NAME¶
CRYPTO_THREADID_set_callback, CRYPTO_THREADID_get_callback,
CRYPTO_THREADID_current, CRYPTO_THREADID_cmp, CRYPTO_THREADID_cpy,
CRYPTO_THREADID_hash, CRYPTO_set_locking_callback, CRYPTO_num_locks,
CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread support
SYNOPSIS¶
#include <openssl/crypto.h>
/* Don't use this structure directly. */
typedef struct crypto_threadid_st
{
void *ptr;
unsigned long val;
} CRYPTO_THREADID;
/* Only use CRYPTO_THREADID_set_[numeric|pointer]() within callbacks */
void CRYPTO_THREADID_set_numeric(CRYPTO_THREADID *id, unsigned long val);
void CRYPTO_THREADID_set_pointer(CRYPTO_THREADID *id, void *ptr);
int CRYPTO_THREADID_set_callback(void (*threadid_func)(CRYPTO_THREADID *));
void (*CRYPTO_THREADID_get_callback(void))(CRYPTO_THREADID *);
void CRYPTO_THREADID_current(CRYPTO_THREADID *id);
int CRYPTO_THREADID_cmp(const CRYPTO_THREADID *a,
const CRYPTO_THREADID *b);
void CRYPTO_THREADID_cpy(CRYPTO_THREADID *dest,
const CRYPTO_THREADID *src);
unsigned long CRYPTO_THREADID_hash(const CRYPTO_THREADID *id);
int CRYPTO_num_locks(void);
/* struct CRYPTO_dynlock_value needs to be defined by the user */
struct CRYPTO_dynlock_value;
void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
(*dyn_create_function)(char *file, int line));
void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
(int mode, struct CRYPTO_dynlock_value *l,
const char *file, int line));
void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
(struct CRYPTO_dynlock_value *l, const char *file, int line));
int CRYPTO_get_new_dynlockid(void);
void CRYPTO_destroy_dynlockid(int i);
void CRYPTO_lock(int mode, int n, const char *file, int line);
#define CRYPTO_w_lock(type) \
CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
#define CRYPTO_w_unlock(type) \
CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
#define CRYPTO_r_lock(type) \
CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__)
#define CRYPTO_r_unlock(type) \
CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__)
#define CRYPTO_add(addr,amount,type) \
CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
DESCRIPTION¶
OpenSSL can safely be used in multi-threaded applications provided that at least
two callback functions are set, locking_function and threadid_func.
locking_function(int mode, int n, const char *file, int line) is needed to
perform locking on shared data structures. (Note that OpenSSL uses a number of
global data structures that will be implicitly shared whenever multiple
threads use OpenSSL.) Multi-threaded applications will crash at random if it
is not set.
locking_function() must be able to handle up to
CRYPTO_num_locks()
different mutex locks. It sets the
n-th lock if
mode &
CRYPTO_LOCK, and releases it otherwise.
file and
line are the file number of the function setting the
lock. They can be useful for debugging.
threadid_func(CRYPTO_THREADID *id) is needed to record the currently-executing
thread's identifier into
id. The implementation of this callback should
not fill in
id directly, but should use
CRYPTO_THREADID_set_numeric() if thread IDs are numeric, or
CRYPTO_THREADID_set_pointer() if they are pointer-based. If the
application does not register such a callback using
CRYPTO_THREADID_set_callback(), then a default implementation is used -
on Windows and BeOS this uses the system's default thread identifying APIs,
and on all other platforms it uses the address of
errno. The latter is
satisfactory for thread-safety if and only if the platform has a thread-local
error number facility.
Once
threadid_func() is registered, or if the built-in default
implementation is to be used;
- •
- CRYPTO_THREADID_current() records the currently-executing thread ID
into the given id object.
- •
- CRYPTO_THREADID_cmp() compares two thread IDs (returning zero for
equality, ie. the same semantics as memcmp()).
- •
- CRYPTO_THREADID_cpy() duplicates a thread ID value,
- •
- CRYPTO_THREADID_hash() returns a numeric value usable as a
hash-table key. This is usually the exact numeric or pointer-based thread
ID used internally, however this also handles the unusual case where
pointers are larger than 'long' variables and the platform's thread IDs
are pointer-based - in this case, mixing is done to attempt to produce a
unique numeric value even though it is not as wide as the platform's true
thread IDs.
Additionally, OpenSSL supports dynamic locks, and sometimes, some parts of
OpenSSL need it for better performance. To enable this, the following is
required:
- •
- Three additional callback function, dyn_create_function, dyn_lock_function
and dyn_destroy_function.
- •
- A structure defined with the data that each lock needs to handle.
struct CRYPTO_dynlock_value has to be defined to contain whatever structure is
needed to handle locks.
dyn_create_function(const char *file, int line) is needed to create a lock.
Multi-threaded applications might crash at random if it is not set.
dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line) is
needed to perform locking off dynamic lock numbered n. Multi-threaded
applications might crash at random if it is not set.
dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is needed to
destroy the lock l. Multi-threaded applications might crash at random if it is
not set.
CRYPTO_get_new_dynlockid() is used to create locks. It will call
dyn_create_function for the actual creation.
CRYPTO_destroy_dynlockid() is used to destroy locks. It will call
dyn_destroy_function for the actual destruction.
CRYPTO_lock() is used to lock and unlock the locks. mode is a bitfield
describing what should be done with the lock. n is the number of the lock as
returned from
CRYPTO_get_new_dynlockid(). mode can be combined from the
following values. These values are pairwise exclusive, with undefined
behaviour if misused (for example, CRYPTO_READ and CRYPTO_WRITE should not be
used together):
CRYPTO_LOCK 0x01
CRYPTO_UNLOCK 0x02
CRYPTO_READ 0x04
CRYPTO_WRITE 0x08
RETURN VALUES¶
CRYPTO_num_locks() returns the required number of locks.
CRYPTO_get_new_dynlockid() returns the index to the newly created lock.
The other functions return no values.
NOTES¶
You can find out if OpenSSL was configured with thread support:
#define OPENSSL_THREAD_DEFINES
#include <openssl/opensslconf.h>
#if defined(OPENSSL_THREADS)
// thread support enabled
#else
// no thread support
#endif
Also, dynamic locks are currently not used internally by OpenSSL, but may do so
in the future.
EXAMPLES¶
crypto/threads/mttest.c shows examples of the callback functions on
Solaris, Irix and Win32.
HISTORY¶
CRYPTO_set_locking_callback() is available in all versions of SSLeay and
OpenSSL.
CRYPTO_num_locks() was added in OpenSSL 0.9.4. All functions
dealing with dynamic locks were added in OpenSSL 0.9.5b-dev.
CRYPTO_THREADID and associated functions were introduced in OpenSSL
1.0.0 to replace (actually, deprecate) the previous
CRYPTO_set_id_callback(),
CRYPTO_get_id_callback(), and
CRYPTO_thread_id() functions which assumed thread IDs to always be
represented by 'unsigned long'.
SEE ALSO¶
crypto(3)