From 43bbbdf9613c46bf1059b92c844e9bc41837f525 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Tue, 20 Jun 2017 10:18:58 +0900 Subject: [PATCH 2/4] Support channel binding 'tls-unique' in SCRAM This is the basic feature set using OpenSSL to support the feature. In order to allow the frontend and the backend to fetch the sent and expected TLS finish messages, a PG-like API is added to be able to make the interface pluggable for other SSL implementations. --- doc/src/sgml/protocol.sgml | 24 +++-- src/backend/libpq/auth-scram.c | 151 +++++++++++++++++++++++++------ src/backend/libpq/auth.c | 86 +++++++++++++++--- src/backend/libpq/be-secure-openssl.c | 24 +++++ src/include/libpq/libpq-be.h | 1 + src/include/libpq/scram.h | 10 +- src/interfaces/libpq/fe-auth-scram.c | 105 ++++++++++++++++----- src/interfaces/libpq/fe-auth.c | 43 ++++++++- src/interfaces/libpq/fe-auth.h | 4 +- src/interfaces/libpq/fe-secure-openssl.c | 26 ++++++ src/interfaces/libpq/libpq-int.h | 5 +- 11 files changed, 404 insertions(+), 75 deletions(-) diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index 76d1c13cc4..37ae7276e5 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -1461,10 +1461,11 @@ SELCT 1/0; SASL is a framework for authentication in connection-oriented -protocols. At the moment, PostgreSQL implements only one SASL -authentication mechanism, SCRAM-SHA-256, but more might be added in the -future. The below steps illustrate how SASL authentication is performed in -general, while the next subsection gives more details on SCRAM-SHA-256. +protocols. At the moment, PostgreSQL implements only two SASL +authentication mechanisms, SCRAM-SHA-256 and SCRAM-SHA-256-PLUS, but more +might be added in the future. The below steps illustrate how SASL +authentication is performed in general, while the next subsection gives +more details on SCRAM-SHA-256 and SCRAM-SHA-256-PLUS. @@ -1549,7 +1550,10 @@ the password is in. -Channel binding has not been implemented yet. +Channel binding is supported in builds with SSL support, and +uses as mechanism name SCRAM-SHA-256-PLUS for this purpose as +defined per IANA. The only channel binding type supported by the server +is tls-unique. @@ -1558,14 +1562,18 @@ the password is in. The server sends an AuthenticationSASL message. It includes a list of SASL authentication mechanisms that the server can accept. + SCRAM-SHA-256 and SCRAM-SHA-256-PLUS are the + two mechanism names that the server lists in this message. Support for + channel binding is not included if the server is built without SSL + support and if the connection attempt is done without SSL. The client responds by sending a SASLInitialResponse message, which - indicates the chosen mechanism, SCRAM-SHA-256. In the Initial - Client response field, the message contains the SCRAM - client-first-message. + indicates the chosen mechanism, SCRAM-SHA-256 or + SCRAM-SHA-256-PLUS. In the Initial Client response field, + the message contains the SCRAM client-first-message. diff --git a/src/backend/libpq/auth-scram.c b/src/backend/libpq/auth-scram.c index 9161c885e1..c90fa2981a 100644 --- a/src/backend/libpq/auth-scram.c +++ b/src/backend/libpq/auth-scram.c @@ -17,8 +17,6 @@ * by the SASLprep profile, we skip the SASLprep pre-processing and use * the raw bytes in calculating the hash. * - * - Channel binding is not supported yet. - * * * The password stored in pg_authid consists of the iteration count, salt, * StoredKey and ServerKey. @@ -112,6 +110,10 @@ typedef struct const char *username; /* username from startup packet */ + bool ssl_in_use; + char *tls_finish_message; + int tls_finish_len; + int iterations; char *salt; /* base64-encoded */ uint8 StoredKey[SCRAM_KEY_LEN]; @@ -168,7 +170,11 @@ static char *scram_mock_salt(const char *username); * it will fail, as if an incorrect password was given. */ void * -pg_be_scram_init(const char *username, const char *shadow_pass) +pg_be_scram_init(const char *username, + const char *shadow_pass, + bool ssl_in_use, + char *tls_finish_message, + int tls_finish_len) { scram_state *state; bool got_verifier; @@ -176,6 +182,9 @@ pg_be_scram_init(const char *username, const char *shadow_pass) state = (scram_state *) palloc0(sizeof(scram_state)); state->state = SCRAM_AUTH_INIT; state->username = username; + state->ssl_in_use = ssl_in_use; + state->tls_finish_message = tls_finish_message; + state->tls_finish_len = tls_finish_len; /* * Parse the stored password verifier. @@ -773,31 +782,93 @@ read_client_first_message(scram_state *state, char *input) *------ */ - /* read gs2-cbind-flag */ + /* + * Read gs2-cbind-flag. Server handles its value as described in RFC 5802, + * section 6 dealing with channel binding. + */ switch (*input) { case 'n': - /* Client does not support channel binding */ + /* + * Client does not support channel binding, this is authorized + * only in builds not supporting SSL. If SSL is supported, the + * server cannot support this option either. + */ +#ifdef USE_SSL + if (state->ssl_in_use) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("client does not support SCRAM channel binding, but server needs it for SSL connections"))); + else + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("client does not support SCRAM channel binding, but server does"))); +#endif + input++; + if (*input != ',') + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("malformed SCRAM message"), + errdetail("Comma expected, but found character \"%s\".", + sanitize_char(*input)))); input++; break; case 'y': - /* Client supports channel binding, but we're not doing it today */ + /* + * Client supports channel binding, but we're not doing it today + * in the context of a non-SSL connection. Complain though if + * the client is trying to trick the server in not doing channel + * binding with a downgrade attack if a SSL connection is + * attempted. + */ + if (state->ssl_in_use) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("client support SCRAM channel binding, but server needs it for SSL connections"))); + input++; + if (*input != ',') + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("malformed SCRAM message"), + errdetail("Comma expected, but found character \"%s\".", + sanitize_char(*input)))); input++; break; case 'p': + { +#ifdef USE_SSL + char *channel_name; - /* - * Client requires channel binding. We don't support it. - * - * RFC 5802 specifies a particular error code, - * e=server-does-support-channel-binding, for this. But it can - * only be sent in the server-final message, and we don't want to - * go through the motions of the authentication, knowing it will - * fail, just to send that error message. - */ - ereport(ERROR, - (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), - errmsg("client requires SCRAM channel binding, but it is not supported"))); + if (!state->ssl_in_use) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("client supports SCRAM channel binding, but server does not need it for non-SSL connections"))); + + /* + * Read value provided by client, only tls-unique is supported + * for now. + */ + channel_name = read_attr_value(&input, 'p'); + if (strcmp(channel_name, SCRAM_CHANNEL_TLS_UNIQUE) != 0) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + (errmsg("unexpected SCRAM channel-binding type")))); +#else + /* + * Client requires channel binding. We don't support it. + * + * RFC 5802 specifies a particular error code, + * e=server-does-support-channel-binding, for this. But it + * can only be sent in the server-final message, and we don't + * want to go through the motions of the authentication, + * knowing it will fail, just to send that error message. + */ + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("client requires SCRAM channel binding, but it is not supported"))); +#endif + } + break; default: ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), @@ -805,13 +876,6 @@ read_client_first_message(scram_state *state, char *input) errdetail("Unexpected channel-binding flag \"%s\".", sanitize_char(*input)))); } - if (*input != ',') - ereport(ERROR, - (errcode(ERRCODE_PROTOCOL_VIOLATION), - errmsg("malformed SCRAM message"), - errdetail("Comma expected, but found character \"%s\".", - sanitize_char(*input)))); - input++; /* * Forbid optional authzid (authorization identity). We don't support it. @@ -1032,14 +1096,47 @@ read_client_final_message(scram_state *state, char *input) */ /* - * Read channel-binding. We don't support channel binding, so it's - * expected to always be "biws", which is "n,,", base64-encoded. + * Read channel-binding. We don't support channel binding for builds + * without SSL support, so it's expected to always be "biws" in this case, + * which is "n,,", base64-encoded. In builds supporting SSL, "biws" is + * used for Non-SSL connection attempts, and for SSL connections the + * client has to provide channel binding value. */ channel_binding = read_attr_value(&p, 'c'); +#ifdef USE_SSL + if (state->ssl_in_use) + { + char *enc_tls_message; + int enc_tls_len; + + enc_tls_message = palloc(pg_b64_enc_len(state->tls_finish_len) + 1); + enc_tls_len = pg_b64_encode(state->tls_finish_message, + state->tls_finish_len, + enc_tls_message); + enc_tls_message[enc_tls_len] = '\0'; + + /* + * Compare the value sent by the client with the TLS finish message + * expected by the server. + */ + if (strcmp(channel_binding, enc_tls_message) != 0) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + (errmsg("no match for SCRAM channel-binding attribute in client-final-message")))); + } + else + { + if (strcmp(channel_binding, "biws") != 0) + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + (errmsg("unexpected SCRAM channel-binding attribute in client-final-message")))); + } +#else if (strcmp(channel_binding, "biws") != 0) ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), (errmsg("unexpected SCRAM channel-binding attribute in client-final-message")))); +#endif state->client_final_nonce = read_attr_value(&p, 'r'); /* ignore optional extensions */ diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c index cb30fc7b71..ee9bce03a2 100644 --- a/src/backend/libpq/auth.c +++ b/src/backend/libpq/auth.c @@ -859,10 +859,14 @@ CheckSCRAMAuth(Port *port, char *shadow_pass, char **logdetail) void *scram_opaq; char *output = NULL; int outputlen = 0; - char *input; + char *input, *p; + char *sasl_mechs; int inputlen; + int listlen = 0; int result; bool initial; + char *tls_finish = NULL; + int tls_finish_len = 0; /* * SASL auth is not supported for protocol versions before 3, because it @@ -879,12 +883,49 @@ CheckSCRAMAuth(Port *port, char *shadow_pass, char **logdetail) /* * Send the SASL authentication request to user. It includes the list of - * authentication mechanisms (which is trivial, because we only support - * SCRAM-SHA-256 at the moment). The extra "\0" is for an empty string to - * terminate the list. + * authentication mechanisms that are supported: + * - SCRAM-SHA-256, which is the mechanism with the same name. + * - SCRAM-SHA-256-PLUS, which is SCRAM-SHA-256 with channel binding. This + * is advertised to the client only if connection is attempted with SSL. + * The order of mechanisms is advertised in decreasing order of importance. + * The extra "\0" is for an empty string to terminate the list, and each + * mechanism listed needs to be separated with "\0". */ - sendAuthRequest(port, AUTH_REQ_SASL, SCRAM_SHA256_NAME "\0", - strlen(SCRAM_SHA256_NAME) + 2); + listlen = 0; + sasl_mechs = (char *) palloc(strlen(SCRAM_SHA256_PLUS_NAME) + + strlen(SCRAM_SHA256_NAME) + 3); + p = sasl_mechs; + + /* add SCRAM-SHA-256-PLUS, which depends on if SSL is in use */ + if (port->ssl_in_use) + { + strcpy(p, SCRAM_SHA256_PLUS_NAME); + listlen += strlen(SCRAM_SHA256_PLUS_NAME) + 1; + p += strlen(SCRAM_SHA256_PLUS_NAME) + 1; + } + + /* add generic SCRAM-SHA-256 */ + strcpy(p, SCRAM_SHA256_NAME); + listlen += strlen(SCRAM_SHA256_NAME) + 1; + p += strlen(SCRAM_SHA256_NAME) + 1; + + /* put "\0" to mark that list is finished */ + p[0] = '\0'; + listlen++; + + sendAuthRequest(port, AUTH_REQ_SASL, sasl_mechs, listlen); + pfree(sasl_mechs); + +#ifdef USE_SSL + /* + * Fetch the data related to the SSL finish message to be used in the + * exchange. + */ + if (port->ssl_in_use) + { + tls_finish = be_tls_get_peer_finish(port, &tls_finish_len); + } +#endif /* * Initialize the status tracker for message exchanges. @@ -897,7 +938,11 @@ CheckSCRAMAuth(Port *port, char *shadow_pass, char **logdetail) * This is because we don't want to reveal to an attacker what usernames * are valid, nor which users have a valid password. */ - scram_opaq = pg_be_scram_init(port->user_name, shadow_pass); + scram_opaq = pg_be_scram_init(port->user_name, + shadow_pass, + port->ssl_in_use, + tls_finish, + tls_finish_len); /* * Loop through SASL message exchange. This exchange can consist of @@ -946,17 +991,36 @@ CheckSCRAMAuth(Port *port, char *shadow_pass, char **logdetail) const char *selected_mech; /* - * We only support SCRAM-SHA-256 at the moment, so anything else - * is an error. + * We only support SCRAM-SHA-256 and SCRAM-SHA-256-PLUS at the + * moment, so anything else is an error. */ selected_mech = pq_getmsgrawstring(&buf); - if (strcmp(selected_mech, SCRAM_SHA256_NAME) != 0) + if (strcmp(selected_mech, SCRAM_SHA256_NAME) != 0 && + strcmp(selected_mech, SCRAM_SHA256_PLUS_NAME) != 0) { ereport(ERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), - errmsg("client selected an invalid SASL authentication mechanism"))); + errmsg("client selected an invalid SASL authentication mechanism"), + errdetail("Incorrect SASL mechanism name specified"))); } +#ifdef USE_SSL + /* + * If an SSL connection is attempted, check for downgrade attacks. + * A connection is not allowed to specify SCRAM-SHA-256 if its + * -PLUS version has been submitted back to the client, which is + * the default. + */ + if (port->ssl_in_use && + strcmp(selected_mech, SCRAM_SHA256_NAME) == 0) + { + ereport(ERROR, + (errcode(ERRCODE_PROTOCOL_VIOLATION), + errmsg("client selected invalid SASL authentication mechanism"), + errdetail("Channel binding published to client but not selected."))); + } +#endif + inputlen = pq_getmsgint(&buf, 4); if (inputlen == -1) input = NULL; diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c index fe15227a77..d063a587d0 100644 --- a/src/backend/libpq/be-secure-openssl.c +++ b/src/backend/libpq/be-secure-openssl.c @@ -1215,6 +1215,30 @@ be_tls_get_peerdn_name(Port *port, char *ptr, size_t len) ptr[0] = '\0'; } +/* + * Routine to get the expected TLS finish message information from the + * client, useful for authorization when doing channel binding. + * + * Result is a palloc'd copy of the TLS finish message with its size. + */ +char * +be_tls_get_peer_finish(Port *port, int *len) +{ + char dummy[1]; + char *result; + + /* + * OpenSSL does not offer an API to get directly the length of the + * expected TLS finish message, so just do a dummy call to grab this + * information to allow caller to do an allocation with a correct size. + */ + *len = SSL_get_peer_finished(port->ssl, dummy, sizeof(dummy)); + result = (char *) palloc(*len * sizeof(char)); + (void) SSL_get_peer_finished(port->ssl, result, *len); + + return result; +} + /* * Convert an X509 subject name to a cstring. * diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h index 7bde744d51..5d59d79822 100644 --- a/src/include/libpq/libpq-be.h +++ b/src/include/libpq/libpq-be.h @@ -209,6 +209,7 @@ extern bool be_tls_get_compression(Port *port); extern void be_tls_get_version(Port *port, char *ptr, size_t len); extern void be_tls_get_cipher(Port *port, char *ptr, size_t len); extern void be_tls_get_peerdn_name(Port *port, char *ptr, size_t len); +extern char *be_tls_get_peer_finish(Port *port, int *len); #endif extern ProtocolVersion FrontendProtocol; diff --git a/src/include/libpq/scram.h b/src/include/libpq/scram.h index 0166e1945d..91cebe9a9b 100644 --- a/src/include/libpq/scram.h +++ b/src/include/libpq/scram.h @@ -13,8 +13,12 @@ #ifndef PG_SCRAM_H #define PG_SCRAM_H -/* Name of SCRAM-SHA-256 per IANA */ +/* Name of SCRAM mechanisms per IANA */ #define SCRAM_SHA256_NAME "SCRAM-SHA-256" +#define SCRAM_SHA256_PLUS_NAME "SCRAM-SHA-256-PLUS" /* with channel binding */ + +/* Channel binding names */ +#define SCRAM_CHANNEL_TLS_UNIQUE "tls-unique" /* Status codes for message exchange */ #define SASL_EXCHANGE_CONTINUE 0 @@ -22,7 +26,9 @@ #define SASL_EXCHANGE_FAILURE 2 /* Routines dedicated to authentication */ -extern void *pg_be_scram_init(const char *username, const char *shadow_pass); +extern void *pg_be_scram_init(const char *username, const char *shadow_pass, + bool ssl_in_use, char *tls_finish_message, + int tls_finish_len); extern int pg_be_scram_exchange(void *opaq, char *input, int inputlen, char **output, int *outputlen, char **logdetail); diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c index edfd42df85..e37a0cce27 100644 --- a/src/interfaces/libpq/fe-auth-scram.c +++ b/src/interfaces/libpq/fe-auth-scram.c @@ -17,6 +17,7 @@ #include "common/base64.h" #include "common/saslprep.h" #include "common/scram-common.h" +#include "libpq/scram.h" #include "fe-auth.h" /* These are needed for getpid(), in the fallback implementation */ @@ -44,6 +45,9 @@ typedef struct /* These are supplied by the user */ const char *username; char *password; + bool ssl_in_use; + char *tls_finish_message; + int tls_finish_len; /* We construct these */ uint8 SaltedPassword[SCRAM_KEY_LEN]; @@ -81,7 +85,11 @@ static bool pg_frontend_random(char *dst, int len); * Initialize SCRAM exchange status. */ void * -pg_fe_scram_init(const char *username, const char *password) +pg_fe_scram_init(const char *username, + const char *password, + bool ssl_in_use, + char *tls_finish_message, + int tls_finish_len) { fe_scram_state *state; char *prep_password; @@ -93,6 +101,9 @@ pg_fe_scram_init(const char *username, const char *password) memset(state, 0, sizeof(fe_scram_state)); state->state = FE_SCRAM_INIT; state->username = username; + state->ssl_in_use = ssl_in_use; + state->tls_finish_message = tls_finish_message; + state->tls_finish_len = tls_finish_len; /* Normalize the password with SASLprep, if possible */ rc = pg_saslprep(password, &prep_password); @@ -297,9 +308,10 @@ static char * build_client_first_message(fe_scram_state *state, PQExpBuffer errormessage) { char raw_nonce[SCRAM_RAW_NONCE_LEN + 1]; - char *buf; - char buflen; + char *result; + int channel_info_len; int encoded_len; + PQExpBufferData buf; /* * Generate a "raw" nonce. This is converted to ASCII-printable form by @@ -328,26 +340,55 @@ build_client_first_message(fe_scram_state *state, PQExpBuffer errormessage) * prepared with SASLprep, the message parsing would fail if it includes * '=' or ',' characters. */ - buflen = 8 + strlen(state->client_nonce) + 1; - buf = malloc(buflen); - if (buf == NULL) - { - printfPQExpBuffer(errormessage, - libpq_gettext("out of memory\n")); - return NULL; - } - snprintf(buf, buflen, "n,,n=,r=%s", state->client_nonce); + initPQExpBuffer(&buf); - state->client_first_message_bare = strdup(buf + 3); + /* + * First build the query field for channel binding. If the client is not + * built with SSL support, it cannot support channel binding so it needs + * to use "n" to let the server know. If built with SSL support, client + * needs to use "y" to let the server know that client has such support + * but that it is not using it as a non-SSL connection is requested. + * Finally if a SSL connection is done, use p=cb-name, for which only + * "tls-unique" is supported now. + */ +#ifdef USE_SSL + if (state->ssl_in_use) + appendPQExpBuffer(&buf, "p=%s", SCRAM_CHANNEL_TLS_UNIQUE); + else + appendPQExpBuffer(&buf, "y"); +#else + appendPQExpBuffer(&buf, "n"); +#endif + + if (PQExpBufferDataBroken(buf)) + goto oom_error; + + channel_info_len = buf.len; + + appendPQExpBuffer(&buf, ",,n=,r=%s", state->client_nonce); + if (PQExpBufferDataBroken(buf)) + goto oom_error; + + /* + * The first message content needs to be saved without channel binding + * information. + */ + state->client_first_message_bare = strdup(buf.data + channel_info_len + 2); if (!state->client_first_message_bare) - { - free(buf); - printfPQExpBuffer(errormessage, - libpq_gettext("out of memory\n")); - return NULL; - } + goto oom_error; - return buf; + result = strdup(buf.data); + if (result == NULL) + goto oom_error; + + termPQExpBuffer(&buf); + return result; + +oom_error: + termPQExpBuffer(&buf); + printfPQExpBuffer(errormessage, + libpq_gettext("out of memory\n")); + return NULL; } /* @@ -365,8 +406,30 @@ build_client_final_message(fe_scram_state *state, PQExpBuffer errormessage) /* * Construct client-final-message-without-proof. We need to remember it * for verifying the server proof in the final step of authentication. + * Client needs to provide a b64 encoded string of the TLS finish message + * only if a SSL connection is attempted. */ - appendPQExpBuffer(&buf, "c=biws,r=%s", state->nonce); +#ifdef USE_SSL + if (state->ssl_in_use) + { + appendPQExpBuffer(&buf, "c="); + if (!enlargePQExpBuffer(&buf, pg_b64_enc_len(state->tls_finish_len))) + goto oom_error; + buf.len += pg_b64_encode(state->tls_finish_message, + state->tls_finish_len, + buf.data + buf.len); + buf.data[buf.len] = '\0'; + } + else + appendPQExpBuffer(&buf, "c=biws"); +#else + appendPQExpBuffer(&buf, "c=biws"); +#endif + + if (PQExpBufferDataBroken(buf)) + goto oom_error; + + appendPQExpBuffer(&buf, ",r=%s", state->nonce); if (PQExpBufferDataBroken(buf)) goto oom_error; diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c index 382558f3f8..05f04be10a 100644 --- a/src/interfaces/libpq/fe-auth.c +++ b/src/interfaces/libpq/fe-auth.c @@ -504,7 +504,8 @@ pg_SASL_init(PGconn *conn, int payloadlen) /* * Parse the list of SASL authentication mechanisms in the * AuthenticationSASL message, and select the best mechanism that we - * support. (Only SCRAM-SHA-256 is supported at the moment.) + * support. SCRAM-SHA-256 and SCRAM-SHA-256-PLUS are the only ones + * supported at the moment. */ selected_mechanism = NULL; for (;;) @@ -532,9 +533,12 @@ pg_SASL_init(PGconn *conn, int payloadlen) /* * Do we support this mechanism? */ - if (strcmp(mechanism_buf.data, SCRAM_SHA256_NAME) == 0) + if (strcmp(mechanism_buf.data, SCRAM_SHA256_NAME) == 0 || + strcmp(mechanism_buf.data, SCRAM_SHA256_PLUS_NAME) == 0) { char *password; + char *tls_finish = NULL; + int tls_finish_len = 0; conn->password_needed = true; password = conn->connhost[conn->whichhost].password; @@ -547,10 +551,41 @@ pg_SASL_init(PGconn *conn, int payloadlen) goto error; } - conn->sasl_state = pg_fe_scram_init(conn->pguser, password); +#ifdef USE_SSL + /* Fetch information about the TLS finish message */ + if (conn->ssl_in_use) + { + tls_finish = pgtls_get_finish(conn, &tls_finish_len); + if (tls_finish == NULL) + goto oom_error; + } +#endif + + conn->sasl_state = pg_fe_scram_init(conn->pguser, + password, + conn->ssl_in_use, + tls_finish, + tls_finish_len); if (!conn->sasl_state) goto oom_error; - selected_mechanism = SCRAM_SHA256_NAME; + + /* + * Select the mechanism to use by default. If SSL connection + * is attempted, the server will expect the -PLUS mechanism. + * If not, fallback to SCRAM-SHA-256. + */ +#ifdef USE_SSL + if (conn->ssl_in_use && + strcmp(mechanism_buf.data, SCRAM_SHA256_PLUS_NAME) == 0) + selected_mechanism = SCRAM_SHA256_PLUS_NAME; + else if (!conn->ssl_in_use && + strcmp(mechanism_buf.data, SCRAM_SHA256_NAME) == 0) + selected_mechanism = SCRAM_SHA256_NAME; +#else + /* No channel binding can be selected without SSL support */ + if (strcmp(mechanism_buf.data, SCRAM_SHA256_NAME) == 0) + selected_mechanism = SCRAM_SHA256_NAME; +#endif } } diff --git a/src/interfaces/libpq/fe-auth.h b/src/interfaces/libpq/fe-auth.h index 5dc6bb5341..ee3dd7f96c 100644 --- a/src/interfaces/libpq/fe-auth.h +++ b/src/interfaces/libpq/fe-auth.h @@ -23,7 +23,9 @@ extern int pg_fe_sendauth(AuthRequest areq, int payloadlen, PGconn *conn); extern char *pg_fe_getauthname(PQExpBuffer errorMessage); /* Prototypes for functions in fe-auth-scram.c */ -extern void *pg_fe_scram_init(const char *username, const char *password); +extern void *pg_fe_scram_init(const char *username, const char *password, + bool ssl_in_use, char *tls_finish_message, + int tls_finish_len); extern void pg_fe_scram_free(void *opaq); extern void pg_fe_scram_exchange(void *opaq, char *input, int inputlen, char **output, int *outputlen, diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c index 2f29820e82..84a6e3c322 100644 --- a/src/interfaces/libpq/fe-secure-openssl.c +++ b/src/interfaces/libpq/fe-secure-openssl.c @@ -393,6 +393,32 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len) return n; } +/* + * Get the TLS finish message sent during last handshake + * + * This information is useful for callers doing channel binding during + * authentication. + */ +char * +pgtls_get_finish(PGconn *conn, int *len) +{ + char dummy[1]; + char *result; + + /* + * OpenSSL does not offer an API to get directly the length of the + * TLS finish message sent, so first do a dummy call to grab this + * information and then do an allocation with the correct size. + */ + *len = SSL_get_finished(conn->ssl, dummy, sizeof(dummy)); + result = malloc(*len); + if (result == NULL) + return NULL; + (void) SSL_get_finished(conn->ssl, result, *len); + return result; +} + + /* ------------------------------------------------------------ */ /* OpenSSL specific code */ /* ------------------------------------------------------------ */ diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index 42913604e3..0eb8b60c95 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -453,11 +453,13 @@ struct pg_conn /* Assorted state for SASL, SSL, GSS, etc */ void *sasl_state; + /* SSL structures */ + bool ssl_in_use; + #ifdef USE_SSL bool allow_ssl_try; /* Allowed to try SSL negotiation */ bool wait_ssl_try; /* Delay SSL negotiation until after * attempting normal connection */ - bool ssl_in_use; #ifdef USE_OPENSSL SSL *ssl; /* SSL status, if have SSL connection */ X509 *peer; /* X509 cert of server */ @@ -668,6 +670,7 @@ extern void pgtls_close(PGconn *conn); extern ssize_t pgtls_read(PGconn *conn, void *ptr, size_t len); extern bool pgtls_read_pending(PGconn *conn); extern ssize_t pgtls_write(PGconn *conn, const void *ptr, size_t len); +extern char *pgtls_get_finish(PGconn *conn, int *len); /* * this is so that we can check if a connection is non-blocking internally -- 2.14.1