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 2c7264e42b633f62534ebf4fb11b6e668f84b749..e26b48390a95644f588cc82ada0b4f31feba370a 100644 (file)
--- a/crypto/sm2/sm2_crypt.c
+++ b/crypto/sm2/sm2_crypt.c
@@ -312,6 +312,10 @@ int ossl_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_ex(libctx);
     if (ctx == NULL) {