From 285613c60a7aff5daaf281c67002483b0d26e715 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 2 Apr 2025 16:41:45 +0300 Subject: [PATCH] libpq: Add min/max_protocol_version connection options All supported version of the PostgreSQL server send the NegotiateProtocolVersion message when an unsupported minor protocol version is requested by a client. But many other applications that implement the PostgreSQL protocol (connection poolers, or other databases) do not, and the same is true for PostgreSQL server versions older than 9.3. Connecting to such other applications thus fails if a client requests a protocol version different than 3.0. This patch adds a max_protocol_version connection option to libpq that specifies the protocol version that libpq should request from the server. Currently only 3.0 is supported, but that will change in a future commit that bumps the protocol version. Even after that version bump the default will likely stay 3.0 for the time being. Once more of the ecosystem supports the NegotiateProtocolVersion message we might want to change the default to the latest minor version. This also adds the similar min_protocol_version connection option, to allow the client to specify that connecting should fail if a lower protocol version is attempted by the server. This can be used to ensure that certain protocol features are used, which can be particularly useful if those features impact security. Author: Jelte Fennema-Nio Reviewed-by: Robert Haas (earlier versions) Discussion: https://www.postgresql.org/message-id/CAGECzQTfc_O%2BHXqAo5_-xG4r3EFVsTefUeQzSvhEyyLDba-O9w@mail.gmail.com Discussion: https://www.postgresql.org/message-id/CAGECzQRbAGqJnnJJxTdKewTsNOovUt4bsx3NFfofz3m2j-t7tA@mail.gmail.com --- doc/src/sgml/libpq.sgml | 68 +++++++++++ doc/src/sgml/protocol.sgml | 33 +++-- src/include/libpq/pqcomm.h | 3 +- src/interfaces/libpq/fe-connect.c | 88 +++++++++++++- src/interfaces/libpq/fe-protocol3.c | 18 +++ src/interfaces/libpq/libpq-int.h | 4 + .../modules/libpq_pipeline/libpq_pipeline.c | 113 +++++++++++++++++- 7 files changed, 315 insertions(+), 12 deletions(-) diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index b359fbff295..d7051190320 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -2144,6 +2144,54 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname + + min_protocol_version + + + Specifies the minimum protocol version to allow for the connection. + The default is to allow any version of the + PostgreSQL protocol supported by libpq, + which currently means 3.0. If the server + does not support at least this protocol version the connection will be + closed. + + + + The current supported values are + 3.0, 3.2, + and latest. The latest value is + equivalent to the latest protocol version supported by the libpq + version being used, which is currently 3.2. + + + + + + max_protocol_version + + + Specifies the protocol version to request from the server. + The default is to use version 3.0 of the + PostgreSQL protocol, unless the connection + string specifies a feature that relies on a higher protocol version, + in which case the latest version supported by libpq is used. If the + server does not support the protocol version requested by the client, + the connection is automatically downgraded to a lower minor protocol + version that the server supports. After the connection attempt has + completed you can use to + find out which exact protocol version was negotiated. + + + + The current supported values are + 3.0, 3.2, + and latest. The latest value is + equivalent to the latest protocol version supported by the libpq + version being used, which is currently 3.2. + + + + ssl_max_protocol_version @@ -9329,6 +9377,26 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough) linkend="libpq-connect-load-balance-hosts"/> connection parameter. + + + + + PGMINPROTOCOLVERSION + + PGMINPROTOCOLVERSION behaves the same as the connection parameter. + + + + + + + PGMAXPROTOCOLVERSION + + PGMAXPROTOCOLVERSION behaves the same as the connection parameter. + + diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index 6008f3ac5f8..628da4cd7cc 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -18,17 +18,23 @@ - This document describes version 3.0 of the protocol, implemented in - PostgreSQL 7.4 and later. For descriptions - of the earlier protocol versions, see previous releases of the - PostgreSQL documentation. A single server + This document describes version 3.2 of the protocol, introduced in + PostgreSQL version 18. The server and the libpq + client library are backwards compatible with protocol version 3.0, + implemented in PostgreSQL 7.4 and later. + For descriptions of earlier protocol versions, see previous releases of the + PostgreSQL documentation. + + + + A single server can support multiple protocol versions. The initial startup-request message tells the server which protocol version the client is attempting to use. If the major version requested by the client is not supported by the server, the connection will be rejected (for example, this would occur if the client requested protocol version 4.0, which does not exist as of this writing). If the minor version requested by the client is not - supported by the server (e.g., the client requests version 3.1, but the + supported by the server (e.g., the client requests version 3.2, but the server supports only 3.0), the server may either reject the connection or may respond with a NegotiateProtocolVersion message containing the highest minor protocol version which it supports. The client may then choose either @@ -36,6 +42,13 @@ to abort the connection. + + The protocol negotiation was introduced in + PostgreSQL version 9.3.21. Earlier versions would + reject the connection if the client requested a minor version that was not + supported by the server. + + In order to serve multiple clients efficiently, the server launches a new backend process for each client. @@ -413,8 +426,14 @@ this message indicates the highest supported minor version. This message will also be sent if the client requested unsupported protocol options (i.e., beginning with _pq_.) in the - startup packet. This message will be followed by an ErrorResponse or - a message indicating the success or failure of authentication. + startup packet. + + + After this message, the authentication will continue using the version + indicated by the server. If the client does not support the older + version, it should immediately close the connection. If the server + does not send this message, it supports the client's requested + protocol version and all the protocol options. diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h index 46b37e0e4eb..0aceb7147c7 100644 --- a/src/include/libpq/pqcomm.h +++ b/src/include/libpq/pqcomm.h @@ -91,11 +91,10 @@ is_unixsock_path(const char *path) /* * The earliest and latest frontend/backend protocol version supported. - * (Only protocol version 3 is currently supported) */ #define PG_PROTOCOL_EARLIEST PG_PROTOCOL(3,0) -#define PG_PROTOCOL_LATEST PG_PROTOCOL(3,0) +#define PG_PROTOCOL_LATEST PG_PROTOCOL(3,2) typedef uint32 ProtocolVersion; /* FE/BE protocol version number */ diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index 0256753bd3e..5e3275ffd76 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -325,6 +325,16 @@ static const internalPQconninfoOption PQconninfoOptions[] = { "Require-Auth", "", 14, /* sizeof("scram-sha-256") == 14 */ offsetof(struct pg_conn, require_auth)}, + {"min_protocol_version", "PGMINPROTOCOLVERSION", + NULL, NULL, + "Min-Protocol-Version", "", 6, /* sizeof("latest") = 6 */ + offsetof(struct pg_conn, min_protocol_version)}, + + {"max_protocol_version", "PGMAXPROTOCOLVERSION", + NULL, NULL, + "Max-Protocol-Version", "", 6, /* sizeof("latest") = 6 */ + offsetof(struct pg_conn, max_protocol_version)}, + {"ssl_min_protocol_version", "PGSSLMINPROTOCOLVERSION", "TLSv1.2", NULL, "SSL-Minimum-Protocol-Version", "", 8, /* sizeof("TLSv1.x") == 8 */ offsetof(struct pg_conn, ssl_min_protocol_version)}, @@ -483,6 +493,7 @@ static void pgpassfileWarning(PGconn *conn); static void default_threadlock(int acquire); static bool sslVerifyProtocolVersion(const char *version); static bool sslVerifyProtocolRange(const char *min, const char *max); +static bool pqParseProtocolVersion(const char *value, ProtocolVersion *result, PGconn *conn, const char *context); /* global variable because fe-auth.c needs to access it */ @@ -2081,6 +2092,48 @@ pqConnectOptions2(PGconn *conn) } } + if (conn->min_protocol_version) + { + if (!pqParseProtocolVersion(conn->min_protocol_version, &conn->min_pversion, conn, "min_protocol_version")) + { + conn->status = CONNECTION_BAD; + return false; + } + } + else + { + conn->min_pversion = PG_PROTOCOL_EARLIEST; + } + + if (conn->max_protocol_version) + { + if (!pqParseProtocolVersion(conn->max_protocol_version, &conn->max_pversion, conn, "max_protocol_version")) + { + conn->status = CONNECTION_BAD; + return false; + } + } + else + { + /* + * To not break connecting to older servers/poolers that do not yet + * support NegotiateProtocolVersion, default to the 3.0 protocol at + * least for a while longer. Except when min_protocol_version is set + * to something larger, then we might as well default to the latest. + */ + if (conn->min_pversion > PG_PROTOCOL(3, 0)) + conn->max_pversion = PG_PROTOCOL_LATEST; + else + conn->max_pversion = PG_PROTOCOL(3, 0); + } + + if (conn->min_pversion > conn->max_pversion) + { + conn->status = CONNECTION_BAD; + libpq_append_conn_error(conn, "min_protocol_version is greater than max_protocol_version"); + return false; + } + /* * Resolve special "auto" client_encoding from the locale */ @@ -3084,7 +3137,7 @@ keep_going: /* We will come back to here until there is * must persist across individual connection attempts, but we must * reset them when we start to consider a new server. */ - conn->pversion = PG_PROTOCOL(3, 0); + conn->pversion = conn->max_pversion; conn->send_appname = true; conn->failed_enc_methods = 0; conn->current_enc_method = 0; @@ -4102,6 +4155,7 @@ keep_going: /* We will come back to here until there is /* OK, we read the message; mark data consumed */ pqParseDone(conn, conn->inCursor); + goto keep_going; } @@ -8157,6 +8211,38 @@ error: return false; } +/* + * Parse and try to interpret "value" as a ProtocolVersion value, and if + * successful, store it in *result. + */ +static bool +pqParseProtocolVersion(const char *value, ProtocolVersion *result, PGconn *conn, + const char *context) +{ + if (strcmp(value, "latest") == 0) + { + *result = PG_PROTOCOL_LATEST; + return true; + } + if (strcmp(value, "3.0") == 0) + { + *result = PG_PROTOCOL(3, 0); + return true; + } + + /* 3.1 never existed, we went straight from 3.0 to 3.2 */ + + if (strcmp(value, "3.2") == 0) + { + *result = PG_PROTOCOL(3, 2); + return true; + } + + libpq_append_conn_error(conn, "invalid %s value: \"%s\"", + context, value); + return false; +} + /* * To keep the API consistent, the locking stubs are always provided, even * if they are not required. diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c index 43e3519e4bd..7ba49ea4592 100644 --- a/src/interfaces/libpq/fe-protocol3.c +++ b/src/interfaces/libpq/fe-protocol3.c @@ -1432,6 +1432,13 @@ pqGetNegotiateProtocolVersion3(PGconn *conn) goto failure; } + /* 3.1 never existed, we went straight from 3.0 to 3.2 */ + if (their_version == PG_PROTOCOL(3, 1)) + { + libpq_append_conn_error(conn, "received invalid protocol negotiation message: server requests downgrade to non-existent 3.1 protocol version"); + goto failure; + } + if (num < 0) { libpq_append_conn_error(conn, "received invalid protocol negotiation message: server reported negative number of unsupported parameters"); @@ -1444,6 +1451,17 @@ pqGetNegotiateProtocolVersion3(PGconn *conn) goto failure; } + if (their_version < conn->min_pversion) + { + libpq_append_conn_error(conn, "server only supports protocol version %d.%d, but min_protocol_version was set to %d.%d", + PG_PROTOCOL_MAJOR(their_version), + PG_PROTOCOL_MINOR(their_version), + PG_PROTOCOL_MAJOR(conn->min_pversion), + PG_PROTOCOL_MINOR(conn->min_pversion)); + + goto failure; + } + /* the version is acceptable */ conn->pversion = their_version; diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index d9f2e9ad743..232e0b00f75 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -417,6 +417,8 @@ struct pg_conn char *gsslib; /* What GSS library to use ("gssapi" or * "sspi") */ char *gssdelegation; /* Try to delegate GSS credentials? (0 or 1) */ + char *min_protocol_version; /* minimum used protocol version */ + char *max_protocol_version; /* maximum used protocol version */ char *ssl_min_protocol_version; /* minimum TLS protocol version */ char *ssl_max_protocol_version; /* maximum TLS protocol version */ char *target_session_attrs; /* desired session properties */ @@ -539,6 +541,8 @@ struct pg_conn void *scram_client_key_binary; /* binary SCRAM client key */ size_t scram_server_key_len; void *scram_server_key_binary; /* binary SCRAM server key */ + ProtocolVersion min_pversion; /* protocol version to request */ + ProtocolVersion max_pversion; /* protocol version to request */ /* Miscellaneous stuff */ int be_pid; /* PID of backend --- needed for cancels */ diff --git a/src/test/modules/libpq_pipeline/libpq_pipeline.c b/src/test/modules/libpq_pipeline/libpq_pipeline.c index ac9ac95135f..9a3c0236325 100644 --- a/src/test/modules/libpq_pipeline/libpq_pipeline.c +++ b/src/test/modules/libpq_pipeline/libpq_pipeline.c @@ -206,15 +206,17 @@ copy_connection(PGconn *conn) PQconninfoOption *opts = PQconninfo(conn); const char **keywords; const char **vals; - int nopts = 1; - int i = 0; + int nopts = 0; + int i; for (PQconninfoOption *opt = opts; opt->keyword != NULL; ++opt) nopts++; + nopts++; /* for the NULL terminator */ keywords = pg_malloc(sizeof(char *) * nopts); vals = pg_malloc(sizeof(char *) * nopts); + i = 0; for (PQconninfoOption *opt = opts; opt->keyword != NULL; ++opt) { if (opt->val) @@ -1405,6 +1407,110 @@ test_prepared(PGconn *conn) fprintf(stderr, "ok\n"); } +/* + * Test max_protocol_version options. + */ +static void +test_protocol_version(PGconn *conn) +{ + const char **keywords; + const char **vals; + int nopts; + PQconninfoOption *opts = PQconninfo(conn); + int protocol_version; + int max_protocol_version_index; + int i; + + /* + * Prepare keywords/vals arrays, copied from the existing connection, with + * an extra slot for 'max_protocol_version'. + */ + nopts = 0; + for (PQconninfoOption *opt = opts; opt->keyword != NULL; ++opt) + nopts++; + nopts++; /* max_protocol_version */ + nopts++; /* NULL terminator */ + + keywords = pg_malloc0(sizeof(char *) * nopts); + vals = pg_malloc0(sizeof(char *) * nopts); + + i = 0; + for (PQconninfoOption *opt = opts; opt->keyword != NULL; ++opt) + { + if (opt->val) + { + keywords[i] = opt->keyword; + vals[i] = opt->val; + i++; + } + } + + max_protocol_version_index = i; + keywords[i] = "max_protocol_version"; /* value is filled in below */ + i++; + keywords[i] = vals[i] = NULL; + + /* + * Test max_protocol_version=3.0 + */ + vals[max_protocol_version_index] = "3.0"; + conn = PQconnectdbParams(keywords, vals, false); + + if (PQstatus(conn) != CONNECTION_OK) + pg_fatal("Connection to database failed: %s", + PQerrorMessage(conn)); + + protocol_version = PQfullProtocolVersion(conn); + if (protocol_version != 30000) + pg_fatal("expected 30000, got %d", protocol_version); + + PQfinish(conn); + + /* + * Test max_protocol_version=3.1. It's not valid, we went straight from + * 3.0 to 3.2. + */ + vals[max_protocol_version_index] = "3.1"; + conn = PQconnectdbParams(keywords, vals, false); + + if (PQstatus(conn) != CONNECTION_BAD) + pg_fatal("Connecting with max_protocol_version 3.1 should have failed."); + + PQfinish(conn); + + /* + * Test max_protocol_version=3.2 + */ + vals[max_protocol_version_index] = "3.2"; + conn = PQconnectdbParams(keywords, vals, false); + + if (PQstatus(conn) != CONNECTION_OK) + pg_fatal("Connection to database failed: %s", + PQerrorMessage(conn)); + + protocol_version = PQfullProtocolVersion(conn); + if (protocol_version != 30002) + pg_fatal("expected 30002, got %d", protocol_version); + + PQfinish(conn); + + /* + * Test max_protocol_version=latest. 'latest' currently means '3.2'. + */ + vals[max_protocol_version_index] = "latest"; + conn = PQconnectdbParams(keywords, vals, false); + + if (PQstatus(conn) != CONNECTION_OK) + pg_fatal("Connection to database failed: %s", + PQerrorMessage(conn)); + + protocol_version = PQfullProtocolVersion(conn); + if (protocol_version != 30002) + pg_fatal("expected 30002, got %d", protocol_version); + + PQfinish(conn); +} + /* Notice processor: print notices, and count how many we got */ static void notice_processor(void *arg, const char *message) @@ -2153,6 +2259,7 @@ print_test_list(void) printf("pipeline_idle\n"); printf("pipelined_insert\n"); printf("prepared\n"); + printf("protocol_version\n"); printf("simple_pipeline\n"); printf("singlerow\n"); printf("transaction\n"); @@ -2263,6 +2370,8 @@ main(int argc, char **argv) test_pipelined_insert(conn, numrows); else if (strcmp(testname, "prepared") == 0) test_prepared(conn); + else if (strcmp(testname, "protocol_version") == 0) + test_protocol_version(conn); else if (strcmp(testname, "simple_pipeline") == 0) test_simple_pipeline(conn); else if (strcmp(testname, "singlerow") == 0) -- 2.30.2