@@ -3710,7 +3710,7 @@ For a sample script that performs PAM authentication, see
in the OpenVPN source distribution.
.\"*********************************************************
.TP
-.B \-\-auth\-gen\-token [lifetime]
+.B \-\-auth\-gen\-token [lifetime] [auth]
After successful user/password authentication, the OpenVPN
server will with this option generate a temporary
authentication token and push that to client. On the following
@@ -3730,6 +3730,14 @@ This feature is useful for environments which is configured
to use One Time Passwords (OTP) as part of the user/password
authentications and that authentication mechanism does not
implement any auth\-token support.
+
+When the auth keyword is present the normal authentication
+method will be called even if auth-token succeeds. This allows
+the normal to still check the validity of the account and do other
+checks. The normal auth method can infer that the auth-token has been
+successful from the password starting with SESS_ID_
+(invalid auth-token fail early and the normal authentication will not
+be called) and the presence of a 'session_id' environment variable.
.\"*********************************************************
.TP
.B \-\-opt\-verify
@@ -17,6 +17,11 @@
const char *auth_token_pem_name = "OpenVPN auth-token server key";
+#define AUTH_TOKEN_SESSION_ID_LEN 12
+#if AUTH_TOKEN_SESSION_ID_LEN % 3
+#error AUTH_TOKEN_SESSION_ID_LEN needs to be multiple a 3
+#endif
+
static struct key_type
auth_token_kt(void)
{
@@ -37,7 +42,47 @@ auth_token_kt(void)
}
-void auth_token_write_server_key_file(const char *filename)
+
+void
+add_session_token_env(struct tls_session *session, struct tls_multi *multi,
+ const struct user_pass *up)
+{
+ if (!multi->opt.auth_token_generate)
+ {
+ return;
+ }
+
+ /* If reach reach this point with a SESS_ID prefixed password
+ * we passed auth-token checks */
+ if (memcmp_constant_time(SESSION_ID_PREFIX, up->password,
+ strlen(SESSION_ID_PREFIX))==0)
+ {
+ setenv_str(session->opt->es, "session_state", "Authenticated");
+ ASSERT(multi->auth_token);
+ }
+ else
+ {
+ setenv_str(session->opt->es, "session_state", "Initial");
+ /* Generate initial token to have it for the management interface */
+ if (!multi->auth_token)
+ {
+ generate_auth_token(up, multi);
+ }
+ }
+ /*
+ * In the auth-token the auth token is already base64 encoded
+ * and being a multiple of 4 ensure that it a multiple of bytes
+ * in the encoding
+ */
+ char session_id[AUTH_TOKEN_SESSION_ID_LEN*2] = {0};
+ memcpy(session_id, multi->auth_token + sizeof(SESSION_ID_PREFIX),
+ AUTH_TOKEN_SESSION_ID_LEN*8/6);
+
+ setenv_str(session->opt->es, "session_id", session_id);
+}
+
+void
+auth_token_write_server_key_file(const char *filename)
{
write_pem_key_file(filename, auth_token_pem_name);
}
@@ -123,7 +168,7 @@ auth_token_init_secret(struct key_ctx *key_ctx, const char *key_file,
}
void
-generate_auth_token(struct user_pass *up, struct tls_multi *multi)
+generate_auth_token(const struct user_pass *up, struct tls_multi *multi)
{
struct gc_arena gc = gc_new();
@@ -134,6 +179,8 @@ generate_auth_token(struct user_pass *up, struct tls_multi *multi)
hmac_ctx_t *ctx = multi->opt.auth_token_key.hmac;
ASSERT(hmac_ctx_size(ctx) == 256/8);
+ uint8_t sessid[AUTH_TOKEN_SESSION_ID_LEN];
+
if (multi->auth_token)
{
/* Just enough space to fit 8 bytes+ 1 extra to decode a non padded
@@ -146,36 +193,54 @@ generate_auth_token(struct user_pass *up, struct tls_multi *multi)
* reuse the same session id and timestamp and null terminate it at
* for base64 decode it only decodes the session id part of it
*/
- char *old_tsamp_initial = multi->auth_token + strlen(SESSION_ID_PREFIX);
+ char *old_sessid = multi->auth_token + strlen(SESSION_ID_PREFIX);
+ char *old_tsamp_initial = old_sessid + AUTH_TOKEN_SESSION_ID_LEN*8/6;
old_tsamp_initial[12] = '\0';
ASSERT(openvpn_base64_decode(old_tsamp_initial, old_tstamp_decode, 9) == 9);
initial_timestamp = *((uint64_t *)(old_tstamp_decode));
+ old_tsamp_initial[0] = '\0';
+ ASSERT(openvpn_base64_decode(old_sessid, sessid, AUTH_TOKEN_SESSION_ID_LEN)==AUTH_TOKEN_SESSION_ID_LEN);
+
+
/* free the auth-token, we will replace it with a new one */
free(multi->auth_token);
}
+ else if (!rand_bytes(sessid, AUTH_TOKEN_SESSION_ID_LEN))
+ {
+ msg( M_FATAL, "Failed to get enough randomness for "
+ "authentication token");
+ }
+
+ /* Calculate the HMAC */
+ /* We enforce up->username to be \0 terminated in ssl.c.. Allowing username
+ * with \0 in them is asking for troubles in so many ways anyway that we
+ * ignore that corner case here
+ */
uint8_t hmac_output[256/8];
hmac_ctx_reset(ctx);
hmac_ctx_update(ctx, (uint8_t *) up->username, (int)strlen(up->username));
+ hmac_ctx_update(ctx, sessid, AUTH_TOKEN_SESSION_ID_LEN);
hmac_ctx_update(ctx, (uint8_t *) &initial_timestamp, sizeof(initial_timestamp));
hmac_ctx_update(ctx, (uint8_t *) ×tamp, sizeof(timestamp));
hmac_ctx_final(ctx, hmac_output);
/* Construct the unencoded session token */
struct buffer token = alloc_buf_gc(
- 2*sizeof(uint64_t) + 256/8, &gc);
+ 2*sizeof(uint64_t) + AUTH_TOKEN_SESSION_ID_LEN + 256/8, &gc);
+ ASSERT(buf_write(&token, sessid, sizeof(sessid)));
ASSERT(buf_write(&token, &initial_timestamp, sizeof(initial_timestamp)));
ASSERT(buf_write(&token, ×tamp, sizeof(timestamp)));
ASSERT(buf_write(&token, hmac_output, sizeof(hmac_output)));
- char* b64output;
+ char *b64output;
openvpn_base64_encode(BPTR(&token), BLEN(&token), &b64output);
struct buffer session_token = alloc_buf_gc(
- strlen(SESSION_ID_PREFIX) + strlen (b64output) + 1, &gc);
+ strlen(SESSION_ID_PREFIX) + strlen(b64output) + 1, &gc);
ASSERT(buf_write(&session_token, SESSION_ID_PREFIX, strlen(SESSION_ID_PREFIX)));
ASSERT(buf_write(&session_token, b64output, (int)strlen(b64output)));
@@ -185,8 +250,8 @@ generate_auth_token(struct user_pass *up, struct tls_multi *multi)
multi->auth_token = strdup((char *)BPTR(&session_token));
- dmsg(D_SHOW_KEYS, "Generated token for client: %s",
- multi->auth_token);
+ dmsg(D_SHOW_KEYS, "Generated token for client: %s (%s)",
+ multi->auth_token, up->username);
gc_free(&gc);
}
@@ -199,13 +264,14 @@ verify_auth_token(struct user_pass *up, struct tls_multi *multi,
* Base64 is <= input and input is < USER_PASS_LEN, so using USER_PASS_LEN
* is safe here but a bit overkill
*/
- char b64decoded[USER_PASS_LEN];
+ uint8_t b64decoded[USER_PASS_LEN];
int decoded_len = openvpn_base64_decode(up->password + strlen(SESSION_ID_PREFIX),
- b64decoded, USER_PASS_LEN);
+ b64decoded, USER_PASS_LEN);
/* Ensure that the decoded data is at least the size of the
* timestamp + hmac */
- int expected_len = 2 * sizeof(int64_t) + 32;
+
+ int expected_len = 2 * sizeof(int64_t) + AUTH_TOKEN_SESSION_ID_LEN + 32;
if (decoded_len != expected_len)
{
@@ -216,14 +282,15 @@ verify_auth_token(struct user_pass *up, struct tls_multi *multi,
hmac_ctx_t *ctx = multi->opt.auth_token_key.hmac;
ASSERT(hmac_ctx_size(ctx) == 256/8);
- hmac_ctx_reset(ctx);
- hmac_ctx_update(ctx, (uint8_t *) up->username, strlen(up->username));
- hmac_ctx_update(ctx, (uint8_t *) b64decoded, sizeof(int64_t));
-
uint8_t hmac_output[256/8];
+
+ hmac_ctx_reset(ctx);
+ hmac_ctx_update(ctx, (uint8_t *) up->username, (int)strlen(up->username));
+ hmac_ctx_update(ctx, b64decoded, expected_len - 256/8);
hmac_ctx_final(ctx, hmac_output);
- const uint8_t *tstamp_initial = b64decoded;
+ const uint8_t *sessid = b64decoded;
+ const uint8_t *tstamp_initial = sessid + AUTH_TOKEN_SESSION_ID_LEN;
const uint8_t *tstamp = tstamp_initial + sizeof(int64_t);
const uint8_t *hmac = tstamp + sizeof(int64_t);
@@ -234,7 +301,8 @@ verify_auth_token(struct user_pass *up, struct tls_multi *multi,
if (validhmac != 0)
{
- msg(M_WARN, "--auth-token-gen: HMAC on token from client failed");
+ msg(M_WARN, "--auth-token-gen: HMAC on token from client failed (%s), %s",
+ up->password, up->username);
return false;
}
@@ -285,7 +353,7 @@ verify_auth_token(struct user_pass *up, struct tls_multi *multi,
/* If we accepted a token without prior session, i.e.
* initial auth via token on new connection, we need
* to store the auth-token in multi->auth_token, so
- * the initial timestamp can be extracted from it
+ * the initial timestamp and session id can be extracted from it
*/
if (!multi->auth_token)
{
@@ -293,6 +361,7 @@ verify_auth_token(struct user_pass *up, struct tls_multi *multi,
}
generate_auth_token(up, multi);
+
/* Auth token already sent to client, update auth-token */
if (multi->auth_token_initial)
{
@@ -34,7 +34,8 @@
*
* Format of the auth-token (before base64 encode)
*
- * uint64 timestamp (4 bytes)|uint64 timestamp (4 bytes)|sha256-hmac(32 bytes)
+ * session id(12 bytes)|uint64 timestamp (4 bytes)|
+ * uint64 timestamp (4 bytes)|sha256-hmac(32 bytes)
*
* The first timestamp is the time the token was initially created and is used to
* determine the maximum renewable time of the token. We always include this even
@@ -44,13 +45,17 @@
* to determine if this token has been renewed in the acceptable time range
* (2 * renogiation timeout)
*
+ * The session is a random string of 12 byte (or 16 in base64) that is not used by
+ * OpenVPN itself but kept intact so that external logging/managment can track the
+ * session multiple reconnects/servers
+ *
* The hmac is calculated over the username contactinated with the
* raw auth-token bytes to include authentication of the username in the token
*
* we prepend the session id with SESS_ID_ before sending it to the client
*/
void
-generate_auth_token(struct user_pass *up, struct tls_multi *multi);
+generate_auth_token(const struct user_pass *up, struct tls_multi *multi);
/**
* Verifies the auth token to be in the format that generate_auth_token
@@ -82,6 +87,14 @@ auth_token_init_secret(struct key_ctx *key_ctx, const char *key_file,
void auth_token_write_server_key_file(const char *filename);
+/**
+ * Put the session id, and auth token status into the environment
+ * if auth-token is enabled
+ *
+ */
+void add_session_token_env(struct tls_session *session, struct tls_multi *multi,
+ const struct user_pass *up);
+
/**
* Wipes the authentication token out of the memory, frees and cleans up
* related buffers and flags
@@ -2866,6 +2866,7 @@ do_init_crypto_tls(struct context *c, const unsigned int flags)
to.auth_user_pass_file = options->auth_user_pass_file;
to.auth_token_generate = options->auth_token_generate;
to.auth_token_lifetime = options->auth_token_lifetime;
+ to.auth_token_call_auth = options->auth_token_call_auth;
to.auth_token_key = c->c1.ks.auth_token_key;
#endif
@@ -2736,7 +2736,9 @@ env_filter_match(const char *env_str, const int env_filter_level)
"ifconfig_pool_netmask=",
"time_duration=",
"bytes_sent=",
- "bytes_received="
+ "bytes_received=",
+ "session_id=",
+ "session_state="
};
if (env_filter_level == 0)
@@ -6768,11 +6768,23 @@ add_option(struct options *options,
&options->auth_user_pass_verify_script,
p[1], "auth-user-pass-verify", true);
}
- else if (streq(p[0], "auth-gen-token"))
+ else if (streq(p[0], "auth-gen-token") && !p[3])
{
VERIFY_PERMISSION(OPT_P_GENERAL);
options->auth_token_generate = true;
options->auth_token_lifetime = p[1] ? positive_atoi(p[1]) : 0;
+ if (p[2])
+ {
+ if (streq(p[2], "auth"))
+ {
+ options->auth_token_call_auth = true;
+ }
+ else
+ {
+ msg(msglevel, "Invalid argument to auth-gen_token: %s", p[2]);
+ }
+ }
+
}
else if (streq(p[0], "auth-gen-token-secret") && p[1] && (!p[2]
|| (p[2] && streq(p[1], INLINE_FILE_TAG))))
@@ -460,7 +460,8 @@ struct options
bool auth_user_pass_verify_script_via_file;
bool auth_token_generate;
bool auth_token_gen_secret_file;
- unsigned int auth_token_lifetime;
+ bool auth_token_call_auth;
+ int auth_token_lifetime;
const char *auth_token_secret_file;
const char *auth_token_secret_file_inline;
@@ -310,6 +310,7 @@ struct tls_options
bool auth_token_generate; /**< Generate auth-tokens on successful
* user/pass auth,seet via
* options->auth_token_generate. */
+ bool auth_token_call_auth; /**< always call normal authentication */
unsigned int auth_token_lifetime;
struct key_ctx auth_token_key;
@@ -1051,7 +1051,8 @@ tls_authenticate_key(struct tls_multi *multi, const unsigned int mda_key_id, con
* Verify the user name and password using a script
*/
static bool
-verify_user_pass_script(struct tls_session *session, const struct user_pass *up)
+verify_user_pass_script(struct tls_session *session, struct tls_multi *multi,
+ const struct user_pass *up)
{
struct gc_arena gc = gc_new();
struct argv argv = argv_new();
@@ -1100,6 +1101,9 @@ verify_user_pass_script(struct tls_session *session, const struct user_pass *up)
/* setenv client real IP address */
setenv_untrusted(session);
+ /* add auth-token environment */
+ add_session_token_env(session, multi, up);
+
/* format command line */
argv_parse_cmd(&argv, session->opt->auth_user_pass_verify_script);
argv_printf_cat(&argv, "%s", tmp_file);
@@ -1133,7 +1137,8 @@ done:
* Verify the username and password using a plugin
*/
static int
-verify_user_pass_plugin(struct tls_session *session, const struct user_pass *up)
+verify_user_pass_plugin(struct tls_session *session, struct tls_multi *multi,
+ const struct user_pass *up)
{
int retval = OPENVPN_PLUGIN_FUNC_ERROR;
#ifdef PLUGIN_DEF_AUTH
@@ -1153,6 +1158,8 @@ verify_user_pass_plugin(struct tls_session *session, const struct user_pass *up)
/* setenv client real IP address */
setenv_untrusted(session);
+ /* add auth-token environment */
+ add_session_token_env(session, multi, up);
#ifdef PLUGIN_DEF_AUTH
/* generate filename for deferred auth control file */
if (!key_state_gen_auth_control_file(ks, session->opt))
@@ -1196,7 +1203,9 @@ cleanup:
#define KMDA_DEF 3
static int
-verify_user_pass_management(struct tls_session *session, const struct user_pass *up)
+verify_user_pass_management(struct tls_session *session,
+ struct tls_multi* multi,
+ const struct user_pass *up)
{
int retval = KMDA_ERROR;
struct key_state *ks = &session->key[KS_PRIMARY]; /* primary key */
@@ -1214,6 +1223,11 @@ verify_user_pass_management(struct tls_session *session, const struct user_pass
/* setenv client real IP address */
setenv_untrusted(session);
+ /*
+ * if we are using auth-gen-token, send also the session id of auth gen token to
+ * allow the management to figure out if it is a new session or a continued one
+ */
+ add_session_token_env(session, multi, up);
if (management)
{
management_notify_client_needing_auth(management, ks->mda_key_id, session->opt->mda_context, session->opt->es);
@@ -1257,7 +1271,14 @@ verify_user_pass(struct user_pass *up, struct tls_multi *multi,
string_mod_remap_name(up->username);
string_mod(up->password, CC_PRINT, CC_CRLF, '_');
- /* If server is configured with --auth-gen-token and the client sends
+ /*
+ * If auth token succeeds we skip the auth
+ * methods unless otherwise specified
+ */
+ bool skip_auth = false;
+
+ /*
+ * If server is configured with --auth-gen-token and the client sends
* something that looks like an authentication token, this
* round will be done internally using the token instead of
* calling any external authentication modules.
@@ -1266,8 +1287,6 @@ verify_user_pass(struct user_pass *up, struct tls_multi *multi,
memcmp_constant_time(SESSION_ID_PREFIX, up->password,
strlen(SESSION_ID_PREFIX))==0)
{
- unsigned int ssl_flags = session->opt->ssl_flags;
-
/* Ensure that the username has not changed */
if (!tls_lock_username(multi, up->username))
{
@@ -1286,40 +1305,41 @@ verify_user_pass(struct user_pass *up, struct tls_multi *multi,
}
else
{
- ks->authenticated = true;
-
- if (ssl_flags & SSLF_USERNAME_AS_COMMON_NAME)
- {
- set_common_name(session, up->username);
- }
msg(M_WARN, "TLS: Username/auth-token authentication "
- "succeeded for username '%s' %s",
- up->username,
- (ssl_flags & SSLF_USERNAME_AS_COMMON_NAME) ? "[CN SET]" : "");
+ "succeeded for username '%s'",
+ up->username);
+ if (!session->opt->auth_token_call_auth)
+ skip_auth = true;
}
- return;
}
/* call plugin(s) and/or script */
-#ifdef MANAGEMENT_DEF_AUTH
- if (man_def_auth == KMDA_DEF)
+ if (!skip_auth)
{
- man_def_auth = verify_user_pass_management(session, up);
- }
+#ifdef MANAGEMENT_DEF_AUTH
+ if (man_def_auth==KMDA_DEF)
+ {
+ man_def_auth = verify_user_pass_management(session, multi, up);
+ }
#endif
- if (plugin_defined(session->opt->plugins, OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY))
- {
- s1 = verify_user_pass_plugin(session, up);
- }
- if (session->opt->auth_user_pass_verify_script)
- {
- s2 = verify_user_pass_script(session, up);
+ if (plugin_defined(session->opt->plugins, OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY))
+ {
+ s1 = verify_user_pass_plugin(session, multi, up);
+ }
+
+ if (session->opt->auth_user_pass_verify_script)
+ {
+ s2 = verify_user_pass_script(session, multi, up);
+ }
}
/* check sizing of username if it will become our common name */
- if ((session->opt->ssl_flags & SSLF_USERNAME_AS_COMMON_NAME) && strlen(up->username) > TLS_USERNAME_LEN)
+ if ((session->opt->ssl_flags & SSLF_USERNAME_AS_COMMON_NAME) &&
+ strlen(up->username)>TLS_USERNAME_LEN)
{
- msg(D_TLS_ERRORS, "TLS Auth Error: --username-as-common name specified and username is longer than the maximum permitted Common Name length of %d characters", TLS_USERNAME_LEN);
+ msg(D_TLS_ERRORS,
+ "TLS Auth Error: --username-as-common name specified and username is longer than the maximum permitted Common Name length of %d characters",
+ TLS_USERNAME_LEN);
s1 = OPENVPN_PLUGIN_FUNC_ERROR;
}
From: Arne Schwabe <arne@openvpn.net> This allows an external authentication method (e.g. management interface) to track the connection and distinguish a reconnection from multiple connections. --- doc/openvpn.8 | 10 +++- src/openvpn/auth_token.c | 105 ++++++++++++++++++++++++++++++++------- src/openvpn/auth_token.h | 17 ++++++- src/openvpn/init.c | 1 + src/openvpn/manage.c | 4 +- src/openvpn/options.c | 14 +++++- src/openvpn/options.h | 3 +- src/openvpn/ssl_common.h | 1 + src/openvpn/ssl_verify.c | 78 ++++++++++++++++++----------- 9 files changed, 180 insertions(+), 53 deletions(-)