| Message ID | 1520265024-2129-1-git-send-email-arne@rfc2549.org |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [Openvpn-devel,v2] Rework OpenVPN auth-token support | expand |
Hi, Based on the commit message this appears to cover all that is wrong with current auth-token implementation. I haven't carefully reviewed the code or tested it, but some initial remarks that looks relevant. On Mon, Mar 5, 2018 at 10:50 AM, Arne Schwabe <arne@rfc2549.org> wrote: > Auth-token is documented as a token that the client will use instead > of a auth-token. When using an external auth-token script and OTP > authentication, it is useful to have this token survive on reconnect > (e.g. mobile device roaming). On the other hand if the token does > expire, the client should fall back to the previous authentication > methd (e.g. user/pass) or ask for a OTP password again. > > Behaviour of OpenVPN client (prior to this patch) is to never fallback > to the previous authentication method. Depending on auth-retry it > either quit or tried endlessly with an expired token. Since > auth-gen-token tokens expire on reconnect, a client will not survive a > reconnect. While this is mostly true, there is one point missing here. That being the main reason for this email, here goes: While its true that, on SIGUSR1, the client does retry with auth-token it's only a minor nuisance: it leads to an AUTH_FAILED and then the client does go back to prompting for username/password (assuming auth-retry is enabled). The real sticky problem is when authentication fails during a TLS reneg due to an expired auth-token. The client won't realize why the reneg did not complete and will repeatedly try to renegotiate using the expired (or invalid) token. The reason for this is that the server does not send back an AUTH_FAILED message in such cases. I want to stress this point: when the server sends back AUTH_FAILED, the client does behave somewhat sanely, but not otherwise. And on that count this patch appears to be lacking. It teaches the client to forget the token during SIGUSR1 restarts which is good, but does not teach the server to send back AUTH_FAILED in all instances of auth failures. > > This patch changes the client behaviour: > > - Treat a failed auth when using an auth-token as a soft error (USR1) > and clean the auth-token falling back to the original auth method We could be more graceful here by not triggering USR1 -- clearing the token is enough as that will automatically cause the client to fall back to auth-user-pass prompting. I say graceful because some failures do not need a restart, only a re-attempt to authenticate with a valid username/password. > > - Implement a new pushable option forget-token-reconnect that forces > to forget an auth-token when reconnecting I would have liked to see this as the default behaviour: IMO the "right" way to use auth-token is to expire it on reconnect but if some existing external scripts want it otherwise, fine... > > - Sending IV_PROTO=3 to signal that it is safe to send this client an > expiring auth-token Once the server side auth-failure handling is fixed this will be less of a concern. But a new IV_PROTO value cant hurt. > > The behaviour of the server option auth-gen-token: > > - Automatically push forget-token-reconnect to avoid a failed > authentication after reconnect Yes. Unless "forget on reconnect" becomes the only possible client behaviour :) > > - By default only send auth-token to clients that will gracefully > handle auth-token to avoid having clients not able to reconnect I suppose this is regarding expiring tokens, not permanent tokens. > > - Add a force option to auth-gen-token that allow to ignore if the > client can handle auth-tokens > > Patch V2: properly formatted commit message, fix openvpn3 detection ... snipped... > diff --git a/src/openvpn/push.c b/src/openvpn/push.c > index 6a30e479..efe4e5a5 100644 > --- a/src/openvpn/push.c > +++ b/src/openvpn/push.c > @@ -53,25 +53,31 @@ receive_auth_failed(struct context *c, const struct buffer *buffer) > msg(M_VERB0, "AUTH: Received control message: %s", BSTR(buffer)); > c->options.no_advance = true; > > - if (c->options.pull) > - { > - switch (auth_retry_get()) > + if (c->options.pull) { > + /* Before checking how to react on AUTH_FAILED, first check if the failed authed might be > + * the result of an expired auth-token */ > + if (ssl_clean_auth_token()) > { This is not going to work. The only time the server sends back AUTH_FAILED is during the initial connection. See that send_auth_failed() is called only during PUSH request processing[*]. So, failure due to token expiry that normally happens during a reneg[*] will not trigger AUTH_FAILED and the client will continue trying reneg until the previous TLS session expires (1 hour?). This is a basic limitation of the present implementation and I do not see it being addressed by the patch. Other than this, the patch is looking good. Selva [*] Unless management-client-auth is in use. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
Am 06.03.18 um 22:04 schrieb Selva Nair: > Hi, > > Based on the commit message this appears to cover all that is wrong > with current auth-token implementation. I haven't carefully reviewed the > code or tested it, but some initial remarks that looks relevant. > > On Mon, Mar 5, 2018 at 10:50 AM, Arne Schwabe <arne@rfc2549.org> wrote: >> Auth-token is documented as a token that the client will use instead >> of a auth-token. When using an external auth-token script and OTP >> authentication, it is useful to have this token survive on reconnect >> (e.g. mobile device roaming). On the other hand if the token does >> expire, the client should fall back to the previous authentication >> methd (e.g. user/pass) or ask for a OTP password again. >> >> Behaviour of OpenVPN client (prior to this patch) is to never fallback >> to the previous authentication method. Depending on auth-retry it >> either quit or tried endlessly with an expired token. Since >> auth-gen-token tokens expire on reconnect, a client will not survive a >> reconnect. > > While this is mostly true, there is one point missing here. That being > the main reason for this email, here goes: > > While its true that, on SIGUSR1, the client does retry with auth-token > it's only a minor nuisance: it leads to an AUTH_FAILED and > then the client does go back to prompting for username/password > (assuming auth-retry is enabled). The real sticky problem is when > authentication fails during a TLS reneg due to an expired auth-token. > The client won't realize why the reneg did not complete and will > repeatedly try to renegotiate using the expired (or invalid) token. The > reason for this is that the server does not send back an AUTH_FAILED > message in such cases. > > I want to stress this point: when the server sends back AUTH_FAILED, > the client does behave somewhat sanely, but not otherwise. And on that > count this patch appears to be lacking. It teaches the client to forget the > token during SIGUSR1 restarts which is good, but does not teach the server > to send back AUTH_FAILED in all instances of auth failures. I think failed authentication during a renogiation is also a valid issue that this patch does not address and the behaviour is somewhat broken, also for non auth-token usage. I would prefer to fix that thing in a sperate patch. This patch mainly focuses on fixing auth-gen-token and client interaction as much as possible. >> >> This patch changes the client behaviour: >> >> - Treat a failed auth when using an auth-token as a soft error (USR1) >> and clean the auth-token falling back to the original auth method > > We could be more graceful here by not triggering USR1 -- clearing the > token is enough as that will automatically cause the client to fall > back to auth-user-pass prompting. I say graceful because some failures > do not need a restart, only a re-attempt to authenticate with > a valid username/password. > Currently this code is only triggered on inital connnection (as the server fails to send AUTH_FAILED as you noted before). I have not checked how easy it is for the client to send a second key_exchange message. >> >> - Implement a new pushable option forget-token-reconnect that forces >> to forget an auth-token when reconnecting > > I would have liked to see this as the default behaviour: IMO the "right" > way to use auth-token is to expire it on reconnect but if some > existing external scripts want it otherwise, fine... That is something we should discuss. I did here err on the side of caution and not break existing setups since currently the only working that that does not break on reconnect is one where auth-tokens are valid after reconnect and changing this default would break those scnearios and in the past we have most times erred on the side of caution and compatibility. >> >> - Sending IV_PROTO=3 to signal that it is safe to send this client an >> expiring auth-token > > Once the server side auth-failure handling is fixed this will be less > of a concern. But a new IV_PROTO value cant hurt. You still need the ability in the client to actually be able to forget and the server needs to know if the client supports forgetting and it is safe to send the auth-token. > >> >> The behaviour of the server option auth-gen-token: >> >> - Automatically push forget-token-reconnect to avoid a failed >> authentication after reconnect > > Yes. Unless "forget on reconnect" becomes the only possible client > behaviour :) Sure but then we should add a keep-token-reconnect to support "OTP with often roaming clients" scenario. > >> >> - By default only send auth-token to clients that will gracefully >> handle auth-token to avoid having clients not able to reconnect > > I suppose this is regarding expiring tokens, not permanent tokens. Yes, since auth-gen-token has no permanent tokens (they only valid for the session and after reconnect are invalid), they expire instantly when a client reconnects. >> - switch (auth_retry_get()) >> + if (c->options.pull) { >> + /* Before checking how to react on AUTH_FAILED, first check if the failed authed might be >> + * the result of an expired auth-token */ >> + if (ssl_clean_auth_token()) >> { > > This is not going to work. The only time the server sends back > AUTH_FAILED is during the initial connection. See that > send_auth_failed() is called only during PUSH request processing[*]. At least it fixes a client's behaviour with this patch with server that has the default auth-gen-token without expiry set. :) > So, failure due to token expiry that normally happens during a reneg[*] > will not trigger AUTH_FAILED and the client will continue trying reneg > until the previous TLS session expires (1 hour?). This is a > basic limitation of the present implementation and I do not see it > being addressed by the patch. I will look into sending AUTH_FAILED also without management-client-auth. Arne ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
On 07/03/18 12:52, Arne Schwabe wrote: >> So, failure due to token expiry that normally happens during a reneg[*] >> will not trigger AUTH_FAILED and the client will continue trying reneg >> until the previous TLS session expires (1 hour?). This is a >> basic limitation of the present implementation and I do not see it >> being addressed by the patch. > > I will look into sending AUTH_FAILED also without management-client-auth. Just a quick response. AUTH_FAILED can provide an explanation which the client can pick up and act upon. I did that in an earlier attempt, but it required lots of refactoring as the send_control() function depends on a few structs not being available where the token failures can be tackled. See this mail thread for details: Message-Id: 1477918318-18561-1-git-send-email-davids@openvpn.net Mail archive: <https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg12848.html> This approach is what James initially recommended me to do, and this approach of providing a failure message back to the client should already be supported in OpenVPN 3 and the OpenVPN Connect clients. This messaging I believe is already used by the Access Server and Private Tunnel. OpenVPN 2 in client mode, could in these cases catch this "message" and ask for user credentials again. In regards to having the tokens survive reconnect, I agree. But lets try to split this challenge into a few more minor patches. The challenge I see with starting with a new IV_PROTO=3 is that this also requires support in the OpenVPN 3 library as well. I believe the "expiring auth-token" feature would be better handled with proper AUTH_FAILED signalling. I'll have a closer look (hopefully) later today, just wanted to give this quick feedback before its too late.
Hi, On Wed, Mar 7, 2018 at 6:52 AM, Arne Schwabe <arne@rfc2549.org> wrote: > Am 06.03.18 um 22:04 schrieb Selva Nair: > .. >> I want to stress this point: when the server sends back AUTH_FAILED, >> the client does behave somewhat sanely, but not otherwise. And on that >> count this patch appears to be lacking. It teaches the client to forget the >> token during SIGUSR1 restarts which is good, but does not teach the server >> to send back AUTH_FAILED in all instances of auth failures. > > > I think failed authentication during a renogiation is also a valid issue > that this patch does not address and the behaviour is somewhat broken, > also for non auth-token usage. I would prefer to fix that thing in a > sperate patch. This patch mainly focuses on fixing auth-gen-token and > client interaction as much as possible. That is fine. In that case let's not pretend that an expiring auth-token using auth-gen-token is a supported feature. Disable it in the server until we have the ability to send AUTH_FAILED in such cases. > > >>> >>> This patch changes the client behaviour: >>> >>> - Treat a failed auth when using an auth-token as a soft error (USR1) >>> and clean the auth-token falling back to the original auth method >> >> We could be more graceful here by not triggering USR1 -- clearing the >> token is enough as that will automatically cause the client to fall >> back to auth-user-pass prompting. I say graceful because some failures >> do not need a restart, only a re-attempt to authenticate with >> a valid username/password. >> > > Currently this code is only triggered on inital connnection (as the > server fails to send AUTH_FAILED as you noted before). I have not > checked how easy it is for the client to send a second key_exchange message. Agreed SIGUSR1 is appropriate for initial failure, but initial failure happens with auth-token only because the client does not forget the token during SIGUSR1/SIGHUP reconnects. Once it learns to do that (as this patch does), there are no "initial failures" with auth-token (more on that below). > > >>> >>> - Implement a new pushable option forget-token-reconnect that forces >>> to forget an auth-token when reconnecting >> >> I would have liked to see this as the default behaviour: IMO the "right" >> way to use auth-token is to expire it on reconnect but if some >> existing external scripts want it otherwise, fine... > > That is something we should discuss. I did here err on the side of > caution and not break existing setups since currently the only working > that that does not break on reconnect is one where auth-tokens are valid > after reconnect and changing this default would break those scnearios > and in the past we have most times erred on the side of caution and > compatibility. Agreed, if external scripts that implement auth-token without using auth-gen-token wants to reuse the token, fine.. > > > >>> - switch (auth_retry_get()) >>> + if (c->options.pull) { >>> + /* Before checking how to react on AUTH_FAILED, first check if the failed authed might be >>> + * the result of an expired auth-token */ >>> + if (ssl_clean_auth_token()) >>> { >> >> This is not going to work. The only time the server sends back >> AUTH_FAILED is during the initial connection. See that >> send_auth_failed() is called only during PUSH request processing[*]. > > At least it fixes a client's behaviour with this patch with server that > has the default auth-gen-token without expiry set. :) Not really -- that gets fixed by forget-token-reconnect which is pushed when auth-gen-token is set. So I think this code path will never get exercised. As this patch will push forget-token-reconnect, every restart will call ssl_clean_auth_token() from init.c so the client will use the username/password, not any previously set token. As AUTH_FAILED is received only during such first attempts, there is no token to clean at that point and thus this will be skipped. It will "mysteriously" start to get exercised if/when we later fix AUTH_FAILED. So better leave it out of this patch. Or am I missing something? Selva ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
A bit more thorough review this time. On 05/03/18 16:50, Arne Schwabe wrote: [...snip...] > > This patch changes the client behaviour: > > - Treat a failed auth when using an auth-token as a soft error (USR1) > and clean the auth-token falling back to the original auth method Conceptually, this makes sense. > - Implement a new pushable option forget-token-reconnect that forces > to forget an auth-token when reconnecting This I am not happy about. We should use an AUTH_FAILED,SESSION:$message approach instead. This is what OpenVPN 3 based clients expects, and it should actually do (read: behave) as the previous point. OpenVPN 2 does not do that, today, so it would need to be taught that instead. > - Sending IV_PROTO=3 to signal that it is safe to send this client an > expiring auth-token And as we shouldn't need forget-token-reconnect, this would also not be needed. > The behaviour of the server option auth-gen-token: > > - Automatically push forget-token-reconnect to avoid a failed > authentication after reconnect This should not be needed with the AUTH_FAILED,SESSION:$message approach. > - By default only send auth-token to clients that will gracefully > handle auth-token to avoid having clients not able to reconnect What do you mean with "gracefully handle auth-token"? By fixing OpenVPN 2's behaviour (as suggested above), it should behave gracefully by default. And I'd be willing to /consider/ this fix even to OpenVPN 2.3 code base, for those who can't upgrade. But it will be a hard sell, though; OpenVPN 2.4 is over a year old already. > - Add a force option to auth-gen-token that allow to ignore if the > client can handle auth-tokens And this should also not be needed. I'll admit I might see this with a bit too narrow perspective. But how I have understood this issue is that OpenVPN 2.x does not behave correctly as it doesn't understand *why* the authentication failed. If the client side would understand why auth failed, then it can query the user for credentials again - which I believe should resolve the current issues ... Or have I missed something?
Hi, ...some good stuff snipped... > > I'll admit I might see this with a bit too narrow perspective. But how I have > understood this issue is that OpenVPN 2.x does not behave correctly as it > doesn't understand *why* the authentication failed. If the client side would > understand why auth failed, then it can query the user for credentials again - > which I believe should resolve the current issues ... Or have I missed something? I hope we are slowly spiralling towards a solution; not going around in circles... Anyway, to reiterate: we currently have two issues. (i) client is not told when authentication fails during reneg and (ii) client doesn't know that auth-gen-token's token is not reusable across reconnects (SIGHUP and SIGUSR1). Fixing (i) does not fix (ii). But (ii) easier to fix although we could keep arguing whether a forget-token-reconnect should be used or not etc.. (i) is the trickier, though I'm not convinced it requires so much refactoring. Anyway, if there is an immediate solution to (i) it may be better to fix (ii) along with it. Else just fixing (ii) along the lines Arne has proposed looks like the way to go. Selva ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
On 08/03/18 00:22, Selva Nair wrote: > Hi, > > ...some good stuff snipped... > >> >> I'll admit I might see this with a bit too narrow perspective. But how I have >> understood this issue is that OpenVPN 2.x does not behave correctly as it >> doesn't understand *why* the authentication failed. If the client side would >> understand why auth failed, then it can query the user for credentials again - >> which I believe should resolve the current issues ... Or have I missed something? > > I hope we are slowly spiralling towards a solution; not going around > in circles... > > Anyway, to reiterate: we currently have two issues. (i) client is not > told when authentication fails during reneg > and (ii) client doesn't know that auth-gen-token's token is not > reusable across reconnects > (SIGHUP and SIGUSR1). Okay, (i) is handled with AUTH_FAILED,SESSION messages today in OpenVPN 3. OpenVPN 2 should be taught to do the same - both server and client side. In regards to (ii), that is an implementation detail which I would say is incorrect with --auth-gen-token. As I am the one who implemented that feature, I would rather have this fixed so auth-gen-token works across restarts. Another new feature I can accept, is to enable rotating the auth-tokens. This is currently not possible. Not a need-to-have feature now, but more a nice-to-have. > Fixing (i) does not fix (ii). But (ii) easier to fix although we could > keep arguing whether a forget-token-reconnect should be used or not > etc.. > (i) is the trickier, though I'm not convinced it requires so much refactoring. > > Anyway, if there is an immediate solution to (i) it may be better to > fix (ii) along with it. Else just fixing (ii) along the lines Arne has > proposed looks like the way to go. Arne's approach with forget-token and IV_PROTO=3 diverges how OpenVPN 2 and OpenVPN 3 behaves. This is *not* an option for this issue. The reason is that OpenVPN Access Server 2.5 is now shipping with an unmodified (to my knowledge, at least) upstream OpenVPN 2.4. This server integrates well with the OpenVPN Connect clients, which we have for Android, iOS, macOS and Windows (All OpenVPN 3 based). It would be sad if the community side fixes something which isn't really an issue (as part of the solution is already there); we're just doing it wrong currently. The current approach by Arne would also require support in OpenVPN 3 too; and I doubt this approach will get easily accepted there. Also beware that more and more users will start deploying OpenVPN 3 based clients too; it is already widespread on iOS. And there are efforts on getting OpenVPN Connect into even more appstores for different platforms. On top of that, in addition to the new open source openvpn3-linux client, there will also be put some efforts to at least provide more mature reference implementation clients for Windows and macOS too. Plus Arne is also poking at using OpenVPN 3 in his Android client. Many of them will definitely connect against OpenVPN 2.x based servers; so OpenVPN 2 and OpenVPN 3 need to be well aligned. (With that said, I'm not saying OpenVPN 3 supports all OpenVPN 2 features 100% today, but the most important features are there - like authentication).
Hi, On Wed, Mar 7, 2018 at 6:52 PM, David Sommerseth <openvpn@sf.lists.topphemmelig.net> wrote: > On 08/03/18 00:22, Selva Nair wrote: >> Hi, >> >> ...some good stuff snipped... >> >>> >>> I'll admit I might see this with a bit too narrow perspective. But how I have >>> understood this issue is that OpenVPN 2.x does not behave correctly as it >>> doesn't understand *why* the authentication failed. If the client side would >>> understand why auth failed, then it can query the user for credentials again - >>> which I believe should resolve the current issues ... Or have I missed something? >> >> I hope we are slowly spiralling towards a solution; not going around >> in circles... >> >> Anyway, to reiterate: we currently have two issues. (i) client is not >> told when authentication fails during reneg >> and (ii) client doesn't know that auth-gen-token's token is not >> reusable across reconnects >> (SIGHUP and SIGUSR1). > > Okay, (i) is handled with AUTH_FAILED,SESSION messages today in OpenVPN 3. > OpenVPN 2 should be taught to do the same - both server and client side. > > In regards to (ii), that is an implementation detail which I would say is > incorrect with --auth-gen-token. As I am the one who implemented that > feature, I would rather have this fixed so auth-gen-token works across restarts. > Well, IMO, fixing (i) is more important than (ii). It would also make it easy to add support for dynamic auth through scripts and plugin, for example. Currently not possible because a specially crafted "reason" for AUTH_FAILED cannot be sent back unless management-client-auth is used. Unrelated to auth-token but a sorely missing feature. That said, personally I prefer management-client-auth to using scripts and the former works fine as is. Regarding (ii), reusing auth-token across SIGHUP and SIGUSR1 reconnects could have security implications. At the minimum we should treat auth-token as a high value asset on the client side and not send it to management (at least on the Windows GUI it currently shows up in plain text in the status log). In the current state of things, the client-side management has no use for the actual value of the token as it cant override the client daemon's handling of it. Selva ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
diff --git a/doc/openvpn.8 b/doc/openvpn.8 index d1fb4ec6..02c51a10 100644 --- a/doc/openvpn.8 +++ b/doc/openvpn.8 @@ -3058,7 +3058,8 @@ IV_LZO_STUB=1 \-\- if client was built with LZO stub capability IV_LZ4=1 \-\- if the client supports LZ4 compressions. -IV_PROTO=2 \-\- if the client supports peer\-id floating mechansim +IV_PROTO=3 \-\- if the client supports peer\-id floating mechansim (2 or greater) and +fallback to normal authentication after a failed auth-token authentication (3 or greater) IV_NCP=2 \-\- negotiable ciphers, client supports .B \-\-cipher @@ -3664,7 +3665,7 @@ 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] [force] 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 @@ -3684,6 +3685,12 @@ 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. + +The +.B force +option will send auth-token even if the client does not signal +proper auth-token support on reconnect and will fail on reconnect with +failed authentication. This is the behaviour of versions prior to 2.4.6. .\"********************************************************* .TP .B \-\-opt\-verify @@ -5337,7 +5344,33 @@ push "auth\-token UNIQUE_TOKEN_VALUE" into the file/buffer for dynamic configuration data. This will then make the OpenVPN server to push this value to the client, which replaces the local password with the -UNIQUE_TOKEN_VALUE. +UNIQUE_TOKEN_VALUE. If you want the client (2.4.6+) to forget the token when +reconnecting also use: + +.nf +.ft 3 +.in +4 +push "forget\-token\-reconnect" +.in -4 +.ft +.fi + +Newer clients (2.4.6+) will fall back to the original password method +after a failed auth-token attempt. Older clients will keep using the token +value and react acording to +.B \-\-auth-retry +. +.\********************************************************** +.TP +.B forget\-token\-reconnect + +Normally a client will retry an auth-token after a reconnect (e.g. USR1 triggered). +If the token fails, the client will fall back to the original method and make an additional +connection attempt. If the token is only valid for a single connection this option can be used +to skip the first attempt on reconnect. The +.B +auth\-gen\-token +option automatically pushes this option. .\"********************************************************* .TP .B \-\-tls\-verify cmd diff --git a/src/openvpn/init.c b/src/openvpn/init.c index 36c1a4c4..59be55e8 100644 --- a/src/openvpn/init.c +++ b/src/openvpn/init.c @@ -2750,6 +2750,7 @@ 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_generate_force = options->auth_token_generate_force; #endif to.x509_track = options->x509_track; @@ -3390,6 +3391,9 @@ do_close_tls(struct context *c) md_ctx_cleanup(c->c2.pulled_options_state); md_ctx_free(c->c2.pulled_options_state); } + + if (c->options.forget_token_on_reconnect) + ssl_clean_auth_token(); } /* diff --git a/src/openvpn/misc.c b/src/openvpn/misc.c index 72ffc406..e41198ee 100644 --- a/src/openvpn/misc.c +++ b/src/openvpn/misc.c @@ -1258,7 +1258,7 @@ purge_user_pass(struct user_pass *up, const bool force) * don't show warning if the pass has been replaced by a token: this is an * artificial "auth-nocache" */ - else if (!warn_shown && (!up->tokenized)) + else if (!warn_shown) { msg(M_WARN, "WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this"); warn_shown = true; @@ -1266,14 +1266,18 @@ purge_user_pass(struct user_pass *up, const bool force) } void -set_auth_token(struct user_pass *up, const char *token) +set_auth_token(struct user_pass *up, struct user_pass *tk, const char *token) { - if (token && strlen(token) && up && up->defined && !up->nocache) + + if (token && strlen(token) && up && up->defined) { - CLEAR(up->password); - strncpynt(up->password, token, USER_PASS_LEN); - up->tokenized = true; + strncpynt(tk->password, token, USER_PASS_LEN); + strncpynt(tk->username, up->username, USER_PASS_LEN); + tk->defined = true; } + + /* Cleans user/pass for nocache */ + purge_user_pass(up, false); } /* diff --git a/src/openvpn/misc.h b/src/openvpn/misc.h index dad6a5de..68ec6a94 100644 --- a/src/openvpn/misc.h +++ b/src/openvpn/misc.h @@ -168,7 +168,6 @@ struct user_pass { bool defined; bool nocache; - bool tokenized; /* true if password has been substituted by a token */ bool wait_for_push; /* true if this object is waiting for a push-reply */ /* max length of username/password */ @@ -250,7 +249,7 @@ void fail_user_pass(const char *prefix, void purge_user_pass(struct user_pass *up, const bool force); -void set_auth_token(struct user_pass *up, const char *token); +void set_auth_token(struct user_pass *up, struct user_pass *tk, const char *token); /* * Process string received by untrusted peer before diff --git a/src/openvpn/options.c b/src/openvpn/options.c index cea143b8..0dc6cc5c 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -883,6 +883,7 @@ init_options(struct options *o, const bool init_gc) /* P2MP server context features */ #if P2MP_SERVER o->auth_token_generate = false; + o->auth_token_generate_force = false; /* Set default --tmp-dir */ #ifdef _WIN32 @@ -1334,6 +1335,7 @@ show_p2mp_parms(const struct options *o) SHOW_STR(auth_user_pass_verify_script); SHOW_BOOL(auth_user_pass_verify_script_via_file); SHOW_BOOL(auth_token_generate); + SHOW_BOOL(auth_token_generate_force); SHOW_INT(auth_token_lifetime); #if PORT_SHARE SHOW_STR(port_share_host); @@ -6718,11 +6720,13 @@ 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] && streq(p[2], "force")) + options->auth_token_generate_force = true; } else if (streq(p[0], "client-connect") && p[1]) { @@ -7791,6 +7795,11 @@ add_option(struct options *options, } #endif } + else if (streq(p[0], "forget-token-reconnect") && !p[1]) + { + VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_ECHO); + options->forget_token_on_reconnect = true; + } else if (streq(p[0], "single-session") && !p[1]) { VERIFY_PERMISSION(OPT_P_GENERAL); diff --git a/src/openvpn/options.h b/src/openvpn/options.h index d9a5b372..5e3a999e 100644 --- a/src/openvpn/options.h +++ b/src/openvpn/options.h @@ -443,6 +443,7 @@ struct options const char *auth_user_pass_verify_script; bool auth_user_pass_verify_script_via_file; bool auth_token_generate; + bool auth_token_generate_force; unsigned int auth_token_lifetime; #if PORT_SHARE char *port_share_host; @@ -457,6 +458,7 @@ struct options unsigned int push_option_types_found; const char *auth_user_pass_file; struct options_pre_pull *pre_pull; + bool forget_token_on_reconnect; int scheduled_exit_interval; diff --git a/src/openvpn/push.c b/src/openvpn/push.c index 6a30e479..efe4e5a5 100644 --- a/src/openvpn/push.c +++ b/src/openvpn/push.c @@ -53,25 +53,31 @@ receive_auth_failed(struct context *c, const struct buffer *buffer) msg(M_VERB0, "AUTH: Received control message: %s", BSTR(buffer)); c->options.no_advance = true; - if (c->options.pull) - { - switch (auth_retry_get()) + if (c->options.pull) { + /* Before checking how to react on AUTH_FAILED, first check if the failed authed might be + * the result of an expired auth-token */ + if (ssl_clean_auth_token()) { - case AR_NONE: - c->sig->signal_received = SIGTERM; /* SOFT-SIGTERM -- Auth failure error */ - break; - - case AR_INTERACT: - ssl_purge_auth(false); - - case AR_NOINTERACT: - c->sig->signal_received = SIGUSR1; /* SOFT-SIGUSR1 -- Auth failure error */ - break; - - default: - ASSERT(0); + c->sig->signal_received = SIGUSR1; /* SOFT-SIGUSR1 -- Auth failure error */ + c->sig->signal_text = "auth-failure (auth-token)"; + } else { + switch (auth_retry_get()) { + case AR_NONE: + c->sig->signal_received = SIGTERM; /* SOFT-SIGTERM -- Auth failure error */ + break; + + case AR_INTERACT: + ssl_purge_auth(false); + + case AR_NOINTERACT: + c->sig->signal_received = SIGUSR1; /* SOFT-SIGUSR1 -- Auth failure error */ + break; + + default: + ASSERT(0); + } + c->sig->signal_text = "auth-failure"; } - c->sig->signal_text = "auth-failure"; #ifdef ENABLE_MANAGEMENT if (management) { @@ -325,7 +331,6 @@ static bool prepare_push_reply(struct context *c, struct gc_arena *gc, struct push_list *push_list) { - const char *optstr = NULL; struct tls_multi *tls_multi = c->c2.tls_multi; const char *const peer_info = tls_multi->peer_info; struct options *o = &c->options; @@ -355,18 +360,33 @@ prepare_push_reply(struct context *c, struct gc_arena *gc, 0, gc)); } - /* Send peer-id if client supports it */ - optstr = peer_info ? strstr(peer_info, "IV_PROTO=") : NULL; + /* Extract the version info from IV_PROTO */ + const char* optstr = peer_info ? strstr(peer_info, "IV_PROTO=") : NULL; + int protover = 0; if (optstr) { - int proto = 0; - int r = sscanf(optstr, "IV_PROTO=%d", &proto); - if ((r == 1) && (proto >= 2)) - { - push_option_fmt(gc, push_list, M_USAGE, "peer-id %d", - tls_multi->peer_id); - tls_multi->use_peer_id = true; - } + int r = sscanf(optstr, "IV_PROTO=%d", &protover); + if (r != 1) + protover = 0; + } + + /* OpenVPN 3 C++ core *always* forgets the auth-token at the end of a session, check if client + * is an OpenVPN 3 client */ + int clientmajor=0; + optstr = peer_info ? strstr(peer_info, "IV_VER=") : NULL; + if (optstr) + { + int r = sscanf(optstr, "IV_VER=%d", &clientmajor); + if (r != 1) + clientmajor=0; + } + + /* Send peer-id if client supports it */ + if (protover >= 2) + { + push_option_fmt(gc, push_list, M_USAGE, "peer-id %d", + tls_multi->peer_id); + tls_multi->use_peer_id = true; } /* Push cipher if client supports Negotiable Crypto Parameters */ @@ -400,12 +420,25 @@ prepare_push_reply(struct context *c, struct gc_arena *gc, /* If server uses --auth-gen-token and we have an auth token * to send to the client + * Also push forget-token-reconnect since our token is only valid for + * a sigle connection. Older clients will just ignore the option */ if (false == tls_multi->auth_token_sent && NULL != tls_multi->auth_token) { - push_option_fmt(gc, push_list, M_USAGE, - "auth-token %s", tls_multi->auth_token); - tls_multi->auth_token_sent = true; + if (protover >= 3 || clientmajor == 3 || o->auth_token_generate_force) + { + push_option_fmt(gc, push_list, M_USAGE, + "auth-token %s", tls_multi->auth_token); + push_option_fmt(gc, push_list, M_USAGE, + "forget-token-reconnect"); + tls_multi->auth_token_sent = true; + } + else + { + msg(D_TLS_DEBUG_LOW, "Not sending auth-token to client since it will not " + "properly reconnect. (Use force option to auth-gen-token " + "to force sending)"); + } } return true; } diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index d758c31a..d90b914d 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -398,6 +398,7 @@ pem_password_callback(char *buf, int size, int rwflag, void *u) static bool auth_user_pass_enabled; /* GLOBAL */ static struct user_pass auth_user_pass; /* GLOBAL */ +static struct user_pass auth_token; /* GLOBAL */ #ifdef ENABLE_CLIENT_CR static char *auth_challenge; /* GLOBAL */ @@ -407,7 +408,7 @@ void auth_user_pass_setup(const char *auth_file, const struct static_challenge_info *sci) { auth_user_pass_enabled = true; - if (!auth_user_pass.defined) + if (!auth_user_pass.defined && !auth_token.defined) { #if AUTO_USERID get_user_pass_auto_userid(&auth_user_pass, auth_file); @@ -449,7 +450,7 @@ ssl_set_auth_nocache(void) { passbuf.nocache = true; auth_user_pass.nocache = true; - /* wait for push-reply, because auth-token may invert nocache */ + /* wait for push-reply, because auth-token may still need the username */ auth_user_pass.wait_for_push = true; } @@ -459,15 +460,18 @@ ssl_set_auth_nocache(void) void ssl_set_auth_token(const char *token) { - if (auth_user_pass.nocache) - { - msg(M_INFO, - "auth-token received, disabling auth-nocache for the " - "authentication token"); - auth_user_pass.nocache = false; - } + set_auth_token(&auth_user_pass, &auth_token, token); +} - set_auth_token(&auth_user_pass, token); +/* + * Cleans an auth token and checks if it was active + */ +bool +ssl_clean_auth_token (void) +{ + bool wasdefined = auth_token.defined; + purge_user_pass(&auth_token, true); + return wasdefined; } /* @@ -2270,8 +2274,9 @@ push_peer_info(struct buffer *buf, struct tls_session *session) buf_printf(&out, "IV_PLAT=win\n"); #endif - /* support for P_DATA_V2 */ - buf_printf(&out, "IV_PROTO=2\n"); + /* support for P_DATA_V2 and + * fallback to normal authentication after a failed auth-token authentication */ + buf_printf(&out, "IV_PROTO=3\n"); /* support for Negotiable Crypto Paramters */ if (session->opt->ncp_enabled @@ -2377,19 +2382,23 @@ key_method_2_write(struct buffer *buf, struct tls_session *session) #else auth_user_pass_setup(session->opt->auth_user_pass_file, NULL); #endif - if (!write_string(buf, auth_user_pass.username, -1)) + struct user_pass* up = &auth_user_pass; + + /* If we have a valid auth-token, send that instead of real username/password */ + if (auth_token.defined) + up = &auth_token; + + if (!write_string(buf, up->username, -1)) { goto error; } - if (!write_string(buf, auth_user_pass.password, -1)) + else if (!write_string(buf, up->password, -1)) { goto error; } /* if auth-nocache was specified, the auth_user_pass object reaches * a "complete" state only after having received the push-reply * message. - * This is the case because auth-token statement in a push-reply would - * invert its nocache. * * For this reason, skip the purge operation here if no push-reply * message has been received yet. diff --git a/src/openvpn/ssl.h b/src/openvpn/ssl.h index a2501c9b..116e76a1 100644 --- a/src/openvpn/ssl.h +++ b/src/openvpn/ssl.h @@ -428,6 +428,8 @@ void ssl_purge_auth(const bool auth_user_pass_only); void ssl_set_auth_token(const char *token); +bool ssl_clean_auth_token(void); + #ifdef ENABLE_CLIENT_CR /* * ssl_get_auth_challenge will parse the server-pushed auth-failed diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h index 08ef6ffa..d39380d4 100644 --- a/src/openvpn/ssl_common.h +++ b/src/openvpn/ssl_common.h @@ -299,6 +299,8 @@ struct tls_options const char *auth_user_pass_file; bool auth_token_generate; /**< Generate auth-tokens on successful user/pass auth, * set via options->auth_token_generate. */ + bool auth_token_generate_force; /* Sent auth-tokens even if the client will not reconnect + * properly with them */ unsigned int auth_token_lifetime; /* use the client-config-dir as a positive authenticator */