Initial commit

http.go

@@ -0,0 +1,129 @@
+package cerberus
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"golang.org/x/net/html"
+	"golang.org/x/net/html/atom"
+)
+
+var (
+	ErrNoRedirect  = errors.New("No redirect to challenge page.")
+	ErrParseFailed = errors.New("Failed to parse challenge from HTML data tags.")
+)
+
+func NewChallenge(hc http.Client, host string) (Challenge, error) {
+	u, err := parseHost(host)
+	if err != nil {
+		return Challenge{}, err
+	}
+
+	// Update host url in case we get redirected across domains.
+	hc.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+		rh := req.URL.Host
+		if rh != u.Host && strings.HasPrefix(rh, "kiwifarms") {
+			u.Host = rh
+		}
+
+		return nil
+	}
+
+	resp, err := hc.Get(u.String())
+	if err != nil {
+		return Challenge{}, err
+	}
+	defer resp.Body.Close()
+
+	// Check for 203 status
+	if resp.StatusCode != 203 {
+		return Challenge{}, ErrNoRedirect
+	}
+
+	// Kept separate from the return because of the defer.
+	c, err := parseTags(resp.Body)
+	if err != nil {
+		return Challenge{}, err
+	}
+	c.host = u
+
+	return c, nil
+}
+
+func Submit(hc http.Client, s Solution) (string, error) {
+	resp, err := postSolution(hc, s)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	return resp.Header.Get("Set-Cookie"), nil
+}
+
+func postSolution(hc http.Client, s Solution) (*http.Response, error) {
+	// Ensure the POST url parses properly before passing the string.
+	u, err := url.Parse(fmt.Sprintf("%s://%s/.ttrs/challenge", s.host.Scheme, s.host.Hostname()))
+	if err != nil {
+		return nil, err
+	}
+
+	return hc.PostForm(u.String(), url.Values{
+		"salt":     []string{s.Salt},
+		"redirect": []string{s.Redirect},
+		"nonce":    []string{fmt.Sprint(s.Nonce)},
+	})
+}
+
+func parseHost(addr string) (*url.URL, error) {
+	// Guess https as protocol if one wasn't provided and hope it parses.
+	if !strings.Contains(addr, "://") {
+		addr = "https://" + addr
+	}
+
+	u, err := url.Parse(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	return u, nil
+}
+
+func parseTags(r io.Reader) (Challenge, error) {
+	c := Challenge{}
+
+	z := html.NewTokenizer(r)
+	for i := z.Next(); i != html.ErrorToken; i = z.Next() {
+		tk := z.Token()
+		if tk.DataAtom == atom.Html {
+			for _, a := range tk.Attr {
+				switch a.Key {
+				case "data-ttrs-challenge":
+					c.Salt = a.Val
+				case "data-ttrs-difficulty":
+					diff, err := strconv.Atoi(a.Val)
+					if err != nil {
+						return c, ErrParseFailed
+					}
+					c.Diff = uint32(diff)
+				case "data-ttrs-steps":
+					steps, err := strconv.Atoi(a.Val)
+					if err != nil {
+						return c, ErrParseFailed
+					}
+					c.Steps = uint32(steps)
+				}
+			}
+		}
+	}
+
+	if c.Salt == "" {
+		return c, ErrParseFailed
+	}
+
+	return c, nil
+}