Skip to content

Commit a3c17b2

Browse files
peterepetere
committed
Distrust external OpenSSL clients; clear err queue
OpenSSL has an unfortunate tendency to mix per-session state error handling with per-thread error handling. This can cause problems when programs that link to libpq with OpenSSL enabled have some other use of OpenSSL; without care, one caller of OpenSSL may cause problems for the other caller. Backend code might similarly be affected, for example when a third party extension independently uses OpenSSL without taking the appropriate precautions. To fix, don't trust other users of OpenSSL to clear the per-thread error queue. Instead, clear the entire per-thread queue ahead of certain I/O operations when it appears that there might be trouble (these I/O operations mostly need to call SSL_get_error() to check for success, which relies on the queue being empty). This is slightly aggressive, but it's pretty clear that the other callers have a very dubious claim to ownership of the per-thread queue. Do this is both frontend and backend code. Finally, be more careful about clearing our own error queue, so as to not cause these problems ourself. It's possibly that control previously did not always reach SSLerrmessage(), where ERR_get_error() was supposed to be called to clear the queue's earliest code. Make sure ERR_get_error() is always called, so as to spare other users of OpenSSL the possibility of similar problems caused by libpq (as opposed to problems caused by a third party OpenSSL library like PHP's OpenSSL extension). Again, do this is both frontend and backend code. See bug #12799 and https://bugs.php.net/bug.php?id=68276 Based on patches by Dave Vitek and Peter Eisentraut. From: Peter Geoghegan <pg@bowt.ie>
1 parent ab32a40 commit a3c17b2

File tree

2 files changed

+102
-45
lines changed

2 files changed

+102
-45
lines changed

‎src/backend/libpq/be-secure-openssl.c

Lines changed: 49 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -78,7 +78,7 @@ static DH *tmp_dh_cb(SSL *s, int is_export, int keylength);
7878
static int verify_cb(int, X509_STORE_CTX *);
7979
static void info_cb(const SSL *ssl, int type, int args);
8080
static void initialize_ecdh(void);
81-
static const char *SSLerrmessage(void);
81+
static const char *SSLerrmessage(unsigned long ecode);
8282

8383
static char *X509_NAME_to_cstring(X509_NAME *name);
8484

@@ -182,7 +182,7 @@ be_tls_init(void)
182182
if (!SSL_context)
183183
ereport(FATAL,
184184
(errmsg("could not create SSL context: %s",
185-
SSLerrmessage())));
185+
SSLerrmessage(ERR_get_error()))));
186186

187187
/*
188188
* Disable OpenSSL's moving-write-buffer sanity check, because it
@@ -198,7 +198,7 @@ be_tls_init(void)
198198
ereport(FATAL,
199199
(errcode(ERRCODE_CONFIG_FILE_ERROR),
200200
errmsg("could not load server certificate file \"%s\": %s",
201-
ssl_cert_file, SSLerrmessage())));
201+
ssl_cert_file, SSLerrmessage(ERR_get_error()))));
202202

203203
if (stat(ssl_key_file, &buf) != 0)
204204
ereport(FATAL,
@@ -228,12 +228,12 @@ be_tls_init(void)
228228
SSL_FILETYPE_PEM) != 1)
229229
ereport(FATAL,
230230
(errmsg("could not load private key file \"%s\": %s",
231-
ssl_key_file, SSLerrmessage())));
231+
ssl_key_file, SSLerrmessage(ERR_get_error()))));
232232

233233
if (SSL_CTX_check_private_key(SSL_context) != 1)
234234
ereport(FATAL,
235235
(errmsg("check of private key failed: %s",
236-
SSLerrmessage())));
236+
SSLerrmessage(ERR_get_error()))));
237237
}
238238

239239
/* set up ephemeral DH keys, and disallow SSL v2/v3 while at it */
@@ -262,7 +262,7 @@ be_tls_init(void)
262262
(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
263263
ereport(FATAL,
264264
(errmsg("could not load root certificate file \"%s\": %s",
265-
ssl_ca_file, SSLerrmessage())));
265+
ssl_ca_file, SSLerrmessage(ERR_get_error()))));
266266
}
267267

268268
/*----------
@@ -293,7 +293,7 @@ be_tls_init(void)
293293
else
294294
ereport(FATAL,
295295
(errmsg("could not load SSL certificate revocation list file \"%s\": %s",
296-
ssl_crl_file, SSLerrmessage())));
296+
ssl_crl_file, SSLerrmessage(ERR_get_error()))));
297297
}
298298
}
299299

@@ -330,6 +330,7 @@ be_tls_open_server(Port *port)
330330
int r;
331331
int err;
332332
int waitfor;
333+
unsigned long ecode;
333334

334335
Assert(!port->ssl);
335336
Assert(!port->peer);
@@ -339,24 +340,44 @@ be_tls_open_server(Port *port)
339340
ereport(COMMERROR,
340341
(errcode(ERRCODE_PROTOCOL_VIOLATION),
341342
errmsg("could not initialize SSL connection: %s",
342-
SSLerrmessage())));
343+
SSLerrmessage(ERR_get_error()))));
343344
return -1;
344345
}
345346
if (!my_SSL_set_fd(port, port->sock))
346347
{
347348
ereport(COMMERROR,
348349
(errcode(ERRCODE_PROTOCOL_VIOLATION),
349350
errmsg("could not set SSL socket: %s",
350-
SSLerrmessage())));
351+
SSLerrmessage(ERR_get_error()))));
351352
return -1;
352353
}
353354
port->ssl_in_use = true;
354355

355356
aloop:
357+
/*
358+
* Prepare to call SSL_get_error() by clearing thread's OpenSSL error
359+
* queue. In general, the current thread's error queue must be empty
360+
* before the TLS/SSL I/O operation is attempted, or SSL_get_error()
361+
* will not work reliably. An extension may have failed to clear the
362+
* per-thread error queue following another call to an OpenSSL I/O
363+
* routine.
364+
*/
365+
ERR_clear_error();
356366
r = SSL_accept(port->ssl);
357367
if (r <= 0)
358368
{
359369
err = SSL_get_error(port->ssl, r);
370+
371+
/*
372+
* Other clients of OpenSSL in the backend may fail to call
373+
* ERR_get_error(), but we always do, so as to not cause problems
374+
* for OpenSSL clients that don't call ERR_clear_error()
375+
* defensively. Be sure that this happens by calling now.
376+
* SSL_get_error() relies on the OpenSSL per-thread error queue
377+
* being intact, so this is the earliest possible point
378+
* ERR_get_error() may be called.
379+
*/
380+
ecode = ERR_get_error();
360381
switch (err)
361382
{
362383
case SSL_ERROR_WANT_READ:
@@ -390,7 +411,7 @@ be_tls_open_server(Port *port)
390411
ereport(COMMERROR,
391412
(errcode(ERRCODE_PROTOCOL_VIOLATION),
392413
errmsg("could not accept SSL connection: %s",
393-
SSLerrmessage())));
414+
SSLerrmessage(ecode))));
394415
break;
395416
case SSL_ERROR_ZERO_RETURN:
396417
ereport(COMMERROR,
@@ -499,10 +520,13 @@ be_tls_read(Port *port, void *ptr, size_t len, int *waitfor)
499520
{
500521
ssize_t n;
501522
int err;
523+
unsigned long ecode;
502524

503525
errno = 0;
526+
ERR_clear_error();
504527
n = SSL_read(port->ssl, ptr, len);
505528
err = SSL_get_error(port->ssl, n);
529+
ecode = (err != SSL_ERROR_NONE || n < 0) ? ERR_get_error() : 0;
506530
switch (err)
507531
{
508532
case SSL_ERROR_NONE:
@@ -529,7 +553,7 @@ be_tls_read(Port *port, void *ptr, size_t len, int *waitfor)
529553
case SSL_ERROR_SSL:
530554
ereport(COMMERROR,
531555
(errcode(ERRCODE_PROTOCOL_VIOLATION),
532-
errmsg("SSL error: %s", SSLerrmessage())));
556+
errmsg("SSL error: %s", SSLerrmessage(ecode))));
533557
/* fall through */
534558
case SSL_ERROR_ZERO_RETURN:
535559
errno = ECONNRESET;
@@ -556,10 +580,13 @@ be_tls_write(Port *port, void *ptr, size_t len, int *waitfor)
556580
{
557581
ssize_t n;
558582
int err;
583+
unsigned long ecode;
559584

560585
errno = 0;
586+
ERR_clear_error();
561587
n = SSL_write(port->ssl, ptr, len);
562588
err = SSL_get_error(port->ssl, n);
589+
ecode = (err != SSL_ERROR_NONE || n < 0) ? ERR_get_error() : 0;
563590
switch (err)
564591
{
565592
case SSL_ERROR_NONE:
@@ -586,7 +613,7 @@ be_tls_write(Port *port, void *ptr, size_t len, int *waitfor)
586613
case SSL_ERROR_SSL:
587614
ereport(COMMERROR,
588615
(errcode(ERRCODE_PROTOCOL_VIOLATION),
589-
errmsg("SSL error: %s", SSLerrmessage())));
616+
errmsg("SSL error: %s", SSLerrmessage(ecode))));
590617
/* fall through */
591618
case SSL_ERROR_ZERO_RETURN:
592619
errno = ECONNRESET;
@@ -742,7 +769,8 @@ load_dh_file(int keylength)
742769
{
743770
if (DH_check(dh, &codes) == 0)
744771
{
745-
elog(LOG, "DH_check error (%s): %s", fnbuf, SSLerrmessage());
772+
elog(LOG, "DH_check error (%s): %s", fnbuf,
773+
SSLerrmessage(ERR_get_error()));
746774
return NULL;
747775
}
748776
if (codes & DH_CHECK_P_NOT_PRIME)
@@ -782,7 +810,7 @@ load_dh_buffer(const char *buffer, size_t len)
782810
if (dh == NULL)
783811
ereport(DEBUG2,
784812
(errmsg_internal("DH load buffer: %s",
785-
SSLerrmessage())));
813+
SSLerrmessage(ERR_get_error()))));
786814
BIO_free(bio);
787815

788816
return dh;
@@ -948,26 +976,26 @@ initialize_ecdh(void)
948976
}
949977

950978
/*
951-
* Obtain reason string for last SSL error
979+
* Obtain reason string for passed SSL errcode
980+
*
981+
* ERR_get_error() is used by caller to get errcode to pass here.
952982
*
953983
* Some caution is needed here since ERR_reason_error_string will
954984
* return NULL if it doesn't recognize the error code. We don't
955985
* want to return NULL ever.
956986
*/
957987
static const char *
958-
SSLerrmessage(void)
988+
SSLerrmessage(unsigned long ecode)
959989
{
960-
unsigned long errcode;
961990
const char *errreason;
962991
static char errbuf[32];
963992

964-
errcode = ERR_get_error();
965-
if (errcode == 0)
993+
if (ecode == 0)
966994
return _("no SSL error reported");
967-
errreason = ERR_reason_error_string(errcode);
995+
errreason = ERR_reason_error_string(ecode);
968996
if (errreason != NULL)
969997
return errreason;
970-
snprintf(errbuf, sizeof(errbuf), _("SSL error code %lu"), errcode);
998+
snprintf(errbuf, sizeof(errbuf), _("SSL error code %lu"), ecode);
971999
return errbuf;
9721000
}
9731001

0 commit comments

Comments
 (0)