From b63dd3d88f479947ef7fb7cbf5db27de66ae0654 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 27 Jun 2020 12:47:58 -0400 Subject: [PATCH] Add hints about protocol-version-related SSL connection failures. OpenSSL's native reports about problems related to protocol version restrictions are pretty opaque and inconsistent. When we get an SSL error that is plausibly due to this, emit a hint message that includes the range of SSL protocol versions we (think we) are allowing. This should at least get the user thinking in the right direction to resolve the problem, even if the hint isn't totally accurate, which it might not be for assorted reasons. Back-patch to v13 where we increased the default minimum protocol version, thereby increasing the risk of this class of failure. Patch by me, reviewed by Daniel Gustafsson Discussion: https://postgr.es/m/a9408304-4381-a5af-d259-e55d349ae4ce@2ndquadrant.com --- src/backend/libpq/be-secure-openssl.c | 67 +++++++++++++++++++++++- src/include/common/openssl.h | 23 +++++++- src/interfaces/libpq/fe-secure-openssl.c | 39 ++++++++++++++ 3 files changed, 127 insertions(+), 2 deletions(-) diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c index 8adf64c78e..d1cf455ab4 100644 --- a/src/backend/libpq/be-secure-openssl.c +++ b/src/backend/libpq/be-secure-openssl.c @@ -72,6 +72,7 @@ static bool dummy_ssl_passwd_cb_called = false; static bool ssl_is_server_start; static int ssl_protocol_version_to_openssl(int v); +static const char *ssl_protocol_version_to_string(int v); /* ------------------------------------------------------------ */ /* Public interface */ @@ -365,6 +366,7 @@ be_tls_open_server(Port *port) int err; int waitfor; unsigned long ecode; + bool give_proto_hint; Assert(!port->ssl); Assert(!port->peer); @@ -451,10 +453,50 @@ aloop: errmsg("could not accept SSL connection: EOF detected"))); break; case SSL_ERROR_SSL: + switch (ERR_GET_REASON(ecode)) + { + /* + * UNSUPPORTED_PROTOCOL, WRONG_VERSION_NUMBER, and + * TLSV1_ALERT_PROTOCOL_VERSION have been observed + * when trying to communicate with an old OpenSSL + * library, or when the client and server specify + * disjoint protocol ranges. NO_PROTOCOLS_AVAILABLE + * occurs if there's a local misconfiguration (which + * can happen despite our checks, if openssl.cnf + * injects a limit we didn't account for). It's not + * very clear what would make OpenSSL return the other + * codes listed here, but a hint about protocol + * versions seems like it's appropriate for all. + */ + case SSL_R_NO_PROTOCOLS_AVAILABLE: + case SSL_R_UNSUPPORTED_PROTOCOL: + case SSL_R_BAD_PROTOCOL_VERSION_NUMBER: + case SSL_R_UNKNOWN_PROTOCOL: + case SSL_R_UNKNOWN_SSL_VERSION: + case SSL_R_UNSUPPORTED_SSL_VERSION: + case SSL_R_VERSION_TOO_HIGH: + case SSL_R_VERSION_TOO_LOW: + case SSL_R_WRONG_SSL_VERSION: + case SSL_R_WRONG_VERSION_NUMBER: + case SSL_R_TLSV1_ALERT_PROTOCOL_VERSION: + give_proto_hint = true; + break; + default: + give_proto_hint = false; + break; + } ereport(COMMERROR, (errcode(ERRCODE_PROTOCOL_VIOLATION), errmsg("could not accept SSL connection: %s", - SSLerrmessage(ecode)))); + SSLerrmessage(ecode)), + give_proto_hint ? + errhint("This may indicate that the client does not support any SSL protocol version between %s and %s.", + ssl_min_protocol_version ? + ssl_protocol_version_to_string(ssl_min_protocol_version) : + MIN_OPENSSL_TLS_VERSION, + ssl_max_protocol_version ? + ssl_protocol_version_to_string(ssl_max_protocol_version) : + MAX_OPENSSL_TLS_VERSION) : 0)); break; case SSL_ERROR_ZERO_RETURN: ereport(COMMERROR, @@ -1328,6 +1370,29 @@ ssl_protocol_version_to_openssl(int v) return -1; } +/* + * Likewise provide a mapping to strings. + */ +static const char * +ssl_protocol_version_to_string(int v) +{ + switch (v) + { + case PG_TLS_ANY: + return "any"; + case PG_TLS1_VERSION: + return "TLSv1"; + case PG_TLS1_1_VERSION: + return "TLSv1.1"; + case PG_TLS1_2_VERSION: + return "TLSv1.2"; + case PG_TLS1_3_VERSION: + return "TLSv1.3"; + } + + return "(unrecognized)"; +} + static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart) diff --git a/src/include/common/openssl.h b/src/include/common/openssl.h index 47fa129994..9d1c681d9f 100644 --- a/src/include/common/openssl.h +++ b/src/include/common/openssl.h @@ -17,12 +17,33 @@ #ifdef USE_OPENSSL #include +/* + * OpenSSL doesn't provide any very nice way to identify the min/max + * protocol versions the library supports, so we fake it as best we can. + * Note in particular that this doesn't account for restrictions that + * might be specified in the installation's openssl.cnf. + * + * We disable SSLv3 and older in library setup, so TLSv1 is the oldest + * protocol version of interest. + */ +#define MIN_OPENSSL_TLS_VERSION "TLSv1" + +#if defined(TLS1_3_VERSION) +#define MAX_OPENSSL_TLS_VERSION "TLSv1.3" +#elif defined(TLS1_2_VERSION) +#define MAX_OPENSSL_TLS_VERSION "TLSv1.2" +#elif defined(TLS1_1_VERSION) +#define MAX_OPENSSL_TLS_VERSION "TLSv1.1" +#else +#define MAX_OPENSSL_TLS_VERSION "TLSv1" +#endif + /* src/common/protocol_openssl.c */ #ifndef SSL_CTX_set_min_proto_version extern int SSL_CTX_set_min_proto_version(SSL_CTX *ctx, int version); extern int SSL_CTX_set_max_proto_version(SSL_CTX *ctx, int version); #endif -#endif +#endif /* USE_OPENSSL */ #endif /* COMMON_OPENSSL_H */ diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c index 2d813ef5f9..b5b2006b75 100644 --- a/src/interfaces/libpq/fe-secure-openssl.c +++ b/src/interfaces/libpq/fe-secure-openssl.c @@ -1304,6 +1304,45 @@ open_client_SSL(PGconn *conn) libpq_gettext("SSL error: %s\n"), err); SSLerrfree(err); + switch (ERR_GET_REASON(ecode)) + { + /* + * UNSUPPORTED_PROTOCOL, WRONG_VERSION_NUMBER, and + * TLSV1_ALERT_PROTOCOL_VERSION have been observed + * when trying to communicate with an old OpenSSL + * library, or when the client and server specify + * disjoint protocol ranges. + * NO_PROTOCOLS_AVAILABLE occurs if there's a + * local misconfiguration (which can happen + * despite our checks, if openssl.cnf injects a + * limit we didn't account for). It's not very + * clear what would make OpenSSL return the other + * codes listed here, but a hint about protocol + * versions seems like it's appropriate for all. + */ + case SSL_R_NO_PROTOCOLS_AVAILABLE: + case SSL_R_UNSUPPORTED_PROTOCOL: + case SSL_R_BAD_PROTOCOL_VERSION_NUMBER: + case SSL_R_UNKNOWN_PROTOCOL: + case SSL_R_UNKNOWN_SSL_VERSION: + case SSL_R_UNSUPPORTED_SSL_VERSION: + case SSL_R_VERSION_TOO_HIGH: + case SSL_R_VERSION_TOO_LOW: + case SSL_R_WRONG_SSL_VERSION: + case SSL_R_WRONG_VERSION_NUMBER: + case SSL_R_TLSV1_ALERT_PROTOCOL_VERSION: + appendPQExpBuffer(&conn->errorMessage, + libpq_gettext("This may indicate that the server does not support any SSL protocol version between %s and %s.\n"), + conn->ssl_min_protocol_version ? + conn->ssl_min_protocol_version : + MIN_OPENSSL_TLS_VERSION, + conn->ssl_max_protocol_version ? + conn->ssl_max_protocol_version : + MAX_OPENSSL_TLS_VERSION); + break; + default: + break; + } pgtls_close(conn); return PGRES_POLLING_FAILED; }