🥚 添加 amazon 平台

src/main/java/me/zhyd/oauth/utils/PkceUtil.java

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+package me.zhyd.oauth.utils;
+
+import java.nio.charset.StandardCharsets;
+
+/**
+ * 该配置仅用于支持 PKCE 模式的平台，针对无服务应用，不推荐使用隐式授权，推荐使用 PKCE 模式
+ *
+ * @author yadong.zhang (yadong.zhang0415(a)gmail.com)
+ * @version 1.0.0
+ * @since 1.0.0
+ */
+public class PkceUtil {
+
+    public static String generateCodeVerifier() {
+        String randomStr = RandomUtil.randomString(50);
+        return Base64Utils.encodeUrlSafe(randomStr);
+    }
+
+    /**
+     * 适用于 OAuth 2.0 PKCE 增强协议
+     *
+     * @param codeChallengeMethod s256 / plain
+     * @param codeVerifier        客户端生产的校验码
+     * @return code challenge
+     */
+    public static String generateCodeChallenge(String codeChallengeMethod, String codeVerifier) {
+        if ("S256".equalsIgnoreCase(codeChallengeMethod)) {
+            // https://tools.ietf.org/html/rfc7636#section-4.2
+            // code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier)))
+            return newStringUsAscii(Base64Utils.encodeUrlSafe(Sha256.digest(codeVerifier), true));
+        } else {
+            return codeVerifier;
+        }
+    }
+
+    public static String newStringUsAscii(byte[] bytes) {
+        return new String(bytes, StandardCharsets.US_ASCII);
+    }
+}

src/main/java/me/zhyd/oauth/utils/RandomUtil.java

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+package me.zhyd.oauth.utils;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+/**
+ * 生成随机字符串
+ *
+ * @author yadong.zhang (yadong.zhang0415(a)gmail.com)
+ * @version 1.0.0
+ * @since 1.16.0
+ */
+public class RandomUtil {
+
+    /**
+     * 用于随机选的字符和数字
+     */
+    public static final String BASE_CHAR_NUMBER = "abcdefghijklmnopqrstuvwxyz0123456789";
+
+    /**
+     * 获得一个随机的字符串
+     *
+     * @param length 字符串的长度
+     * @return 指定长度的随机字符串
+     */
+    public static String randomString(int length) {
+        final StringBuilder sb = new StringBuilder(length);
+
+        if (length < 1) {
+            length = 1;
+        }
+        int baseLength = BASE_CHAR_NUMBER.length();
+        for (int i = 0; i < length; i++) {
+            int number = ThreadLocalRandom.current().nextInt(baseLength);
+            sb.append(BASE_CHAR_NUMBER.charAt(number));
+        }
+        return sb.toString();
+    }
+}

src/main/java/me/zhyd/oauth/utils/Sha256.java

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+package me.zhyd.oauth.utils;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ * SHA256 加密
+ *
+ * @author yadong.zhang (yadong.zhang0415(a)gmail.com)
+ * @version 1.0.0
+ * @since 1.16.0
+ */
+public class Sha256 {
+
+    public static byte[] digest(String str) {
+        MessageDigest messageDigest;
+        try {
+            messageDigest = MessageDigest.getInstance("SHA-256");
+            messageDigest.update(str.getBytes(StandardCharsets.UTF_8));
+            return messageDigest.digest();
+        } catch (NoSuchAlgorithmException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}