feat: usos sign-in, private calendar feed and timetable archive

internal/usos/oauth.go

@@ -0,0 +1,92 @@
+package usos
+
+import (
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha1"
+	"encoding/base64"
+	"encoding/hex"
+	"net/url"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const unreserved = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+
+func percentEncode(s string) string {
+	var b strings.Builder
+	for i := range len(s) {
+		c := s[i]
+		if strings.IndexByte(unreserved, c) >= 0 {
+			b.WriteByte(c)
+			continue
+		}
+		b.WriteByte('%')
+		b.WriteString(strings.ToUpper(hex.EncodeToString([]byte{c})))
+	}
+	return b.String()
+}
+
+func signature(method, endpoint string, params url.Values, consumerSecret, tokenSecret string) string {
+	pairs := make([]string, 0, len(params))
+	for key, values := range params {
+		for _, value := range values {
+			pairs = append(pairs, percentEncode(key)+"="+percentEncode(value))
+		}
+	}
+	sort.Strings(pairs)
+	base := method + "&" + percentEncode(endpoint) + "&" + percentEncode(strings.Join(pairs, "&"))
+	mac := hmac.New(sha1.New, []byte(percentEncode(consumerSecret)+"&"+percentEncode(tokenSecret)))
+	mac.Write([]byte(base))
+	return base64.StdEncoding.EncodeToString(mac.Sum(nil))
+}
+
+func nonce() string {
+	buf := make([]byte, 16)
+	if _, err := rand.Read(buf); err != nil {
+		panic(err)
+	}
+	return hex.EncodeToString(buf)
+}
+
+func (c *Client) authorization(endpoint string, token *Token, params url.Values) (header string, body url.Values) {
+	oauth := url.Values{
+		"oauth_consumer_key":     {c.Key},
+		"oauth_nonce":            {nonce()},
+		"oauth_signature_method": {"HMAC-SHA1"},
+		"oauth_timestamp":        {strconv.FormatInt(time.Now().Unix(), 10)},
+		"oauth_version":          {"1.0"},
+	}
+	tokenSecret := ""
+	if token != nil {
+		oauth.Set("oauth_token", token.Key)
+		tokenSecret = token.Secret
+	}
+	body = url.Values{}
+	all := url.Values{}
+	for key, values := range params {
+		if strings.HasPrefix(key, "oauth_") {
+			oauth[key] = values
+		} else {
+			body[key] = values
+		}
+		all[key] = values
+	}
+	for key, values := range oauth {
+		all[key] = values
+	}
+	oauth.Set("oauth_signature", signature("POST", endpoint, all, c.Secret, tokenSecret))
+
+	keys := make([]string, 0, len(oauth))
+	for key := range oauth {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	parts := make([]string, 0, len(keys))
+	for _, key := range keys {
+		parts = append(parts, key+`="`+percentEncode(oauth.Get(key))+`"`)
+	}
+	return "OAuth " + strings.Join(parts, ", "), body
+}