diff --git a/src/hsm/cvc.c b/src/hsm/cvc.c
index 478c7e5..2c5954c 100644
--- a/src/hsm/cvc.c
+++ b/src/hsm/cvc.c
@@ -392,6 +392,13 @@ const uint8_t *cvc_get_pub(const uint8_t *data, size_t len, size_t *olen) {
     return NULL;
 }
 
+const uint8_t *cvc_get_ext(const uint8_t *data, size_t len, size_t *olen) {
+    if ((data = cvc_get_body(data, len, olen)) != NULL) {
+        return cvc_get_field(data, len, olen, 0x65);
+    }
+    return NULL;
+}
+
 extern PUK puk_store[MAX_PUK_STORE_ENTRIES];
 extern int puk_store_entries;
 
diff --git a/src/hsm/cvc.h b/src/hsm/cvc.h
index 2305153..90c2774 100644
--- a/src/hsm/cvc.h
+++ b/src/hsm/cvc.h
@@ -43,6 +43,7 @@ extern const uint8_t *cvc_get_field(const uint8_t *data, size_t len, size_t *ole
 extern const uint8_t *cvc_get_car(const uint8_t *data, size_t len, size_t *olen);
 extern const uint8_t *cvc_get_chr(const uint8_t *data, size_t len, size_t *olen);
 extern const uint8_t *cvc_get_pub(const uint8_t *data, size_t len, size_t *olen);
+extern const uint8_t *cvc_get_ext(const uint8_t *data, size_t len, size_t *olen);
 extern int cvc_verify(const uint8_t *cert, size_t cert_len, const uint8_t *ca, size_t ca_len);
 extern mbedtls_ecp_group_id cvc_inherite_ec_group(const uint8_t *ca, size_t ca_len);
 extern int puk_verify(const uint8_t *sig, size_t sig_len, const uint8_t *hash, size_t hash_len, const uint8_t *ca, size_t ca_len);