fix length check per-kind bug

fix(selector): handle broken "Pass" cases

capability/command/command.go

@@ -1,54 +1,11 @@
 package command
 
 import (
-	"errors"
 	"fmt"
 	"strings"
 )
 
-const (
-	separator = "/"
-)
-
-// ErrNew indicates that the wrapped error was encountered while creating
-// a new Command.
-var ErrNew = errors.New("failed to create Command from elems")
-
-// ErrParse indicates that the wrapped error was encountered while
-// attempting to parse a string as a Command.
-var ErrParse = errors.New("failed to parse Command")
-
-// ErrorJoin indicates that the wrapped error was encountered while
-// attempting to join a new segment to a Command.
-var ErrJoin = errors.New("failed to join segments to Command")
-
-// ErrRequiresLeadingSlash is returned when a parsing a string that
-// doesn't start with a [leading slash character].
-//
-// [leading slash character]: https://github.com/ucan-wg/spec#segment-structure
-var ErrRequiresLeadingSlash = parseError("a command requires a leading slash character")
-
-// ErrDisallowsTrailingSlash is returned when parsing a string that [ends
-// with a trailing slash character].
-//
-// [ends with a trailing slash character]: https://github.com/ucan-wg/spec#segment-structure
-var ErrDisallowsTrailingSlash = parseError("a command must not include a trailing slash")
-
-// ErrUCANNamespaceReserved is returned to indicate that a Command's
-// first segment would contain the [reserved "ucan" namespace].
-//
-// [reserved "ucan" namespace]: https://github.com/ucan-wg/spec#ucan-namespace
-var ErrUCANNamespaceReserved = errors.New("the UCAN namespace is reserved")
-
-// ErrRequiresLowercase is returned if a Command contains, or would contain,
-// [uppercase unicode characters].
-//
-// [uppercase unicode characters]: https://github.com/ucan-wg/spec#segment-structure
-var ErrRequiresLowercase = parseError("UCAN path segments must must not contain upper-case characters")
-
-func parseError(msg string) error {
-	return fmt.Errorf("%w: %s", ErrParse, msg)
-}
+const separator = "/"
 
 var _ fmt.Stringer = (*Command)(nil)
 
@@ -66,18 +23,8 @@ type Command struct {
 // New creates a validated command from the provided list of segment
 // strings.  An error is returned if an invalid Command would be
 // formed
-func New(segments ...string) (*Command, error) {
-	return newCommand(ErrNew, segments...)
-}
-
-func newCommand(err error, segments ...string) (*Command, error) {
-	if len(segments) > 0 && segments[0] == "ucan" {
-		return nil, fmt.Errorf("%w: %w", err, ErrUCANNamespaceReserved)
-	}
-
-	cmd := Command{segments}
-
-	return &cmd, nil
+func New(segments ...string) *Command {
+	return &Command{segments: segments}
 }
 
 // Parse verifies that the provided string contains the required
@@ -100,7 +47,16 @@ func Parse(s string) (*Command, error) {
 
 	// The leading slash will result in the first element from strings.Split
 	// being an empty string which is removed as strings.Join will ignore it.
-	return newCommand(ErrParse, strings.Split(s, "/")[1:]...)
+	return &Command{strings.Split(s, "/")[1:]}, nil
+}
+
+// MustParse is the same as Parse, but panic() if the parsing fail.
+func MustParse(s string) *Command {
+	c, err := Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return c
 }
 
 // [Top] is the most powerful capability.
@@ -111,22 +67,19 @@ func Parse(s string) (*Command, error) {
 //
 // [Top]: https://github.com/ucan-wg/spec#-aka-top
 func Top() *Command {
-	cmd, _ := New()
-
-	return cmd
+	return New()
 }
 
 // IsValid returns true if the provided string is a valid UCAN command.
 func IsValid(s string) bool {
 	_, err := Parse(s)
-
 	return err == nil
 }
 
 // Join appends segments to the end of this command using the required
 // segment separator.
-func (c *Command) Join(segments ...string) (*Command, error) {
-	return newCommand(ErrJoin, append(c.segments, segments...)...)
+func (c *Command) Join(segments ...string) *Command {
+	return &Command{append(c.segments, segments...)}
 }
 
 // Segments returns the ordered segments that comprise the Command as a
@@ -138,5 +91,5 @@ func (c *Command) Segments() []string {
 // String returns the composed representation the command.  This is also
 // the required wire representation (before IPLD encoding occurs.)
 func (c *Command) String() string {
-	return "/" + strings.Join([]string(c.segments), "/")
+	return "/" + strings.Join(c.segments, "/")
 }

capability/command/command_errors.go

@@ -0,0 +1,21 @@
+package command
+
+import "fmt"
+
+// ErrRequiresLeadingSlash is returned when a parsing a string that
+// doesn't start with a [leading slash character].
+//
+// [leading slash character]: https://github.com/ucan-wg/spec#segment-structure
+var ErrRequiresLeadingSlash = fmt.Errorf("a command requires a leading slash character")
+
+// ErrDisallowsTrailingSlash is returned when parsing a string that [ends
+// with a trailing slash character].
+//
+// [ends with a trailing slash character]: https://github.com/ucan-wg/spec#segment-structure
+var ErrDisallowsTrailingSlash = fmt.Errorf("a command must not include a trailing slash")
+
+// ErrRequiresLowercase is returned if a Command contains, or would contain,
+// [uppercase unicode characters].
+//
+// [uppercase unicode characters]: https://github.com/ucan-wg/spec#segment-structure
+var ErrRequiresLowercase = fmt.Errorf("UCAN path segments must must not contain upper-case characters")

capability/command/command_test.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/stretchr/testify/require"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/command"
+	"github.com/ucan-wg/go-ucan/capability/command"
 )
 
 func TestTop(t *testing.T) {
@@ -73,7 +73,6 @@ func TestParseCommand(t *testing.T) {
 				t.Parallel()
 
 				cmd, err := command.Parse(testcase.inp)
-				require.ErrorIs(t, err, command.ErrParse)
 				require.ErrorIs(t, err, testcase.err)
 				require.Nil(t, cmd)
 			})
@@ -134,20 +133,6 @@ func invalidTestcases(t *testing.T) []errorTestcase {
 			},
 			err: command.ErrDisallowsTrailingSlash,
 		},
-		{
-			testcase: testcase{
-				name: "only reserved ucan namespace",
-				inp:  "/ucan",
-			},
-			err: command.ErrUCANNamespaceReserved,
-		},
-		{
-			testcase: testcase{
-				name: "reserved ucan namespace prefix",
-				inp:  "/ucan/elem0/elem1/elem2",
-			},
-			err: command.ErrUCANNamespaceReserved,
-		},
 		{
 			testcase: testcase{
 				name: "uppercase character are present",

capability/policy/ipld.go

@@ -9,7 +9,7 @@ import (
 	"github.com/ipld/go-ipld-prime/must"
 	"github.com/ipld/go-ipld-prime/node/basicnode"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/capability/policy/selector"
 )
 
 func FromIPLD(node datamodel.Node) (Policy, error) {
@@ -40,14 +40,14 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 	}
 	op := must.String(opNode)
 
-	arg2AsSelector := func() (selector.Selector, error) {
+	arg2AsSelector := func(op string) (selector.Selector, error) {
 		nd, _ := node.LookupByIndex(1)
 		if nd.Kind() != datamodel.Kind_String {
-			return nil, ErrNotAString(path + "1/")
+			return nil, ErrNotAString(combinePath(path, op, 1))
 		}
 		sel, err := selector.Parse(must.String(nd))
 		if err != nil {
-			return nil, ErrInvalidSelector(path+"1/", err)
+			return nil, ErrInvalidSelector(combinePath(path, op, 1), err)
 		}
 		return sel, nil
 	}
@@ -57,7 +57,7 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 		switch op {
 		case KindNot:
 			arg2, _ := node.LookupByIndex(1)
-			statement, err := statementFromIPLD(path+"1/", arg2)
+			statement, err := statementFromIPLD(combinePath(path, op, 1), arg2)
 			if err != nil {
 				return nil, err
 			}
@@ -65,7 +65,7 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 
 		case KindAnd, KindOr:
 			arg2, _ := node.LookupByIndex(1)
-			statement, err := statementsFromIPLD(path+"1/", arg2)
+			statement, err := statementsFromIPLD(combinePath(path, op, 1), arg2)
 			if err != nil {
 				return nil, err
 			}
@@ -77,7 +77,7 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 	case 3:
 		switch op {
 		case KindEqual, KindLessThan, KindLessThanOrEqual, KindGreaterThan, KindGreaterThanOrEqual:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
@@ -85,28 +85,31 @@ func statementFromIPLD(path string, node datamodel.Node) (Statement, error) {
 			return equality{kind: op, selector: sel, value: arg3}, nil
 
 		case KindLike:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
 			pattern, _ := node.LookupByIndex(2)
 			if pattern.Kind() != datamodel.Kind_String {
-				return nil, ErrNotAString(path + "2/")
+				return nil, ErrNotAString(combinePath(path, op, 2))
 			}
 			res, err := Like(sel, must.String(pattern))
 			if err != nil {
-				return nil, ErrInvalidPattern(path+"2/", err)
+				return nil, ErrInvalidPattern(combinePath(path, op, 2), err)
 			}
 			return res, nil
 
 		case KindAll, KindAny:
-			sel, err := arg2AsSelector()
+			sel, err := arg2AsSelector(op)
 			if err != nil {
 				return nil, err
 			}
-			statementsNodes, _ := node.LookupByIndex(2)
-			statements, err := statementsFromIPLD(path+"1/", statementsNodes)
-			return quantifier{kind: op, selector: sel, statements: statements}, nil
+			statementsNode, _ := node.LookupByIndex(2)
+			statement, err := statementFromIPLD(combinePath(path, op, 1), statementsNode)
+			if err != nil {
+				return nil, err
+			}
+			return quantifier{kind: op, selector: sel, statement: statement}, nil
 
 		default:
 			return nil, ErrUnrecognizedOperator(path, op)
@@ -123,7 +126,7 @@ func statementsFromIPLD(path string, node datamodel.Node) ([]Statement, error) {
 		return nil, ErrNotATuple(path)
 	}
 	if node.Length() == 0 {
-		return nil, ErrEmptyList(path)
+		return nil, nil
 	}
 
 	res := make([]Statement, node.Length())
@@ -243,7 +246,7 @@ func statementToIPLD(statement Statement) (datamodel.Node, error) {
 		if err != nil {
 			return nil, err
 		}
-		args, err := statementsToIPLD(statement.statements)
+		args, err := statementToIPLD(statement.statement)
 		if err != nil {
 			return nil, err
 		}
@@ -260,3 +263,7 @@ func statementToIPLD(statement Statement) (datamodel.Node, error) {
 
 	return list.Build(), nil
 }
+
+func combinePath(prev string, operator string, index int) string {
+	return fmt.Sprintf("%s%d-%s/", prev, index, operator)
+}

capability/policy/ipld_errors.go

@@ -35,10 +35,6 @@ func ErrNotATuple(path string) error {
 	return errWithPath{path: path, msg: "not a tuple"}
 }
 
-func ErrEmptyList(path string) error {
-	return errWithPath{path: path, msg: "empty list"}
-}
-
 func safeStr(str string) string {
 	if len(str) > 10 {
 		return str[:10]

capability/policy/ipld_test.go

@@ -11,16 +11,14 @@ import (
 func TestIpldRoundTrip(t *testing.T) {
 	const illustrativeExample = `
 [
-    ["==", ".status", "draft"],
-    ["all", ".reviewer", [
-		["like", ".email", "*@example.com"]]
-	],
-    ["any", ".tags", [ 
-		["or", [
-			["==", ".", "news"], 
-			["==", ".", "press"]]
-      ]]
-	]
+  ["==", ".status", "draft"],
+  ["all", ".reviewer", ["like", ".email", "*@example.com"]],
+  ["any", ".tags", 
+    ["or", [
+      ["==", ".", "news"], 
+      ["==", ".", "press"]
+    ]]
+  ]
 ]`
 
 	for _, tc := range []struct {

capability/policy/match.go

@@ -8,7 +8,7 @@ import (
 	"github.com/ipld/go-ipld-prime/datamodel"
 	"github.com/ipld/go-ipld-prime/must"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/capability/policy/selector"
 )
 
 // Match determines if the IPLD node matches the policy document.
@@ -26,11 +26,22 @@ func matchStatement(statement Statement, node ipld.Node) bool {
 	switch statement.Kind() {
 	case KindEqual:
 		if s, ok := statement.(equality); ok {
-			one, _, err := selector.Select(s.selector, node)
-			if err != nil || one == nil {
+			one, many, err := selector.Select(s.selector, node)
+			if err != nil {
 				return false
 			}
-			return datamodel.DeepEqual(s.value, one)
+			if one != nil {
+				return datamodel.DeepEqual(s.value, one)
+			}
+			if many != nil {
+				for _, n := range many {
+					if eq := datamodel.DeepEqual(s.value, n); eq {
+						return true
+					}
+				}
+			}
+
+			return false
 		}
 	case KindGreaterThan:
 		if s, ok := statement.(equality); ok {
@@ -110,7 +121,7 @@ func matchStatement(statement Statement, node ipld.Node) bool {
 				return false
 			}
 			for _, n := range many {
-				ok := Match(s.statements, n)
+				ok := matchStatement(s.statement, n)
 				if !ok {
 					return false
 				}
@@ -119,16 +130,25 @@ func matchStatement(statement Statement, node ipld.Node) bool {
 		}
 	case KindAny:
 		if s, ok := statement.(quantifier); ok {
-			_, many, err := selector.Select(s.selector, node)
-			if err != nil || many == nil {
+			one, many, err := selector.Select(s.selector, node)
+			if err != nil {
 				return false
 			}
-			for _, n := range many {
-				ok := Match(s.statements, n)
+			if one != nil {
+				ok := matchStatement(s.statement, one)
 				if ok {
 					return true
 				}
 			}
+			if many != nil {
+				for _, n := range many {
+					ok := matchStatement(s.statement, n)
+					if ok {
+						return true
+					}
+				}
+			}
+
 			return false
 		}
 	}

capability/policy/match_test.go

@@ -6,12 +6,13 @@ import (
 
 	"github.com/ipfs/go-cid"
 	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
 	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
 	"github.com/ipld/go-ipld-prime/node/basicnode"
 	"github.com/stretchr/testify/require"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/literal"
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/capability/policy/literal"
+	"github.com/ucan-wg/go-ucan/capability/policy/selector"
 )
 
 func TestMatch(t *testing.T) {
@@ -400,8 +401,7 @@ func TestMatch(t *testing.T) {
 			pol := Policy{
 				Any(
 					selector.MustParse(".[]"),
-					GreaterThan(selector.MustParse(".value"), literal.Int(10)),
-					LessThan(selector.MustParse(".value"), literal.Int(50)),
+					GreaterThan(selector.MustParse(".value"), literal.Int(60)),
 				),
 			}
 			ok := Match(pol, nd)
@@ -418,3 +418,75 @@ func TestMatch(t *testing.T) {
 		})
 	})
 }
+
+func TestPolicyExamples(t *testing.T) {
+	makeNode := func(data string) ipld.Node {
+		nd, err := ipld.Decode([]byte(data), dagjson.Decode)
+		require.NoError(t, err)
+		return nd
+	}
+
+	evaluate := func(statement string, data ipld.Node) bool {
+		// we need to wrap statement with [] to make them a policy
+		policy := fmt.Sprintf("[%s]", statement)
+
+		pol, err := FromDagJson(policy)
+		require.NoError(t, err)
+		return Match(pol, data)
+	}
+
+	t.Run("And", func(t *testing.T) {
+		data := makeNode(`{ "name": "Katie", "age": 35, "nationalities": ["Canadian", "South African"] }`)
+
+		require.True(t, evaluate(`["and", []]`, data))
+		require.True(t, evaluate(`
+["and", [
+  ["==", ".name", "Katie"], 
+  [">=", ".age", 21]
+]]`, data))
+		require.False(t, evaluate(`
+["and", [
+  ["==", ".name", "Katie"], 
+  [">=", ".age", 21], 
+  ["==", ".nationalities", ["American"]]
+]]`, data))
+	})
+
+	t.Run("Or", func(t *testing.T) {
+		data := makeNode(`{ "name": "Katie", "age": 35, "nationalities": ["Canadian", "South African"] }`)
+
+		require.True(t, evaluate(`["or", []]`, data))
+		require.True(t, evaluate(`
+		["or", [
+		  ["==", ".name", "Katie"],
+		  [">", ".age", 45]
+		]]
+		`, data))
+
+	})
+
+	t.Run("Not", func(t *testing.T) {
+		data := makeNode(`{ "name": "Katie", "nationalities": ["Canadian", "South African"] }`)
+
+		require.True(t, evaluate(`
+["not", 
+  ["and", [
+    ["==", ".name", "Katie"], 
+    ["==", ".nationalities", ["American"]]
+  ]]
+]
+`, data))
+	})
+
+	t.Run("All", func(t *testing.T) {
+		data := makeNode(`{"a": [{"b": 1}, {"b": 2}, {"z": [7, 8, 9]}]}`)
+
+		require.False(t, evaluate(`["all", ".a", [">", ".b", 0]]`, data))
+	})
+
+	t.Run("Any", func(t *testing.T) {
+		data := makeNode(`{"a": [{"b": 1}, {"b": 2}, {"z": [7, 8, 9]}]}`)
+
+		require.True(t, evaluate(`["any", ".a", ["==", ".b", 2]]`, data))
+	})
+}

capability/policy/policy.go

@@ -6,7 +6,7 @@ import (
 	"github.com/gobwas/glob"
 	"github.com/ipld/go-ipld-prime"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/capability/policy/selector"
 )
 
 const (
@@ -40,23 +40,23 @@ func (e equality) Kind() string {
 }
 
 func Equal(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindEqual, selector, value}
+	return equality{kind: KindEqual, selector: selector, value: value}
 }
 
 func GreaterThan(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindGreaterThan, selector, value}
+	return equality{kind: KindGreaterThan, selector: selector, value: value}
 }
 
 func GreaterThanOrEqual(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindGreaterThanOrEqual, selector, value}
+	return equality{kind: KindGreaterThanOrEqual, selector: selector, value: value}
 }
 
 func LessThan(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindLessThan, selector, value}
+	return equality{kind: KindLessThan, selector: selector, value: value}
 }
 
 func LessThanOrEqual(selector selector.Selector, value ipld.Node) Statement {
-	return equality{KindLessThanOrEqual, selector, value}
+	return equality{kind: KindLessThanOrEqual, selector: selector, value: value}
 }
 
 type negation struct {
@@ -68,7 +68,7 @@ func (n negation) Kind() string {
 }
 
 func Not(stmt Statement) Statement {
-	return negation{stmt}
+	return negation{statement: stmt}
 }
 
 type connective struct {
@@ -81,11 +81,11 @@ func (c connective) Kind() string {
 }
 
 func And(stmts ...Statement) Statement {
-	return connective{KindAnd, stmts}
+	return connective{kind: KindAnd, statements: stmts}
 }
 
 func Or(stmts ...Statement) Statement {
-	return connective{KindOr, stmts}
+	return connective{kind: KindOr, statements: stmts}
 }
 
 type wildcard struct {
@@ -103,23 +103,23 @@ func Like(selector selector.Selector, pattern string) (Statement, error) {
 	if err != nil {
 		return nil, err
 	}
-	return wildcard{selector, pattern, g}, nil
+	return wildcard{selector: selector, pattern: pattern, glob: g}, nil
 }
 
 type quantifier struct {
-	kind       string
-	selector   selector.Selector
-	statements []Statement
+	kind      string
+	selector  selector.Selector
+	statement Statement
 }
 
 func (n quantifier) Kind() string {
 	return n.kind
 }
 
-func All(selector selector.Selector, policy ...Statement) Statement {
-	return quantifier{KindAll, selector, policy}
+func All(selector selector.Selector, statement Statement) Statement {
+	return quantifier{kind: KindAll, selector: selector, statement: statement}
 }
 
-func Any(selector selector.Selector, policy ...Statement) Statement {
-	return quantifier{KindAny, selector, policy}
+func Any(selector selector.Selector, statement Statement) Statement {
+	return quantifier{kind: KindAny, selector: selector, statement: statement}
 }

capability/policy/selector/selector.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/ipld/go-ipld-prime"
 	"github.com/ipld/go-ipld-prime/datamodel"
+	"github.com/ipld/go-ipld-prime/node/basicnode"
 	"github.com/ipld/go-ipld-prime/schema"
 )
 
@@ -86,120 +87,292 @@ func resolve(sel Selector, subject ipld.Node, at []string) (ipld.Node, []ipld.No
 	for i, seg := range sel {
 		if seg.Identity() {
 			continue
-		} else if seg.Iterator() {
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				var many []ipld.Node
-				it := cur.ListIterator()
-				for {
-					if it.Done() {
-						break
-					}
+		}
 
-					k, v, err := it.Next()
+		// 1st level: handle the different segment types (iterator, field, slice, index)
+		// 2nd level: handle different node kinds (list, map, string, bytes)
+		switch {
+		case seg.Iterator():
+			if cur == nil || cur.Kind() == datamodel.Kind_Null {
+				if seg.Optional() {
+					// build empty list
+					nb := basicnode.Prototype.List.NewBuilder()
+					assembler, err := nb.BeginList(0)
 					if err != nil {
 						return nil, nil, err
 					}
 
-					key := fmt.Sprintf("%d", k)
-					o, m, err := resolve(sel[i+1:], v, append(at[:], key))
-					if err != nil {
+					if err = assembler.Finish(); err != nil {
 						return nil, nil, err
 					}
 
-					if m != nil {
-						many = append(many, m...)
-					} else {
-						many = append(many, o)
-					}
+					return nb.Build(), nil, nil
+				} else {
+					return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
 				}
-				return nil, many, nil
-			} else if cur != nil && cur.Kind() == datamodel.Kind_Map {
-				var many []ipld.Node
-				it := cur.MapIterator()
-				for {
-					if it.Done() {
-						break
-					}
-
-					k, v, err := it.Next()
-					if err != nil {
-						return nil, nil, err
-					}
-
-					key, _ := k.AsString()
-					o, m, err := resolve(sel[i+1:], v, append(at[:], key))
-					if err != nil {
-						return nil, nil, err
-					}
-
-					if m != nil {
-						many = append(many, m...)
-					} else {
-						many = append(many, o)
-					}
-				}
-				return nil, many, nil
-			} else if seg.Optional() {
-				cur = nil
 			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
+				var many []ipld.Node
+				switch cur.Kind() {
+				case datamodel.Kind_List:
+					it := cur.ListIterator()
+					for !it.Done() {
+						_, v, err := it.Next()
+						if err != nil {
+							return nil, nil, err
+						}
+
+						// check if there are more iterator segments
+						if len(sel) > i+1 && sel[i+1].Iterator() {
+							if v.Kind() == datamodel.Kind_List {
+								// recursively resolve the remaining selector segments
+								var o ipld.Node
+								var m []ipld.Node
+								o, m, err = resolve(sel[i+1:], v, at)
+								if err != nil {
+									// if the segment is optional and an error occurs, skip the current iteration.
+									if seg.Optional() {
+										continue
+									} else {
+										return nil, nil, err
+									}
+								}
+								if m != nil {
+									many = append(many, m...)
+								} else if o != nil {
+									many = append(many, o)
+								}
+							} else {
+								// if the current value is not a list and the next segment is optional, skip the current iteration
+								if sel[i+1].Optional() {
+									continue
+								} else {
+									return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(v)), at)
+								}
+							}
+						} else {
+							// if there are no more iterator segments, append the current value to the result
+							many = append(many, v)
+						}
+					}
+				case datamodel.Kind_Map:
+					it := cur.MapIterator()
+					for !it.Done() {
+						_, v, err := it.Next()
+						if err != nil {
+							return nil, nil, err
+						}
+
+						if len(sel) > i+1 && sel[i+1].Iterator() {
+							if v.Kind() == datamodel.Kind_List {
+								var o ipld.Node
+								var m []ipld.Node
+								o, m, err = resolve(sel[i+1:], v, at)
+								if err != nil {
+									if seg.Optional() {
+										continue
+									} else {
+										return nil, nil, err
+									}
+								}
+								if m != nil {
+									many = append(many, m...)
+								} else if o != nil {
+									many = append(many, o)
+								}
+							} else {
+								if sel[i+1].Optional() {
+									continue
+								} else {
+									return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(v)), at)
+								}
+							}
+						} else {
+							many = append(many, v)
+						}
+					}
+				default:
+					return nil, nil, newResolutionError(fmt.Sprintf("can not iterate over kind: %s", kindString(cur)), at)
+				}
+
+				return nil, many, nil
 			}
 
-		} else if seg.Field() != "" {
+		case seg.Field() != "":
 			at = append(at, seg.Field())
-			if cur != nil && cur.Kind() == datamodel.Kind_Map {
-				n, err := cur.LookupByString(seg.Field())
-				if err != nil {
-					if isMissing(err) {
-						if seg.Optional() {
-							cur = nil
+			if cur == nil {
+				if seg.Optional() {
+					cur = nil
+				} else {
+					return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
+				}
+			} else {
+				switch cur.Kind() {
+				case datamodel.Kind_Map:
+					n, err := cur.LookupByString(seg.Field())
+					if err != nil {
+						if isMissing(err) {
+							if seg.Optional() {
+								cur = nil
+							} else {
+								return nil, nil, newResolutionError(fmt.Sprintf("object has no field named: %s", seg.Field()), at)
+							}
 						} else {
-							return nil, nil, newResolutionError(fmt.Sprintf("object has no field named: %s", seg.Field()), at)
+							return nil, nil, err
 						}
 					} else {
-						return nil, nil, err
+						cur = n
+					}
+				case datamodel.Kind_List:
+					var many []ipld.Node
+					it := cur.ListIterator()
+					for !it.Done() {
+						_, v, err := it.Next()
+						if err != nil {
+							return nil, nil, err
+						}
+						if v.Kind() == datamodel.Kind_Map {
+							n, err := v.LookupByString(seg.Field())
+							if err == nil {
+								many = append(many, n)
+							}
+						}
+					}
+					if len(many) > 0 {
+						cur = nil
+						return nil, many, nil
+					} else if seg.Optional() {
+						cur = nil
+					} else {
+						return nil, nil, newResolutionError(fmt.Sprintf("no elements in list have field named: %s", seg.Field()), at)
+					}
+				default:
+					if seg.Optional() {
+						cur = nil
+					} else {
+						return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
 					}
 				}
-				cur = n
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
 			}
-		} else if seg.Slice() != nil {
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				return nil, nil, newResolutionError("list slice selection not yet implemented", at)
-			} else if cur != nil && cur.Kind() == datamodel.Kind_Bytes {
-				return nil, nil, newResolutionError("bytes slice selection not yet implemented", at)
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not index: %s on kind: %s", seg.Field(), kindString(cur)), at)
-			}
-		} else {
-			at = append(at, fmt.Sprintf("%d", seg.Index()))
-			if cur != nil && cur.Kind() == datamodel.Kind_List {
-				idx := int64(seg.Index())
-				if idx < 0 {
-					idx = cur.Length() + idx
+
+		case seg.Slice() != nil:
+			if cur == nil {
+				if seg.Optional() {
+					cur = nil
+				} else {
+					return nil, nil, newResolutionError(fmt.Sprintf("can not slice on kind: %s", kindString(cur)), at)
 				}
-				n, err := cur.LookupByIndex(idx)
-				if err != nil {
-					if isMissing(err) {
+			} else {
+				slice := seg.Slice()
+				var start, end, length int64
+				switch cur.Kind() {
+				case datamodel.Kind_List:
+					length = cur.Length()
+					start, end = resolveSliceIndices(slice, length)
+				case datamodel.Kind_Bytes:
+					b, _ := cur.AsBytes()
+					length = int64(len(b))
+					start, end = resolveSliceIndices(slice, length)
+				case datamodel.Kind_String:
+					str, _ := cur.AsString()
+					length = int64(len(str))
+					start, end = resolveSliceIndices(slice, length)
+				default:
+					return nil, nil, newResolutionError(fmt.Sprintf("can not slice on kind: %s", kindString(cur)), at)
+				}
+
+				if start < 0 || end < start || end > length {
+					if seg.Optional() {
+						cur = nil
+					} else {
+						return nil, nil, newResolutionError(fmt.Sprintf("slice out of bounds: [%d:%d]", start, end), at)
+					}
+				} else {
+					switch cur.Kind() {
+					case datamodel.Kind_List:
+						if end > cur.Length() {
+							end = cur.Length()
+						}
+						nb := basicnode.Prototype.List.NewBuilder()
+						assembler, _ := nb.BeginList(int64(end - start))
+						for i := start; i < end; i++ {
+							item, _ := cur.LookupByIndex(int64(i))
+							assembler.AssembleValue().AssignNode(item)
+						}
+						assembler.Finish()
+						cur = nb.Build()
+					case datamodel.Kind_Bytes:
+						b, _ := cur.AsBytes()
+						l := int64(len(b))
+						if end > l {
+							end = l
+						}
+						cur = basicnode.NewBytes(b[start:end])
+					case datamodel.Kind_String:
+						str, _ := cur.AsString()
+						l := int64(len(str))
+						if end > l {
+							end = l
+						}
+						cur = basicnode.NewString(str[start:end])
+					}
+				}
+			}
+
+		default:
+			at = append(at, fmt.Sprintf("%d", seg.Index()))
+			if cur == nil {
+				if seg.Optional() {
+					cur = nil
+				} else {
+					return nil, nil, newResolutionError(fmt.Sprintf("can not access index: %d on kind: %s", seg.Index(), kindString(cur)), at)
+				}
+			} else {
+				idx := seg.Index()
+				switch cur.Kind() {
+				case datamodel.Kind_List:
+					if idx < 0 {
+						idx = int(cur.Length()) + idx
+					}
+					if idx < 0 || idx >= int(cur.Length()) {
 						if seg.Optional() {
 							cur = nil
 						} else {
 							return nil, nil, newResolutionError(fmt.Sprintf("index out of bounds: %d", seg.Index()), at)
 						}
 					} else {
-						return nil, nil, err
+						cur, _ = cur.LookupByIndex(int64(idx))
 					}
+				case datamodel.Kind_String:
+					str, _ := cur.AsString()
+					if idx < 0 {
+						idx = len(str) + idx
+					}
+					if idx < 0 || idx >= len(str) {
+						if seg.Optional() {
+							cur = nil
+						} else {
+							return nil, nil, newResolutionError(fmt.Sprintf("index out of bounds: %d", seg.Index()), at)
+						}
+					} else {
+						cur = basicnode.NewString(string(str[idx]))
+					}
+				case datamodel.Kind_Bytes:
+					b, _ := cur.AsBytes()
+					if idx < 0 {
+						idx = len(b) + idx
+					}
+					if idx < 0 || idx >= len(b) {
+						if seg.Optional() {
+							cur = nil
+						} else {
+							return nil, nil, newResolutionError(fmt.Sprintf("index out of bounds: %d", seg.Index()), at)
+						}
+					} else {
+						cur = basicnode.NewInt(int64(b[idx]))
+					}
+				default:
+					return nil, nil, newResolutionError(fmt.Sprintf("can not access index: %d on kind: %s", seg.Index(), kindString(cur)), at)
 				}
-				cur = n
-			} else if seg.Optional() {
-				cur = nil
-			} else {
-				return nil, nil, newResolutionError(fmt.Sprintf("can not access field: %s on kind: %s", seg.Field(), kindString(cur)), at)
 			}
 		}
 	}
@@ -207,6 +380,42 @@ func resolve(sel Selector, subject ipld.Node, at []string) (ipld.Node, []ipld.No
 	return cur, nil, nil
 }
 
+// resolveSliceIndices resolves the start and end indices for slicing a list or byte array.
+//
+// It takes the slice indices from the selector segment and the length of the list or byte array,
+// and returns the resolved start and end indices. Negative indices are supported.
+//
+// Parameters:
+//   - slice: The slice indices from the selector segment.
+//   - length: The length of the list or byte array being sliced.
+//
+// Returns:
+//   - start: The resolved start index for slicing.
+//   - end: The resolved end index for slicing.
+func resolveSliceIndices(slice []int, length int64) (int64, int64) {
+	start, end := int64(0), length
+	if len(slice) > 0 {
+		start = int64(slice[0])
+		if start < 0 {
+			start = length + start
+			if start < 0 {
+				start = 0
+			}
+		}
+	}
+	if len(slice) > 1 {
+		end = int64(slice[1])
+		if end <= 0 {
+			end = length + end
+			if end < start {
+				end = start
+			}
+		}
+	}
+
+	return start, end
+}
+
 func kindString(n datamodel.Node) string {
 	if n == nil {
 		return "null"

capability/policy/selector/supported_test.go

@@ -12,7 +12,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/policy/selector"
+	"github.com/ucan-wg/go-ucan/capability/policy/selector"
 )
 
 // TestSupported Forms runs tests against the Selector according to the
@@ -30,14 +30,14 @@ func TestSupportedForms(t *testing.T) {
 	for _, testcase := range []Testcase{
 		{Name: "Identity", Selector: `.`, Input: `{"x":1}`, Output: `{"x":1}`},
 		{Name: "Iterator", Selector: `.[]`, Input: `[1, 2]`, Output: `[1, 2]`},
-		{Name: "Optional Null Iterator", Selector: `.[]?`, Input: `null`, Output: `()`},
+		{Name: "Optional Null Iterator", Selector: `.[]?`, Input: `null`, Output: `[]`},
 		{Name: "Optional Iterator", Selector: `.[][]?`, Input: `[[1], 2, [3]]`, Output: `[1, 3]`},
 		{Name: "Object Key", Selector: `.x`, Input: `{"x": 1 }`, Output: `1`},
 		{Name: "Quoted Key", Selector: `.["x"]`, Input: `{"x": 1}`, Output: `1`},
 		{Name: "Index", Selector: `.[0]`, Input: `[1, 2]`, Output: `1`},
 		{Name: "Negative Index", Selector: `.[-1]`, Input: `[1, 2]`, Output: `2`},
 		{Name: "String Index", Selector: `.[0]`, Input: `"Hi"`, Output: `"H"`},
-		{Name: "Bytes Index", Selector: `.[0]`, Input: `{"/":{"bytes":"AAE"}`, Output: `0`},
+		{Name: "Bytes Index", Selector: `.[0]`, Input: `{"/":{"bytes":"AAE"}}`, Output: `0`},
 		{Name: "Array Slice", Selector: `.[0:2]`, Input: `[0, 1, 2]`, Output: `[0, 1]`},
 		{Name: "Array Slice", Selector: `.[1:]`, Input: `[0, 1, 2]`, Output: `[1, 2]`},
 		{Name: "Array Slice", Selector: `.[:2]`, Input: `[0, 1, 2]`, Output: `[0, 1]`},

delegation/view.go

@@ -6,9 +6,9 @@ import (
 
 	"github.com/ipld/go-ipld-prime/datamodel"
 
-	"github.com/ucan-wg/go-ucan/v1/capability/command"
-	"github.com/ucan-wg/go-ucan/v1/capability/policy"
-	"github.com/ucan-wg/go-ucan/v1/did"
+	"github.com/ucan-wg/go-ucan/capability/command"
+	"github.com/ucan-wg/go-ucan/capability/policy"
+	"github.com/ucan-wg/go-ucan/did"
 )
 
 type View struct {

go.mod

@@ -1,4 +1,4 @@
-module github.com/ucan-wg/go-ucan/v1
+module github.com/ucan-wg/go-ucan
 
 go 1.21
 
@@ -8,24 +8,27 @@ require (
 	github.com/gobwas/glob v0.2.3
 	github.com/ipfs/go-cid v0.4.1
 	github.com/ipld/go-ipld-prime v0.21.0
-	github.com/multiformats/go-multibase v0.0.3
-	github.com/multiformats/go-varint v0.0.6
+	github.com/libp2p/go-libp2p v0.36.2
+	github.com/multiformats/go-multibase v0.2.0
+	github.com/multiformats/go-multicodec v0.9.0
+	github.com/multiformats/go-varint v0.0.7
 	github.com/stretchr/testify v1.9.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
-	github.com/minio/sha256-simd v1.0.0 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.8 // indirect
+	github.com/minio/sha256-simd v1.0.1 // indirect
 	github.com/mr-tron/base58 v1.2.0 // indirect
-	github.com/multiformats/go-base32 v0.0.3 // indirect
-	github.com/multiformats/go-base36 v0.1.0 // indirect
+	github.com/multiformats/go-base32 v0.1.0 // indirect
+	github.com/multiformats/go-base36 v0.2.0 // indirect
 	github.com/multiformats/go-multihash v0.2.3 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/polydawn/refmt v0.89.0 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
-	golang.org/x/crypto v0.1.0 // indirect
-	golang.org/x/sys v0.1.0 // indirect
+	golang.org/x/crypto v0.25.0 // indirect
+	golang.org/x/sys v0.22.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	lukechampine.com/blake3 v1.1.6 // indirect
+	lukechampine.com/blake3 v1.3.0 // indirect
 )

go.sum

@@ -17,30 +17,30 @@ github.com/ipld/go-ipld-prime v0.21.0 h1:n4JmcpOlPDIxBcY037SVfpd1G+Sj1nKZah0m6QH
 github.com/ipld/go-ipld-prime v0.21.0/go.mod h1:3RLqy//ERg/y5oShXXdx5YIp50cFGOanyMctpPjsvxQ=
 github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
 github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
-github.com/klauspost/cpuid/v2 v2.0.4/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
-github.com/klauspost/cpuid/v2 v2.0.9 h1:lgaqFMSdTdQYdZ04uHyN2d/eKdOMyi2YLSvlQIBFYa4=
-github.com/klauspost/cpuid/v2 v2.0.9/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
+github.com/klauspost/cpuid/v2 v2.2.8 h1:+StwCXwm9PdpiEkPyzBXIy+M9KUb4ODm0Zarf1kS5BM=
+github.com/klauspost/cpuid/v2 v2.2.8/go.mod h1:Lcz8mBdAVJIBVzewtcLocK12l3Y+JytZYpaMropDUws=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-github.com/minio/sha256-simd v1.0.0 h1:v1ta+49hkWZyvaKwrQB8elexRqm6Y0aMLjCNsrYxo6g=
-github.com/minio/sha256-simd v1.0.0/go.mod h1:OuYzVNI5vcoYIAmbIvHPl3N3jUzVedXbKy5RFepssQM=
-github.com/mr-tron/base58 v1.1.0/go.mod h1:xcD2VGqlgYjBdcBLw+TuYLr8afG+Hj8g2eTVqeSzSU8=
+github.com/libp2p/go-libp2p v0.36.2 h1:BbqRkDaGC3/5xfaJakLV/BrpjlAuYqSB0lRvtzL3B/U=
+github.com/libp2p/go-libp2p v0.36.2/go.mod h1:XO3joasRE4Eup8yCTTP/+kX+g92mOgRaadk46LmPhHY=
+github.com/minio/sha256-simd v1.0.1 h1:6kaan5IFmwTNynnKKpDHe6FWHohJOHhCPchzK49dzMM=
+github.com/minio/sha256-simd v1.0.1/go.mod h1:Pz6AKMiUdngCLpeTL/RJY1M9rUuPMYujV5xJjtbRSN8=
 github.com/mr-tron/base58 v1.2.0 h1:T/HDJBh4ZCPbU39/+c3rRvE0uKBQlU27+QI8LJ4t64o=
 github.com/mr-tron/base58 v1.2.0/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
-github.com/multiformats/go-base32 v0.0.3 h1:tw5+NhuwaOjJCC5Pp82QuXbrmLzWg7uxlMFp8Nq/kkI=
-github.com/multiformats/go-base32 v0.0.3/go.mod h1:pLiuGC8y0QR3Ue4Zug5UzK9LjgbkL8NSQj0zQ5Nz/AA=
-github.com/multiformats/go-base36 v0.1.0 h1:JR6TyF7JjGd3m6FbLU2cOxhC0Li8z8dLNGQ89tUg4F4=
-github.com/multiformats/go-base36 v0.1.0/go.mod h1:kFGE83c6s80PklsHO9sRn2NCoffoRdUUOENyW/Vv6sM=
-github.com/multiformats/go-multibase v0.0.3 h1:l/B6bJDQjvQ5G52jw4QGSYeOTZoAwIO77RblWplfIqk=
-github.com/multiformats/go-multibase v0.0.3/go.mod h1:5+1R4eQrT3PkYZ24C3W2Ue2tPwIdYQD509ZjSb5y9Oc=
+github.com/multiformats/go-base32 v0.1.0 h1:pVx9xoSPqEIQG8o+UbAe7DNi51oej1NtK+aGkbLYxPE=
+github.com/multiformats/go-base32 v0.1.0/go.mod h1:Kj3tFY6zNr+ABYMqeUNeGvkIC/UYgtWibDcT0rExnbI=
+github.com/multiformats/go-base36 v0.2.0 h1:lFsAbNOGeKtuKozrtBsAkSVhv1p9D0/qedU9rQyccr0=
+github.com/multiformats/go-base36 v0.2.0/go.mod h1:qvnKE++v+2MWCfePClUEjE78Z7P2a1UV0xHgWc0hkp4=
+github.com/multiformats/go-multibase v0.2.0 h1:isdYCVLvksgWlMW9OZRYJEa9pZETFivncJHmHnnd87g=
+github.com/multiformats/go-multibase v0.2.0/go.mod h1:bFBZX4lKCA/2lyOFSAoKH5SS6oPyjtnzK/XTFDPkNuk=
 github.com/multiformats/go-multicodec v0.9.0 h1:pb/dlPnzee/Sxv/j4PmkDRxCOi3hXTz3IbPKOXWJkmg=
 github.com/multiformats/go-multicodec v0.9.0/go.mod h1:L3QTQvMIaVBkXOXXtVmYE+LI16i14xuaojr/H7Ai54k=
 github.com/multiformats/go-multihash v0.2.3 h1:7Lyc8XfX/IY2jWb/gI7JP+o7JEq9hOa7BFvVU9RSh+U=
 github.com/multiformats/go-multihash v0.2.3/go.mod h1:dXgKXCXjBzdscBLk9JkjINiEsCKRVch90MdaGiKsvSM=
-github.com/multiformats/go-varint v0.0.6 h1:gk85QWKxh3TazbLxED/NlDVv8+q+ReFJk7Y2W/KhfNY=
-github.com/multiformats/go-varint v0.0.6/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
+github.com/multiformats/go-varint v0.0.7 h1:sWSGR+f/eu5ABZA2ZpYKBILXTTs9JWpdEM/nEGOHFS8=
+github.com/multiformats/go-varint v0.0.7/go.mod h1:r8PUYw/fD/SjBCiKOoDlGF6QawOELpZAu9eioSos/OU=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/polydawn/refmt v0.89.0 h1:ADJTApkvkeBZsN0tBTx8QjpD9JkmxbKp0cxfr9qszm4=
@@ -61,14 +61,17 @@ github.com/urfave/cli v1.22.10/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60Nt
 github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0 h1:GDDkbFiaK8jsSDJfjId/PEGEShv6ugrt4kYsC5UIDaQ=
 github.com/warpfork/go-wish v0.0.0-20220906213052-39a1cc7a02d0/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.1.0 h1:MDRAIl0xIo9Io2xV565hzXHw3zVseKrJKodhohM5CjU=
-golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
+golang.org/x/crypto v0.25.0 h1:ypSNr+bnYL2YhwoMt2zPxHFmbAN1KZs/njMG3hxUp30=
+golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
-golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
+golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+google.golang.org/protobuf v1.34.2 h1:6xV6lTsCfpGD21XK49h7MhtcApnLqkfYgPcdHftf6hg=
+google.golang.org/protobuf v1.34.2/go.mod h1:qYOHts0dSfpeUzUFpOMr/WGzszTmLH+DiWniOlNbLDw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
@@ -76,5 +79,5 @@ gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-lukechampine.com/blake3 v1.1.6 h1:H3cROdztr7RCfoaTpGZFQsrqvweFLrqS73j7L7cmR5c=
-lukechampine.com/blake3 v1.1.6/go.mod h1:tkKEOtDkNtklkXtLNEOGNq5tcV90tJiA1vAA12R78LA=
+lukechampine.com/blake3 v1.3.0 h1:sJ3XhFINmHSrYCgl958hscfIa3bw8x4DqMP3u1YvoYE=
+lukechampine.com/blake3 v1.3.0/go.mod h1:0OFRp7fBtAylGVCO40o87sbupkyIGgbpv1+M1k1LM6k=

internal/varsig/varsig.go

@@ -0,0 +1,134 @@
+// Package varsig implements the portion of the [varsig specification]
+// that's needed for the UCAN [Envelope].
+//
+// While the [Envelope] specification has a field that's labelled
+// "VarsigHeader", this field is actually the prefix, header and segments
+// of the body excluding the signature itself (which is a different field
+// in the [Envelope]).
+//
+// Given that [go-ucan] supports a limited number of public key types,
+// and that the signature isn't part of the resulting field, the values
+// that are used are constants.  Note that for key types that are fully
+// specified in the [did:key], the [VarsigHeader] field isn't technically
+// needed and could theoretically conflict with the DID.
+//
+// Treating these values as constants has no impact when issuing or
+// delegating tokens.  When decoding tokens, simply matching the strings
+// will allow us to detect errors but won't provide as much detail (e.g.
+// we can't indicate that the signature was incorrectly generated from
+// a DAG-JSON encoding.)
+//
+// [varsig specification]: https://github.com/ChainAgnostic/varsig
+// [Envelope]:https://github.com/ucan-wg/spec#envelope
+// [go-ucan]: https://github.com/ucan-wg/go-ucan
+package varsig
+
+import (
+	"encoding/base64"
+	"encoding/binary"
+	"errors"
+	"fmt"
+
+	"github.com/libp2p/go-libp2p/core/crypto/pb"
+	"github.com/multiformats/go-multicodec"
+)
+
+const (
+	Prefix = 0x34
+)
+
+// ErrUnknownHeader is returned when it's not possible to decode the
+// provided string into a libp2p public key type.
+var ErrUnknownHeader = errors.New("could not decode unknown header")
+
+// ErrUnknownKeyType is returned when value provided is not a valid
+// libp2p public key type.
+var ErrUnknownKeyType = errors.New("could not encode unsupported key type")
+
+var (
+	decMap = headerToKeyType()
+	encMap = keyTypeToHeader()
+)
+
+// Decode returns either the pb.KeyType associated with the provided Header
+// or an error.
+//
+// Currently, only the four key types supported by the [go-libp2p/core/crypto]
+// library are supported.
+//
+// [go-libp2p/core/crypto]: github.com/libp2p/go-libp2p/core/crypto
+func Decode(header []byte) (pb.KeyType, error) {
+	keyType, ok := decMap[string(header)]
+	if !ok {
+		return -1, fmt.Errorf("%w: %s", ErrUnknownHeader, header)
+	}
+
+	return keyType, nil
+}
+
+// Encode returns either the header associated with the provided pb.KeyType
+// or an error indicating the header was unknown.
+//
+// Currently, only the four key types supported by the [go-libp2p/core/crypto]
+// library are supported.
+//
+// [go-libp2p/core/crypto]: github.com/libp2p/go-libp2p/core/crypto
+func Encode(keyType pb.KeyType) ([]byte, error) {
+	header, ok := encMap[keyType]
+	if !ok {
+		return nil, fmt.Errorf("%w: %s", ErrUnknownKeyType, keyType.String())
+	}
+
+	return []byte(header), nil
+}
+
+func keyTypeToHeader() map[pb.KeyType]string {
+	const rsaSigLen = 0x100
+
+	return map[pb.KeyType]string{
+		pb.KeyType_RSA: header(
+			Prefix,
+			multicodec.RsaPub,
+			multicodec.Sha2_256,
+			rsaSigLen,
+			multicodec.DagCbor,
+		),
+		pb.KeyType_Ed25519: header(
+			Prefix,
+			multicodec.Ed25519Pub,
+			multicodec.DagCbor,
+		),
+		pb.KeyType_Secp256k1: header(
+			Prefix,
+			multicodec.Secp256k1Pub,
+			multicodec.Sha2_256,
+			multicodec.DagCbor,
+		),
+		pb.KeyType_ECDSA: header(
+			Prefix,
+			multicodec.Es256,
+			multicodec.Sha2_256,
+			multicodec.DagCbor,
+		),
+	}
+}
+
+func headerToKeyType() map[string]pb.KeyType {
+	out := make(map[string]pb.KeyType, len(encMap))
+
+	for keyType, header := range encMap {
+		out[header] = keyType
+	}
+
+	return out
+}
+
+func header(vals ...multicodec.Code) string {
+	var buf []byte
+
+	for _, val := range vals {
+		buf = binary.AppendUvarint(buf, uint64(val))
+	}
+
+	return base64.RawStdEncoding.EncodeToString(buf)
+}

internal/varsig/varsig_test.go

@@ -0,0 +1,44 @@
+package varsig_test
+
+import (
+	"encoding/base64"
+	"fmt"
+	"testing"
+
+	"github.com/libp2p/go-libp2p/core/crypto/pb"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/ucan-wg/go-ucan/internal/varsig"
+)
+
+func TestDecode(t *testing.T) {
+	t.Parallel()
+
+	notAHeader := base64.RawStdEncoding.EncodeToString([]byte("not a header"))
+	keyType, err := varsig.Decode([]byte(notAHeader))
+	assert.Equal(t, pb.KeyType(-1), keyType)
+	assert.ErrorIs(t, err, varsig.ErrUnknownHeader)
+}
+
+func ExampleDecode() {
+	keyType, _ := varsig.Decode([]byte("NIUkEoACcQ"))
+	fmt.Println(keyType.String())
+	// Output:
+	// RSA
+}
+
+func TestEncode(t *testing.T) {
+	t.Parallel()
+
+	header, err := varsig.Encode(pb.KeyType(99))
+	assert.Nil(t, header)
+	assert.ErrorIs(t, err, varsig.ErrUnknownKeyType)
+}
+
+func ExampleEncode() {
+	header, _ := varsig.Encode(pb.KeyType_RSA)
+	fmt.Println(string(header))
+
+	// Output:
+	// NIUkEoACcQ
+}