From 8f3011e793f773c976535f0e0d65e6fa5a1140fa Mon Sep 17 00:00:00 2001
From: Looly <loolly@gmail.com>
Date: Mon, 19 Jul 2021 17:57:55 +0800
Subject: [PATCH] fix Base64.isBase64

---
 CHANGELOG.md                                       |  1 +
 .../src/main/java/cn/hutool/core/codec/Base64.java | 12 +++++++++++-
 .../java/cn/hutool/core/codec/Base64Decoder.java   |  2 +-
 .../test/java/cn/hutool/core/codec/Base64Test.java | 14 +++++++++++++-
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b02f7e54..d1ace38d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 ### 🐣新特性
 * 【core   】     增加FieldsComparator（pr#374@Gitee）
 * 【core   】     FileUtil.del采用Files.delete实现
+* 【core   】     改进Base64.isBase64方法增加等号判断（issue#1710@Github）
 
 ### 🐞Bug修复
 
diff --git a/hutool-core/src/main/java/cn/hutool/core/codec/Base64.java b/hutool-core/src/main/java/cn/hutool/core/codec/Base64.java
index 8564b008e..efa756912 100644
--- a/hutool-core/src/main/java/cn/hutool/core/codec/Base64.java
+++ b/hutool-core/src/main/java/cn/hutool/core/codec/Base64.java
@@ -322,7 +322,7 @@ public class Base64 {
 	 * @return 是否为Base64
 	 * @since 5.7.5
 	 */
-	public static boolean isBase64(String base64){
+	public static boolean isBase64(CharSequence base64){
 		return isBase64(StrUtil.utf8Bytes(base64));
 	}
 
@@ -334,7 +334,17 @@ public class Base64 {
 	 * @since 5.7.5
 	 */
 	public static boolean isBase64(byte[] base64Bytes){
+		boolean hasPadding = false;
 		for (byte base64Byte : base64Bytes) {
+			if(hasPadding){
+				if('=' != base64Byte){
+					// 前一个字符是'='，则后边的字符都必须是'='，即'='只能都位于结尾
+					return false;
+				}
+			} else if('=' == base64Byte){
+				// 发现'=' 标记之
+				hasPadding = true;
+			}
 			if (false == (Base64Decoder.isBase64Code(base64Byte) || isWhiteSpace(base64Byte))) {
 				return false;
 			}
diff --git a/hutool-core/src/main/java/cn/hutool/core/codec/Base64Decoder.java b/hutool-core/src/main/java/cn/hutool/core/codec/Base64Decoder.java
index b71aaccf5..91dd741e8 100644
--- a/hutool-core/src/main/java/cn/hutool/core/codec/Base64Decoder.java
+++ b/hutool-core/src/main/java/cn/hutool/core/codec/Base64Decoder.java
@@ -32,7 +32,7 @@ public class Base64Decoder {
 			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
 			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
 			-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63, // 20-2f + - /
-			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, // 30-3f 0-9
+			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, // 30-3f 0-9，-2的位置是'='
 			-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, // 40-4f A-O
 			15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, // 50-5f P-Z _
 			-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, // 60-6f a-o
diff --git a/hutool-core/src/test/java/cn/hutool/core/codec/Base64Test.java b/hutool-core/src/test/java/cn/hutool/core/codec/Base64Test.java
index 0fd6e4f06..69ac11f06 100644
--- a/hutool-core/src/test/java/cn/hutool/core/codec/Base64Test.java
+++ b/hutool-core/src/test/java/cn/hutool/core/codec/Base64Test.java
@@ -16,7 +16,19 @@ public class Base64Test {
 
 	@Test
 	public void isBase64Test(){
-		Assert.assertTrue(Base64.isBase64(Base64.encode(RandomUtil.randomString(100))));
+		Assert.assertTrue(Base64.isBase64(Base64.encode(RandomUtil.randomString(1000))));
+	}
+
+	@Test
+	public void isBase64Test2(){
+		String base64 = "dW1kb3MzejR3bmljM2J6djAyZzcwbWk5M213Nnk3cWQ3eDJwOHFuNXJsYmMwaXhxbmg0dmxrcmN0anRkbmd3\n" +
+				"ZzcyZWFwanI2NWNneTg2dnp6cmJoMHQ4MHpxY2R6c3pjazZtaQ==";
+		Assert.assertTrue(Base64.isBase64(base64));
+
+		// '=' 不位于末尾
+		base64 = "dW1kb3MzejR3bmljM2J6=djAyZzcwbWk5M213Nnk3cWQ3eDJwOHFuNXJsYmMwaXhxbmg0dmxrcmN0anRkbmd3\n" +
+				"ZzcyZWFwanI2NWNneTg2dnp6cmJoMHQ4MHpxY2R6c3pjazZtaQ=";
+		Assert.assertFalse(Base64.isBase64(base64));
 	}
 
 	@Test