download all delegated roles when doing downloadTargets

Signed-off-by: David Lawrence <david.lawrence@docker.com> (github: endophage)

tuf/client/client.go

@@ -369,9 +369,17 @@ func (c *Client) downloadSnapshot() error {
 	return nil
 }
 
-// downloadTargets is responsible for downloading any targets file
+// downloadTargets downloads all targets and delegated targets for the repository.
-// including delegates roles.
+// It uses a pre-order tree traversal as it's necessary to download parents first
+// to obtain the keys to validate children.
 func (c *Client) downloadTargets(role string) error {
+	stack := utils.NewStack()
+	stack.Push(role)
+	for !stack.Empty() {
+		role, err := stack.PopString()
+		if err != nil {
+			return err
+		}
 		role = data.RoleName(role) // this will really only do something for base targets role
 		if c.local.Snapshot == nil {
 			return ErrMissingMeta{role: role}
@@ -397,6 +405,11 @@ func (c *Client) downloadTargets(role string) error {
 			return err
 		}
 
+		// push delegated roles contained in the targets file onto the stack
+		for _, r := range t.Signed.Delegations.Roles {
+			stack.Push(r.Name)
+		}
+	}
 	return nil
 }
 

tuf/utils/stack.go

@@ -0,0 +1,57 @@
+package utils
+
+import (
+	"fmt"
+)
+
+type ErrEmptyStack struct {
+	action string
+}
+
+func (err ErrEmptyStack) Error() string {
+	return fmt.Sprintf("attempted to %s with empty stack", err.action)
+}
+
+type ErrBadTypeCast struct{}
+
+func (err ErrBadTypeCast) Error() string {
+	return "attempted to do a typed pop and item was not of type"
+}
+
+type Stack []interface{}
+
+func NewStack() *Stack {
+	s := make(Stack, 0)
+	return &s
+}
+
+func (s *Stack) Push(item interface{}) {
+	*s = append(*s, item)
+}
+
+func (s *Stack) Pop() (interface{}, error) {
+	l := len(*s)
+	if l > 0 {
+		item := (*s)[l-1]
+		*s = (*s)[:l-1]
+		return item, nil
+	}
+	return nil, ErrEmptyStack{action: "pop"}
+}
+
+func (s *Stack) PopString() (string, error) {
+	l := len(*s)
+	if l > 0 {
+		item := (*s)[l-1]
+		if item, ok := item.(string); ok {
+			*s = (*s)[:l-1]
+			return item, nil
+		}
+		return "", ErrBadTypeCast{}
+	}
+	return "", ErrEmptyStack{action: "pop"}
+}
+
+func (s Stack) Empty() bool {
+	return len(s) == 0
+}