openssl/crypto/bio/bio_meth.c

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/*
* Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "bio_local.h"
#include "internal/thread_once.h"
CRYPTO_RWLOCK *bio_type_lock = NULL;
static CRYPTO_ONCE bio_type_init = CRYPTO_ONCE_STATIC_INIT;
DEFINE_RUN_ONCE_STATIC(do_bio_type_init)
{
Revert the crypto "global lock" implementation Conceptually, this is a squashed version of: Revert "Address feedback" This reverts commit 75551e07bd2339dfea06ef1d31d69929e13a4495. and Revert "Add CRYPTO_thread_glock_new" This reverts commit ed6b2c7938ec6f07b15745d4183afc276e74c6dd. But there were some intervening commits that made neither revert apply cleanly, so instead do it all as one shot. The crypto global locks were an attempt to cope with the awkward POSIX semantics for pthread_atfork(); its documentation (the "RATIONALE" section) indicates that the expected usage is to have the prefork handler lock all "global" locks, and the parent and child handlers release those locks, to ensure that forking happens with a consistent (lock) state. However, the set of functions available in the child process is limited to async-signal-safe functions, and pthread_mutex_unlock() is not on the list of async-signal-safe functions! The only synchronization primitives that are async-signal-safe are the semaphore primitives, which are not really appropriate for general-purpose usage. However, the state consistency problem that the global locks were attempting to solve is not actually a serious problem, particularly for OpenSSL. That is, we can consider four cases of forking application that might use OpenSSL: (1) Single-threaded, does not call into OpenSSL in the child (e.g., the child calls exec() immediately) For this class of process, no locking is needed at all, since there is only ever a single thread of execution and the only reentrancy is due to signal handlers (which are themselves limited to async-signal-safe operation and should not be doing much work at all). (2) Single-threaded, calls into OpenSSL after fork() The application must ensure that it does not fork() with an unexpected lock held (that is, one that would get unlocked in the parent but accidentally remain locked in the child and cause deadlock). Since OpenSSL does not expose any of its internal locks to the application and the application is single-threaded, the OpenSSL internal locks will be unlocked for the fork(), and the state will be consistent. (OpenSSL will need to reseed its PRNG in the child, but that is an orthogonal issue.) If the application makes use of locks from libcrypto, proper handling for those locks is the responsibility of the application, as for any other locking primitive that is available for application programming. (3) Multi-threaded, does not call into OpenSSL after fork() As for (1), the OpenSSL state is only relevant in the parent, so no particular fork()-related handling is needed. The internal locks are relevant, but there is no interaction with the child to consider. (4) Multi-threaded, calls into OpenSSL after fork() This is the case where the pthread_atfork() hooks to ensure that all global locks are in a known state across fork() would come into play, per the above discussion. However, these "calls into OpenSSL after fork()" are still subject to the restriction to async-signal-safe functions. Since OpenSSL uses all sorts of locking and libc functions that are not on the list of safe functions (e.g., malloc()), this case is not currently usable and is unlikely to ever be usable, independently of the locking situation. So, there is no need to go through contortions to attempt to support this case in the one small area of locking interaction with fork(). In light of the above analysis (thanks @davidben and @achernya), go back to the simpler implementation that does not need to distinguish "library-global" locks or to have complicated atfork handling for locks. Reviewed-by: Kurt Roeckx <kurt@roeckx.be> Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com> (Merged from https://github.com/openssl/openssl/pull/5089)
2018-01-16 15:49:54 +00:00
bio_type_lock = CRYPTO_THREAD_lock_new();
return bio_type_lock != NULL;
}
int BIO_get_new_index(void)
{
static CRYPTO_REF_COUNT bio_count = BIO_TYPE_START;
int newval;
if (!RUN_ONCE(&bio_type_init, do_bio_type_init)) {
BIOerr(BIO_F_BIO_GET_NEW_INDEX, ERR_R_MALLOC_FAILURE);
return -1;
}
if (!CRYPTO_UP_REF(&bio_count, &newval, bio_type_lock))
return -1;
return newval;
}
BIO_METHOD *BIO_meth_new(int type, const char *name)
{
BIO_METHOD *biom = OPENSSL_zalloc(sizeof(BIO_METHOD));
if (biom == NULL
|| (biom->name = OPENSSL_strdup(name)) == NULL) {
OPENSSL_free(biom);
BIOerr(BIO_F_BIO_METH_NEW, ERR_R_MALLOC_FAILURE);
return NULL;
}
biom->type = type;
return biom;
}
void BIO_meth_free(BIO_METHOD *biom)
{
if (biom != NULL) {
OPENSSL_free(biom->name);
OPENSSL_free(biom);
}
}
int (*BIO_meth_get_write(const BIO_METHOD *biom)) (BIO *, const char *, int)
{
return biom->bwrite_old;
}
int (*BIO_meth_get_write_ex(const BIO_METHOD *biom)) (BIO *, const char *, size_t,
size_t *)
{
return biom->bwrite;
}
/* Conversion for old style bwrite to new style */
int bwrite_conv(BIO *bio, const char *data, size_t datal, size_t *written)
{
int ret;
if (datal > INT_MAX)
datal = INT_MAX;
ret = bio->method->bwrite_old(bio, data, (int)datal);
if (ret <= 0) {
*written = 0;
return ret;
}
*written = (size_t)ret;
return 1;
}
int BIO_meth_set_write(BIO_METHOD *biom,
int (*bwrite) (BIO *, const char *, int))
{
biom->bwrite_old = bwrite;
biom->bwrite = bwrite_conv;
return 1;
}
int BIO_meth_set_write_ex(BIO_METHOD *biom,
int (*bwrite) (BIO *, const char *, size_t, size_t *))
{
biom->bwrite_old = NULL;
biom->bwrite = bwrite;
return 1;
}
int (*BIO_meth_get_read(const BIO_METHOD *biom)) (BIO *, char *, int)
{
return biom->bread_old;
}
int (*BIO_meth_get_read_ex(const BIO_METHOD *biom)) (BIO *, char *, size_t, size_t *)
{
return biom->bread;
}
/* Conversion for old style bread to new style */
int bread_conv(BIO *bio, char *data, size_t datal, size_t *readbytes)
{
int ret;
if (datal > INT_MAX)
datal = INT_MAX;
ret = bio->method->bread_old(bio, data, (int)datal);
if (ret <= 0) {
*readbytes = 0;
return ret;
}
*readbytes = (size_t)ret;
return 1;
}
int BIO_meth_set_read(BIO_METHOD *biom,
int (*bread) (BIO *, char *, int))
{
biom->bread_old = bread;
biom->bread = bread_conv;
return 1;
}
int BIO_meth_set_read_ex(BIO_METHOD *biom,
int (*bread) (BIO *, char *, size_t, size_t *))
{
biom->bread_old = NULL;
biom->bread = bread;
return 1;
}
int (*BIO_meth_get_puts(const BIO_METHOD *biom)) (BIO *, const char *)
{
return biom->bputs;
}
int BIO_meth_set_puts(BIO_METHOD *biom,
int (*bputs) (BIO *, const char *))
{
biom->bputs = bputs;
return 1;
}
int (*BIO_meth_get_gets(const BIO_METHOD *biom)) (BIO *, char *, int)
{
return biom->bgets;
}
int BIO_meth_set_gets(BIO_METHOD *biom,
int (*bgets) (BIO *, char *, int))
{
biom->bgets = bgets;
return 1;
}
long (*BIO_meth_get_ctrl(const BIO_METHOD *biom)) (BIO *, int, long, void *)
{
return biom->ctrl;
}
int BIO_meth_set_ctrl(BIO_METHOD *biom,
long (*ctrl) (BIO *, int, long, void *))
{
biom->ctrl = ctrl;
return 1;
}
int (*BIO_meth_get_create(const BIO_METHOD *biom)) (BIO *)
{
return biom->create;
}
int BIO_meth_set_create(BIO_METHOD *biom, int (*create) (BIO *))
{
biom->create = create;
return 1;
}
int (*BIO_meth_get_destroy(const BIO_METHOD *biom)) (BIO *)
{
return biom->destroy;
}
int BIO_meth_set_destroy(BIO_METHOD *biom, int (*destroy) (BIO *))
{
biom->destroy = destroy;
return 1;
}
long (*BIO_meth_get_callback_ctrl(const BIO_METHOD *biom)) (BIO *, int, BIO_info_cb *)
{
return biom->callback_ctrl;
}
int BIO_meth_set_callback_ctrl(BIO_METHOD *biom,
long (*callback_ctrl) (BIO *, int,
BIO_info_cb *))
{
biom->callback_ctrl = callback_ctrl;
return 1;
}