Check the plaintext buffer is large enough when decrypting SM2

Previously there was no check that the supplied buffer was large enough.
It was just assumed to be sufficient. Instead we should check and fail if
not.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>

diff --git a/crypto/sm2/sm2_crypt.c b/crypto/sm2/sm2_crypt.c
index 1188abfc6b5756c3bf86fee8ca9e66d22391fec2..00055a4e510e1711bbd040a7c9aa8f94b9112efd 100644 (file)
--- a/crypto/sm2/sm2_crypt.c
+++ b/crypto/sm2/sm2_crypt.c
@@ -294,6 +294,10 @@ int sm2_decrypt(const EC_KEY *key,
     C2 = sm2_ctext->C2->data;
     C3 = sm2_ctext->C3->data;
     msg_len = sm2_ctext->C2->length;
+    if (*ptext_len < (size_t)msg_len) {
+        SM2err(SM2_F_SM2_DECRYPT, SM2_R_BUFFER_TOO_SMALL);
+        goto done;
+    }
 
     ctx = BN_CTX_new();
     if (ctx == NULL) {