NAME
ERR —
OpenSSL error codes
SYNOPSIS
#include
<openssl/err.h>
DESCRIPTION
When a call to the OpenSSL library fails, this is usually signaled
by the return value, and an error code is stored in an error queue
associated with the current thread. The ERR library
provides functions to obtain these error codes and textual error messages.
The
ERR_get_error(3) manpage describes how to access error
codes.
Error codes contain information about where the error occurred, and what went wrong. ERR_GET_LIB(3) describes how to extract this information. A method to obtain human-readable error messages is described in ERR_error_string(3).
ERR_clear_error(3) can be used to clear the error queue.
Note that ERR_remove_state(3) should be used to avoid memory leaks when threads are terminated.
ADDING NEW ERROR CODES TO OPENSSL
See ERR_put_error(3) if you want to record error codes in the OpenSSL error system from within your application.
The remainder of this section is of interest only if you want to add new error codes to OpenSSL or add error codes from external libraries.
When you are using new function or reason codes, run make errors. The necessary #defines will then automatically be added to the sub-library's header file.
Adding new libraries
When adding a new sub-library to OpenSSL, assign it a library
number ERR_LIB_XXX, define a macro
XXXerr()
(both in <openssl/err.h>),
add its name to ERR_str_libraries[] (in
/usr/src/lib/libcrypto/err/err.c), and add
ERR_load_XXX_strings()
to the
ERR_load_crypto_strings()
function (in
/usr/src/lib/libcrypto/err/err_all.c).
Finally, add an entry
L XXX xxx.h xxx_err.cto /usr/src/lib/libcrypto/err/openssl.ec, and add xxx_err.c to the Makefile. Running make errors will then generate a file xxx_err.c, and add all error codes used in the library to xxx.h.
Additionally the library include file must have a certain form. Typically it will initially look like this:
#ifndef HEADER_XXX_H
#define HEADER_XXX_H
#ifdef __cplusplus
extern "C" {
#endif
/* Include files */
#include <openssl/bio.h>
#include <openssl/x509.h>
/* Macros, structures and function prototypes */
/* BEGIN ERROR CODES */
The BEGIN ERROR CODES sequence is used by the error code generation script as the point to place new error codes. Any text after this point will be overwritten when make errors is run. The closing #endif etc. will be automatically added by the script.
The generated C error code file xxx_err.c
will load the header files
<stdio.h>,
<openssl/err.h> and
<openssl/xxx.h> so the
header file must load any additional header files containing any definitions
it uses.
USING ERROR CODES IN EXTERNAL LIBRARIES
It is also possible to use OpenSSL's error code scheme in external libraries. The library needs to load its own codes and call the OpenSSL error code insertion script mkerr.pl explicitly to add codes to the header file and generate the C error code file. This will normally be done if the external library needs to generate new ASN.1 structures but it can also be used to add more general purpose error code handling.
INTERNALS
The error queues are stored in a hash table with one
ERR_STATE entry for each PID.
ERR_get_state()
returns the current thread's ERR_STATE. An
ERR_STATE can hold up to
ERR_NUM_ERRORS error codes. When more error codes
are added, the old ones are overwritten, on the assumption that the most
recent errors are most important.
Error strings are also stored in a
hash table. The hash tables can be obtained by calling
ERR_get_err_state_table()
and
ERR_get_string_table().
SEE ALSO
ERR_clear_error(3), ERR_error_string(3), ERR_get_error(3), ERR_GET_LIB(3), ERR_load_crypto_strings(3), ERR_load_strings(3), ERR_print_errors(3), ERR_put_error(3), ERR_remove_state(3), ERR_set_mark(3), SSL_get_error(3)