Login via OpenID-2.0 (#618)

vendor/github.com/yohcop/openid-go/html_discovery.go

@@ -0,0 +1,77 @@
+package openid
+
+import (
+	"errors"
+	"io"
+
+	"golang.org/x/net/html"
+)
+
+func htmlDiscovery(id string, getter httpGetter) (opEndpoint, opLocalID, claimedID string, err error) {
+	resp, err := getter.Get(id, nil)
+	if err != nil {
+		return "", "", "", err
+	}
+	opEndpoint, opLocalID, err = findProviderFromHeadLink(resp.Body)
+	return opEndpoint, opLocalID, resp.Request.URL.String(), err
+}
+
+func findProviderFromHeadLink(input io.Reader) (opEndpoint, opLocalID string, err error) {
+	tokenizer := html.NewTokenizer(input)
+	inHead := false
+	for {
+		tt := tokenizer.Next()
+		switch tt {
+		case html.ErrorToken:
+			// Even if the document is malformed after we found a
+			// valid <link> tag, ignore and let's be happy with our
+			// openid2.provider and potentially openid2.local_id as well.
+			if len(opEndpoint) > 0 {
+				return
+			}
+			return "", "", tokenizer.Err()
+		case html.StartTagToken, html.EndTagToken, html.SelfClosingTagToken:
+			tk := tokenizer.Token()
+			if tk.Data == "head" {
+				if tt == html.StartTagToken {
+					inHead = true
+				} else {
+					if len(opEndpoint) > 0 {
+						return
+					}
+					return "", "", errors.New(
+						"LINK with rel=openid2.provider not found")
+				}
+			} else if inHead && tk.Data == "link" {
+				provider := false
+				localID := false
+				href := ""
+				for _, attr := range tk.Attr {
+					if attr.Key == "rel" {
+						if attr.Val == "openid2.provider" {
+							provider = true
+						} else if attr.Val == "openid2.local_id" {
+							localID = true
+						} else if attr.Val == "openid.server" {
+							provider = true
+						}
+					} else if attr.Key == "href" {
+						href = attr.Val
+					}
+				}
+				if provider && !localID && len(href) > 0 {
+					opEndpoint = href
+				} else if !provider && localID && len(href) > 0 {
+					opLocalID = href
+				}
+			}
+		}
+	}
+	// At this point we should probably have returned either from
+	// a closing </head> or a tokenizer error (no </head> found).
+	// But just in case.
+	if len(opEndpoint) > 0 {
+		return
+	}
+	return "", "", errors.New("LINK rel=openid2.provider not found")
+}