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tls-server: Consider supported signature algorithms when selecting key/certificate

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This won't work if the client doesn't send a `signature_algorithms`
extension.  But since the default is SHA1/RSA, most will send it to at
least announce stronger hash algorithms if not ECDSA.
This commit is contained in:
Pascal Knecht
2021-02-12 14:35:23 +01:00
committed by Tobias Brunner
parent 06112f3fe2
commit 9803fb82f4
3 changed files with 177 additions and 34 deletions
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src/libtls/tls_server.c
+72 -34
View File
@@ -169,71 +169,109 @@ struct private_tls_server_t {
bool curves_received;
};
/**
* Create an array of an intersection of server and peer supported key types
*/
static array_t *create_common_key_types(chunk_t hashsig,
tls_version_t version_min,
tls_version_t version_max)
{
array_t *key_types;
enumerator_t *enumerator;
key_type_t v, lookup;
uint16_t sig_scheme;
key_types = array_create(sizeof(key_type_t), 8);
enumerator = tls_get_supported_key_types(version_min, version_max);
while (enumerator->enumerate(enumerator, &v))
{
bio_reader_t *reader;
reader = bio_reader_create(hashsig);
while (reader->remaining(reader) &&
reader->read_uint16(reader, &sig_scheme))
{
lookup = tls_signature_scheme_to_key_type(sig_scheme);
if (v == lookup)
{
array_insert(key_types, ARRAY_TAIL, &lookup);
break;
}
}
reader->destroy(reader);
}
enumerator->destroy(enumerator);
return key_types;
}
/**
* Find a cipher suite and a server key
*/
static bool select_suite_and_key(private_tls_server_t *this,
tls_cipher_suite_t *suites, int count)
{
array_t *key_types;
tls_version_t version_min, version_max;
private_key_t *key;
key_type_t type;
key = lib->credmgr->get_private(lib->credmgr, KEY_ANY, this->server,
this->server_auth);
version_min = this->tls->get_version_min(this->tls);
version_max = this->tls->get_version_max(this->tls);
key_types = create_common_key_types(this->hashsig, version_min, version_max);
if (!array_count(key_types))
{
DBG1(DBG_TLS, "no common signature algorithms found");
array_destroy(key_types);
return FALSE;
}
while (array_remove(key_types, ARRAY_HEAD, &type))
{
key = lib->credmgr->get_private(lib->credmgr, type, this->server,
this->server_auth);
if (key)
{
break;
}
}
if (!key)
{
DBG1(DBG_TLS, "no usable TLS server certificate found for '%Y'",
this->server);
array_destroy(key_types);
return FALSE;
}
if (this->tls->get_version_max(this->tls) >= TLS_1_3)
if (version_max >= TLS_1_3)
{
/* currently no support to derive key based on client supported
* signature schemes */
this->suite = this->crypto->select_cipher_suite(this->crypto, suites,
count, KEY_ANY);
if (!this->suite)
{
DBG1(DBG_TLS, "received cipher suites unacceptable");
return FALSE;
}
}
else
{
this->suite = this->crypto->select_cipher_suite(this->crypto, suites,
count,
key->get_type(key));
if (!this->suite)
{ /* no match for this key, try to find another type */
if (key->get_type(key) == KEY_ECDSA)
{
type = KEY_RSA;
}
else
{
type = KEY_ECDSA;
}
key->destroy(key);
this->suite = this->crypto->select_cipher_suite(this->crypto, suites,
count, type);
if (!this->suite)
{
DBG1(DBG_TLS, "received cipher suites unacceptable");
return FALSE;
}
count, type);
while (!this->suite && array_remove(key_types, ARRAY_HEAD, &type))
{ /* find a key and cipher suite for one of the remaining key types */
DESTROY_IF(key);
this->server_auth->destroy(this->server_auth);
this->server_auth = auth_cfg_create();
key = lib->credmgr->get_private(lib->credmgr, type, this->server,
this->server_auth);
if (!key)
if (key)
{
DBG1(DBG_TLS, "received cipher suites unacceptable");
return FALSE;
this->suite = this->crypto->select_cipher_suite(this->crypto,
suites, count,
type);
}
}
}
array_destroy(key_types);
if (!this->suite || !key)
{
DBG1(DBG_TLS, "received cipher suites or signature schemes unacceptable");
return FALSE;
}
DBG1(DBG_TLS, "using key of type %N", key_type_names, key->get_type(key));
this->private = key;
return TRUE;
}