Refactor SSKDF to create the MAC contexts early

The SSKDF implementation fetched the digest(s) for the underlying MAC,
just to get their names and pass those down to the MAC, which in turn
would fetch those same digests again.

This change circumvents this by fetching the MAC and create the MAC
contexts for them directly when this PRF receives the relevant
parameters, thus only having to pass EVP_MAC_CTX pointers around.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9946)

1 files changed, 32 insertions, 53 deletions

diff --git a/providers/common/kdfs/sskdf.c b/providers/common/kdfs/sskdf.c
index 49da1a690f..d74da436a2 100644
--- a/providers/common/kdfs/sskdf.c
+++ b/providers/common/kdfs/sskdf.c
@@ -52,8 +52,8 @@
 
 typedef struct {
     void *provctx;
-    EVP_MAC *mac;       /* H(x) = HMAC_hash OR H(x) = KMAC */
-    PROV_DIGEST digest;
+    EVP_MAC_CTX *macctx;         /* H(x) = HMAC_hash OR H(x) = KMAC */
+    PROV_DIGEST digest;          /* H(x) = hash(x) */
     unsigned char *secret;
     size_t secret_len;
     unsigned char *info;
@@ -207,7 +207,7 @@ static int kmac_init(EVP_MAC_CTX *ctx, const unsigned char *custom,
  *     H(x) = HMAC-hash(salt, x) OR
  *     H(x) = KMAC#(salt, x, outbits, CustomString='KDF')
  */
-static int SSKDF_mac_kdm(EVP_MAC *kdf_mac, const EVP_MD *hmac_md,
+static int SSKDF_mac_kdm(EVP_MAC_CTX *ctx_init,
                          const unsigned char *kmac_custom,
                          size_t kmac_custom_len, size_t kmac_out_len,
                          const unsigned char *salt, size_t salt_len,
@@ -220,30 +220,18 @@ static int SSKDF_mac_kdm(EVP_MAC *kdf_mac, const EVP_MD *hmac_md,
     unsigned char c[4];
     unsigned char mac_buf[EVP_MAX_MD_SIZE];
     unsigned char *out = derived_key;
-    EVP_MAC_CTX *ctx = NULL, *ctx_init = NULL;
+    EVP_MAC_CTX *ctx = NULL;
     unsigned char *mac = mac_buf, *kmac_buffer = NULL;
-    OSSL_PARAM params[3];
-    size_t params_n = 0;
+    OSSL_PARAM params[2], *p = params;
 
     if (z_len > SSKDF_MAX_INLEN || info_len > SSKDF_MAX_INLEN
             || derived_key_len > SSKDF_MAX_INLEN
             || derived_key_len == 0)
         return 0;
 
-    ctx_init = EVP_MAC_CTX_new(kdf_mac);
-    if (ctx_init == NULL)
-        goto end;
-
-    if (hmac_md != NULL) {
-        const char *mdname = EVP_MD_name(hmac_md);
-        params[params_n++] =
-            OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_DIGEST,
-                                             (char *)mdname, 0);
-    }
-    params[params_n++] =
-        OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY, (void *)salt,
-                                          salt_len);
-    params[params_n] = OSSL_PARAM_construct_end();
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
+                                             (void *)salt, salt_len);
+    *p = OSSL_PARAM_construct_end();
 
     if (!EVP_MAC_CTX_set_params(ctx_init, params))
         goto end;
@@ -298,7 +286,6 @@ end:
         OPENSSL_cleanse(mac_buf, sizeof(mac_buf));
 
     EVP_MAC_CTX_free(ctx);
-    EVP_MAC_CTX_free(ctx_init);
     return ret;
 }
 
@@ -316,8 +303,8 @@ static void sskdf_reset(void *vctx)
 {
     KDF_SSKDF *ctx = (KDF_SSKDF *)vctx;
 
+    EVP_MAC_CTX_free(ctx->macctx);
     ossl_prov_digest_reset(&ctx->digest);
-    EVP_MAC_free(ctx->mac);
     OPENSSL_clear_free(ctx->secret, ctx->secret_len);
     OPENSSL_clear_free(ctx->info, ctx->info_len);
     OPENSSL_clear_free(ctx->salt, ctx->salt_len);
@@ -365,33 +352,34 @@ static int sskdf_derive(void *vctx, unsigned char *key, size_t keylen)
         return 0;
     }
 
-    if (ctx->mac != NULL) {
+    if (ctx->macctx != NULL) {
         /* H(x) = KMAC or H(x) = HMAC */
         int ret;
         const unsigned char *custom = NULL;
         size_t custom_len = 0;
         int default_salt_len;
+        EVP_MAC *mac = EVP_MAC_CTX_mac(ctx->macctx);
 
         /*
          * TODO(3.0) investigate the necessity to have all these controls.
          * Why does KMAC require a salt length that's shorter than the MD
          * block size?
          */
-        if (EVP_MAC_is_a(ctx->mac, OSSL_MAC_NAME_HMAC)) {
+        if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_HMAC)) {
             /* H(x) = HMAC(x, salt, hash) */
             if (md == NULL) {
                 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
                 return 0;
             }
-            default_salt_len = EVP_MD_block_size(md);
+            default_salt_len = EVP_MD_size(md);
             if (default_salt_len <= 0)
                 return 0;
-        } else if (EVP_MAC_is_a(ctx->mac, OSSL_MAC_NAME_KMAC128)
-                   || EVP_MAC_is_a(ctx->mac, OSSL_MAC_NAME_KMAC256)) {
+        } else if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128)
+                   || EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC256)) {
             /* H(x) = KMACzzz(x, salt, custom) */
             custom = kmac_custom_str;
             custom_len = sizeof(kmac_custom_str);
-            if (EVP_MAC_is_a(ctx->mac, OSSL_MAC_NAME_KMAC128))
+            if (EVP_MAC_is_a(mac, OSSL_MAC_NAME_KMAC128))
                 default_salt_len = SSKDF_KMAC128_DEFAULT_SALT_SIZE;
             else
                 default_salt_len = SSKDF_KMAC256_DEFAULT_SALT_SIZE;
@@ -408,7 +396,7 @@ static int sskdf_derive(void *vctx, unsigned char *key, size_t keylen)
             }
             ctx->salt_len = default_salt_len;
         }
-        ret = SSKDF_mac_kdm(ctx->mac, md,
+        ret = SSKDF_mac_kdm(ctx->macctx,
                             custom, custom_len, ctx->out_len,
                             ctx->salt, ctx->salt_len,
                             ctx->secret, ctx->secret_len,
@@ -435,43 +423,34 @@ static int x963kdf_derive(void *vctx, unsigned char *key, size_t keylen)
         return 0;
     }
 
-    if (ctx->mac != NULL) {
+    if (ctx->macctx != NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_NOT_SUPPORTED);
         return 0;
-    } else {
-        /* H(x) = hash */
-        if (md == NULL) {
-            ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
-            return 0;
-        }
-        return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
-                              ctx->info, ctx->info_len, 1, key, keylen);
     }
+
+    /* H(x) = hash */
+    if (md == NULL) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
+        return 0;
+    }
+
+    return SSKDF_hash_kdm(md, ctx->secret, ctx->secret_len,
+                          ctx->info, ctx->info_len, 1, key, keylen);
 }
 
 static int sskdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 {
     const OSSL_PARAM *p;
     KDF_SSKDF *ctx = vctx;
-    OPENSSL_CTX *provctx = PROV_LIBRARY_CONTEXT_OF(ctx->provctx);
-    EVP_MAC *mac;
+    OPENSSL_CTX *libctx = PROV_LIBRARY_CONTEXT_OF(ctx->provctx);
     size_t sz;
-    const char *properties = NULL;
 
-    if (!ossl_prov_digest_load_from_params(&ctx->digest, params, provctx))
+    if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
         return 0;
 
-    if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MAC)) != NULL) {
-        EVP_MAC_free(ctx->mac);
-        ctx->mac = NULL;
-
-        mac = EVP_MAC_fetch(PROV_LIBRARY_CONTEXT_OF(ctx->provctx), p->data,
-                            properties);
-        if (mac == NULL)
-            return 0;
-        EVP_MAC_free(ctx->mac);
-        ctx->mac = mac;
-    }
+    if (!ossl_prov_macctx_load_from_params(&ctx->macctx, params,
+                                           NULL, NULL, NULL, libctx))
+        return 0;
 
     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL
         || (p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)