This is ksba.info, produced by makeinfo version 5.2 from ksba.texi. INFO-DIR-SECTION GNU libraries START-INFO-DIR-ENTRY * libksba: (ksba). An X.509 Library. END-INFO-DIR-ENTRY This file documents the KSBA library to access X.509 and CMS data structures. This is edition 1.3.5, last updated 15 March 2013, of 'The KSBA Reference Manual', for Version 1.3.5. Copyright (C) 2002, 2003, 2004 g10 Code GmbH Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The text of the license can be found in the section entitled "Copying".  File: ksba.info, Node: Top, Next: Introduction, Up: (dir) Main Menu ********* This is edition 1.3.5, last updated 15 March 2013, of 'The KSBA Reference Manual', for Version 1.3.5 of the KSBA library. Copyright (C) 2002, 2003, 2004 g10 Code GmbH Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The text of the license can be found in the section entitled "Copying". * Menu: * Introduction:: How to use this manual. * Preparation:: What you should do before using the library. * Certificate Handling:: How to work with X.509 certificates. * CMS:: How to work with CMS (PKCS#7) messages. * CRLs:: How to work with Certificate Revocation Lists. * PKCS10:: How to request certificates. * Utilities:: Various utility functions. * Error Handling:: Error numbers and their meanings. Appendices * Component Labels:: Labels used in string representations. * Copying:: The GNU General Public License says how you can copy and share this manual. Indices * Concept Index:: Index of concepts and programs. * Function and Data Index:: Index of functions, variables and data types. -- The Detailed Node Listing -- Introduction * Getting Started:: * Features:: * Overview:: Preparation * Header:: * Building the source:: Certificate Handling * Creating certificates:: How to create a certificate object. * Retrieving attributes:: How to get the attributes of a certificate. * Setting attributes:: How to set certificates attributes. * User data:: How to associate other data with a certificate. Mastering the Cryptographic Message Syntax * CMS Basics:: * CMS Parser::  File: ksba.info, Node: Introduction, Next: Preparation, Prev: Top, Up: Top 1 Introduction ************** KSBA is a library to make the task of working with X.509 certificates, CMS data and related data more easy. * Menu: * Getting Started:: * Features:: * Overview::  File: ksba.info, Node: Getting Started, Next: Features, Up: Introduction 1.1 Getting Started =================== This manual documents the 'KSBA' library programming interface. All functions and data types provided by the library are explained. The reader is assumed to possess basic knowledge about the implemented protocols. This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the library and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular interface of the library. Experienced programmers might want to start looking at the examples at the end of the manual, and then only read up those parts of the interface which are unclear.  File: ksba.info, Node: Features, Next: Overview, Prev: Getting Started, Up: Introduction 1.2 Features ============ 'KSBA' has a couple of advantages over other libraries doing a similar job, and over open coding the protocols in your application directly. It's Free Software Anybody can use, modify, and redistribute it under the terms of the GNU General Public License (*note Copying::). It hides the low level stuff 'KSBA' a high level interface to the implemented protocols and presents the data in a consistent way. There is no more need to worry about all the nasty details of the protocols. The API gives the C programmer a more usual way of interacting with the data. It copes with the version details X.509 protocols tend to have many different versions and dialects. Applications must usually cope with all of this and it has to be coded over and over again. 'KSBA' hides this by providing just one API which does the Right Thing. Support for new versions and features of the protocols will be added over time.  File: ksba.info, Node: Overview, Prev: Features, Up: Introduction 1.3 Overview ============ The 'KSBA' library is thread-safe as long as objects described by one context are only used by one thread at a time. No initialization is required.  File: ksba.info, Node: Preparation, Next: Certificate Handling, Prev: Introduction, Up: Top 2 Preparation ************* To use 'KSBA', you have to perform some changes to your sources and the build system. The necessary changes are small and explained in the following sections. At the end of this chapter, it is described how the library is initialized, and how the requirements of the library are verified. * Menu: * Header:: * Version Check:: * Building the source::  File: ksba.info, Node: Header, Next: Version Check, Up: Preparation 2.1 Header ========== All interfaces (data types and functions) of the library are defined in the header file 'ksba.h'. You must include this in all programs using the library, either directly or through some other header file, like this: #include The name space of 'KSBA' is 'ksba_*' for function names, 'ksba*' for data types and 'KSBA_*' for other symbols. In addition the same name prefixes with one prepended underscore are reserved for internal use and should never be used by an application.  File: ksba.info, Node: Version Check, Next: Building the source, Prev: Header, Up: Preparation 2.2 Version Check ================= It is often desirable to check that the version of 'KSBA' used is indeed one which fits all requirements. Even with binary compatibility, new features may have been introduced but through peculiarities of the runtime linker an old version gets actually used. So you better check that the version is as expected right after program startup. -- Function: const char * ksba_check_version (const char *REQ_VERSION) Check that the the version of the library is at minimum the one given as a string in REQ_VERSION and return the actual version string of the library; return 'NULL' if the condition is not met. If 'NULL' is passed to this function, no check is done and only the version string is returned. It is a pretty good idea to run this function as soon as possible, because it may also initializes some subsystems. In a multi-threaded environment if should be called before any more threads are created.  File: ksba.info, Node: Building the source, Prev: Version Check, Up: Preparation 2.3 Building the source ======================= If you want to compile a source file including the 'ksba.h' header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compiler's include file search path (via the '-I' option). However, the path to the include file is determined at the time the source is configured. To solve this problem, 'KSBA' ships with a small helper program 'ksba-config' that knows about the path to the include file and other configuration options. The options that need to be added to the compiler invocation at compile time are output by the '--cflags' option of 'ksba-config'. The following example shows how it can be used at the command line: gcc -c foo.c `ksba-config --cflags` Adding the output of 'ksba-config --cflags' to the compiler's command line will ensure that the compiler can find the 'ksba.h' header file. A similar problem occurs when linking the program with the library. Again, the compiler has to find the library files. For this to work, the path to the library files has to be added to the library search path (via the '-L' option). For this, the option '--libs' of 'ksba-config' can be used. For convenience, this option also outputs all other options that are required to link the program with the 'KSBA' libraries (in particular, the '-lksba' option). The example shows how to link 'foo.o' with the 'KSBA' libraries to a program 'foo'. gcc -o foo foo.o `ksba-config --libs` Of course you can also combine both examples to a single command by specifying both options to 'ksba-config': gcc -o foo foo.c `ksba-config --cflags --libs`  File: ksba.info, Node: Certificate Handling, Next: CMS, Prev: Preparation, Up: Top 3 How to work with X.509 certificates. ************************************** One of the most complex data formats are the X.509 certificates. KSBA provides an easy to use interface to handle them. -- Data type: ksba_cert_t The 'ksba_cert_t' type is a handle for an X.509 certificate. -- Data type: ksba_sexp_t The 'ksba_sexp_t' type describes a canonically encoded S-expression stored in a memory buffer. It is alias for 'unsigned char *'. Note that a length argument is not required because the length of such an S-expression is intrinsically available. * Menu: * Creating certificates:: How to create a certificate object. * Retrieving attributes:: How to get the attributes of a certificate. * Setting attributes:: How to set certificates attributes. * User data:: How to associate other data with a certificate.  File: ksba.info, Node: Creating certificates, Next: Retrieving attributes, Up: Certificate Handling 3.1 How to create a certificate object ====================================== This section explains how to create a certificate object, initialize it, copy it and eventually destroy it. -- Function: ksba_cert_t ksba_cert_new (void) The function 'ksba_cert_new' creates a new certificate object and returns a handle for it. The certificate object has initially one reference. The only reason why this function may fail is an out-of-memory condition in which case 'NULL' is returned. You might then get the actual error code using 'gpg_error_from_errno (errno)'. -- Function: void ksba_cert_ref (ksba_cert_t CERT) The function 'ksba_cert_ref' bumps the reference counter of the certificate object up by one. Thus an extra 'ksba_cert_release' is required to actually release the memory used for the object. -- Function: void ksba_cert_release (ksba_cert_t CERT) The function 'ksba_cert_release' reduces the number of references to the certificate object with the handle CERT. If this was the last reference, it will also destroy the object and releases all associated resources. It is okay to pass 'NULL' to the function in which case nothing happens. -- Function: gpg_error_t ksba_cert_read_der (ksba_cert_t CERT, ksba_reader_t READER) Read the next certificate from the READER object and store it in the certificate object CERT for future access. The certificate is parsed and rejected if it has any syntactical or semantical error (i.e. does not match the ASN.1 description). The function returns '0' if the operation was successfully performed. An error code is returned on failure. -- Function: gpg_error_t ksba_cert_init_from_mem (ksba_cert_t CERT, const void *BUFFER, size_t LENGTH) Parse the BUFFER which should contain a DER encoded certificate of LENGTH and initialize the certificate object CERT with it. This function is intended as a convenience function to be used when a certificate is already available in a internal memory buffer. This avoids the extra code needed to setup the reader object. Note that CERT must be a valid certificate object. The function returns '0' if the operation was successfully performed. An error code is returned on failure.  File: ksba.info, Node: Retrieving attributes, Next: Setting attributes, Prev: Creating certificates, Up: Certificate Handling 3.2 How to get the attributes of a certificate ============================================== The functions in this section allow accessing the attributes of a certificate in a well defined manner. An error will be returned if the certificate object has not yet been initialized by means of 'ksba_cert_read_der' or 'ksba_cert_init_from_mem'. -- Function: const unsigned char * ksba_cert_get_image (ksba_cert_t CERT, size_t *R_LENGTH) This function returns a pointer to the DER encoded buffer with the raw certificate. The length of that buffer gets stored at R_LENGTH. This function is useful to export or store the raw certificate. The function returns 'NULL' on error or a pointer to a buffer with the raw certificate data. That pointer is only valid as long as the certificate object CERT is valid and has not been reinitialized. -- Function: gpg_error_t ksba_cert_hash (ksba_cert_t CERT, int WHAT, void (*HASHER)(void *, const void *, size_t length), void *HASHER_ARG) This function feeds the data which is expected to be hashed into the supplied function HASHER, where the first argument passed is HASHER_ARG, the second the pointer to the data to be hashed and the third the length of this data. The function returns '0' on success or an error code when something goes wrong. The HASHER function is not expected to return an error; instead the caller should setup that function in a way to convey encountered errors by means of the HASHER_ARG. Note that a hash function is in general not expected to yield errors anyway. -- Function: const char * ksba_cert_get_digest_algo (ksba_cert_t CERT) Figure out the the digest algorithm used for the signature and return its OID in dotted decimal format. This function is most likely used to setup the hash context before calling 'ksba_cert_hash'. The function returns 'NULL' for an error; on success a constant string with the OID is returned. This string is valid as long the certificate object is valid. -- Function: ksba_sexp_t ksba_cert_get_serial (ksba_cert_t CERT) The function returns the serial number of the certificate CERT. The serial number is an integer returned as an canonical encoded S-expression with just one element. The caller must free the returned value. The value 'NULL' is returned in case of error. -- Function: char * ksba_cert_get_issuer (ksba_cert_t CERT, int IDX) With IDX given as '0', this function returns the Distinguished Name (DN) of the certificate issuer; this usually is the name of a certification authority (CA). The format of the returned string is in accordance with RFC-2253. 'NULL' is returned if the DN is not available; This is a severe error and actually should have been caught by the certificate reading function. With IDX greater than zero, the function may be used to enumerate alternate issuer names. The function returns 'NULL' when there are no more alternate names. Only alternate names recognized by 'libksba' are returned, others are simply skipped. The format of the returned name is either a RFC-2253 formated string which can be detected by checking whether the first character is a letter or digit. RFC-822 conformant email addresses are returned enclosed in angle brackets; the opening angle bracket should be used to detect this. Other formats are returned as an S-Expression in canonical format, so a opening parenthesis should be used to detect this encoding. The name may include binary null characters, thus strlen may return a length shorter than actually used. The real length is implicitly given by the structure of the S-expression, an extra null is appended for safety reasons. The caller must free the returned string using 'ksba_free' or whatever function has been registered as a replacement. -- Function: char * ksba_cert_get_subject (ksba_cert_t CERT, int IDX) With IDX given as '0', this function returns the Distinguished Name (DN) of the certificate's subject. The format of the returned string is in accordance with RFC-2253. 'NULL' is returned if the DN is not available. With IDX greater than zero, the function may be used to enumerate alternate subject names. The function returns 'NULL' when there are no more alternate names. Only alternate names recognized by 'libksba' are returned, others are simply skipped. The format of the returned name is either a RFC-2253 formated string which can be detected by checking whether the first character is a letter or digit. RFC-2822 conform email addresses are returned enclosed in angle brackets; the opening angle bracket should be used to detect this. Other formats are returned as an S-Expression in canonical format, so a opening parenthesis should be used to detect this encoding, the name may include binary null characters, thus strlen may return a length shorter than actually used. The real length is implicitly given by the structure of the S-expression, an extra null is appended for safety reasons. The caller must free the returned string using 'ksba_free' or whatever function has been registered as a replacement. -- Data type: ksba_isotime_t Due to problems with the C data type 'time_t', which will overflow on most 32 bit machines in the year 2038, it was not advisable to use this type for referencing times stored in certificates. Instead, you should use the 'ksba_isotime_t' type, which can represent any time since the year 0. It is implemented as a buffer of 16 bytes and may be handled like a standard string. It should be initialized to zero (i.e. the first byte needs to be 0x00) if it does not hold a valid date. Date values themselves are stored in ISO format and assumed to be referenced from UTC. The string with the date value is always guaranteed to be of length 15 and having a format like: '"19610711T172059"'. Note that the 'T' is required by ISO rules. A simple assignment of these data types is not a good idea. You may use 'strcpy' or better a specialized function like: void copy_time (ksba_isotime_t d, const ksba_isotime_t s) { if (!*s) memset (d, 0, 16); else strcpy (d, s); } For reasons of documentation a special function should also be used to compare such times: int cmp_time (const ksba_isotime_t a, const ksba_isotime_t b) { return strcmp (a, b); } -- Function: gpg_error_t ksba_cert_get_validity (ksba_cert_t CERT, int WHAT, ksba_isotime_t TIMEBUF) Return the validity dates from the certificate. If no value is available an empty date object (i.e. a 'strlen' will be stored at TIMEBUF, otherwise it will receive the date. On failure an error code is returned. To return the 'notBefore' date, the value '0' must be supplied for WHAT; '1' yields the 'notAfter' value. -- Function: ksba_sexp_t ksba_cert_get_public_key (ksba_cert_t CERT) [This needs to get written - for now please see libksba/src/cert.c] -- Function: ksba_sexp_t ksba_cert_get_sig_val (ksba_cert_t CERT) [This needs to get written - for now please see libksba/src/cert.c] -- Function: gpg_error_t ksba_cert_get_extension (ksba_cert_t CERT, int IDX, char const **R_OID, int *R_CRIT, size_t *R_DEROFF, size_t *R_DERLEN) [This needs to get written - for now please see libksba/src/cert.c] -- Function: gpg_error_t ksba_cert_is_ca (ksba_cert_t CERT, int *R_CA, int *R_PATHLEN) Return information on the basicConstraint (2.5.19.19) of CERT. R_CA receives true if this is a CA and only in that case R_PATHLEN is set to the maximum certification path length or -1 if there is no such limitation -- Function: gpg_error_t ksba_cert_get_key_usage (ksba_cert_t CERT, unsigned int *R_FLAGS) Get the key usage flags. The function returns 'GPG_ERR_NO_DATA' if no key usage is specified. The usage flags are as shown in RFC3280, section 4.2.1.3. The key usage flags are represented by a bitmask, and you can test each bit using symbolic constants, which tells you if that usage is set on the certificate. The constants are 'KSBA_KEYUSAGE_DIGITAL_SIGNATURE' Usable for digitalSignature. 'KSBA_KEYUSAGE_NON_REPUDIATION' Usable for nonRepudiation. 'KSBA_KEYUSAGE_KEY_ENCIPHERMENT' Usable for keyEncipherment. 'KSBA_KEYUSAGE_DATA_ENCIPHERMENT' Usable for dataEncipherment. 'KSBA_KEYUSAGE_KEY_AGREEMENT' Usable for for keyAgreement. 'KSBA_KEYUSAGE_KEY_CERT_SIGN' Usable for keyCertSign. 'KSBA_KEYUSAGE_CRL_SIGN' Usable for cRLSign. 'KSBA_KEYUSAGE_ENCIPHER_ONLY' Usable for encipherOnly. 'KSBA_KEYUSAGE_DECIPHER_ONLY' Usable for decipherOnly. These are the basic constraints on usage of a certificate. If you need to get additional constraints, see 'ksba_cert_get_ext_key_usages'. -- Function: gpg_error_t ksba_cert_get_ext_key_usages (ksba_cert_t CERT, char **RESULT) Return a string containing the extended usages for the certificate, delimited by linefeeds. -- Function: gpg_error_t ksba_cert_get_cert_policies (ksba_cert_t CERT, char **R_POLICIES) Return a string with the certificatePolicies delimited by linefeeds. The return values may be extended to carry more information per line, so the caller should only use the first white-space delimited token per line. The function returns 'GPG_ERR_NO_DATA' when this extension is not used. Caller must free the returned value. -- Function: gpg_error_t ksba_cert_get_crl_dist_point (ksba_cert_t CERT, int IDX, ksba_name_t *R_DISTPOINT, ksba_name_t *R_ISSUER, unsigned int *R_REASON) Return the CRLDistPoints given in the certificate extension of certificate CERT. IDX should be iterated starting from 0 until the function returns 'GPG_ERR_EOF'. R_DISTPOINT returns a ksba_name_t object with the distribution point name(s); the return value may be 'NULL' to indicate that this name is not available. R_ISSUER returns the CRL issuer; if the returned value is 'NULL' the caller should assume that the CRL issuer is the same as the certificate issuer. R_REASON returns the reason for the CRL. This is a bit encoded value with no bit set if no reason has been specified in the certificate. The caller may pass 'NULL' to any of the pointer arguments if he is not interested in this value. The return values for R_DISTPOINT and R_ISSUER must be released by the caller using 'ksba_name_release'. -- Function: gpg_error_t ksba_cert_get_subj_key_id (ksba_cert_t CERT, int *R_CRIT, ksba_sexp_t *R_KEYID) Return the subjectKeyIdentifier extension as a simple allocated S-expression at the address of R_KEYID. 0 is returned on success, 'GPG_ERR_NO_DATA' if no such extension is available or any other error code. If R_CRIT is not passed as 'NULL', the critical flag of this is extension is stored at this address. -- Function: gpg_error_t ksba_cert_get_auth_key_id (ksba_cert_t CERT, ksba_sexp_t *R_KEYID, ksba_name_t *R_NAME, ksba_sexp_t *R_SERIAL) Return the authorityKeyIdentifier in R_NAME and R_SERIAL or in R_KEYID. 'GPG_ERR_NO_DATA' is returned if no authorityKeyIdentifier has been found. This error code is also returned if R_KEYID has been given as NULL and only an authorityKeyIdentifier with the keyIdentifier method is available. -- Function: gpg_error_t ksba_cert_get_authority_info_access (ksba_cert_t CERT, int IDX, char **R_METHOD, ksba_name_t *R_LOCATION) Return the authorityInfoAccess attributes. IDX should be iterated starting from 0 until this function returns 'GPG_ERR_EOF'. R_METHOD returns an allocated string with the OID of one item and R_LOCATION returns the GeneralName for that OID. The returned values for R_METHOD and R_LOCATION must be released by the caller unless the function returned an error; the function will however make sure that R_METHOD and R_LOCATION will point to 'NULL' if the function returns an error. See RFC-2459, section 4.2.2.1 for the definition of this attribute. -- Function: gpg_error_t ksba_cert_get_subject_info_access (ksba_cert_t CERT, int IDX, char **R_METHOD, ksba_name_t *R_LOCATION) Return the subjectInfoAccess attributes. IDX should be iterated starting from 0 until this function returns 'GPG_ERR_EOF'. R_METHOD returns an allocated string with the OID of one item and R_LOCATION returns the GeneralName for that OID. The returned values for R_METHOD and R_LOCATION must be released by the caller unless the function returned an error; the function will however make sure that R_METHOD and R_LOCATION will point to 'NULL' if the function returns an error. See RFC-2459, section 4.2.2.2 for the definition of this attribute.  File: ksba.info, Node: Setting attributes, Next: User data, Prev: Retrieving attributes, Up: Certificate Handling 3.3 How to set certificate attributes ===================================== [This needs to be written. For example code see newpg/sm/sign.c]  File: ksba.info, Node: User data, Prev: Setting attributes, Up: Certificate Handling 3.4 How to associate other data with a certificate. =================================================== Certificate objects play a central role in many applications and often it is desirable to associate other data with the certificate to avoid wrapping the certificate object into an own object. 'KSBA' provides a mechanism for this by means of two functions: -- Function: gpg_error_t ksba_cert_set_user_data (ksba_cert_t CERT, const char *KEY, const void *DATA, size_t DATALEN) Stores arbitrary data along with a certificate. The data is expected in the buffer DATA of length DATALEN. It will be stored under the string KEY. If data is already stored under this key it will be replaced by the new data. Using 'NULL' for DATA will effectively delete the data. On error (i.e. out of memory) an already existing data object stored under KEY may get deleted. *Caution:* This function is definitely not thread safe because we don't employ any locking mechanisms. -- Function: gpg_error_t ksba_cert_get_user_data (ksba_cert_t CERT, const char *KEY, void *BUFFER, size_t BUFFERLEN, size_t *DATALEN) Return user data for certificate CERT stored under the string KEY. The caller needs to provide a suitable large BUFFER and the usable length of this buffer in BUFFERLEN. If DATALEN is not 'NULL', the length of the data stored in BUFFER will be stored there. If BUFFER is given as 'NULL', BUFFERLEN will be ignored and the required length of the buffer will be returned at DATALEN. On success 0 is returned. If no data is stored under the given key, 'GPG_ERR_NOT_FOUND' is returned. If the provided buffer is too short and BUFFER is not 'NULL', 'GPG_ERR_BUFFER_TOO_SHORT' will be returned.  File: ksba.info, Node: CMS, Next: CRLs, Prev: Certificate Handling, Up: Top 4 Mastering the Cryptographic Message Syntax ******************************************** The CMS is also known under the name PKCS#7. Is is a cryptographic framework for securing data transactions and storage, much like OpenPGP. It is heavily based on X.509 semantics and for example used with the email encryption protocol S/MIME. * Menu: * CMS Basics:: * CMS Parser::  File: ksba.info, Node: CMS Basics, Next: CMS Parser, Up: CMS 4.1 CMS Basics ============== All operations with the CMS framework require the use of a so called CMS object which is internally used to keep track of the current state and to store some meta information. -- Data type: ksba_cms_t The 'ksba_cms_t' type is used for this CMS object. -- Data type: ksba_stop_reason_t The 'ksba_stop_reason_t' type is an enumeration used for communication between the phases of a parsing or building process. -- Function: ksba_cms_t ksba_cms_new (void) This function creates a new CMS object. The only reason the function may fail is an out-of-memory condition in which case 'NULL' is returned. It is safe for the caller to translate this to the standard error code 'GPG_ERR_ENOMEM'. Any object created with this function should be released after use by using 'ksba_cms_release'. -- Function: void ksba_cms_release (ksba_cms_t CMS) Release all resources associated with the CMS object. It is perfectly okay to pass 'NULL' to this function in which case nothing happens. -- Function: gpg_error_t ksba_cms_set_reader_writer (ksba_cms_t CMS, ksba_reader_t R, ksba_writer_t W) About all usages of the CMS framework require some input and output data (great surprise!). To accomplish this in the most abstract way, no direct output functions are used - instead special reader and writer objects are used instead. Depending on the desired operations either a reader, a writer or both must be given. Associate a reader object with CMS by passing it as R and a writer object by passing it as W. Note that no reference counting is done,so make sure that those objects have a lifetime at least as long as CMS. If you forget to set these objects, you will get an appropriate error later when data is actually to be read or written. The function returns zero on success or an error code when invalid objects are passed.  File: ksba.info, Node: CMS Parser, Prev: CMS Basics, Up: CMS 4.2 CMS Parser ============== KSBA includes a versatile CMS parser for encryption (enveloped data) and digital signing. The parser is capable of handling arbitrary amounts of data without requiring much memory. Well, certain objects are build in memory because it can be assumed that those objects are limited in size; e.g. it does not make sense to use a video clip as the DN despite the fact that the standard does not forbid it. -- Function: gpg_error_t ksba_cms_parse (ksba_cms_t CMS, ksba_stop_reason_t *R_STOPREASON) This is the core function of the parser and commonly used in a loop. The parsing process is divided into several phases to allow the user to get information at the right time and prepare for further processing. The caller has to act on certain stop reasons which are returned by R_STOPREASON and set up things accordingly; KSBA may introduce new stop reasons to let the caller know other details; there is no need for the caller to act on every stop reason; it should only do so for reasons that the caller understands and which are mandatory. The function will return with an error if the caller did not setup things correctly for certain stop reasons. The use of this function is best explained by an example, leaving out all error checking. do { ksba_cms_parse (cms, &stopreason); if (stopreason == KSBA_SR_BEGIN_DATA) { get_recipients (); decrypt_session_key (); setup_bulk_decryption (); } else if (stopreason == KSBA_SR_END_DATA) { remove_padding (); } } while (stopreason != KSBA_SR_READY); This function assumes that the parsed data is so called 'enveloped data'. As CMS provides a common framework for a variety of data formats, it is probably very useful to check the type of that data very early. This can be accomplished by hooking into the stop reason 'KSBA_SR_GOT_CONTENT' and retrieving the content using the following function. -- Function: ksba_content_t ksba_cms_get_content_type (ksba_cms_t CMS, int WHAT) By using a value of '0' for WHAT this function returns the content type of the outer container; using '1' does return the content type of the enclosed object. -- Data type: ksba_content_t The 'ksba_content_t' type is an enumeration used to describe the content of a CMS message. Here is a list of possible values: 'KSBA_CT_NONE' No content type known (value '0') 'KSBA_CT_DATA' The content is plain data, not further interpreted. 'KSBA_CT_SIGNED_DATA' The content is an signed CMS object. This also includes the case of a detached signature where no actual data is included in the message. 'KSBA_CT_ENVELOPED_DATA' The content is encrypted using a session key. 'KSBA_CT_DIGESTED_DATA' Not yet supported 'KSBA_CT_ENCRYPTED_DATA' Not yet supported 'KSBA_CT_AUTH_DATA' Not yet supported -- Function: const char * ksba_cms_get_content_oid (ksba_cms_t CMS, int WHAT) Return the object ID of CMS. This is a constant string valid as long as the context is valid and no new parse is started. This function is similar to 'ksba_cms_get_content_type' but returns the OID actually used in the data. Depending on the value of WHAT different values are returned: Using a value of '0' yields the OID of the outer container, a value of '1' yields the OID of the inner container if available and the value '2' returns the OID of the algorithm used to encrypt the inner container.  File: ksba.info, Node: CRLs, Next: PKCS10, Prev: CMS, Up: Top 5 Certification Revocation Lists ******************************** KSBA also comes with an API to process certification revocation lists. The API is similar to the CMS one but returns the contents entry by entry.  File: ksba.info, Node: PKCS10, Next: Utilities, Prev: CRLs, Up: Top 6 Certification Requests ************************ When using decentral generated keys, it is necessary to send out special formated messages so that a CA can generate the certificate.  File: ksba.info, Node: Utilities, Next: Error Handling, Prev: PKCS10, Up: Top 7 Utilities *********** A few utility function and objects are available. Some of them must be used to support some of the main functions. * Menu: * Names:: General Names object * OIDs:: Object Identifier helpers * DNs:: Distinguished Name helpers  File: ksba.info, Node: Names, Next: OIDs, Up: Utilities 7.1 General Names object ======================== This is an object to handle some of the names used in X.509. We need this object approach because those names may come as a set and there is no other clean way to access them. -- Data type: ksba_name_t The 'ksba_name_t' type is an object to represent names sets. -- Function: void ksba_name_release (ksba_name_t NAME) This function releases the object NAME. Passing 'NULL' is allowed. -- Function: const char * ksba_name_enum (ksba_name_t NAME, int IDX) By iterating IDX up starting with 0, this function returns all General Names stored in NAME. The format of the returned name is either a RFC-2253 formated one which can be detected by checking whether the first character is letter or a digit. RFC 2822 conformant email addresses are returned enclosed in angle brackets, the opening angle bracket should be used to detect this. Other formats are returned as an S-Expression in canonical format, so an opening parenthesis may be used to detect this encoding, in this case the name may include binary null characters, so strlen might return a length shorter than actually used, the real length is implicitly given by the structure of the S-Exp, an extra null is appended for safety reasons. One common format return is a Universal Resource Identifier which has the S-expression: '(uri )'. The returned string has the same lifetime as NAME. -- Function: char * ksba_name_get_uri (ksba_name_t NAME, int IDX) Convenience function to return names representing an URI. Caller must free the returned value. Note that this function should not be used to enumerate the names. Here is an example on how you can use this function to enumerate all URIs: void print_names (ksba_name_t name) { int idx; const char *s; for (idx=0; (s = ksba_name_enum (name, idx)); idx++) { char *p = ksba_name_get_uri (name, idx); if (p) { puts (p); ksba_free (p); } } }  File: ksba.info, Node: OIDs, Next: DNs, Prev: Names, Up: Utilities 7.2 Object Identifier helpers ============================= [This needs to get written - for now please see libksba/src/oids.c]  File: ksba.info, Node: DNs, Prev: OIDs, Up: Utilities 7.3 Distinguished Name helpers ============================== These are helper functions for the so called distinguished names. They are used for example as the issuer and subject name. -- Function: gpg_error_t ksba_dn_teststr (const char *STRING, int SEQ, size_t *RERROFF, size_t *RERRLEN) Assuming that STRING contains an RFC-2253 encoded string, test whether this string may be passed as a valid DN to libksba. On success the functions returns '0'. On error the function returns an error code and stores the offset of the erroneous part at RERROFF. RERRLEN will then receive the length of the erroneous part. This function is mostly useful to test whether a certain component label is supported. SEQ should be passed as '0' for now. Any of RERROFF and RERRLEN may be passed as NULL if the caller is not interested at this value. gpg_error_t ksba_dn_str2der (const char *string, void **rder, size_t *rderlen); gpg_error_t ksba_dn_der2str (const void *der, size_t derlen, char **r_string);  File: ksba.info, Node: Error Handling, Next: Component Labels, Prev: Utilities, Up: Top 8 Error Handling **************** Most functions in 'KSBA' will return an error if they fail. For this reason, the application should always catch the error condition and take appropriate measures, for example by releasing the resources and passing the error up to the caller, or by displaying a descriptive message to the user and canceling the operation. Some error values do not indicate a system error or an error in the operation, but the reasonable result of an operation. For example, if you try to access optional attributes of a certificate that are not present, you get an appropriate error message. Some error values have specific meanings if returned by a specific function. Such cases are described in the documentation of those functions. All error codes are defined by the library 'libgpg-error'. See there for ways to check the error values and print descriptive strings. Please be aware that you can't check directly against an error code but have to do it like this: err = ksba_foo (); if (gpg_err_code (err) == GPG_ERR_EOF) okay = 1; The only exception is that success (i.e. no error) is defined to be '0'; thus you may directly test for success like: if (!ksba_foo ()) okay = 1;  File: ksba.info, Node: Component Labels, Next: Copying, Prev: Error Handling, Up: Top Appendix A Component Labels *************************** RFC-2253 defines the following table with string representations of name components: Label Component OID C countryName 2.5.4.6 CN commonName 2.5.4.3 DC domainComponent 0.9.2342.19200300.100.1.25 L localityName 2.5.4.7 O organizationName 2.5.4.10 OU organizationalUnit 2.5.4.11 ST stateOrProvince 2.5.4.8 STREET streetAddress 2.5.4.9 UID userid 0.9.2342.19200300.100.1.1 They are used internally for converting a DN into its string representation; components not listed in this table will be represented by their OID. For the other direction, i.e. creating a DN from the string representation, KSBA recognizes the following extra labels: Label Component OID ADDR postalAddress 2.5.4.16 BC businessCategory 2.5.4.15 D description 2.5.4.13 EMAIL emailAddress 1.2.840.113549.1.9.1 GN givenName 2.5.4.42 POSTALCODE postalCode 2.5.4.17 PSEUDO pseudonym 2.5.4.65 SERIALNUMBER serialNumber 2.5.4.5 SN surname 2.5.4.4 T title 2.5.4.12  File: ksba.info, Node: Copying, Next: Concept Index, Prev: Component Labels, Up: Top GNU General Public License ************************** Version 3, 29 June 2007 Copyright (C) 2007 Free Software Foundation, Inc. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble ======== The GNU General Public License is a free, copyleft license for software and other kinds of works. The licenses for most software and other practical works are designed to take away your freedom to share and change the works. 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If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation. If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program. Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version. 15. Disclaimer of Warranty. THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. 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ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. Copyright (C) YEAR NAME OF AUTHOR This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . Also add information on how to contact you by electronic and paper mail. If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode: PROGRAM Copyright (C) YEAR NAME OF AUTHOR This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'. This is free software, and you are welcome to redistribute it under certain conditions; type 'show c' for details. The hypothetical commands 'show w' and 'show c' should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an "about box". You should also get your employer (if you work as a programmer) or school, if any, to sign a "copyright disclaimer" for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see . The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read .  File: ksba.info, Node: Concept Index, Next: Function and Data Index, Prev: Copying, Up: Top Concept Index *************  File: ksba.info, Node: Function and Data Index, Prev: Concept Index, Up: Top Function and Data Index *********************** [index] * Menu: * ksba_cert_get_authority_info_access: Retrieving attributes. (line 263) * ksba_cert_get_auth_key_id: Retrieving attributes. (line 254) * ksba_cert_get_cert_policies: Retrieving attributes. (line 216) * ksba_cert_get_crl_dist_point: Retrieving attributes. (line 226) * ksba_cert_get_digest_algo: Retrieving attributes. (line 39) * ksba_cert_get_extension: Retrieving attributes. (line 164) * ksba_cert_get_ext_key_usages: Retrieving attributes. (line 210) * ksba_cert_get_image: Retrieving attributes. (line 11) * ksba_cert_get_issuer: Retrieving attributes. (line 57) * ksba_cert_get_key_usage: Retrieving attributes. (line 177) * ksba_cert_get_public_key: Retrieving attributes. (line 156) * ksba_cert_get_serial: Retrieving attributes. (line 50) * ksba_cert_get_sig_val: Retrieving attributes. (line 160) * ksba_cert_get_subject: Retrieving attributes. (line 84) * ksba_cert_get_subject_info_access: Retrieving attributes. (line 277) * ksba_cert_get_subj_key_id: Retrieving attributes. (line 245) * ksba_cert_get_user_data: User data. (line 26) * ksba_cert_get_validity: Retrieving attributes. (line 145) * ksba_cert_hash: Retrieving attributes. (line 24) * ksba_cert_init_from_mem: Creating certificates. (line 41) * ksba_cert_is_ca: Retrieving attributes. (line 169) * ksba_cert_new: Creating certificates. (line 9) * ksba_cert_read_der: Creating certificates. (line 30) * ksba_cert_ref: Creating certificates. (line 18) * ksba_cert_release: Creating certificates. (line 23) * ksba_cert_set_user_data: User data. (line 11) * ksba_cert_t: Certificate Handling. (line 9) * ksba_check_version: Version Check. (line 12) * ksba_cms_get_content_oid: CMS Parser. (line 89) * ksba_cms_get_content_type: CMS Parser. (line 54) * ksba_cms_new: CMS Basics. (line 16) * ksba_cms_parse: CMS Parser. (line 13) * ksba_cms_release: CMS Basics. (line 25) * ksba_cms_set_reader_writer: CMS Basics. (line 31) * ksba_cms_t: CMS Basics. (line 10) * ksba_content_t: CMS Parser. (line 61) * ksba_dn_teststr: DNs. (line 9) * ksba_isotime_t: Retrieving attributes. (line 109) * ksba_name_enum: Names. (line 17) * ksba_name_get_uri: Names. (line 36) * ksba_name_release: Names. (line 13) * ksba_name_t: Names. (line 10) * ksba_sexp_t: Certificate Handling. (line 12) * ksba_stop_reason_t: CMS Basics. (line 12)  Tag Table: Node: Top740 Node: Introduction2772 Node: Getting Started3050 Node: Features3916 Node: Overview5007 Node: Preparation5256 Node: Header5739 Node: Version Check6335 Node: Building the source7427 Node: Certificate Handling9271 Node: Creating certificates10252 Node: Retrieving attributes12713 Node: Setting attributes26390 Node: User data26655 Node: CMS28565 Node: CMS Basics29024 Node: CMS Parser31087 Node: CRLs35065 Node: PKCS1035348 Node: Utilities35609 Node: Names36013 Node: OIDs38325 Node: DNs38529 Node: Error Handling39660 Node: Component Labels41015 Node: Copying42578 Node: Concept Index80105 Node: Function and Data Index80233  End Tag Table