1 This is /home/wk/s/libksba/doc/ksba.info, produced by makeinfo version
2 4.13 from /home/wk/s/libksba/doc/ksba.texi.
4 INFO-DIR-SECTION GNU libraries
6 * libksba: (ksba). An X.509 Library.
9 This file documents the KSBA library to access X.509 and CMS data
12 This is edition 1.3.2, last updated 15 March 2013, of `The KSBA
13 Reference Manual', for Version 1.3.2.
15 Copyright (C) 2002, 2003, 2004 g10 Code GmbH
17 Permission is granted to copy, distribute and/or modify this document
18 under the terms of the GNU General Public License as published by the
19 Free Software Foundation; either version 3 of the License, or (at your
20 option) any later version. The text of the license can be found in the
21 section entitled "Copying".
24 File: ksba.info, Node: Top, Next: Introduction, Up: (dir)
29 This is edition 1.3.2, last updated 15 March 2013, of `The KSBA
30 Reference Manual', for Version 1.3.2 of the KSBA library.
32 Copyright (C) 2002, 2003, 2004 g10 Code GmbH
34 Permission is granted to copy, distribute and/or modify this document
35 under the terms of the GNU General Public License as published by the
36 Free Software Foundation; either version 3 of the License, or (at your
37 option) any later version. The text of the license can be found in the
38 section entitled "Copying".
42 * Introduction:: How to use this manual.
43 * Preparation:: What you should do before using the library.
44 * Certificate Handling:: How to work with X.509 certificates.
45 * CMS:: How to work with CMS (PKCS#7) messages.
46 * CRLs:: How to work with Certificate Revocation Lists.
47 * PKCS10:: How to request certificates.
48 * Utilities:: Various utility functions.
49 * Error Handling:: Error numbers and their meanings.
53 * Component Labels:: Labels used in string representations.
54 * Copying:: The GNU General Public License says how you
55 can copy and share this manual.
59 * Concept Index:: Index of concepts and programs.
60 * Function and Data Index:: Index of functions, variables and data types.
62 --- The Detailed Node Listing ---
73 * Building the source::
77 * Creating certificates:: How to create a certificate object.
78 * Retrieving attributes:: How to get the attributes of a certificate.
79 * Setting attributes:: How to set certificates attributes.
80 * User data:: How to associate other data with a certificate.
82 Mastering the Cryptographic Message Syntax
88 File: ksba.info, Node: Introduction, Next: Preparation, Prev: Top, Up: Top
93 KSBA is a library to make the task of working with X.509 certificates,
94 CMS data and related data more easy.
103 File: ksba.info, Node: Getting Started, Next: Features, Up: Introduction
108 This manual documents the `KSBA' library programming interface. All
109 functions and data types provided by the library are explained.
111 The reader is assumed to possess basic knowledge about the
112 implemented protocols.
114 This manual can be used in several ways. If read from the beginning
115 to the end, it gives a good introduction into the library and how it
116 can be used in an application. Forward references are included where
117 necessary. Later on, the manual can be used as a reference manual to
118 get just the information needed about any particular interface of the
119 library. Experienced programmers might want to start looking at the
120 examples at the end of the manual, and then only read up those parts of
121 the interface which are unclear.
124 File: ksba.info, Node: Features, Next: Overview, Prev: Getting Started, Up: Introduction
129 `KSBA' has a couple of advantages over other libraries doing a similar
130 job, and over open coding the protocols in your application directly.
133 Anybody can use, modify, and redistribute it under the terms of
134 the GNU General Public License (*note Copying::).
136 It hides the low level stuff
137 `KSBA' a high level interface to the implemented protocols and
138 presents the data in a consistent way. There is no more need to
139 worry about all the nasty details of the protocols. The API gives
140 the C programmer a more usual way of interacting with the data.
142 It copes with the version details
143 X.509 protocols tend to have many different versions and dialects.
144 Applications must usually cope with all of this and it has to be
145 coded over and over again. `KSBA' hides this by providing just
146 one API which does the Right Thing. Support for new versions and
147 features of the protocols will be added over time.
150 File: ksba.info, Node: Overview, Prev: Features, Up: Introduction
155 The `KSBA' library is thread-safe as long as objects described by one
156 context are only used by one thread at a time. No initialization is
160 File: ksba.info, Node: Preparation, Next: Certificate Handling, Prev: Introduction, Up: Top
165 To use `KSBA', you have to perform some changes to your sources and the
166 build system. The necessary changes are small and explained in the
167 following sections. At the end of this chapter, it is described how the
168 library is initialized, and how the requirements of the library are
175 * Building the source::
178 File: ksba.info, Node: Header, Next: Version Check, Up: Preparation
183 All interfaces (data types and functions) of the library are defined in
184 the header file `ksba.h'. You must include this in all programs using
185 the library, either directly or through some other header file, like
190 The name space of `KSBA' is `ksba_*' for function names, `ksba*' for
191 data types and `KSBA_*' for other symbols. In addition the same name
192 prefixes with one prepended underscore are reserved for internal use
193 and should never be used by an application.
196 File: ksba.info, Node: Version Check, Next: Building the source, Prev: Header, Up: Preparation
201 It is often desirable to check that the version of `KSBA' used is indeed
202 one which fits all requirements. Even with binary compatibility, new
203 features may have been introduced but through peculiarities of the
204 runtime linker an old version gets actually used. So you better check
205 that the version is as expected right after program startup.
207 -- Function: const char * ksba_check_version (const char *REQ_VERSION)
208 Check that the the version of the library is at minimum the one
209 given as a string in REQ_VERSION and return the actual version
210 string of the library; return `NULL' if the condition is not met.
211 If `NULL' is passed to this function, no check is done and only the
212 version string is returned. It is a pretty good idea to run this
213 function as soon as possible, because it may also initializes some
214 subsystems. In a multi-threaded environment if should be called
215 before any more threads are created.
218 File: ksba.info, Node: Building the source, Prev: Version Check, Up: Preparation
220 2.3 Building the source
221 =======================
223 If you want to compile a source file including the `ksba.h' header
224 file, you must make sure that the compiler can find it in the directory
225 hierarchy. This is accomplished by adding the path to the directory in
226 which the header file is located to the compiler's include file search
227 path (via the `-I' option).
229 However, the path to the include file is determined at the time the
230 source is configured. To solve this problem, `KSBA' ships with a small
231 helper program `ksba-config' that knows about the path to the include
232 file and other configuration options. The options that need to be
233 added to the compiler invocation at compile time are output by the
234 `--cflags' option of `ksba-config'. The following example shows how it
235 can be used at the command line:
237 gcc -c foo.c `ksba-config --cflags`
239 Adding the output of `ksba-config --cflags' to the compiler's
240 command line will ensure that the compiler can find the `ksba.h' header
243 A similar problem occurs when linking the program with the library.
244 Again, the compiler has to find the library files. For this to work,
245 the path to the library files has to be added to the library search path
246 (via the `-L' option). For this, the option `--libs' of `ksba-config'
247 can be used. For convenience, this option also outputs all other
248 options that are required to link the program with the `KSBA' libraries
249 (in particular, the `-lksba' option). The example shows how to link
250 `foo.o' with the `KSBA' libraries to a program `foo'.
252 gcc -o foo foo.o `ksba-config --libs`
254 Of course you can also combine both examples to a single command by
255 specifying both options to `ksba-config':
257 gcc -o foo foo.c `ksba-config --cflags --libs`
260 File: ksba.info, Node: Certificate Handling, Next: CMS, Prev: Preparation, Up: Top
262 3 How to work with X.509 certificates.
263 **************************************
265 One of the most complex data formats are the X.509 certificates. KSBA
266 provides an easy to use interface to handle them.
268 -- Data type: ksba_cert_t
269 The `ksba_cert_t' type is a handle for an X.509 certificate.
271 -- Data type: ksba_sexp_t
272 The `ksba_sexp_t' type describes a canonically encoded S-expression
273 stored in a memory buffer. It is alias for `unsigned char *'.
274 Note that a length argument is not required because the length of
275 such an S-expression is intrinsically available.
279 * Creating certificates:: How to create a certificate object.
280 * Retrieving attributes:: How to get the attributes of a certificate.
281 * Setting attributes:: How to set certificates attributes.
282 * User data:: How to associate other data with a certificate.
285 File: ksba.info, Node: Creating certificates, Next: Retrieving attributes, Up: Certificate Handling
287 3.1 How to create a certificate object
288 ======================================
290 This section explains how to create a certificate object, initialize it,
291 copy it and eventually destroy it.
293 -- Function: ksba_cert_t ksba_cert_new (void)
294 The function `ksba_cert_new' creates a new certificate object and
295 returns a handle for it. The certificate object has initially one
298 The only reason why this function may fail is an out-of-memory
299 condition in which case `NULL' is returned. You might then get
300 the actual error code using `gpg_error_from_errno (errno)'.
302 -- Function: void ksba_cert_ref (ksba_cert_t CERT)
303 The function `ksba_cert_ref' bumps the reference counter of the
304 certificate object up by one. Thus an extra `ksba_cert_release' is
305 required to actually release the memory used for the object.
307 -- Function: void ksba_cert_release (ksba_cert_t CERT)
308 The function `ksba_cert_release' reduces the number of references
309 to the certificate object with the handle CERT. If this was the
310 last reference, it will also destroy the object and releases all
311 associated resources. It is okay to pass `NULL' to the function
312 in which case nothing happens.
314 -- Function: gpg_error_t ksba_cert_read_der (ksba_cert_t CERT,
315 ksba_reader_t READER)
316 Read the next certificate from the READER object and store it in
317 the certificate object CERT for future access. The certificate is
318 parsed and rejected if it has any syntactical or semantical error
319 (i.e. does not match the ASN.1 description).
321 The function returns `0' if the operation was successfully
322 performed. An error code is returned on failure.
324 -- Function: gpg_error_t ksba_cert_init_from_mem (ksba_cert_t CERT,
325 const void *BUFFER, size_t LENGTH)
326 Parse the BUFFER which should contain a DER encoded certificate of
327 LENGTH and initialize the certificate object CERT with it. This
328 function is intended as a convenience function to be used when a
329 certificate is already available in a internal memory buffer.
330 This avoids the extra code needed to setup the reader object.
331 Note that CERT must be a valid certificate object.
333 The function returns `0' if the operation was successfully
334 performed. An error code is returned on failure.
337 File: ksba.info, Node: Retrieving attributes, Next: Setting attributes, Prev: Creating certificates, Up: Certificate Handling
339 3.2 How to get the attributes of a certificate
340 ==============================================
342 The functions in this section allow accessing the attributes of a
343 certificate in a well defined manner. An error will be returned if the
344 certificate object has not yet been initialized by means of
345 `ksba_cert_read_der' or `ksba_cert_init_from_mem'.
347 -- Function: const unsigned char * ksba_cert_get_image
348 (ksba_cert_t CERT, size_t *R_LENGTH)
349 This function returns a pointer to the DER encoded buffer with the
350 raw certificate. The length of that buffer gets stored at
351 R_LENGTH. This function is useful to export or store the raw
354 The function returns `NULL' on error or a pointer to a buffer with
355 the raw certificate data. That pointer is only valid as long as
356 the certificate object CERT is valid and has not been
359 -- Function: gpg_error_t ksba_cert_hash (ksba_cert_t CERT, int WHAT,
360 void (*HASHER)(void *, const void *, size_t length),
362 This function feeds the data which is expected to be hashed into
363 the supplied function HASHER, where the first argument passed is
364 HASHER_ARG, the second the pointer to the data to be hashed and
365 the third the length of this data.
367 The function returns `0' on success or an error code when something
368 goes wrong. The HASHER function is not expected to return an
369 error; instead the caller should setup that function in a way to
370 convey encountered errors by means of the HASHER_ARG. Note that a
371 hash function is in general not expected to yield errors anyway.
373 -- Function: const char * ksba_cert_get_digest_algo (ksba_cert_t CERT)
374 Figure out the the digest algorithm used for the signature and
375 return its OID in dotted decimal format. This function is most
376 likely used to setup the hash context before calling
379 The function returns `NULL' for an error; on success a constant
380 string with the OID is returned. This string is valid as long the
381 certificate object is valid.
383 -- Function: ksba_sexp_t ksba_cert_get_serial (ksba_cert_t CERT)
384 The function returns the serial number of the certificate CERT.
385 The serial number is an integer returned as an canonical encoded
386 S-expression with just one element. The caller must free the
387 returned value. The value `NULL' is returned in case of error.
389 -- Function: char * ksba_cert_get_issuer (ksba_cert_t CERT, int IDX)
390 With IDX given as `0', this function returns the Distinguished
391 Name (DN) of the certificate issuer; this usually is the name of a
392 certification authority (CA). The format of the returned string
393 is in accordance with RFC-2253. `NULL' is returned if the DN is
394 not available; This is a severe error and actually should have
395 been caught by the certificate reading function.
397 With IDX greater than zero, the function may be used to enumerate
398 alternate issuer names. The function returns `NULL' when there are
399 no more alternate names. Only alternate names recognized by
400 `libksba' are returned, others are simply skipped. The format of
401 the returned name is either a RFC-2253 formated string which can be
402 detected by checking whether the first character is a letter or
403 digit. RFC-822 conformant email addresses are returned enclosed
404 in angle brackets; the opening angle bracket should be used to
405 detect this. Other formats are returned as an S-Expression in
406 canonical format, so a opening parenthesis should be used to
407 detect this encoding. The name may include binary null characters,
408 thus strlen may return a length shorter than actually used. The
409 real length is implicitly given by the structure of the
410 S-expression, an extra null is appended for safety reasons.
412 The caller must free the returned string using `ksba_free' or
413 whatever function has been registered as a replacement.
415 -- Function: char * ksba_cert_get_subject (ksba_cert_t CERT, int IDX)
416 With IDX given as `0', this function returns the Distinguished
417 Name (DN) of the certificate's subject. The format of the
418 returned string is in accordance with RFC-2253. `NULL' is
419 returned if the DN is not available.
421 With IDX greater than zero, the function may be used to enumerate
422 alternate subject names. The function returns `NULL' when there
423 are no more alternate names. Only alternate names recognized by
424 `libksba' are returned, others are simply skipped. The format of
425 the returned name is either a RFC-2253 formated string which can be
426 detected by checking whether the first character is a letter or
427 digit. RFC-2822 conform email addresses are returned enclosed in
428 angle brackets; the opening angle bracket should be used to detect
429 this. Other formats are returned as an S-Expression in canonical
430 format, so a opening parenthesis should be used to detect this
431 encoding, the name may include binary null characters, thus strlen
432 may return a length shorter than actually used. The real length
433 is implicitly given by the structure of the S-expression, an extra
434 null is appended for safety reasons.
436 The caller must free the returned string using `ksba_free' or
437 whatever function has been registered as a replacement.
439 -- Data type: ksba_isotime_t
440 Due to problems with the C data type `time_t', which will overflow
441 on most 32 bit machines in the year 2038, it was not advisable to
442 use this type for referencing times stored in certificates.
443 Instead, you should use the `ksba_isotime_t' type, which can
444 represent any time since the year 0.
446 It is implemented as a buffer of 16 bytes and may be handled like a
447 standard string. It should be initialized to zero (i.e. the first
448 byte needs to be 0x00) if it does not hold a valid date. Date
449 values themselves are stored in ISO format and assumed to be
450 referenced from UTC. The string with the date value is always
451 guaranteed to be of length 15 and having a format like:
452 `"19610711T172059"'. Note that the `T' is required by ISO rules.
454 A simple assignment of these data types is not a good idea. You
455 may use `strcpy' or better a specialized function like:
458 copy_time (ksba_isotime_t d, const ksba_isotime_t s)
466 For reasons of documentation a special function should also be
467 used to compare such times:
470 cmp_time (const ksba_isotime_t a, const ksba_isotime_t b)
472 return strcmp (a, b);
475 -- Function: gpg_error_t ksba_cert_get_validity
476 (ksba_cert_t CERT, int WHAT, ksba_isotime_t TIMEBUF)
477 Return the validity dates from the certificate. If no value is
478 available an empty date object (i.e. a `strlen' will be stored at
479 TIMEBUF, otherwise it will receive the date. On failure an error
482 To return the `notBefore' date, the value `0' must be supplied for
483 WHAT; `1' yields the `notAfter' value.
485 -- Function: ksba_sexp_t ksba_cert_get_public_key (ksba_cert_t CERT)
486 [This needs to get written - for now please see libksba/src/cert.c]
489 -- Function: ksba_sexp_t ksba_cert_get_sig_val (ksba_cert_t CERT)
490 [This needs to get written - for now please see libksba/src/cert.c]
492 -- Function: gpg_error_t ksba_cert_get_extension
493 (ksba_cert_t CERT, int IDX, char const **R_OID, int *R_CRIT, size_t *R_DEROFF, size_t *R_DERLEN)
494 [This needs to get written - for now please see libksba/src/cert.c]
496 -- Function: gpg_error_t ksba_cert_is_ca
497 (ksba_cert_t CERT, int *R_CA, int *R_PATHLEN)
498 Return information on the basicConstraint (2.5.19.19) of CERT.
499 R_CA receives true if this is a CA and only in that case R_PATHLEN
500 is set to the maximum certification path length or -1 if there is
504 -- Function: gpg_error_t ksba_cert_get_key_usage
505 (ksba_cert_t CERT, unsigned int *R_FLAGS)
506 Get the key usage flags. The function returns `GPG_ERR_NO_DATA' if
507 no key usage is specified. The usage flags are as shown in
508 RFC3280, section 4.2.1.3. The key usage flags are represented by a
509 bitmask, and you can test each bit using symbolic constants, which
510 tells you if that usage is set on the certificate. The constants
513 `KSBA_KEYUSAGE_DIGITAL_SIGNATURE'
514 Usable for digitalSignature.
516 `KSBA_KEYUSAGE_NON_REPUDIATION'
517 Usable for nonRepudiation.
519 `KSBA_KEYUSAGE_KEY_ENCIPHERMENT'
520 Usable for keyEncipherment.
522 `KSBA_KEYUSAGE_DATA_ENCIPHERMENT'
523 Usable for dataEncipherment.
525 `KSBA_KEYUSAGE_KEY_AGREEMENT'
526 Usable for for keyAgreement.
528 `KSBA_KEYUSAGE_KEY_CERT_SIGN'
529 Usable for keyCertSign.
531 `KSBA_KEYUSAGE_CRL_SIGN'
534 `KSBA_KEYUSAGE_ENCIPHER_ONLY'
535 Usable for encipherOnly.
537 `KSBA_KEYUSAGE_DECIPHER_ONLY'
538 Usable for decipherOnly.
540 These are the basic constraints on usage of a certificate. If you
541 need to get additional constraints, see
542 `ksba_cert_get_ext_key_usages'.
544 -- Function: gpg_error_t ksba_cert_get_ext_key_usages
545 (ksba_cert_t CERT, char **RESULT)
546 Return a string containing the extended usages for the certificate,
547 delimited by linefeeds.
549 -- Function: gpg_error_t ksba_cert_get_cert_policies
550 (ksba_cert_t CERT, char **R_POLICIES)
551 Return a string with the certificatePolicies delimited by
552 linefeeds. The return values may be extended to carry more
553 information per line, so the caller should only use the first
554 white-space delimited token per line. The function returns
555 `GPG_ERR_NO_DATA' when this extension is not used. Caller must
556 free the returned value.
559 -- Function: gpg_error_t ksba_cert_get_crl_dist_point
560 (ksba_cert_t CERT, int IDX, ksba_name_t *R_DISTPOINT, ksba_name_t *R_ISSUER, unsigned int *R_REASON)
561 Return the CRLDistPoints given in the certificate extension of
562 certificate CERT. IDX should be iterated starting from 0 until
563 the function returns `GPG_ERR_EOF'. R_DISTPOINT returns a
564 ksba_name_t object with the distribution point name(s); the return
565 value may be `NULL' to indicate that this name is not available.
566 R_ISSUER returns the CRL issuer; if the returned value is `NULL'
567 the caller should assume that the CRL issuer is the same as the
568 certificate issuer. R_REASON returns the reason for the CRL.
569 This is a bit encoded value with no bit set if no reason has been
570 specified in the certificate.
572 The caller may pass `NULL' to any of the pointer arguments if he is
573 not interested in this value. The return values for R_DISTPOINT
574 and R_ISSUER must be released by the caller using
577 -- Function: gpg_error_t ksba_cert_get_subj_key_id
578 (ksba_cert_t CERT, int *R_CRIT, ksba_sexp_t *R_KEYID)
579 Return the subjectKeyIdentifier extension as a simple allocated
580 S-expression at the address of R_KEYID. 0 is returned on success,
581 `GPG_ERR_NO_DATA' if no such extension is available or any other
582 error code. If R_CRIT is not passed as `NULL', the critical flag
583 of this is extension is stored at this address.
585 -- Function: gpg_error_t ksba_cert_get_auth_key_id
586 (ksba_cert_t CERT, ksba_sexp_t *R_KEYID, ksba_name_t *R_NAME, ksba_sexp_t *R_SERIAL)
587 Return the authorityKeyIdentifier in R_NAME and R_SERIAL or in
588 R_KEYID. `GPG_ERR_NO_DATA' is returned if no
589 authorityKeyIdentifier has been found. This error code is also
590 returned if R_KEYID has been given as NULL and only an
591 authorityKeyIdentifier with the keyIdentifier method is available.
593 -- Function: gpg_error_t ksba_cert_get_authority_info_access
594 (ksba_cert_t CERT, int IDX, char **R_METHOD, ksba_name_t *R_LOCATION)
595 Return the authorityInfoAccess attributes. IDX should be iterated
596 starting from 0 until this function returns `GPG_ERR_EOF'.
597 R_METHOD returns an allocated string with the OID of one item and
598 R_LOCATION returns the GeneralName for that OID. The returned
599 values for R_METHOD and R_LOCATION must be released by the caller
600 unless the function returned an error; the function will however
601 make sure that R_METHOD and R_LOCATION will point to `NULL' if the
602 function returns an error.
604 See RFC-2459, section 4.2.2.1 for the definition of this attribute.
606 -- Function: gpg_error_t ksba_cert_get_subject_info_access
607 (ksba_cert_t CERT, int IDX, char **R_METHOD, ksba_name_t *R_LOCATION)
608 Return the subjectInfoAccess attributes. IDX should be iterated
609 starting from 0 until this function returns `GPG_ERR_EOF'.
610 R_METHOD returns an allocated string with the OID of one item and
611 R_LOCATION returns the GeneralName for that OID. The returned
612 values for R_METHOD and R_LOCATION must be released by the caller
613 unless the function returned an error; the function will however
614 make sure that R_METHOD and R_LOCATION will point to `NULL' if the
615 function returns an error.
617 See RFC-2459, section 4.2.2.2 for the definition of this attribute.
620 File: ksba.info, Node: Setting attributes, Next: User data, Prev: Retrieving attributes, Up: Certificate Handling
622 3.3 How to set certificate attributes
623 =====================================
625 [This needs to be written. For example code see newpg/sm/sign.c]
628 File: ksba.info, Node: User data, Prev: Setting attributes, Up: Certificate Handling
630 3.4 How to associate other data with a certificate.
631 ===================================================
633 Certificate objects play a central role in many applications and often
634 it is desirable to associate other data with the certificate to avoid
635 wrapping the certificate object into an own object. `KSBA' provides a
636 mechanism for this by means of two functions:
638 -- Function: gpg_error_t ksba_cert_set_user_data
639 (ksba_cert_t CERT, const char *KEY, const void *DATA, size_t DATALEN)
640 Stores arbitrary data along with a certificate. The data is
641 expected in the buffer DATA of length DATALEN. It will be stored
642 under the string KEY. If data is already stored under this key it
643 will be replaced by the new data. Using `NULL' for DATA will
644 effectively delete the data.
646 On error (i.e. out of memory) an already existing data object
647 stored under KEY may get deleted.
649 *Caution:* This function is definitely not thread safe because we
650 don't employ any locking mechanisms.
652 -- Function: gpg_error_t ksba_cert_get_user_data (ksba_cert_t CERT,
653 const char *KEY, void *BUFFER, size_t BUFFERLEN,
655 Return user data for certificate CERT stored under the string KEY.
656 The caller needs to provide a suitable large BUFFER and the usable
657 length of this buffer in BUFFERLEN. If DATALEN is not `NULL', the
658 length of the data stored in BUFFER will be stored there.
660 If BUFFER is given as `NULL', BUFFERLEN will be ignored and the
661 required length of the buffer will be returned at DATALEN.
663 On success 0 is returned. If no data is stored under the given
664 key, `GPG_ERR_NOT_FOUND' is returned. If the provided buffer is
665 too short and BUFFER is not `NULL', `GPG_ERR_BUFFER_TOO_SHORT'
671 File: ksba.info, Node: CMS, Next: CRLs, Prev: Certificate Handling, Up: Top
673 4 Mastering the Cryptographic Message Syntax
674 ********************************************
676 The CMS is also known under the name PKCS#7. Is is a cryptographic
677 framework for securing data transactions and storage, much like
678 OpenPGP. It is heavily based on X.509 semantics and for example used
679 with the email encryption protocol S/MIME.
687 File: ksba.info, Node: CMS Basics, Next: CMS Parser, Up: CMS
692 All operations with the CMS framework require the use of a so called CMS
693 object which is internally used to keep track of the current state and
694 to store some meta information.
696 -- Data type: ksba_cms_t
697 The `ksba_cms_t' type is used for this CMS object.
699 -- Data type: ksba_stop_reason_t
700 The `ksba_stop_reason_t' type is an enumeration used for
701 communication between the phases of a parsing or building process.
703 -- Function: ksba_cms_t ksba_cms_new (void)
704 This function creates a new CMS object. The only reason the
705 function may fail is an out-of-memory condition in which case
706 `NULL' is returned. It is safe for the caller to translate this
707 to the standard error code `GPG_ERR_ENOMEM'. Any object created
708 with this function should be released after use by using
711 -- Function: void ksba_cms_release (ksba_cms_t CMS)
712 Release all resources associated with the CMS object. It is
713 perfectly okay to pass `NULL' to this function in which case
716 -- Function: gpg_error_t ksba_cms_set_reader_writer
717 (ksba_cms_t CMS, ksba_reader_t R, ksba_writer_t W)
718 About all usages of the CMS framework require some input and
719 output data (great surprise!). To accomplish this in the most
720 abstract way, no direct output functions are used - instead
721 special reader and writer objects are used instead. Depending on
722 the desired operations either a reader, a writer or both must be
723 given. Associate a reader object with CMS by passing it as R and
724 a writer object by passing it as W. Note that no reference
725 counting is done,so make sure that those objects have a lifetime
726 at least as long as CMS.
728 If you forget to set these objects, you will get an appropriate
729 error later when data is actually to be read or written. The
730 function returns zero on success or an error code when invalid
734 File: ksba.info, Node: CMS Parser, Prev: CMS Basics, Up: CMS
739 KSBA includes a versatile CMS parser for encryption (enveloped data)
740 and digital signing. The parser is capable of handling arbitrary
741 amounts of data without requiring much memory. Well, certain objects
742 are build in memory because it can be assumed that those objects are
743 limited in size; e.g. it does not make sense to use a video clip as the
744 DN despite the fact that the standard does not forbid it.
746 -- Function: gpg_error_t ksba_cms_parse
747 (ksba_cms_t CMS, ksba_stop_reason_t *R_STOPREASON)
748 This is the core function of the parser and commonly used in a
749 loop. The parsing process is divided into several phases to allow
750 the user to get information at the right time and prepare for
751 further processing. The caller has to act on certain stop reasons
752 which are returned by R_STOPREASON and set up things accordingly;
753 KSBA may introduce new stop reasons to let the caller know other
754 details; there is no need for the caller to act on every stop
755 reason; it should only do so for reasons that the caller
756 understands and which are mandatory. The function will return
757 with an error if the caller did not setup things correctly for
758 certain stop reasons.
760 The use of this function is best explained by an example, leaving
761 out all error checking.
764 ksba_cms_parse (cms, &stopreason);
765 if (stopreason == KSBA_SR_BEGIN_DATA)
768 decrypt_session_key ();
769 setup_bulk_decryption ();
771 else if (stopreason == KSBA_SR_END_DATA)
776 while (stopreason != KSBA_SR_READY);
777 This function assumes that the parsed data is so called `enveloped
780 As CMS provides a common framework for a variety of data formats, it
781 is probably very useful to check the type of that data very early.
782 This can be accomplished by hooking into the stop reason
783 `KSBA_SR_GOT_CONTENT' and retrieving the content using the following
786 -- Function: ksba_content_t ksba_cms_get_content_type
787 (ksba_cms_t CMS, int WHAT)
788 By using a value of `0' for WHAT this function returns the content
789 type of the outer container; using `1' does return the content
790 type of the enclosed object.
792 -- Data type: ksba_content_t
793 The `ksba_content_t' type is an enumeration used to describe
794 the content of a CMS message. Here is a list of possible
798 No content type known (value `0')
801 The content is plain data, not further interpreted.
803 `KSBA_CT_SIGNED_DATA'
804 The content is an signed CMS object. This also includes
805 the case of a detached signature where no actual data is
806 included in the message.
808 `KSBA_CT_ENVELOPED_DATA'
809 The content is encrypted using a session key.
811 `KSBA_CT_DIGESTED_DATA'
814 `KSBA_CT_ENCRYPTED_DATA'
820 -- Function: const char * ksba_cms_get_content_oid
821 (ksba_cms_t CMS, int WHAT)
822 Return the object ID of CMS. This is a constant string valid as
823 long as the context is valid and no new parse is started. This
824 function is similar to `ksba_cms_get_content_type' but returns the
825 OID actually used in the data. Depending on the value of WHAT
826 different values are returned: Using a value of `0' yields the OID
827 of the outer container, a value of `1' yields the OID of the inner
828 container if available and the value `2' returns the OID of the
829 algorithm used to encrypt the inner container.
832 File: ksba.info, Node: CRLs, Next: PKCS10, Prev: CMS, Up: Top
834 5 Certification Revocation Lists
835 ********************************
837 KSBA also comes with an API to process certification revocation lists.
838 The API is similar to the CMS one but returns the contents entry by
842 File: ksba.info, Node: PKCS10, Next: Utilities, Prev: CRLs, Up: Top
844 6 Certification Requests
845 ************************
847 When using decentral generated keys, it is necessary to send out special
848 formated messages so that a CA can generate the certificate.
853 File: ksba.info, Node: Utilities, Next: Error Handling, Prev: PKCS10, Up: Top
858 A few utility function and objects are available. Some of them must be
859 used to support some of the main functions.
863 * Names:: General Names object
864 * OIDs:: Object Identifier helpers
865 * DNs:: Distinguished Name helpers
868 File: ksba.info, Node: Names, Next: OIDs, Up: Utilities
870 7.1 General Names object
871 ========================
873 This is an object to handle some of the names used in X.509. We need
874 this object approach because those names may come as a set and there is
875 no other clean way to access them.
877 -- Data type: ksba_name_t
878 The `ksba_name_t' type is an object to represent names sets.
880 -- Function: void ksba_name_release (ksba_name_t NAME)
881 This function releases the object NAME. Passing `NULL' is allowed.
883 -- Function: const char * ksba_name_enum (ksba_name_t NAME, int IDX)
884 By iterating IDX up starting with 0, this function returns all
885 General Names stored in NAME. The format of the returned name is
886 either a RFC-2253 formated one which can be detected by checking
887 whether the first character is letter or a digit. RFC 2822
888 conformant email addresses are returned enclosed in angle
889 brackets, the opening angle bracket should be used to detect this.
890 Other formats are returned as an S-Expression in canonical format,
891 so an opening parenthesis may be used to detect this encoding, in
892 this case the name may include binary null characters, so strlen
893 might return a length shorter than actually used, the real length
894 is implicitly given by the structure of the S-Exp, an extra null
895 is appended for safety reasons. One common format return is a
896 Universal Resource Identifier which has the S-expression: `(uri
899 The returned string has the same lifetime as NAME.
901 -- Function: char * ksba_name_get_uri (ksba_name_t NAME, int IDX)
902 Convenience function to return names representing an URI. Caller
903 must free the returned value. Note that this function should not
904 be used to enumerate the names.
906 Here is an example on how you can use this function to enumerate
910 print_names (ksba_name_t name)
915 for (idx=0; (s = ksba_name_enum (name, idx)); idx++)
917 char *p = ksba_name_get_uri (name, idx);
927 File: ksba.info, Node: OIDs, Next: DNs, Prev: Names, Up: Utilities
929 7.2 Object Identifier helpers
930 =============================
932 [This needs to get written - for now please see libksba/src/oids.c]
935 File: ksba.info, Node: DNs, Prev: OIDs, Up: Utilities
937 7.3 Distinguished Name helpers
938 ==============================
940 These are helper functions for the so called distinguished names. They
941 are used for example as the issuer and subject name.
943 -- Function: gpg_error_t ksba_dn_teststr (const char *STRING, int SEQ,
944 size_t *RERROFF, size_t *RERRLEN)
945 Assuming that STRING contains an RFC-2253 encoded string, test
946 whether this string may be passed as a valid DN to libksba. On
947 success the functions returns `0'. On error the function returns
948 an error code and stores the offset of the erroneous part at
949 RERROFF. RERRLEN will then receive the length of the erroneous
952 This function is mostly useful to test whether a certain component
953 label is supported. SEQ should be passed as `0' for now. Any of
954 RERROFF and RERRLEN may be passed as NULL if the caller is not
955 interested at this value.
958 gpg_error_t ksba_dn_str2der (const char *string, void **rder, size_t
961 gpg_error_t ksba_dn_der2str (const void *der, size_t derlen, char
967 File: ksba.info, Node: Error Handling, Next: Component Labels, Prev: Utilities, Up: Top
972 Most functions in `KSBA' will return an error if they fail. For this
973 reason, the application should always catch the error condition and
974 take appropriate measures, for example by releasing the resources and
975 passing the error up to the caller, or by displaying a descriptive
976 message to the user and canceling the operation.
978 Some error values do not indicate a system error or an error in the
979 operation, but the reasonable result of an operation. For example, if
980 you try to access optional attributes of a certificate that are not
981 present, you get an appropriate error message. Some error values have
982 specific meanings if returned by a specific function. Such cases are
983 described in the documentation of those functions.
985 All error codes are defined by the library `libgpg-error'. See
986 there for ways to check the error values and print descriptive strings.
987 Please be aware that you can't check directly against an error code but
988 have to do it like this:
991 if (gpg_err_code (err) == GPG_ERR_EOF)
994 The only exception is that success (i.e. no error) is defined to be
995 `0'; thus you may directly test for success like:
1001 File: ksba.info, Node: Component Labels, Next: Copying, Prev: Error Handling, Up: Top
1003 Appendix A Component Labels
1004 ***************************
1006 RFC-2253 defines the following table with string representations of name
1011 C countryName 2.5.4.6
1012 CN commonName 2.5.4.3
1013 DC domainComponent 0.9.2342.19200300.100.1.25
1014 L localityName 2.5.4.7
1015 O organizationName 2.5.4.10
1016 OU organizationalUnit 2.5.4.11
1017 ST stateOrProvince 2.5.4.8
1018 STREET streetAddress 2.5.4.9
1019 UID userid 0.9.2342.19200300.100.1.1
1021 They are used internally for converting a DN into its string
1022 representation; components not listed in this table will be represented
1025 For the other direction, i.e. creating a DN from the string
1026 representation, KSBA recognizes the following extra labels:
1030 ADDR postalAddress 2.5.4.16
1031 BC businessCategory 2.5.4.15
1032 D description 2.5.4.13
1033 EMAIL emailAddress 1.2.840.113549.1.9.1
1034 GN givenName 2.5.4.42
1035 POSTALCODE postalCode 2.5.4.17
1036 PSEUDO pseudonym 2.5.4.65
1037 SERIALNUMBER serialNumber 2.5.4.5
1042 File: ksba.info, Node: Copying, Next: Concept Index, Prev: Component Labels, Up: Top
1044 GNU General Public License
1045 **************************
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1502 9. Acceptance Not Required for Having Copies.
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1608 unless you entered into that arrangement, or that patent license
1609 was granted, prior to 28 March 2007.
1611 Nothing in this License shall be construed as excluding or limiting
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1615 12. No Surrender of Others' Freedom.
1617 If conditions are imposed on you (whether by court order,
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1629 13. Use with the GNU Affero General Public License.
1631 Notwithstanding any other provision of this License, you have
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1640 14. Revised Versions of this License.
1642 The Free Software Foundation may publish revised and/or new
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1644 Such new versions will be similar in spirit to the present
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1686 THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
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1692 17. Interpretation of Sections 15 and 16.
1694 If the disclaimer of warranty and limitation of liability provided
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1702 END OF TERMS AND CONDITIONS
1703 How to Apply These Terms to Your New Programs
1704 =============================================
1706 If you develop a new program, and you want it to be of the greatest
1707 possible use to the public, the best way to achieve this is to make it
1708 free software which everyone can redistribute and change under these
1711 To do so, attach the following notices to the program. It is safest
1712 to attach them to the start of each source file to most effectively
1713 state the exclusion of warranty; and each file should have at least the
1714 "copyright" line and a pointer to where the full notice is found.
1716 ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
1717 Copyright (C) YEAR NAME OF AUTHOR
1719 This program is free software: you can redistribute it and/or modify
1720 it under the terms of the GNU General Public License as published by
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1722 your option) any later version.
1724 This program is distributed in the hope that it will be useful, but
1725 WITHOUT ANY WARRANTY; without even the implied warranty of
1726 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
1727 General Public License for more details.
1729 You should have received a copy of the GNU General Public License
1730 along with this program. If not, see `http://www.gnu.org/licenses/'.
1732 Also add information on how to contact you by electronic and paper mail.
1734 If the program does terminal interaction, make it output a short notice
1735 like this when it starts in an interactive mode:
1737 PROGRAM Copyright (C) YEAR NAME OF AUTHOR
1738 This program comes with ABSOLUTELY NO WARRANTY; for details
1739 type `show w'. This is free software, and you are
1740 welcome to redistribute it under certain conditions;
1741 type `show c' for details.
1743 The hypothetical commands `show w' and `show c' should show the
1744 appropriate parts of the General Public License. Of course, your
1745 program's commands might be different; for a GUI interface, you would
1748 You should also get your employer (if you work as a programmer) or
1749 school, if any, to sign a "copyright disclaimer" for the program, if
1750 necessary. For more information on this, and how to apply and follow
1751 the GNU GPL, see `http://www.gnu.org/licenses/'.
1753 The GNU General Public License does not permit incorporating your
1754 program into proprietary programs. If your program is a subroutine
1755 library, you may consider it more useful to permit linking proprietary
1756 applications with the library. If this is what you want to do, use the
1757 GNU Lesser General Public License instead of this License. But first,
1758 please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.
1761 File: ksba.info, Node: Concept Index, Next: Function and Data Index, Prev: Copying, Up: Top
1769 File: ksba.info, Node: Function and Data Index, Prev: Concept Index, Up: Top
1771 Function and Data Index
1772 ***********************
1777 * ksba_cert_get_auth_key_id: Retrieving attributes.
1779 * ksba_cert_get_authority_info_access: Retrieving attributes.
1781 * ksba_cert_get_cert_policies: Retrieving attributes.
1783 * ksba_cert_get_crl_dist_point: Retrieving attributes.
1785 * ksba_cert_get_digest_algo: Retrieving attributes.
1787 * ksba_cert_get_ext_key_usages: Retrieving attributes.
1789 * ksba_cert_get_extension: Retrieving attributes.
1791 * ksba_cert_get_image: Retrieving attributes.
1793 * ksba_cert_get_issuer: Retrieving attributes.
1795 * ksba_cert_get_key_usage: Retrieving attributes.
1797 * ksba_cert_get_public_key: Retrieving attributes.
1799 * ksba_cert_get_serial: Retrieving attributes.
1801 * ksba_cert_get_sig_val: Retrieving attributes.
1803 * ksba_cert_get_subj_key_id: Retrieving attributes.
1805 * ksba_cert_get_subject: Retrieving attributes.
1807 * ksba_cert_get_subject_info_access: Retrieving attributes.
1809 * ksba_cert_get_user_data: User data. (line 28)
1810 * ksba_cert_get_validity: Retrieving attributes.
1812 * ksba_cert_hash: Retrieving attributes.
1814 * ksba_cert_init_from_mem: Creating certificates.
1816 * ksba_cert_is_ca: Retrieving attributes.
1818 * ksba_cert_new: Creating certificates.
1820 * ksba_cert_read_der: Creating certificates.
1822 * ksba_cert_ref: Creating certificates.
1824 * ksba_cert_release: Creating certificates.
1826 * ksba_cert_set_user_data: User data. (line 13)
1827 * ksba_cert_t: Certificate Handling.
1829 * ksba_check_version: Version Check. (line 13)
1830 * ksba_cms_get_content_oid: CMS Parser. (line 89)
1831 * ksba_cms_get_content_type: CMS Parser. (line 55)
1832 * ksba_cms_new: CMS Basics. (line 18)
1833 * ksba_cms_parse: CMS Parser. (line 15)
1834 * ksba_cms_release: CMS Basics. (line 26)
1835 * ksba_cms_set_reader_writer: CMS Basics. (line 32)
1836 * ksba_cms_t: CMS Basics. (line 11)
1837 * ksba_content_t: CMS Parser. (line 60)
1838 * ksba_dn_teststr: DNs. (line 11)
1839 * ksba_isotime_t: Retrieving attributes.
1841 * ksba_name_enum: Names. (line 17)
1842 * ksba_name_get_uri: Names. (line 35)
1843 * ksba_name_release: Names. (line 14)
1844 * ksba_name_t: Names. (line 11)
1845 * ksba_sexp_t: Certificate Handling.
1847 * ksba_stop_reason_t: CMS Basics. (line 14)
1853 Node: Introduction
\7f2821
1854 Node: Getting Started
\7f3099
1855 Node: Features
\7f3965
1856 Node: Overview
\7f5056
1857 Node: Preparation
\7f5305
1859 Node: Version Check
\7f6384
1860 Node: Building the source
\7f7475
1861 Node: Certificate Handling
\7f9319
1862 Node: Creating certificates
\7f10300
1863 Node: Retrieving attributes
\7f12756
1864 Node: Setting attributes
\7f26404
1865 Node: User data
\7f26669
1867 Node: CMS Basics
\7f29050
1868 Node: CMS Parser
\7f31112
1870 Node: PKCS10
\7f35361
1871 Node: Utilities
\7f35628
1875 Node: Error Handling
\7f39680
1876 Node: Component Labels
\7f41034
1877 Node: Copying
\7f42524
1878 Node: Concept Index
\7f80067
1879 Node: Function and Data Index
\7f80215