Add null digest implementation to the default provider

This is necessary to keep compatibility with 1.1.1.

Fixes #16660

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17016)

(cherry picked from commit bef9b48e5071cdd2b41a4f486d1bcb5e14b2a5c3)

5 files changed, 70 insertions, 10 deletions

diff --git a/providers/defltprov.c b/providers/defltprov.c
index 62258da723..6e669fbdfb 100644
--- a/providers/defltprov.c
+++ b/providers/defltprov.c
@@ -148,6 +148,7 @@ static const OSSL_ALGORITHM deflt_digests[] = {
     { PROV_NAMES_MD5_SHA1, "provider=default", ossl_md5_sha1_functions },
 #endif /* OPENSSL_NO_MD5 */
 
+    { PROV_NAMES_NULL, "provider=default", ossl_nullmd_functions },
     { NULL, NULL, NULL }
 };
 
diff --git a/providers/implementations/digests/build.info b/providers/implementations/digests/build.info
index 2c2b0c3db0..c6508b6e85 100644
--- a/providers/implementations/digests/build.info
+++ b/providers/implementations/digests/build.info
@@ -9,6 +9,7 @@ $SHA3_GOAL=../../libdefault.a ../../libfips.a
 $BLAKE2_GOAL=../../libdefault.a
 $SM3_GOAL=../../libdefault.a
 $MD5_GOAL=../../libdefault.a
+$NULL_GOAL=../../libdefault.a
 
 $MD2_GOAL=../../liblegacy.a
 $MD4_GOAL=../../liblegacy.a
@@ -22,6 +23,8 @@ SOURCE[$COMMON_GOAL]=digestcommon.c
 SOURCE[$SHA2_GOAL]=sha2_prov.c
 SOURCE[$SHA3_GOAL]=sha3_prov.c
 
+SOURCE[$NULL_GOAL]=null_prov.c
+
 IF[{- !$disabled{blake2} -}]
   SOURCE[$BLAKE2_GOAL]=blake2_prov.c blake2b_prov.c blake2s_prov.c
 ENDIF
diff --git a/providers/implementations/digests/null_prov.c b/providers/implementations/digests/null_prov.c
new file mode 100644
index 0000000000..b220a1966f
--- /dev/null
+++ b/providers/implementations/digests/null_prov.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <openssl/crypto.h>
+#include "prov/digestcommon.h"
+#include "prov/implementations.h"
+
+typedef struct {
+    unsigned char nothing;
+} NULLMD_CTX;
+
+static int null_init(NULLMD_CTX *ctx)
+{
+    return 1;
+}
+
+static int null_update(NULLMD_CTX *ctx, const void *data, size_t datalen)
+{
+    return 1;
+}
+
+static int null_final(unsigned char *md, NULLMD_CTX *ctx)
+{
+    return 1;
+}
+
+/*
+ * We must override the PROV_FUNC_DIGEST_FINAL as dgstsize == 0
+ * and that would cause compilation warnings with the default implementation.
+ */
+#undef PROV_FUNC_DIGEST_FINAL
+#define PROV_FUNC_DIGEST_FINAL(name, dgstsize, fin)                            \
+static OSSL_FUNC_digest_final_fn name##_internal_final;                        \
+static int name##_internal_final(void *ctx, unsigned char *out, size_t *outl,  \
+                                 size_t outsz)                                 \
+{                                                                              \
+    if (ossl_prov_is_running() && fin(out, ctx)) {                             \
+        *outl = dgstsize;                                                      \
+        return 1;                                                              \
+    }                                                                          \
+    return 0;                                                                  \
+}
+
+IMPLEMENT_digest_functions(nullmd, NULLMD_CTX,
+                           0, 0, 0,
+                           null_init, null_update, null_final)
diff --git a/providers/implementations/include/prov/digestcommon.h b/providers/implementations/include/prov/digestcommon.h
index b0ed83648d..abdb8bb2ad 100644
--- a/providers/implementations/include/prov/digestcommon.h
+++ b/providers/implementations/include/prov/digestcommon.h
@@ -35,6 +35,18 @@ static int name##_get_params(OSSL_PARAM params[])                              \
 { OSSL_FUNC_DIGEST_GETTABLE_PARAMS,                                            \
   (void (*)(void))ossl_digest_default_gettable_params }
 
+# define PROV_FUNC_DIGEST_FINAL(name, dgstsize, fin)                           \
+static OSSL_FUNC_digest_final_fn name##_internal_final;                        \
+static int name##_internal_final(void *ctx, unsigned char *out, size_t *outl,  \
+                                 size_t outsz)                                 \
+{                                                                              \
+    if (ossl_prov_is_running() && outsz >= dgstsize && fin(out, ctx)) {        \
+        *outl = dgstsize;                                                      \
+        return 1;                                                              \
+    }                                                                          \
+    return 0;                                                                  \
+}
+
 # define PROV_DISPATCH_FUNC_DIGEST_CONSTRUCT_START(                            \
     name, CTX, blksize, dgstsize, flags, upd, fin)                             \
 static OSSL_FUNC_digest_newctx_fn name##_newctx;                               \
@@ -58,16 +70,7 @@ static void *name##_dupctx(void *ctx)                                          \
         *ret = *in;                                                            \
     return ret;                                                                \
 }                                                                              \
-static OSSL_FUNC_digest_final_fn name##_internal_final;                        \
-static int name##_internal_final(void *ctx, unsigned char *out, size_t *outl,  \
-                                 size_t outsz)                                 \
-{                                                                              \
-    if (ossl_prov_is_running() && outsz >= dgstsize && fin(out, ctx)) {        \
-        *outl = dgstsize;                                                      \
-        return 1;                                                              \
-    }                                                                          \
-    return 0;                                                                  \
-}                                                                              \
+PROV_FUNC_DIGEST_FINAL(name, dgstsize, fin)                                    \
 PROV_FUNC_DIGEST_GET_PARAM(name, blksize, dgstsize, flags)                     \
 const OSSL_DISPATCH ossl_##name##_functions[] = {                              \
     { OSSL_FUNC_DIGEST_NEWCTX, (void (*)(void))name##_newctx },                \
diff --git a/providers/implementations/include/prov/implementations.h b/providers/implementations/include/prov/implementations.h
index 73e1823742..30e5e4cd77 100644
--- a/providers/implementations/include/prov/implementations.h
+++ b/providers/implementations/include/prov/implementations.h
@@ -36,6 +36,7 @@ extern const OSSL_DISPATCH ossl_md4_functions[];
 extern const OSSL_DISPATCH ossl_mdc2_functions[];
 extern const OSSL_DISPATCH ossl_wp_functions[];
 extern const OSSL_DISPATCH ossl_ripemd160_functions[];
+extern const OSSL_DISPATCH ossl_nullmd_functions[];
 
 /* Ciphers */
 extern const OSSL_DISPATCH ossl_null_functions[];