitivity through evaluation

Mark sensitivity on a value. However, when the value is encoded to send to the
provider to produce a changeset we must remove the marks, so unmark the value
and remark it with the saved path afterwards

command/format/diff.go

@@ -125,10 +125,21 @@ func ResourceChange(
 	changeV.Change.Before = objchange.NormalizeObjectFromLegacySDK(changeV.Change.Before, schema)
 	changeV.Change.After = objchange.NormalizeObjectFromLegacySDK(changeV.Change.After, schema)
 
-	result := p.writeBlockBodyDiff(schema, changeV.Before, changeV.After, 6, path)
-	if result.bodyWritten {
-		p.buf.WriteString("\n")
-		p.buf.WriteString(strings.Repeat(" ", 4))
+	// Now that the change is decoded, add back the marks at the defined paths
+	// change.Markinfo
+	changeV.Change.After, _ = cty.Transform(changeV.Change.After, func(p cty.Path, v cty.Value) (cty.Value, error) {
+		if p.Equals(change.ValMarks.Path) {
+			// TODO The mark is at change.Markinfo.Marks and it would be proper
+			// to iterate through that set here
+			return v.Mark("sensitive"), nil
+		}
+		return v, nil
+	})
+
+	bodyWritten := p.writeBlockBodyDiff(schema, changeV.Before, changeV.After, 6, path)
+	if bodyWritten {
+		buf.WriteString("\n")
+		buf.WriteString(strings.Repeat(" ", 4))
 	}
 	buf.WriteString("}\n")
 
@@ -586,6 +597,12 @@ func (p *blockBodyDiffPrinter) writeNestedBlockDiff(name string, label *string,
 }
 
 func (p *blockBodyDiffPrinter) writeValue(val cty.Value, action plans.Action, indent int) {
+	// Could check specifically for the sensitivity marker
+	if val.IsMarked() {
+		p.buf.WriteString("(sensitive)")
+		return
+	}
+
 	if !val.IsKnown() {
 		p.buf.WriteString("(known after apply)")
 		return
@@ -1284,7 +1301,8 @@ func ctyGetAttrMaybeNull(val cty.Value, name string) cty.Value {
 	// This allows us to avoid spurious diffs
 	// until we introduce null to the SDK.
 	attrValue := val.GetAttr(name)
-	if ctyEmptyString(attrValue) {
+	// If the value is marked, the ctyEmptyString function will fail
+	if !val.ContainsMarked() && ctyEmptyString(attrValue) {
 		return cty.NullVal(attrType)
 	}
 

plans/changes.go

@@ -341,7 +341,7 @@ func (c *Change) Encode(ty cty.Type) (*ChangeSrc, error) {
 	if err != nil {
 		return nil, err
 	}
-	afterDV, err := NewDynamicValue(c.After, ty)
+	afterDV, err, marks := NewDynamicValueMarks(c.After, ty)
 	if err != nil {
 		return nil, err
 	}
@@ -350,5 +350,6 @@ func (c *Change) Encode(ty cty.Type) (*ChangeSrc, error) {
 		Action:   c.Action,
 		Before:   beforeDV,
 		After:    afterDV,
+		ValMarks: marks,
 	}, nil
 }

plans/changes_src.go

@@ -6,6 +6,7 @@ import (
 	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/states"
 	"github.com/zclconf/go-cty/cty"
+	ctymsgpack "github.com/zclconf/go-cty/cty/msgpack"
 )
 
 // ResourceInstanceChangeSrc is a not-yet-decoded ResourceInstanceChange.
@@ -156,6 +157,9 @@ type ChangeSrc struct {
 	// but have not yet been decoded from the serialized value used for
 	// storage.
 	Before, After DynamicValue
+
+	// Marked Paths
+	ValMarks *ctymsgpack.MarkInfo
 }
 
 // Decode unmarshals the raw representations of the before and after values

plans/dynamic_value.go

@@ -55,6 +55,26 @@ func NewDynamicValue(val cty.Value, ty cty.Type) (DynamicValue, error) {
 	return DynamicValue(buf), nil
 }
 
+// NewDynamicValueMarks returns a new dynamic value along with a
+// associated marking info for the value
+func NewDynamicValueMarks(val cty.Value, ty cty.Type) (DynamicValue, error, *ctymsgpack.MarkInfo) {
+	// If we're given cty.NilVal (the zero value of cty.Value, which is
+	// distinct from a typed null value created by cty.NullVal) then we'll
+	// assume the caller is trying to represent the _absense_ of a value,
+	// and so we'll return a nil DynamicValue.
+	if val == cty.NilVal {
+		return DynamicValue(nil), nil, nil
+	}
+
+	// Currently our internal encoding is msgpack, via ctymsgpack.
+	buf, err, marks := ctymsgpack.MarshalWithMarks(val, ty)
+	if err != nil {
+		return nil, err, marks
+	}
+
+	return DynamicValue(buf), nil, marks
+}
+
 // Decode retrieves the effective value from the receiever by interpreting the
 // serialized form against the given type constraint. For correct results,
 // the type constraint must match (or be consistent with) the one that was

terraform/eval_diff.go

@@ -141,6 +141,25 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 		return nil, diags.Err()
 	}
 
+	var markedPath cty.Path
+	// var marks cty.ValueMarks
+	if configVal.ContainsMarked() {
+		// store the marked values so we can re-mark them later after
+		// we've sent things over the wire. Right now this stores
+		// one path for proof of concept, but we should store multiple
+		cty.Walk(configVal, func(p cty.Path, v cty.Value) (bool, error) {
+			if v.IsMarked() {
+				markedPath = p
+				return false, nil
+				// marks = v.Marks()
+			}
+			return true, nil
+		})
+		// Unmark the value for sending over the wire
+		// to providers as marks cannot be serialized
+		configVal, _ = configVal.UnmarkDeep()
+	}
+
 	metaConfigVal := cty.NullVal(cty.DynamicPseudoType)
 	if n.ProviderMetas != nil {
 		if m, ok := n.ProviderMetas[n.ProviderAddr.Provider]; ok && m != nil {
@@ -235,6 +254,15 @@ func (n *EvalDiff) Eval(ctx EvalContext) (interface{}, error) {
 	}
 
 	plannedNewVal := resp.PlannedState
+
+	// Add the mark back to the planned new value
+	plannedNewVal, _ = cty.Transform(plannedNewVal, func(p cty.Path, v cty.Value) (cty.Value, error) {
+		if p.Equals(markedPath) {
+			return v.Mark("sensitive"), nil
+		}
+		return v, nil
+	})
+
 	plannedPrivate := resp.PlannedPrivate
 
 	if plannedNewVal == cty.NilVal {

terraform/evaluate.go

@@ -292,6 +292,10 @@ func (d *evaluationStateData) GetInputVariable(addr addrs.InputVariable, rng tfd
 		val = cty.UnknownVal(wantType)
 	}
 
+	if config.Sensitive {
+		val = val.Mark("sensitive")
+	}
+
 	return val, diags
 }
 

vendor/github.com/zclconf/go-cty/cty/json/marshal.go

@@ -10,7 +10,8 @@ import (
 
 func marshal(val cty.Value, t cty.Type, path cty.Path, b *bytes.Buffer) error {
 	if val.IsMarked() {
-		return path.NewErrorf("value has marks, so it cannot be seralized")
+		// For now, dump the marks when serializing JSON for POC purposes
+		val, _ = val.UnmarkDeep()
 	}
 
 	// If we're going to decode as DynamicPseudoType then we need to save

vendor/github.com/zclconf/go-cty/cty/msgpack/marshal.go

@@ -41,6 +41,36 @@ func Marshal(val cty.Value, ty cty.Type) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+// This type should (likely) be a map of paths
+// and marks, so that multiple marks can be found
+// in case of a value containing multiple marked values
+type MarkInfo struct {
+	Marks cty.ValueMarks
+	Path  cty.Path
+}
+
+func MarshalWithMarks(val cty.Value, ty cty.Type) ([]byte, error, *MarkInfo) {
+	markInfo := MarkInfo{}
+	if val.ContainsMarked() {
+		// store the marked values so we can re-mark them later after
+		// we've sent things over the wire
+		cty.Walk(val, func(p cty.Path, v cty.Value) (bool, error) {
+			if v.IsMarked() {
+				markInfo.Path = p
+				markInfo.Marks = v.Marks()
+			}
+			return true, nil
+		})
+		val, _ = val.UnmarkDeep()
+	}
+	by, err := Marshal(val, ty)
+	if err != nil {
+		return nil, err, &markInfo
+	}
+
+	return by, nil, &markInfo
+}
+
 func marshal(val cty.Value, ty cty.Type, path cty.Path, enc *msgpack.Encoder) error {
 	if val.IsMarked() {
 		return path.NewErrorf("value has marks, so it cannot be seralized")