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heimdal/lib/krb5/doxygen.c
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/*
* Copyright (c) 2007-2008 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "krb5_locl.h"
/**
*
*/
/*! @mainpage Heimdal Kerberos 5 library
*
* @section intro Introduction
*
* Heimdal libkrb5 library is a implementation of the Kerberos
* protocol.
*
* Kerberos is a system for authenticating users and services on a
* network. It is built upon the assumption that the network is
* ``unsafe''. For example, data sent over the network can be
* eavesdropped and altered, and addresses can also be faked.
* Therefore they cannot be used for authentication purposes.
*
*
* - @ref krb5_introduction
* - @ref krb5_principal_intro
* - @ref krb5_ccache_intro
* - @ref krb5_keytab_intro
*
* If you want to know more about the file formats that is used by
* Heimdal, please see: @ref krb5_fileformats
*
* The project web page: http://www.h5l.org/
*
*/
/** @defgroup krb5 Heimdal Kerberos 5 library */
/** @defgroup krb5_address Heimdal Kerberos 5 address functions */
/** @defgroup krb5_principal Heimdal Kerberos 5 principal functions */
/** @defgroup krb5_ccache Heimdal Kerberos 5 credential cache functions */
/** @defgroup krb5_crypto Heimdal Kerberos 5 cryptography functions */
/** @defgroup krb5_credential Heimdal Kerberos 5 credential handing functions */
/** @defgroup krb5_deprecated Heimdal Kerberos 5 deprecated functions */
/** @defgroup krb5_digest Heimdal Kerberos 5 digest service */
/** @defgroup krb5_error Heimdal Kerberos 5 error reporting functions */
/** @defgroup krb5_keytab Heimdal Kerberos 5 keytab handling functions */
/** @defgroup krb5_ticket Heimdal Kerberos 5 ticket functions */
/** @defgroup krb5_pac Heimdal Kerberos 5 PAC handling functions */
/** @defgroup krb5_v4compat Heimdal Kerberos 4 compatiblity functions */
/** @defgroup krb5_storage Heimdal Kerberos 5 storage functions */
/** @defgroup krb5_support Heimdal Kerberos 5 support functions */
/** @defgroup krb5_auth Heimdal Kerberos 5 authentication functions */
/**
* @page krb5_introduction Introduction to the Kerberos 5 API
* @section api_overview Kerberos 5 API Overview
*
* All functions are documented in manual pages. This section tries
* to give an overview of the major components used in Kerberos
* library, and point to where to look for a specific function.
*
* @subsection intro_krb5_context Kerberos context
*
* A kerberos context (krb5_context) holds all per thread state. All
* global variables that are context specific are stored in this
* structure, including default encryption types, credential cache
* (for example, a ticket file), and default realms.
*
* See the manual page for krb5_init_context() how to create a context
* and module @ref krb5 for more information about the functions.
*
* @subsection intro_krb5_auth_context Kerberos authentication context
*
* Kerberos authentication context (krb5_auth_context) holds all
* context related to an authenticated connection, in a similar way to
* the kerberos context that holds the context for the thread or
* process.
*
* The krb5_auth_context is used by various functions that are
* directly related to authentication between the
* server/client. Example of data that this structure contains are
* various flags, addresses of client and server, port numbers,
* keyblocks (and subkeys), sequence numbers, replay cache, and
* checksum types.
*
* @subsection intro_krb5_principal Kerberos principal
*
* The Kerberos principal is the structure that identifies a user or
* service in Kerberos. The structure that holds the principal is the
* krb5_principal. There are function to extract the realm and
* elements of the principal, but most applications have no reason to
* inspect the content of the structure.
*
* The are several ways to create a principal (with different degree of
* portability), and one way to free it.
*
* See also the page @ref krb5_principal_intro for more information and also
* module @ref krb5_principal.
*
* @subsection intro_krb5_ccache Credential cache
*
* A credential cache holds the tickets for a user. A given user can
* have several credential caches, one for each realm where the user
* have the initial tickets (the first krbtgt).
*
* The credential cache data can be stored internally in different
* way, each of them for different proposes. File credential (FILE)
* caches and processes based (KCM) caches are for permanent
* storage. While memory caches (MEMORY) are local caches to the local
* process.
*
* Caches are opened with krb5_cc_resolve() or created with
* krb5_cc_new_unique().
*
* If the cache needs to be opened again (using krb5_cc_resolve())
* krb5_cc_close() will close the handle, but not the remove the
* cache. krb5_cc_destroy() will zero out the cache, remove the cache
* so it can no longer be referenced.
*
* See also @ref krb5_ccache_intro and @ref krb5_ccache .
*
* @subsection intro_krb5_error_code Kerberos errors
*
* Kerberos errors are based on the com_err library. All error codes are
* 32-bit signed numbers, the first 24 bits define what subsystem the
* error originates from, and last 8 bits are 255 error codes within the
* library. Each error code have fixed string associated with it. For
* example, the error-code -1765328383 have the symbolic name
* KRB5KDC_ERR_NAME_EXP, and associated error string ``Client's entry in
* database has expired''.
*
* This is a great improvement compared to just getting one of the unix
* error-codes back. However, Heimdal have an extention to pass back
* customised errors messages. Instead of getting ``Key table entry not
* found'', the user might back ``failed to find
* host/host.example.com\@EXAMLE.COM(kvno 3) in keytab /etc/krb5.keytab
* (des-cbc-crc)''. This improves the chance that the user find the
* cause of the error so you should use the customised error message
* whenever it's available.
*
* See also module @ref krb5_error .
*
*
* @subsection intro_krb5_keytab Keytab management
*
* A keytab is a storage for locally stored keys. Heimdal includes keytab
* support for Kerberos 5 keytabs, Kerberos 4 srvtab, AFS-KeyFile's,
* and for storing keys in memory.
*
* Keytabs are used for servers and long-running services.
*
* See also @ref krb5_keytab_intro and @ref krb5_keytab .
*
* @subsection intro_krb5_crypto Kerberos crypto
*
* Heimdal includes a implementation of the Kerberos crypto framework,
* all crypto operations.
*
* See also module @ref krb5_crypto .
*
* @section kerberos5_client Walkthrough of a sample Kerberos 5 client
*
* This example contains parts of a sample TCP Kerberos 5 clients, if you
* want a real working client, please look in appl/test directory in
* the Heimdal distribution.
*
* All Kerberos error-codes that are returned from kerberos functions in
* this program are passed to krb5_err, that will print a
* descriptive text of the error code and exit. Graphical programs can
* convert error-code to a human readable error-string with the
* krb5_get_err_text() function.
*
* Note that you should not use any Kerberos function before
* krb5_init_context() have completed successfully. That is the
* reason err() is used when krb5_init_context() fails.
*
* First the client needs to call krb5_init_context to initialise
* the Kerberos 5 library. This is only needed once per thread
* in the program. If the function returns a non-zero value it indicates
* that either the Kerberos implementation is failing or it's disabled on
* this host.
*
* @code
* #include <krb5.h>
*
* int
* main(int argc, char **argv)
* {
* krb5_context context;
*
* if (krb5_init_context(&context))
* errx (1, "krb5_context");
* @endcode
*
* Now the client wants to connect to the host at the other end. The
* preferred way of doing this is using getaddrinfo (for
* operating system that have this function implemented), since getaddrinfo
* is neutral to the address type and can use any protocol that is available.
*
* @code
* struct addrinfo *ai, *a;
* struct addrinfo hints;
* int error;
*
* memset (&hints, 0, sizeof(hints));
* hints.ai_socktype = SOCK_STREAM;
* hints.ai_protocol = IPPROTO_TCP;
*
* error = getaddrinfo (hostname, "pop3", &hints, &ai);
* if (error)
* errx (1, "%s: %s", hostname, gai_strerror(error));
*
* for (a = ai; a != NULL; a = a->ai_next) {
* int s;
*
* s = socket (a->ai_family, a->ai_socktype, a->ai_protocol);
* if (s < 0)
* continue;
* if (connect (s, a->ai_addr, a->ai_addrlen) < 0) {
* warn ("connect(%s)", hostname);
* close (s);
* continue;
* }
* freeaddrinfo (ai);
* ai = NULL;
* }
* if (ai) {
* freeaddrinfo (ai);
* errx ("failed to contact %s", hostname);
* }
* @endcode
*
* Before authenticating, an authentication context needs to be
* created. This context keeps all information for one (to be) authenticated
* connection (see krb5_auth_context).
*
* @code
* status = krb5_auth_con_init (context, &auth_context);
* if (status)
* krb5_err (context, 1, status, "krb5_auth_con_init");
* @endcode
*
* For setting the address in the authentication there is a help function
* krb5_auth_con_setaddrs_from_fd() that does everything that is needed
* when given a connected file descriptor to the socket.
*
* @code
* status = krb5_auth_con_setaddrs_from_fd (context,
* auth_context,
* &sock);
* if (status)
* krb5_err (context, 1, status,
* "krb5_auth_con_setaddrs_from_fd");
* @endcode
*
* The next step is to build a server principal for the service we want
* to connect to. (See also krb5_sname_to_principal().)
*
* @code
* status = krb5_sname_to_principal (context,
* hostname,
* service,
* KRB5_NT_SRV_HST,
* &server);
* if (status)
* krb5_err (context, 1, status, "krb5_sname_to_principal");
* @endcode
*
* The client principal is not passed to krb5_sendauth()
* function, this causes the krb5_sendauth() function to try to figure it
* out itself.
*
* The server program is using the function krb5_recvauth() to
* receive the Kerberos 5 authenticator.
*
* In this case, mutual authentication will be tried. That means that the server
* will authenticate to the client. Using mutual authentication
* is good since it enables the user to verify that they are talking to the
* right server (a server that knows the key).
*
* If you are using a non-blocking socket you will need to do all work of
* krb5_sendauth() yourself. Basically you need to send over the
* authenticator from krb5_mk_req() and, in case of mutual
* authentication, verifying the result from the server with
* krb5_rd_rep().
*
* @code
* status = krb5_sendauth (context,
* &auth_context,
* &sock,
* VERSION,
* NULL,
* server,
* AP_OPTS_MUTUAL_REQUIRED,
* NULL,
* NULL,
* NULL,
* NULL,
* NULL,
* NULL);
* if (status)
* krb5_err (context, 1, status, "krb5_sendauth");
* @endcode
*
* Once authentication has been performed, it is time to send some
* data. First we create a krb5_data structure, then we sign it with
* krb5_mk_safe() using the auth_context that contains the
* session-key that was exchanged in the
* krb5_sendauth()/krb5_recvauth() authentication
* sequence.
*
* @code
* data.data = "hej";
* data.length = 3;
*
* krb5_data_zero (&packet);
*
* status = krb5_mk_safe (context,
* auth_context,
* &data,
* &packet,
* NULL);
* if (status)
* krb5_err (context, 1, status, "krb5_mk_safe");
* @endcode
*
* And send it over the network.
*
* @code
* len = packet.length;
* net_len = htonl(len);
*
* if (krb5_net_write (context, &sock, &net_len, 4) != 4)
* err (1, "krb5_net_write");
* if (krb5_net_write (context, &sock, packet.data, len) != len)
* err (1, "krb5_net_write");
* @endcode
*
* To send encrypted (and signed) data krb5_mk_priv() should be
* used instead. krb5_mk_priv() works the same way as
* krb5_mk_safe(), with the exception that it encrypts the data
* in addition to signing it.
*
* @code
* data.data = "hemligt";
* data.length = 7;
*
* krb5_data_free (&packet);
*
* status = krb5_mk_priv (context,
* auth_context,
* &data,
* &packet,
* NULL);
* if (status)
* krb5_err (context, 1, status, "krb5_mk_priv");
* @endcode
*
* And send it over the network.
*
* @code
* len = packet.length;
* net_len = htonl(len);
*
* if (krb5_net_write (context, &sock, &net_len, 4) != 4)
* err (1, "krb5_net_write");
* if (krb5_net_write (context, &sock, packet.data, len) != len)
* err (1, "krb5_net_write");
*
* @endcode
*
* The server is using krb5_rd_safe() and
* krb5_rd_priv() to verify the signature and decrypt the packet.
*
* @section intro_krb5_verify_user Validating a password in an application
*
* See the manual page for krb5_verify_user().
*
* @section mit_differences API differences to MIT Kerberos
*
* This section is somewhat disorganised, but so far there is no overall
* structure to the differences, though some of the have their root in
* that Heimdal uses an ASN.1 compiler and MIT doesn't.
*
* @subsection mit_krb5_principal Principal and realms
*
* Heimdal stores the realm as a krb5_realm, that is a char *.
* MIT Kerberos uses a krb5_data to store a realm.
*
* In Heimdal krb5_principal doesn't contain the component
* name_type; it's instead stored in component
* name.name_type. To get and set the nametype in Heimdal, use
* krb5_principal_get_type() and
* krb5_principal_set_type().
*
* For more information about principal and realms, see
* krb5_principal.
*
* @subsection mit_krb5_error_code Error messages
*
* To get the error string, Heimdal uses
* krb5_get_error_message() or, if NULL is returned,
* krb5_get_err_text(). This is to return custom error messages
* (like ``Can't find host/datan.example.com\@CODE.COM in
* /etc/krb5.conf.'' instead of a ``Key table entry not found'' that
* error_message returns.
*
* Heimdal uses a threadsafe(r) version of the com_err interface; the
* global com_err table isn't initialised. Then
* error_message returns quite a boring error string (just
* the error code itself).
*
*
*/
/**
*
*
* @page krb5_fileformats File formats
*
* @section fileformats File formats
*
* This section documents the diffrent file formats that are used in
* Heimdal and other Kerberos implementations.
*
* @subsection file_keytab keytab
*
* The keytab binary format is not a standard format. The format has
* evolved and may continue to. It is however understood by several
* Kerberos implementations including Heimdal, MIT, Sun's Java ktab and
* are created by the ktpass.exe utility from Windows. So it has
* established itself as the defacto format for storing Kerberos keys.
*
* The following C-like structure definitions illustrate the MIT keytab
* file format. All values are in network byte order. All text is ASCII.
*
* @code
* keytab {
* uint16_t file_format_version; # 0x502
* keytab_entry entries[*];
* };
*
* keytab_entry {
* int32_t size;
* uint16_t num_components; # subtract 1 if version 0x501
* counted_octet_string realm;
* counted_octet_string components[num_components];
* uint32_t name_type; # not present if version 0x501
* uint32_t timestamp;
* uint8_t vno8;
* keyblock key;
* uint32_t vno; #only present if >= 4 bytes left in entry
* };
*
* counted_octet_string {
* uint16_t length;
* uint8_t data[length];
* };
*
* keyblock {
* uint16_t type;
* counted_octet_string;
* };
* @endcode
*
* All numbers are stored in network byteorder (big endian) format.
*
* The keytab file format begins with the 16 bit file_format_version which
* at the time this document was authored is 0x502. The format of older
* keytabs is described at the end of this document.
*
* The file_format_version is immediately followed by an array of
* keytab_entry structures which are prefixed with a 32 bit size indicating
* the number of bytes that follow in the entry. Note that the size should be
* evaluated as signed. This is because a negative value indicates that the
* entry is in fact empty (e.g. it has been deleted) and that the negative
* value of that negative value (which is of course a positive value) is
* the offset to the next keytab_entry. Based on these size values alone
* the entire keytab file can be traversed.
*
* The size is followed by a 16 bit num_components field indicating the
* number of counted_octet_string components in the components array.
*
* The num_components field is followed by a counted_octet_string
* representing the realm of the principal.
*
* A counted_octet_string is simply an array of bytes prefixed with a 16
* bit length. For the realm and name components, the counted_octet_string
* bytes are ASCII encoded text with no zero terminator.
*
* Following the realm is the components array that represents the name of
* the principal. The text of these components may be joined with slashs
* to construct the typical SPN representation. For example, the service
* principal HTTP/www.foo.net\@FOO.NET would consist of name components
* "HTTP" followed by "www.foo.net".
*
* Following the components array is the 32 bit name_type (e.g. 1 is
* KRB5_NT_PRINCIPAL, 2 is KRB5_NT_SRV_INST, 5 is KRB5_NT_UID, etc). In
* practice the name_type is almost certainly 1 meaning KRB5_NT_PRINCIPAL.
*
* The 32 bit timestamp indicates the time the key was established for that
* principal. The value represents the number of seconds since Jan 1, 1970.
*
* The 8 bit vno8 field is the version number of the key. This value is
* overridden by the 32 bit vno field if it is present. The vno8 field is
* filled with the lower 8 bits of the 32 bit protocol kvno field.
*
* The keyblock structure consists of a 16 bit value indicating the
* encryption type and is a counted_octet_string containing the key. The
* encryption type is the same as the Kerberos standard (e.g. 3 is
* des-cbc-md5, 23 is arcfour-hmac-md5, etc).
*
* The last field of the keytab_entry structure is optional. If the size of
* the keytab_entry indicates that there are at least 4 bytes remaining,
* a 32 bit value representing the key version number is present. This
* value supersedes the 8 bit vno8 value preceeding the keyblock.
*
* Older keytabs with a file_format_version of 0x501 are different in
* three ways:
*
* - All integers are in host byte order [1].
* - The num_components field is 1 too large (i.e. after decoding, decrement by 1).
* - The 32 bit name_type field is not present.
*
* [1] The file_format_version field should really be treated as two
* separate 8 bit quantities representing the major and minor version
* number respectively.
*
* @subsection file_hdb_dump Heimdal database dump file
*
* Format of the Heimdal text dump file as of Heimdal 0.6.3:
*
* Each line in the dump file is one entry in the database.
*
* Each field of a line is separated by one or more spaces, with the
* exception of fields consisting of principals containing spaces, where
* space can be quoted with \ and \ is quoted by \.
*
* Fields and their types are:
*
* @code
* Quoted princial (quote character is \) [string]
* Keys [keys]
* Created by [event]
* Modified by [event optional]
* Valid start time [time optional]
* Valid end time [time optional]
* Password end valid time [time optional]
* Max lifetime of ticket [time optional]
* Max renew time of ticket [integer optional]
* Flags [hdb flags]
* Generation number [generation optional]
* Extensions [extentions optional]
* @endcode
*
* Fields following these silently are ignored.
*
* All optional fields will be skipped if they fail to parse (or comprise
* the optional field marker of "-", w/o quotes).
*
* Example:
*
* @code
* fred\@CODE.COM 27:1:16:e8b4c8fc7e60b9e641dcf4cff3f08a701d982a2f89ba373733d26ca59ba6c789666f6b8bfcf169412bb1e5dceb9b33cda29f3412:-:1:3:4498a933881178c744f4232172dcd774c64e81fa6d05ecdf643a7e390624a0ebf3c7407a:-:1:2:b01934b13eb795d76f3a80717d469639b4da0cfb644161340ef44fdeb375e54d684dbb85:-:1:1:ea8e16d8078bf60c781da90f508d4deccba70595258b9d31888d33987cd31af0c9cced2e:- 20020415130120:admin\@CODE.COM 20041221112428:fred\@CODE.COM - - - 86400 604800 126 20020415130120:793707:28 -
* @endcode
*
* Encoding of types are as follows:
*
* - keys
*
* @code
* kvno:[masterkvno:keytype:keydata:salt]{zero or more separated by :}
* @endcode
*
* kvno is the key version number.
*
* keydata is hex-encoded
*
* masterkvno is the kvno of the database master key. If this field is
* empty, the kadmin load and merge operations will encrypt the key data
* with the master key if there is one. Otherwise the key data will be
* imported asis.
*
* salt is encoded as "-" (no/default salt) or
*
* @code
* salt-type /
* salt-type / "string"
* salt-type / hex-encoded-data
* @endcode
*
* keytype is the protocol enctype number; see enum ENCTYPE in
* include/krb5_asn1.h for values.
*
* Example:
* @code
* 27:1:16:e8b4c8fc7e60b9e641dcf4cff3f08a701d982a2f89ba373733d26ca59ba6c789666f6b8bfcf169412bb1e5dceb9b33cda29f3412:-:1:3:4498a933881178c744f4232172dcd774c64e81fa6d05ecdf643a7e390624a0ebf3c7407a:-:1:2:b01934b13eb795d76f3a80717d469639b4da0cfb644161340ef44fdeb375e54d684dbb85:-:1:1:ea8e16d8078bf60c781da90f508d4deccba70595258b9d31888d33987cd31af0c9cced2e:-
* @endcode
*
*
* @code
* kvno=27,{key: masterkvno=1,keytype=des3-cbc-sha1,keydata=..., default salt}...
* @endcode
*
* - time
*
* Format of the time is: YYYYmmddHHMMSS, corresponding to strftime
* format "%Y%m%d%k%M%S".
*
* Time is expressed in UTC.
*
* Time can be optional (using -), when the time 0 is used.
*
* Example:
*
* @code
* 20041221112428
* @endcode
*
* - event
*
* @code
* time:principal
* @endcode
*
* time is as given in format time
*
* principal is a string. Not quoting it may not work in earlier
* versions of Heimdal.
*
* Example:
* @code
* 20041221112428:bloggs\@CODE.COM
* @endcode
*
* - hdb flags
*
* Integer encoding of HDB flags, see HDBFlags in lib/hdb/hdb.asn1. Each
* bit in the integer is the same as the bit in the specification.
*
* - generation:
*
* @code
* time:usec:gen
* @endcode
*
*
* usec is a the microsecond, integer.
* gen is generation number, integer.
*
* The generation can be defaulted (using '-') or the empty string
*
* - extensions:
*
* @code
* first-hex-encoded-HDB-Extension[:second-...]
* @endcode
*
* HDB-extension is encoded the DER encoded HDB-Extension from
* lib/hdb/hdb.asn1. Consumers HDB extensions should be aware that
* unknown entires needs to be preserved even thought the ASN.1 data
* content might be unknown. There is a critical flag in the data to show
* to the KDC that the entry MUST be understod if the entry is to be
* used.
*
*
*/
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