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kex, pki, server, options: Filter algorithms in FIPS mode

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When in FIPS mode, filter the algorithms to enable only the allowed
ones.  If any algorithm is explicitly set through options or
configuration file, they are kept.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Anderson Toshiyuki Sasaki
2019-05-22 18:33:14 +02:00
committed by Andreas Schneider
parent 56041dc784
commit 54d76098ed
5 changed files with 137 additions and 14 deletions
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82
src/kex.c
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@@ -136,11 +136,55 @@
#define KEY_EXCHANGE_SUPPORTED \
GEX_SHA1 \
KEY_EXCHANGE
#define KEX_METHODS_SIZE 10
/* RFC 8308 */
#define KEX_EXTENSION_CLIENT "ext-info-c"
/* Allowed algorithms in FIPS mode */
#define FIPS_ALLOWED_CIPHERS "aes256-gcm@openssh.com,"\
"aes256-ctr,"\
"aes256-cbc,"\
"aes128-gcm@openssh.com,"\
"aes128-ctr,"\
"aes128-cbc"
#define FIPS_ALLOWED_PUBLIC_KEY_ALGORITHMS "ecdsa-sha2-nistp521,"\
"ecdsa-sha2-nistp384,"\
"ecdsa-sha2-nistp256,"\
"rsa-sha2-512,"\
"rsa-sha2-256"
#define FIPS_ALLOWED_KEX "ecdh-sha2-nistp256,"\
"ecdh-sha2-nistp384,"\
"ecdh-sha2-nistp521,"\
"diffie-hellman-group-exchange-sha256,"\
"diffie-hellman-group16-sha512,"\
"diffie-hellman-group18-sha512"
#define FIPS_ALLOWED_MACS "hmac-sha2-256-etm@openssh.com,"\
"hmac-sha1-etm@openssh.com,"\
"hmac-sha2-512-etm@openssh.com,"\
"hmac-sha2-256,"\
"hmac-sha1,"\
"hmac-sha2-512"
/* NOTE: This is a fixed API and the index is defined by ssh_kex_types_e */
static const char *fips_methods[] = {
FIPS_ALLOWED_KEX,
FIPS_ALLOWED_PUBLIC_KEY_ALGORITHMS,
FIPS_ALLOWED_CIPHERS,
FIPS_ALLOWED_CIPHERS,
FIPS_ALLOWED_MACS,
FIPS_ALLOWED_MACS,
ZLIB,
ZLIB,
"",
"",
NULL
};
/* NOTE: This is a fixed API and the index is defined by ssh_kex_types_e */
static const char *default_methods[] = {
KEY_EXCHANGE,
@@ -211,6 +255,14 @@ const char *ssh_kex_get_description(uint32_t algo) {
return ssh_kex_descriptions[algo];
}
const char *ssh_kex_get_fips_methods(uint32_t algo) {
if (algo >= KEX_METHODS_SIZE) {
return NULL;
}
return fips_methods[algo];
}
/**
* @internal
* @brief returns whether the first client key exchange algorithm or
@@ -600,8 +652,13 @@ int ssh_set_client_kex(ssh_session session)
for (i = 0; i < KEX_METHODS_SIZE; i++) {
wanted = session->opts.wanted_methods[i];
if (wanted == NULL)
wanted = default_methods[i];
if (wanted == NULL) {
if (ssh_fips_mode()) {
wanted = fips_methods[i];
} else {
wanted = default_methods[i];
}
}
client->methods[i] = strdup(wanted);
if (client->methods[i] == NULL) {
ssh_set_error_oom(session);
@@ -823,6 +880,27 @@ char *ssh_keep_known_algos(enum ssh_kex_types_e algo, const char *list)
return ssh_find_all_matching(supported_methods[algo], list);
}
/**
* @internal
*
* @brief Return a new allocated string containing only the FIPS allowed
* algorithms from the list.
*
* @param[in] algo The type of the methods to filter
* @param[in] list The list to be filtered
*
* @return A new allocated list containing only the FIPS allowed algorithms from
* the list; NULL in case of error.
*/
char *ssh_keep_fips_algos(enum ssh_kex_types_e algo, const char *list)
{
if (algo > SSH_LANG_S_C) {
return NULL;
}
return ssh_find_all_matching(fips_methods[algo], list);
}
int ssh_make_sessionid(ssh_session session)
{
ssh_string num = NULL;