des: prevent error when using two key triple DES with a random key

Two key 3DES only sets two keys and the random generation errors out if fewer
than three keys are required.  It shouldn't.

Fixes #20212

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from #20224)

(cherry picked from commit 587e040)

providers/implementations/ciphers/cipher_tdes_common.c

@@ -123,13 +123,12 @@ static int tdes_generatekey(PROV_CIPHER_CTX *ctx, void *ptr)
     if (kl == 0 || RAND_priv_bytes_ex(ctx->libctx, ptr, kl, 0) <= 0)
         return 0;
     DES_set_odd_parity(deskey);
-    if (kl >= 16)
+    if (kl >= 16) {
         DES_set_odd_parity(deskey + 1);
-    if (kl >= 24) {
-        DES_set_odd_parity(deskey + 2);
-        return 1;
+        if (kl >= 24)
+            DES_set_odd_parity(deskey + 2);
     }
-    return 0;
+    return 1;
 }
 
 int ossl_tdes_get_ctx_params(void *vctx, OSSL_PARAM params[])

test/destest.c

@@ -838,6 +838,29 @@ static int test_des_check_bad_parity(int n)
 
     return TEST_int_eq(DES_check_key_parity(key), bad_parity_keys[n].expect);
 }
+
+/* Test that two key 3DES can generate a random key without error */
+static int test_des_two_key(void)
+{
+    int res = 0;
+    EVP_CIPHER *cipher = NULL;
+    EVP_CIPHER_CTX *ctx = NULL;
+    unsigned char key[16];
+
+    if (!TEST_ptr(cipher = EVP_CIPHER_fetch(NULL, "DES-EDE-ECB", NULL))
+            || !TEST_ptr(ctx = EVP_CIPHER_CTX_new())
+            || !EVP_CipherInit_ex(ctx, cipher, NULL, NULL, NULL, 1)
+            || !EVP_CIPHER_CTX_set_key_length(ctx, sizeof(key))
+            || !EVP_CIPHER_CTX_rand_key(ctx, key))
+        goto err;
+
+    res = 1;
+ err:
+    EVP_CIPHER_free(cipher);
+    EVP_CIPHER_CTX_free(ctx);
+    return res;
+}
+
 #endif
 
 int setup_tests(void)
@@ -866,6 +889,7 @@ int setup_tests(void)
     ADD_ALL_TESTS(test_des_key_wrap, OSSL_NELEM(test_des_key_wrap_sizes));
     ADD_ALL_TESTS(test_des_weak_keys, OSSL_NELEM(weak_keys));
     ADD_ALL_TESTS(test_des_check_bad_parity, OSSL_NELEM(bad_parity_keys));
+    ADD_TEST(test_des_two_key);
 #endif
     return 1;
 }