From 866e3aef675876900f9bc9d3c5bbb9ab72ec9cdb Mon Sep 17 00:00:00 2001
From: Zhi Guan <guanzhi1980@gmail.com>
Date: Sun, 21 Jun 2026 00:01:32 +0800
Subject: [PATCH] Fix #1900

---
 CMakeLists.txt          |  2 +-
 include/gmssl/version.h |  2 +-
 src/sm2_enc.c           | 16 +++++++++++-----
 tests/sm2_enctest.c     | 36 +++++++++++++++++++++++++++++++++++-
 4 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 18b84348..a46bceba 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -874,7 +874,7 @@ endif()
 #
 set(CPACK_PACKAGE_NAME "GmSSL")
 set(CPACK_PACKAGE_VENDOR "GmSSL develop team")
-set(CPACK_PACKAGE_VERSION "3.2.0-dev.1131")
+set(CPACK_PACKAGE_VERSION "3.2.0-dev.1132")
 set(CPACK_PACKAGE_DESCRIPTION_FILE ${PROJECT_SOURCE_DIR}/README.md)
 set(CPACK_NSIS_MODIFY_PATH ON)
 include(CPack)
diff --git a/include/gmssl/version.h b/include/gmssl/version.h
index d20f4847..9baeec5e 100644
--- a/include/gmssl/version.h
+++ b/include/gmssl/version.h
@@ -18,7 +18,7 @@ extern "C" {
 
 
 #define GMSSL_VERSION_NUM	30200
-#define GMSSL_VERSION_STR	"GmSSL 3.2.0-dev.1131"
+#define GMSSL_VERSION_STR	"GmSSL 3.2.0-dev.1132"
 
 int gmssl_version_num(void);
 const char *gmssl_version_str(void);
diff --git a/src/sm2_enc.c b/src/sm2_enc.c
index 97bf0d3d..e11a4438 100644
--- a/src/sm2_enc.c
+++ b/src/sm2_enc.c
@@ -322,6 +322,9 @@ int sm2_do_decrypt(const SM2_KEY *key, const SM2_CIPHERTEXT *in, uint8_t *out, s
 	uint8_t x2y2[64];
 	SM3_CTX sm3_ctx;
 	uint8_t hash[32];
+	uint8_t plaintext[SM2_MAX_PLAINTEXT_SIZE];
+
+	*outlen = 0;
 
 	// check C1 is on sm2 curve
 	if (sm2_z256_point_from_bytes(&C1, (uint8_t *)&in->point) != 1) {
@@ -334,20 +337,19 @@ int sm2_do_decrypt(const SM2_KEY *key, const SM2_CIPHERTEXT *in, uint8_t *out, s
 
 	// t = KDF(x2 || y2, klen) and check t is not all zeros
 	sm2_z256_point_to_bytes(&C1, x2y2);
-	sm2_kdf(x2y2, 64, in->ciphertext_size, out);
-	if (all_zero(out, in->ciphertext_size)) {
+	sm2_kdf(x2y2, 64, in->ciphertext_size, plaintext);
+	if (all_zero(plaintext, in->ciphertext_size)) {
 		error_print();
 		goto end;
 	}
 
 	// M = C2 xor t
-	gmssl_memxor(out, out, in->ciphertext, in->ciphertext_size);
-	*outlen = in->ciphertext_size;
+	gmssl_memxor(plaintext, plaintext, in->ciphertext, in->ciphertext_size);
 
 	// u = Hash(x2 || M || y2)
 	sm3_init(&sm3_ctx);
 	sm3_update(&sm3_ctx, x2y2, 32);
-	sm3_update(&sm3_ctx, out, in->ciphertext_size);
+	sm3_update(&sm3_ctx, plaintext, in->ciphertext_size);
 	sm3_update(&sm3_ctx, x2y2 + 32, 32);
 	sm3_finish(&sm3_ctx, hash);
 
@@ -356,11 +358,15 @@ int sm2_do_decrypt(const SM2_KEY *key, const SM2_CIPHERTEXT *in, uint8_t *out, s
 		error_print();
 		goto end;
 	}
+	memcpy(out, plaintext, in->ciphertext_size);
+	*outlen = in->ciphertext_size;
 	ret = 1;
 
 end:
 	gmssl_secure_clear(&C1, sizeof(SM2_Z256_POINT));
 	gmssl_secure_clear(x2y2, sizeof(x2y2));
+	gmssl_secure_clear(hash, sizeof(hash));
+	gmssl_secure_clear(plaintext, sizeof(plaintext));
 	return ret;
 }
 
diff --git a/tests/sm2_enctest.c b/tests/sm2_enctest.c
index 7c6db322..2963ce88 100644
--- a/tests/sm2_enctest.c
+++ b/tests/sm2_enctest.c
@@ -113,6 +113,40 @@ static int test_sm2_do_encrypt(void)
 	return 1;
 }
 
+static int test_sm2_do_decrypt_bad_hash_does_not_output_plaintext(void)
+{
+	SM2_KEY sm2_key;
+	uint8_t plaintext[] = "Hello World!";
+	SM2_CIPHERTEXT ciphertext;
+	uint8_t out[SM2_MAX_PLAINTEXT_SIZE];
+	size_t outlen = sizeof(out);
+	size_t i;
+
+	if (sm2_key_generate(&sm2_key) != 1
+		|| sm2_do_encrypt(&sm2_key, plaintext, sizeof(plaintext), &ciphertext) != 1) {
+		error_print();
+		return -1;
+	}
+
+	ciphertext.hash[0] ^= 0x01;
+	memset(out, 0xa5, sizeof(out));
+
+	if (sm2_do_decrypt(&sm2_key, &ciphertext, out, &outlen) != -1
+		|| outlen != 0) {
+		error_print();
+		return -1;
+	}
+	for (i = 0; i < sizeof(out); i++) {
+		if (out[i] != 0xa5) {
+			error_print();
+			return -1;
+		}
+	}
+
+	printf("%s() ok\n", __FUNCTION__);
+	return 1;
+}
+
 static int test_sm2_do_encrypt_fixlen(void)
 {
 	struct {
@@ -323,6 +357,7 @@ int main(void)
 {
 	if (test_sm2_ciphertext() != 1) goto err;
 	if (test_sm2_do_encrypt() != 1) goto err;
+	if (test_sm2_do_decrypt_bad_hash_does_not_output_plaintext() != 1) goto err;
 	if (test_sm2_do_encrypt_fixlen() != 1) goto err;
 	if (test_sm2_encrypt() != 1) goto err;
 	if (test_sm2_encrypt_fixlen() != 1) goto err;
@@ -335,4 +370,3 @@ err:
 	error_print();
 	return -1;
 }
-