Initial commit

auth.go

@@ -0,0 +1,83 @@
+package gin
+
+import (
+	"crypto/subtle"
+	"encoding/base64"
+	"errors"
+	"sort"
+)
+
+type (
+	BasicAuthPair struct {
+		Code string
+		User string
+	}
+	Account struct {
+		User     string
+		Password string
+	}
+
+	Accounts []Account
+	Pairs    []BasicAuthPair
+)
+
+func (a Pairs) Len() int           { return len(a) }
+func (a Pairs) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a Pairs) Less(i, j int) bool { return a[i].Code < a[j].Code }
+
+func processCredentials(accounts Accounts) (Pairs, error) {
+	if len(accounts) == 0 {
+		return nil, errors.New("Empty list of authorized credentials.")
+	}
+	pairs := make(Pairs, 0, len(accounts))
+	for _, account := range accounts {
+		if len(account.User) == 0 || len(account.Password) == 0 {
+			return nil, errors.New("User or password is empty")
+		}
+		base := account.User + ":" + account.Password
+		code := "Basic " + base64.StdEncoding.EncodeToString([]byte(base))
+		pairs = append(pairs, BasicAuthPair{code, account.User})
+	}
+	// We have to sort the credentials in order to use bsearch later.
+	sort.Sort(pairs)
+	return pairs, nil
+}
+
+func searchCredential(pairs Pairs, auth string) string {
+	if len(auth) == 0 {
+		return ""
+	}
+	// Search user in the slice of allowed credentials
+	r := sort.Search(len(pairs), func(i int) bool { return pairs[i].Code >= auth })
+
+	if r < len(pairs) && subtle.ConstantTimeCompare([]byte(pairs[r].Code), []byte(auth)) == 1 {
+		// user is allowed, set UserId to key "user" in this context, the userId can be read later using
+		// c.Get("user"
+		return pairs[r].User
+	} else {
+		return ""
+	}
+}
+
+// Implements a basic Basic HTTP Authorization. It takes as argument a map[string]string where
+// the key is the user name and the value is the password.
+func BasicAuth(accounts Accounts) HandlerFunc {
+
+	pairs, err := processCredentials(accounts)
+	if err != nil {
+		panic(err)
+	}
+	return func(c *Context) {
+		// Search user in the slice of allowed credentials
+		user := searchCredential(pairs, c.Req.Header.Get("Authorization"))
+		if len(user) == 0 {
+			// Credentials doesn't match, we return 401 Unauthorized and abort request.
+			c.Writer.Header().Set("WWW-Authenticate", "Basic realm=\"Authorization Required\"")
+			c.Fail(401, errors.New("Unauthorized"))
+		} else {
+			// user is allowed, set UserId to key "user" in this context, the userId can be read later using
+			// c.Get("user")
+			c.Set("user", user)
+		}
+	}
+}