/
canonicalization.go
177 lines (137 loc) · 3.41 KB
/
canonicalization.go
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package wsse
import (
"fmt"
"sort"
"github.com/beevik/etree"
)
const (
emptyPrefix = ""
xmlnsPrefix = "xmlns"
)
func excC14NCanonicalize(elem *etree.Element) ([]byte, error) {
if err := transformExcC14n(elem); err != nil {
return nil, fmt.Errorf("transform the element (excC14N): %w", err)
}
doc := etree.NewDocument()
doc.SetRoot(elem.Copy())
doc.WriteSettings = etree.WriteSettings{
CanonicalAttrVal: true,
CanonicalEndTags: true,
CanonicalText: true,
}
canonical, err := doc.WriteToBytes()
if err != nil {
return nil, fmt.Errorf("write etree document to bytes: %w", err)
}
return canonical, nil
}
func transformExcC14n(el *etree.Element) error {
err := toExcC14n(nsContext{}, nsContext{}, el)
if err != nil {
return fmt.Errorf("c14n: %w", err)
}
return nil
}
func toExcC14n(ctx, declared nsContext, el *etree.Element) error {
scope, err := ctx.subContext(el)
if err != nil {
return fmt.Errorf("create subcontext: %w", err)
}
utilizedPrefixes := map[string]struct{}{
el.Space: {},
}
var filteredAttrs []etree.Attr
for _, attr := range el.Attr {
if attr.Space != xmlnsPrefix && (attr.Space != emptyPrefix || attr.Key != xmlnsPrefix) {
if attr.Space != emptyPrefix {
utilizedPrefixes[attr.Space] = struct{}{}
}
filteredAttrs = append(filteredAttrs, attr)
}
}
el.Attr = filteredAttrs
declared = declared.copy()
for prefix := range utilizedPrefixes {
if declaredNamespace, ok := declared.prefixes[prefix]; ok {
value, ok := scope.prefixes[prefix]
if ok && declaredNamespace == value {
continue
}
}
ns := scope.prefixes[prefix]
el.Attr = append(el.Attr, declared.declare(prefix, ns))
}
sort.Sort(sortableAttrs(el.Attr))
for _, child := range el.ChildElements() {
err := toExcC14n(scope, declared, child)
if err != nil {
return fmt.Errorf("canonicalize %s to exc c14n: %w", child.FullTag(), err)
}
}
return nil
}
type nsContext struct {
prefixes map[string]string
}
func (ctx nsContext) subContext(el *etree.Element) (nsContext, error) {
nCtx := ctx.copy()
for _, attr := range el.Attr {
if attr.Space == xmlnsPrefix {
nCtx.declare(attr.Key, attr.Value)
} else if attr.Space == emptyPrefix && attr.Key == xmlnsPrefix {
nCtx.declare(emptyPrefix, attr.Value)
}
}
return nCtx, nil
}
func (ctx nsContext) copy() nsContext {
prefixes := make(map[string]string, len(ctx.prefixes)+4)
for k, v := range ctx.prefixes {
prefixes[k] = v
}
return nsContext{prefixes}
}
func (ctx nsContext) declare(prefix, ns string) etree.Attr {
ctx.prefixes[prefix] = ns
if prefix == emptyPrefix {
return etree.Attr{
Key: xmlnsPrefix,
Value: ns,
}
}
return etree.Attr{
Space: xmlnsPrefix,
Key: prefix,
Value: ns,
}
}
type sortableAttrs []etree.Attr
func (a sortableAttrs) Len() int {
return len(a)
}
func (a sortableAttrs) Swap(i, j int) {
a[i], a[j] = a[j], a[i]
}
func (a sortableAttrs) Less(i, j int) bool {
switch {
case a[j].Space == emptyPrefix && a[j].Key == xmlnsPrefix:
return false
case a[i].Space == emptyPrefix && a[i].Key == xmlnsPrefix:
return true
case a[i].Space == xmlnsPrefix:
if a[j].Space == xmlnsPrefix {
return a[i].Key < a[j].Key
}
return true
case a[j].Space == xmlnsPrefix:
return false
case a[i].Space == emptyPrefix:
if a[j].Space == emptyPrefix {
return a[i].Key < a[j].Key
}
return true
case a[j].Space == emptyPrefix:
return false
}
return a[i].Space < a[j].Space
}