/* * 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. * * The internals of the structure should never be accessed directly, * functions exist for extracting information. * * 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. To create a crypto context call krb5_crypto_init(). * * 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_error_message() 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 * * 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(). 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 * uint32_t flags; #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. * * */