void
show_available_ciphers ()
{
const int *ciphers = cipher_list();
#ifndef ENABLE_SMALL
printf ("The following ciphers and cipher modes are available\n"
"for use with " PACKAGE_NAME ". Each cipher shown below may be\n"
"used as a parameter to the --cipher option. The default\n"
"key size is shown as well as whether or not it can be\n"
"changed with the --keysize directive. Using a CBC mode\n"
"is recommended.\n\n");
#endif
while (*ciphers != 0)
{
const cipher_info_t *info = cipher_info_from_type(*ciphers);
if (info && info->mode == POLARSSL_MODE_CBC && is_allowed_data_channel_cipher(info->name))
printf ("%s %d bit default key\n",
cipher_kt_name(info), cipher_kt_key_size(info) * 8);
ciphers++;
}
printf ("\n");
}
/*
* Build a struct key_type.
*/
void
init_key_type (struct key_type *kt, const char *ciphername,
bool ciphername_defined, const char *authname,
bool authname_defined, int keysize,
bool cfb_ofb_allowed, bool warn)
{
CLEAR (*kt);
if (ciphername && ciphername_defined)
{
kt->cipher = cipher_kt_get (ciphername);
kt->cipher_length = cipher_kt_key_size (kt->cipher);
if (keysize > 0 && keysize <= MAX_CIPHER_KEY_LENGTH)
kt->cipher_length = keysize;
/* check legal cipher mode */
{
const unsigned int mode = cipher_kt_mode (kt->cipher);
if (!(mode == OPENVPN_MODE_CBC
#ifdef ALLOW_NON_CBC_CIPHERS
|| (cfb_ofb_allowed && (mode == OPENVPN_MODE_CFB || mode == OPENVPN_MODE_OFB))
#endif
))
#ifdef ENABLE_SMALL
msg (M_FATAL, "Cipher '%s' mode not supported", ciphername);
#else
msg (M_FATAL, "Cipher '%s' uses a mode not supported by " PACKAGE_NAME " in your current configuration. CBC mode is always supported, while CFB and OFB modes are supported only when using SSL/TLS authentication and key exchange mode, and when " PACKAGE_NAME " has been built with ALLOW_NON_CBC_CIPHERS.", ciphername);
#endif
}
}
else
{
if (warn)
msg (M_WARN, "******* WARNING *******: null cipher specified, no encryption will be used");
}
if (authname && authname_defined)
{
kt->digest = md_kt_get (authname);
kt->hmac_length = md_kt_size (kt->digest);
}
else
{
if (warn)
msg (M_WARN, "******* WARNING *******: null MAC specified, no authentication will be used");
}
}
static void
print_cipher(const cipher_kt_t *info)
{
if (info && (cipher_kt_mode_cbc(info)
#ifdef HAVE_AEAD_CIPHER_MODES
|| cipher_kt_mode_aead(info)
#endif
))
{
const char *ssl_only = cipher_kt_mode_cbc(info) ?
"" : ", TLS client/server mode only";
const char *var_key_size = info->flags & MBEDTLS_CIPHER_VARIABLE_KEY_LEN ?
" by default" : "";
printf("%s (%d bit key%s, %d bit block%s)\n",
cipher_kt_name(info), cipher_kt_key_size(info) * 8, var_key_size,
cipher_kt_block_size(info) * 8, ssl_only);
}
}
/*
* Build a struct key_type.
*/
void
init_key_type (struct key_type *kt, const char *ciphername,
bool ciphername_defined, const char *authname,
bool authname_defined, int keysize,
bool cfb_ofb_allowed, bool warn)
{
CLEAR (*kt);
if (ciphername && ciphername_defined)
{
kt->cipher = cipher_kt_get (translate_cipher_name_from_openvpn(ciphername));
kt->cipher_length = cipher_kt_key_size (kt->cipher);
if (keysize > 0 && keysize <= MAX_CIPHER_KEY_LENGTH)
kt->cipher_length = keysize;
/* check legal cipher mode */
{
if (!(cipher_kt_mode_cbc(kt->cipher)
#ifdef ENABLE_OFB_CFB_MODE
|| (cfb_ofb_allowed && cipher_kt_mode_ofb_cfb(kt->cipher))
#endif
))
msg (M_FATAL, "Cipher '%s' mode not supported", ciphername);
}
}
else
{
if (warn)
msg (M_WARN, "******* WARNING *******: null cipher specified, no encryption will be used");
}
if (authname && authname_defined)
{
kt->digest = md_kt_get (authname);
kt->hmac_length = md_kt_size (kt->digest);
}
else
{
if (warn)
msg (M_WARN, "******* WARNING *******: null MAC specified, no authentication will be used");
}
}
static struct key_type
tls_crypt_kt(void)
{
struct key_type kt;
kt.cipher = cipher_kt_get("AES-256-CTR");
kt.digest = md_kt_get("SHA256");
if (!kt.cipher)
{
msg(M_WARN, "ERROR: --tls-crypt requires AES-256-CTR support.");
return (struct key_type) { 0 };
}
if (!kt.digest)
{
msg(M_WARN, "ERROR: --tls-crypt requires HMAC-SHA-256 support.");
return (struct key_type) { 0 };
}
kt.cipher_length = cipher_kt_key_size(kt.cipher);
kt.hmac_length = md_kt_size(kt.digest);
return kt;
}