Check passwords against HaveIBeenPwned (#12716)

* Implement pwn

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Update module

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Apply suggestions mrsdizzie

Co-authored-by: mrsdizzie <info@mrsdizzie.com>

* Add link to HIBP

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add more details to admin command

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add context to pwn

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Consistency and making some noise ;)

Signed-off-by: jolheiser <john.olheiser@gmail.com>

Co-authored-by: mrsdizzie <info@mrsdizzie.com>
Co-authored-by: zeripath <art27@cantab.net>

vendor/go.jolheiser.com/pwn/password.go

@@ -0,0 +1,62 @@
+package pwn
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+const passwordURL = "https://api.pwnedpasswords.com/range/"
+
+// CheckPassword returns the number of times a password has been compromised
+// Adding padding will make requests more secure, however is also slower
+// because artificial responses will be added to the response
+// For more information, see https://www.troyhunt.com/enhancing-pwned-passwords-privacy-with-padding/
+func (c *Client) CheckPassword(pw string, padding bool) (int, error) {
+	if strings.TrimSpace(pw) == "" {
+		return -1, ErrEmptyPassword{}
+	}
+
+	sha := sha1.New()
+	sha.Write([]byte(pw))
+	enc := hex.EncodeToString(sha.Sum(nil))
+	prefix, suffix := enc[:5], enc[5:]
+
+	req, err := newRequest(c.ctx, http.MethodGet, fmt.Sprintf("%s%s", passwordURL, prefix), nil)
+	if err != nil {
+		return -1, nil
+	}
+	if padding {
+		req.Header.Add("Add-Padding", "true")
+	}
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return -1, err
+	}
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return -1, err
+	}
+	defer resp.Body.Close()
+
+	for _, pair := range strings.Split(string(body), "\n") {
+		parts := strings.Split(pair, ":")
+		if len(parts) != 2 {
+			continue
+		}
+		if strings.EqualFold(suffix, parts[0]) {
+			count, err := strconv.ParseInt(strings.TrimSpace(parts[1]), 10, 64)
+			if err != nil {
+				return -1, err
+			}
+			return int(count), nil
+		}
+	}
+	return 0, nil
+}