On Sat, Jun 02, 2018 at 01:08:56PM -0400, Heikki Linnakangas wrote: > On 28/05/18 15:08, Michael Paquier wrote: >> On Mon, May 28, 2018 at 12:26:37PM +0300, Heikki Linnakangas wrote: >> > Sounds good. >> >> Okay. Done this way as attached. If the backend forces anything else >> than SCRAM then the client gets an immediate error if channel binding is >> required, without waiting for the password prompt. > > Thanks! The comments and error messages need some copy-editing:
Thanks Heikki for the input. I have reworked all the points you raised
in the attached.
>> /*
>> * Select the mechanism to use. Pick SCRAM-SHA-256-PLUS over
>> anything
>> * else if a channel binding mode is not 'disable'. Pick
>> SCRAM-SHA-256
>> * if nothing else has already been picked. If we add more
>> mechanisms, a
>> * more refined priority mechanism might become necessary.
>> */
>
> "else if a channel binding mode is not 'disable'" sounds a bit awkward. A
> double negative. (Also, "a" -> "the")
Okay. I have completely rewritten this block. Hopefully that's clearer.
>> + /*
>> + * If client is willing to enforce the use the channel binding but
>> + * it has not been previously selected, because it was either not
>> + * published by the server or could not be selected, then complain
>> + * back. If SSL is not used for this connection, still complain
>> + * similarly, as the client may want channel binding but forgot
>> + * to set it up to do so which could be the case with sslmode=prefer
>> + * for example. This protects from any kind of downgrade attacks
>> + * from rogue servers attempting to bypass channel binding.
>> + */
>
> Instead of "is willing to enforce the use the channel binding", perhaps
> simply "requires channel binding".
Check.
>> + printfPQExpBuffer(&conn->errorMessage,
>> + libpq_gettext("channel binding required for SASL authentication but no
>> valid mechanism could be selected\n"));
>
> Channel binding is a property of SCRAM authentication specifically, it's not
> applicable to other SASL mechanisms. So I'd suggest something like:
>
> "server does not support channel binding, and channel_binding_mode=require
> was used"
Changed as such, except that this is using scram_channel_binding_mode in
the error message.
>> + /*
>> + * Complain if channel binding mechanism is chosen but no channel
>> + * binding type is defined.
>> + */
>> + if (strcmp(selected_mechanism, SCRAM_SHA_256_PLUS_NAME) == 0 &&
>> + conn->scram_channel_binding_type == NULL)
>> + {
>> + printfPQExpBuffer(&conn->errorMessage,
>> + libpq_gettext("SASL authentication mechanism using channel
>> binding supported but no channel binding type defined\n"));
>> + goto error;
>> + }
>
> It's not immediately clear to me from the error message or the comment, when
> this error is thrown. Can this even happen?
No, let's not make this happen then. I have added NULL handling in
connectOptions2 related to the initialization of the options so both
scram_channel_binding_mode and scram_channel_binding_type will never be
NULL like sslmode.
>> + /*
>> + * Before processing any message, perform security-related sanity
>> + * checks. If the client is willing to perform channel binding with
>> + * SCRAM authentication, only a subset of messages can be used so
>> + * as there is no transmission of any password data or such.
>> + */
>
> I'd suggest something like:
>
> "If SCRAM with channel binding is required, refuse all other authentication
> methods. Requiring channel binding implies that the client doesn't trust the
> server, until the SCRAM authentication is completed, so it's important that
> we don't divulge the plaintext password, or perform some weaker
> authentication, even if the server asks for it. In all other authentication
> methods, it's currently assumed that the client trusts the server, either
> implicitly or because the SSL certificate was already verified during the
> SSL handshake."
Check. Thanks for the suggestion.
>> + printfPQExpBuffer(&conn->errorMessage,
>> + libpq_gettext("channel binding required for authentication but invalid
>> protocol used\n"));
>
> If I understand correctly, you get this error, e.g. if you have "password"
> or "sspi" in pg_hba.conf, and the client uses
> "channel_binding_mode=require". "Invalid protocol" doesn't sound right for
> that. Perhaps "channel binding required, but the server requested %s
> authentication".
Right, even "md5" enters in this category if the user has a MD5
verifier, but not if it has a SCRAM verifier. I have done that with
get_auth_request_str(), which maps authentication requests to the
probable hba entry. It feels like cheating to map "trust" to
AUTH_REQ_OK as all methods use it as final message though, even if it is
not triggered by this patch. So I have used no mapping name for it.
> Is it possible to have an error hint here? Perhaps add
> "HINT: change the authentication method to scram-sha-256 in the server's
> pg_hba.conf file".
Hm. A HINT would require something similar to PQresultErrorField for
error hints, which is a fight I not much willing to do just for this
patch. Spawning a new error message with a newline would also be
considered as a new error message. So I discard this one.
I have also added a test with a "password" server which stresses this
code path actually, and I just indented the patch. What do you think?
--
Michael
From b0c90fb1d7925414946e0e97e85088e6e9a5b676 Mon Sep 17 00:00:00 2001 From: Michael Paquier <mich...@paquier.xyz> Date: Tue, 22 May 2018 17:03:48 +0900 Subject: [PATCH] Rework scram_channel_binding to protect from downgrade attacks When a client attempts to connect to a PostgreSQL cluster, it may be possible that it requested channel binding with SCRAM authentication, but that the server tricks the cluster and forcibly downgrades the authentication request. For example, a v10 cluster supports SCRAM but not channel binding so authentication could be achieved without channel binding used. In order to protect from such attacks, rework libpq handling of the connection parameter scram_channel_binding as follows by splitting it into two pieces: - scram_channel_binding_mode, which can use as values "require", "disable" or "prefer". - scram_channel_binding_type, which is similar to the previous scram_channel_binding, except that it does not accept anymore an empty value to mean that channel binding is disabled. "prefer", is the default and behaves so as channel binding is used if available. If the cluster does not support it then it is not used. This does not protect from downgrade attacks. "disable", which is the equivalent of the empty value previously, disables channel binding for all exchanges. "require" makes channel binding a hard requirement for the authentication. For "require", if the cluster does not support channel binding with SCRAM (v10 server) or if SSL is not used, then the connection is refused by libpq, which is something that can happen if SSL is not used (prevention also for users forgetting to use sslmode=require at least in connection strings). This also allows users to enforce the use of SCRAM with channel binding even if the targeted cluster downgrades to "trust" or similar. In order to achieve that, filter authentication request messages before processing them if channel binding is required, authorizing only SASL-related messages. When receiving AUTH_REQ_OK from the server, we check if a SASL exchange has happened and has finished, where the client makes sure that the server knows the connection proof. If the cluster does not publish the -PLUS mechanism, then connection is also refused. Author: Michael Paquier Reviewed-by: Heikki Linnakangas, Robert Haas, Bruce Momjian, Magnus Hagander Discussion: https://postgr.es/m/20180519123557.gb2...@paquier.xyz --- doc/src/sgml/libpq.sgml | 72 ++++++++++++--- doc/src/sgml/release-11.sgml | 2 +- src/interfaces/libpq/fe-auth-scram.c | 43 ++++++--- src/interfaces/libpq/fe-auth.c | 128 +++++++++++++++++++++++++-- src/interfaces/libpq/fe-auth.h | 1 + src/interfaces/libpq/fe-connect.c | 65 ++++++++++++-- src/interfaces/libpq/libpq-int.h | 3 +- src/test/ssl/ServerSetup.pm | 24 +++-- src/test/ssl/t/002_scram.pl | 63 +++++++++++-- 9 files changed, 350 insertions(+), 51 deletions(-) diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index 498b8df988..e80429db3b 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -1238,24 +1238,76 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname </listitem> </varlistentry> - <varlistentry id="libpq-scram-channel-binding" xreflabel="scram_channel_binding"> - <term><literal>scram_channel_binding</literal></term> + <varlistentry id="libpq-scram-channel-binding-mode" xreflabel="scram_channel_binding_mode"> + <term><literal>scram_channel_binding_mode</literal></term> + <listitem> + <para> + This option determines whether channel binding should be used + with <acronym>SCRAM</acronym> authentication. While + <acronym>SCRAM</acronym> alone prevents the replay of transmitted + hashed passwords, channel binding also prevents man-in-the-middle + attacks. There are three modes: + + <variablelist> + <varlistentry> + <term><literal>disable</literal></term> + <listitem> + <para> + Disable the use of channel binding for all connection attempts. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>prefer</literal> (default)</term> + <listitem> + <para> + Use channel binding if available. If the cluster does not + support it, then it is not used. This is the default. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><literal>require</literal></term> + <listitem> + <para> + Require the presence of channel binding for authentication. + If the cluster does not support channel binding or if another + authentication protocol other than <acronym>SCRAM</acronym> is + used, then fail the connection. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + Channel binding is only supported on SSL connections. However, if + the connection is not using SSL, then this setting is ignored except + if <literal>require</literal> is used, in which case the connection + to the cluster is refused even if SSL is not enabled or if the cluster + does not support channel binding as a mechanism to prevent against + authentication downgrade attacks. + </para> + </listitem> + </varlistentry> + + <varlistentry id="libpq-scram-channel-binding-type" xreflabel="scram_channel_binding_type"> + <term><literal>scram_channel_binding_type</literal></term> <listitem> <para> Specifies the channel binding type to use with SCRAM - authentication. While <acronym>SCRAM</acronym> alone prevents - the replay of transmitted hashed passwords, channel binding also - prevents man-in-the-middle attacks. + authentication. </para> <para> The list of channel binding types supported by the server are - listed in <xref linkend="sasl-authentication"/>. An empty value - specifies that the client will not use channel binding. If this + listed in <xref linkend="sasl-authentication"/>. If this parameter is not specified, <literal>tls-unique</literal> is used, - if supported by both server and client. - Channel binding is only supported on SSL connections. If the - connection is not using SSL, then this setting is ignored. + if supported by both server and client. Channel binding is only + supported on SSL connections. If the connection is not using SSL, + then this setting is ignored. </para> <para> diff --git a/doc/src/sgml/release-11.sgml b/doc/src/sgml/release-11.sgml index 7599c6f7a7..15f21fd91a 100644 --- a/doc/src/sgml/release-11.sgml +++ b/doc/src/sgml/release-11.sgml @@ -1246,7 +1246,7 @@ same commits as above replay of transmitted hashed passwords in a later session, <acronym>SCRAM</acronym> with channel binding also prevents man-in-the-middle attacks. The options are <link - linkend="libpq-scram-channel-binding"><option>scram_channel_binding=tls-unique</option></link> + linkend="libpq-scram-channel-binding-type"><option>scram_channel_binding=tls-unique</option></link> and <option>scram_channel_binding=tls-server-end-point</option>. </para> </listitem> diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c index 8415bbb5c6..7b650f6e32 100644 --- a/src/interfaces/libpq/fe-auth-scram.c +++ b/src/interfaces/libpq/fe-auth-scram.c @@ -352,10 +352,9 @@ build_client_first_message(fe_scram_state *state) if (strcmp(state->sasl_mechanism, SCRAM_SHA_256_PLUS_NAME) == 0) { Assert(conn->ssl_in_use); - appendPQExpBuffer(&buf, "p=%s", conn->scram_channel_binding); + appendPQExpBuffer(&buf, "p=%s", conn->scram_channel_binding_type); } - else if (conn->scram_channel_binding == NULL || - strlen(conn->scram_channel_binding) == 0) + else if (strcmp(conn->scram_channel_binding_mode, "disable") == 0) { /* * Client has chosen to not show to server that it supports channel @@ -438,7 +437,8 @@ build_client_final_message(fe_scram_state *state) char *cbind_input; size_t cbind_input_len; - if (strcmp(conn->scram_channel_binding, SCRAM_CHANNEL_BINDING_TLS_UNIQUE) == 0) + if (strcmp(conn->scram_channel_binding_type, + SCRAM_CHANNEL_BINDING_TLS_UNIQUE) == 0) { #ifdef USE_SSL cbind_data = pgtls_get_finished(state->conn, &cbind_data_len); @@ -446,7 +446,7 @@ build_client_final_message(fe_scram_state *state) goto oom_error; #endif } - else if (strcmp(conn->scram_channel_binding, + else if (strcmp(conn->scram_channel_binding_type, SCRAM_CHANNEL_BINDING_TLS_END_POINT) == 0) { /* Fetch hash data of server's SSL certificate */ @@ -478,14 +478,14 @@ build_client_final_message(fe_scram_state *state) termPQExpBuffer(&buf); printfPQExpBuffer(&conn->errorMessage, libpq_gettext("empty channel binding data for channel binding type \"%s\"\n"), - conn->scram_channel_binding); + conn->scram_channel_binding_type); return NULL; } appendPQExpBuffer(&buf, "c="); /* p=type,, */ - cbind_header_len = 4 + strlen(conn->scram_channel_binding); + cbind_header_len = 4 + strlen(conn->scram_channel_binding_type); cbind_input_len = cbind_header_len + cbind_data_len; cbind_input = malloc(cbind_input_len); if (!cbind_input) @@ -494,7 +494,7 @@ build_client_final_message(fe_scram_state *state) goto oom_error; } snprintf(cbind_input, cbind_input_len, "p=%s,,", - conn->scram_channel_binding); + conn->scram_channel_binding_type); memcpy(cbind_input + cbind_header_len, cbind_data, cbind_data_len); if (!enlargePQExpBuffer(&buf, pg_b64_enc_len(cbind_input_len))) @@ -509,8 +509,7 @@ build_client_final_message(fe_scram_state *state) free(cbind_data); free(cbind_input); } - else if (conn->scram_channel_binding == NULL || - strlen(conn->scram_channel_binding) == 0) + else if (strcmp(conn->scram_channel_binding_mode, "disable") == 0) appendPQExpBuffer(&buf, "c=biws"); /* base64 of "n,," */ else if (conn->ssl_in_use) appendPQExpBuffer(&buf, "c=eSws"); /* base64 of "y,," */ @@ -811,6 +810,30 @@ pg_fe_scram_build_verifier(const char *password) return result; } +/* + * Check if a SCRAM exchange has been finished or not. This can + * be used for security-related checks. + */ +bool +pg_fe_scram_exchange_finished(PGconn *conn) +{ + fe_scram_state *state; + + if (conn == NULL || + conn->sasl_state == NULL) + return false; + + state = (fe_scram_state *) conn->sasl_state; + + /* + * A exchange is considered as complete only once the server signature has + * been checked. + */ + if (state->state != FE_SCRAM_FINISHED) + return false; + return true; +} + /* * Random number generator. */ diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c index 3b2073a47f..3d15257721 100644 --- a/src/interfaces/libpq/fe-auth.c +++ b/src/interfaces/libpq/fe-auth.c @@ -525,14 +525,15 @@ pg_SASL_init(PGconn *conn, int payloadlen) break; /* - * Select the mechanism to use. Pick SCRAM-SHA-256-PLUS over anything - * else if a channel binding type is set. Pick SCRAM-SHA-256 if - * nothing else has already been picked. If we add more mechanisms, a - * more refined priority mechanism might become necessary. + * Select the mechanism to use. SCRAM-SHA-256-PLUS is the first + * choice when the following conditions are met: the channel binding + * mode is not "disable", SSL is used and server has advertised this + * SASL mechanism. Pick SCRAM-SHA-256 as a second choice if nothing + * else has already been picked. If we add more mechanisms, a more + * refined priority mechanism might become necessary. */ if (conn->ssl_in_use && - conn->scram_channel_binding && - strlen(conn->scram_channel_binding) > 0 && + strcmp(conn->scram_channel_binding_mode, "disable") != 0 && strcmp(mechanism_buf.data, SCRAM_SHA_256_PLUS_NAME) == 0) selected_mechanism = SCRAM_SHA_256_PLUS_NAME; else if (strcmp(mechanism_buf.data, SCRAM_SHA_256_NAME) == 0 && @@ -547,6 +548,23 @@ pg_SASL_init(PGconn *conn, int payloadlen) goto error; } + /* + * If client requires channel binding but it has not been previously + * selected, because it was either not published by the server or could + * not be selected, then complain back. If SSL is not used for this + * connection, still complain similarly, as the client may want channel + * binding but forgot to set it up to do so which could be the case with + * sslmode=prefer for example. This protects from any kind of downgrade + * attacks from rogue servers attempting to bypass channel binding. + */ + if (strcmp(conn->scram_channel_binding_mode, "require") == 0 && + strcmp(selected_mechanism, SCRAM_SHA_256_PLUS_NAME) != 0) + { + printfPQExpBuffer(&conn->errorMessage, + libpq_gettext("server does not support channel binding, and scram_channel_binding_mode=require was used\n")); + goto error; + } + /* * Now that the SASL mechanism has been chosen for the exchange, * initialize its state information. @@ -821,6 +839,59 @@ pg_password_sendauth(PGconn *conn, const char *password, AuthRequest areq) return ret; } +/* + * Helper function able to translate authentication request codes to + * to the related authentication types, useful for error messages. + */ +static const char * +get_auth_request_str(AuthRequest areq) +{ + const char *areq_name = "???"; + + switch (areq) + { + case AUTH_REQ_KRB4: /* not supported */ + case AUTH_REQ_KRB5: /* not supported */ + areq_name = "kerberos"; + break; + case AUTH_REQ_PASSWORD: + areq_name = "password"; + break; + case AUTH_REQ_CRYPT: /* not supported */ + areq_name = "crypt"; + break; + case AUTH_REQ_MD5: + areq_name = "md5"; + break; + case AUTH_REQ_SCM_CREDS: + areq_name = "scm"; /* removed as of 9.1 */ + break; + case AUTH_REQ_GSS: + case AUTH_REQ_GSS_CONT: + areq_name = "gssapi"; + break; + case AUTH_REQ_SSPI: + areq_name = "sspi"; + break; + case AUTH_REQ_SASL: + case AUTH_REQ_SASL_CONT: + case AUTH_REQ_SASL_FIN: + areq_name = "sasl"; + break; + + /* + * This can map directly to "trust", or anything else as final + * message, so there is no way to know what this is precisely. + */ + case AUTH_REQ_OK: + /* fall through */ + default: + break; + } + + return areq_name; +} + /* * pg_fe_sendauth * client demux routine for processing an authentication request @@ -835,6 +906,51 @@ pg_password_sendauth(PGconn *conn, const char *password, AuthRequest areq) int pg_fe_sendauth(AuthRequest areq, int payloadlen, PGconn *conn) { + /* + * If SCRAM with channel binding is required, refuse all other + * authentication methods. Requiring channel binding implies that the + * client doesn't trust the server, until the SCRAM authentication is + * completed, so it's important that we don't divulge the plaintext + * password, or perform some weaker authentication, even if the server + * asks for it. In all other authentication methods, it is currently + * assumed that the client trusts the server, either implicitly or because + * the SSL certificate was already verified during the SSL handshake. + */ + if (strcmp(conn->scram_channel_binding_mode, "require") == 0) + { + switch (areq) + { + case AUTH_REQ_OK: + + /* + * Make sure that the client has not been tricked and that a + * full SASL exchange has happened. This happens at this + * stage as it could be possible that a backend with "trust" + * sends directly this message type. + */ + if (!pg_fe_scram_exchange_finished(conn)) + { + printfPQExpBuffer(&conn->errorMessage, + libpq_gettext("channel binding required for authentication but SASL exchange is not finished\n")); + return STATUS_ERROR; + } + break; + + /* Those are used for the SASL exchange */ + case AUTH_REQ_SASL: + case AUTH_REQ_SASL_CONT: + case AUTH_REQ_SASL_FIN: + break; + + default: + printfPQExpBuffer(&conn->errorMessage, + libpq_gettext("channel binding required, but the server requested authentication \"%s\"\n"), + get_auth_request_str(areq)); + return STATUS_ERROR; + } + } + + /* Now process the request */ switch (areq) { case AUTH_REQ_OK: diff --git a/src/interfaces/libpq/fe-auth.h b/src/interfaces/libpq/fe-auth.h index a8a27c24a6..bf41bb4343 100644 --- a/src/interfaces/libpq/fe-auth.h +++ b/src/interfaces/libpq/fe-auth.h @@ -31,5 +31,6 @@ extern void pg_fe_scram_exchange(void *opaq, char *input, int inputlen, char **output, int *outputlen, bool *done, bool *success); extern char *pg_fe_scram_build_verifier(const char *password); +extern bool pg_fe_scram_exchange_finished(PGconn *conn); #endif /* FE_AUTH_H */ diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index a7e969d7c1..328a0adfc0 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -123,7 +123,8 @@ static int ldapServiceLookup(const char *purl, PQconninfoOption *options, #define DefaultOption "" #define DefaultAuthtype "" #define DefaultTargetSessionAttrs "any" -#define DefaultSCRAMChannelBinding SCRAM_CHANNEL_BINDING_TLS_UNIQUE +#define DefaultSCRAMChannelBindingMode "prefer" +#define DefaultSCRAMChannelBindingType SCRAM_CHANNEL_BINDING_TLS_UNIQUE #ifdef USE_SSL #define DefaultSSLMode "prefer" #else @@ -264,10 +265,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = { "TCP-Keepalives-Count", "", 10, /* strlen(INT32_MAX) == 10 */ offsetof(struct pg_conn, keepalives_count)}, - {"scram_channel_binding", NULL, DefaultSCRAMChannelBinding, NULL, - "SCRAM-Channel-Binding", "D", + {"scram_channel_binding_mode", NULL, DefaultSCRAMChannelBindingMode, NULL, + "SCRAM-Channel-Binding-Mode", "D", + 8, /* sizeof("require") == 8 */ + offsetof(struct pg_conn, scram_channel_binding_mode)}, + + {"scram_channel_binding_type", NULL, DefaultSCRAMChannelBindingType, NULL, + "SCRAM-Channel-Binding-Type", "D", 21, /* sizeof("tls-server-end-point") == 21 */ - offsetof(struct pg_conn, scram_channel_binding)}, + offsetof(struct pg_conn, scram_channel_binding_type)}, /* * ssl options are allowed even without client SSL support because the @@ -1166,6 +1172,51 @@ connectOptions2(PGconn *conn) goto oom_error; } + /* validate scram_channel_binding_mode option */ + if (conn->scram_channel_binding_mode) + { + if (strcmp(conn->scram_channel_binding_mode, "prefer") != 0 && + strcmp(conn->scram_channel_binding_mode, "disable") != 0 && + strcmp(conn->scram_channel_binding_mode, "require") != 0) + { + conn->status = CONNECTION_BAD; + printfPQExpBuffer(&conn->errorMessage, + libpq_gettext("invalid scram_channel_binding_mode value: \"%s\"\n"), + conn->scram_channel_binding_mode); + return false; + } + } + else + { + conn->scram_channel_binding_mode = + strdup(DefaultSCRAMChannelBindingMode); + if (!conn->scram_channel_binding_mode) + goto oom_error; + } + + /* validate scram_channel_binding_type option */ + if (conn->scram_channel_binding_type) + { + if (strcmp(conn->scram_channel_binding_type, + SCRAM_CHANNEL_BINDING_TLS_UNIQUE) != 0 && + strcmp(conn->scram_channel_binding_type, + SCRAM_CHANNEL_BINDING_TLS_END_POINT) != 0) + { + conn->status = CONNECTION_BAD; + printfPQExpBuffer(&conn->errorMessage, + libpq_gettext("invalid scram_channel_binding_type value: \"%s\"\n"), + conn->scram_channel_binding_type); + return false; + } + } + else + { + conn->scram_channel_binding_type = + strdup(DefaultSCRAMChannelBindingType); + if (!conn->scram_channel_binding_type) + goto oom_error; + } + /* * Resolve special "auto" client_encoding from the locale */ @@ -3476,8 +3527,10 @@ freePGconn(PGconn *conn) free(conn->keepalives_interval); if (conn->keepalives_count) free(conn->keepalives_count); - if (conn->scram_channel_binding) - free(conn->scram_channel_binding); + if (conn->scram_channel_binding_mode) + free(conn->scram_channel_binding_mode); + if (conn->scram_channel_binding_type) + free(conn->scram_channel_binding_type); if (conn->sslmode) free(conn->sslmode); if (conn->sslcert) diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index 9a586ff25a..ddcd442ad0 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -349,7 +349,8 @@ struct pg_conn * retransmits */ char *keepalives_count; /* maximum number of TCP keepalive * retransmits */ - char *scram_channel_binding; /* SCRAM channel binding type */ + char *scram_channel_binding_mode; /* SCRAM channel binding mode */ + char *scram_channel_binding_type; /* type of SCRAM channel binding */ char *sslmode; /* SSL mode (require,prefer,allow,disable) */ char *sslcompression; /* SSL compression (0 or 1) */ char *sslkey; /* client key filename */ diff --git a/src/test/ssl/ServerSetup.pm b/src/test/ssl/ServerSetup.pm index 1cd3badaa1..89311a5eec 100644 --- a/src/test/ssl/ServerSetup.pm +++ b/src/test/ssl/ServerSetup.pm @@ -27,6 +27,7 @@ use Test::More; use Exporter 'import'; our @EXPORT = qw( configure_test_server_for_ssl + configure_hba_for_ssl switch_server_cert test_connect_fails test_connect_ok @@ -132,7 +133,7 @@ sub configure_test_server_for_ssl $node->restart; # Change pg_hba after restart because hostssl requires ssl=on - configure_hba_for_ssl($node, $serverhost, $authmethod); + configure_hba_for_ssl($node, $serverhost, "hostssl", $authmethod); return; } @@ -160,7 +161,7 @@ sub switch_server_cert sub configure_hba_for_ssl { - my ($node, $serverhost, $authmethod) = @_; + my ($node, $serverhost, $hosttype, $authmethod) = @_; my $pgdata = $node->data_dir; # Only accept SSL connections from localhost. Our tests don't depend on this @@ -171,15 +172,20 @@ sub configure_hba_for_ssl print $hba "# TYPE DATABASE USER ADDRESS METHOD\n"; print $hba - "hostssl trustdb all $serverhost/32 $authmethod\n"; + "$hosttype trustdb all $serverhost/32 $authmethod\n"; print $hba - "hostssl trustdb all ::1/128 $authmethod\n"; - print $hba - "hostssl certdb all $serverhost/32 cert\n"; - print $hba - "hostssl certdb all ::1/128 cert\n"; + "$hosttype trustdb all ::1/128 $authmethod\n"; + # Certificate authentication is only authorized with hostssl + # as entry type. + if ($hosttype eq "hostssl") + { + print $hba + "$hosttype certdb all $serverhost/32 cert\n"; + print $hba + "$hosttype certdb all ::1/128 cert\n"; + } close $hba; return; } -1; \ No newline at end of file +1; diff --git a/src/test/ssl/t/002_scram.pl b/src/test/ssl/t/002_scram.pl index 52a8f458cb..88c21fdba3 100644 --- a/src/test/ssl/t/002_scram.pl +++ b/src/test/ssl/t/002_scram.pl @@ -13,7 +13,7 @@ if ($ENV{with_openssl} ne 'yes') plan skip_all => 'SSL not supported by this build'; } -my $number_of_tests = 6; +my $number_of_tests = 15; # This is the hostname used to connect to the server. my $SERVERHOSTADDR = '127.0.0.1'; @@ -52,30 +52,77 @@ test_connect_ok($common_connstr, '', # Channel binding settings test_connect_ok( $common_connstr, - "scram_channel_binding=tls-unique", + "scram_channel_binding_mode='require' scram_channel_binding_type=tls-unique", "SCRAM authentication with tls-unique as channel binding"); -test_connect_ok($common_connstr, "scram_channel_binding=''", +test_connect_ok($common_connstr, "scram_channel_binding_mode='disable'", "SCRAM authentication without channel binding"); if ($supports_tls_server_end_point) { test_connect_ok( $common_connstr, - "scram_channel_binding=tls-server-end-point", + "scram_channel_binding_mode='require' scram_channel_binding_type=tls-server-end-point", "SCRAM authentication with tls-server-end-point as channel binding"); } else { test_connect_fails( $common_connstr, - "scram_channel_binding=tls-server-end-point", + "scram_channel_binding_mode='require' scram_channel_binding_type=tls-server-end-point", qr/channel binding type "tls-server-end-point" is not supported by this build/, "SCRAM authentication with tls-server-end-point as channel binding"); $number_of_tests++; } test_connect_fails( $common_connstr, - "scram_channel_binding=not-exists", - qr/unsupported SCRAM channel-binding type/, - "SCRAM authentication with invalid channel binding"); + "scram_channel_binding_mode=not-exists", + qr/invalid scram_channel_binding_mode value/, + "SCRAM authentication with invalid channel binding mode"); +test_connect_fails( + $common_connstr, + "scram_channel_binding_type=not-exists", + qr/invalid scram_channel_binding_type value/, + "SCRAM authentication with invalid channel binding type"); + +# Downgrade attack tests +# Update server's pg_hba.conf with "trust" level and try to +# connect to the server with tls-unique. +configure_hba_for_ssl($node, $SERVERHOSTADDR, "hostssl", "trust"); +$node->reload; +test_connect_fails( + $common_connstr, + "scram_channel_binding_mode=require", + qr/channel binding required for authentication but SASL exchange is not finished/, + "Connection to \"trust\" server refused with mode require"); + +# Now test "md5" level, which should pass as user has a SCRAM verifier. +configure_hba_for_ssl($node, $SERVERHOSTADDR, "hostssl", "md5"); +$node->reload; +test_connect_ok($common_connstr, "scram_channel_binding_mode=require", + "SCRAM authentication with channel binding required"); + +# Now test "password" level, which should fail as client requires +# channel binding. +configure_hba_for_ssl($node, $SERVERHOSTADDR, "hostssl", "password"); +$node->reload; +test_connect_fails( + $common_connstr, + "scram_channel_binding_mode=require", + qr/channel binding required, but the server requested authentication "password"/, + "Connection to \"password\" server refused with mode require"); + +# Now a tricky one, update pg_hba.conf so as non-SSL connections +# are authorized. Requiring channel binding should fail, with +# incorrect SASL mechanism received from server. Note that this +# can trigger only with SCRAM used without SSL, or pre-10 servers +# which have no channel binding support. +configure_hba_for_ssl($node, $SERVERHOSTADDR, "hostnossl", "scram-sha-256"); +$node->reload; +$common_connstr = + "user=ssltestuser dbname=trustdb sslmode=disable hostaddr=$SERVERHOSTADDR"; +test_connect_fails( + $common_connstr, + "scram_channel_binding_mode=require", + qr/server does not support channel binding, and scram_channel_binding_mode=require was used/, + "Connection to \"trust\" server refused with required tls-unique"); done_testing($number_of_tests); -- 2.17.0
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