Support setting SM2 ID

zero-length ID is allowed, but it's not allowed to skip the ID.

Fixes: #6534

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7113)

crypto/include/internal/evp_int.h

diff --git a/crypto/include/internal/evp_int.h b/crypto/include/internal/evp_int.h
index 3264b3d..d86aed3 100644
--- a/crypto/include/internal/evp_int.h
+++ b/crypto/include/internal/evp_int.h
@@ -10,6 +10,12 @@
 #include <openssl/evp.h>
 #include "internal/refcount.h"
 
+/*
+ * Don't free up md_ctx->pctx in EVP_MD_CTX_reset, use the reserved flag
+ * values in evp.h
+ */
+#define EVP_MD_CTX_FLAG_KEEP_PKEY_CTX   0x0400
+
 struct evp_pkey_ctx_st {
     /* Method associated with this operation */
     const EVP_PKEY_METHOD *pmeth;

crypto/include/internal/sm2.h

diff --git a/crypto/include/internal/sm2.h b/crypto/include/internal/sm2.h
index 26a9066..5c5cd4b 100644
--- a/crypto/include/internal/sm2.h
+++ b/crypto/include/internal/sm2.h
@@ -20,15 +20,14 @@
 /* The default user id as specified in GM/T 0009-2012 */
 #  define SM2_DEFAULT_USERID "1234567812345678"
 
-int sm2_compute_userid_digest(uint8_t *out,
-                              const EVP_MD *digest,
-                              const uint8_t *id,
-                              const size_t id_len,
-                              const EC_KEY *key);
+int sm2_compute_z_digest(uint8_t *out,
+                         const EVP_MD *digest,
+                         const uint8_t *id,
+                         const size_t id_len,
+                         const EC_KEY *key);
 
 /*
- * SM2 signature operation. Computes ZA (user id digest) and then signs
- * H(ZA || msg) using SM2
+ * SM2 signature operation. Computes Z and then signs H(Z || msg) using SM2
  */
 ECDSA_SIG *sm2_do_sign(const EC_KEY *key,
                        const EVP_MD *digest,

crypto/include/internal/sm2err.h

diff --git a/crypto/include/internal/sm2err.h b/crypto/include/internal/sm2err.h
index 9a7e2b6..4b8536d 100644
--- a/crypto/include/internal/sm2err.h
+++ b/crypto/include/internal/sm2err.h
@@ -28,7 +28,7 @@
 #  define SM2_F_PKEY_SM2_INIT                              111
 #  define SM2_F_PKEY_SM2_SIGN                              112
 #  define SM2_F_SM2_COMPUTE_MSG_HASH                       100
-#  define SM2_F_SM2_COMPUTE_USERID_DIGEST                  101
+#  define SM2_F_SM2_COMPUTE_Z_DIGEST                       113
 #  define SM2_F_SM2_DECRYPT                                102
 #  define SM2_F_SM2_ENCRYPT                                103
 #  define SM2_F_SM2_PLAINTEXT_SIZE                         104
@@ -43,13 +43,13 @@
 #  define SM2_R_ASN1_ERROR                                 100
 #  define SM2_R_BAD_SIGNATURE                              101
 #  define SM2_R_BUFFER_TOO_SMALL                           107
+#  define SM2_R_ID_TOO_LARGE                               111
 #  define SM2_R_INVALID_CURVE                              108
 #  define SM2_R_INVALID_DIGEST                             102
 #  define SM2_R_INVALID_DIGEST_TYPE                        103
 #  define SM2_R_INVALID_ENCODING                           104
 #  define SM2_R_INVALID_FIELD                              105
 #  define SM2_R_NO_PARAMETERS_SET                          109
-#  define SM2_R_USER_ID_TOO_LARGE                          106
 
 # endif
 #endif