although AES is a variable length cipher, AES EVP methods have a fixed key length

crypto/evp/e_aes.c

@@ -111,7 +111,7 @@ static int aes_counter (EVP_CIPHER_CTX *ctx, unsigned char *out,
 static const EVP_CIPHER aes_128_ctr_cipher=
 	{
 	NID_aes_128_ctr,1,16,16,
-	EVP_CIPH_VARIABLE_LENGTH|EVP_CIPH_CUSTOM_IV,
+	EVP_CIPH_CUSTOM_IV,
 	aes_init_key,
 	aes_counter,
 	NULL,
@@ -128,7 +128,7 @@ const EVP_CIPHER *EVP_aes_128_ctr (void)
 static const EVP_CIPHER aes_192_ctr_cipher=
 	{
 	NID_aes_192_ctr,1,24,16,
-	EVP_CIPH_VARIABLE_LENGTH|EVP_CIPH_CUSTOM_IV,
+	EVP_CIPH_CUSTOM_IV,
 	aes_init_key,
 	aes_counter,
 	NULL,
@@ -145,7 +145,7 @@ const EVP_CIPHER *EVP_aes_192_ctr (void)
 static const EVP_CIPHER aes_256_ctr_cipher=
 	{
 	NID_aes_256_ctr,1,32,16,
-	EVP_CIPH_VARIABLE_LENGTH|EVP_CIPH_CUSTOM_IV,
+	EVP_CIPH_CUSTOM_IV,
 	aes_init_key,
 	aes_counter,
 	NULL,