The
krb5_auth_context structure holds all context related to an authenticated connection, in a similar way to
krb5_context that holds the context for the thread or process.
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-type.
krb5_auth_con_init() allocates and initializes the
krb5_auth_context structure. Default values can be changed with
krb5_auth_con_setcksumtype() and
krb5_auth_con_setflags(). The
auth_context structure must be freed by
krb5_auth_con_free().
krb5_auth_con_getflags(),
krb5_auth_con_setflags(),
krb5_auth_con_addflags() and
krb5_auth_con_removeflags() gets and modifies the flags for a
krb5_auth_context structure. Possible flags to set are:
KRB5_AUTH_CONTEXT_DO_SEQUENCE
Generate and check sequence-number on each packet.
KRB5_AUTH_CONTEXT_DO_TIME
Check timestamp on incoming packets.
KRB5_AUTH_CONTEXT_RET_SEQUENCE, KRB5_AUTH_CONTEXT_RET_TIME
Return sequence numbers and time stamps in the outdata parameters.
KRB5_AUTH_CONTEXT_CLEAR_FORWARDED_CRED
will force
krb5_get_forwarded_creds() and
krb5_fwd_tgt_creds() to create unencrypted )
ENCTYPE_NULL) credentials. This is for use with old MIT server and JAVA based servers as they can't handle encrypted
KRB-CRED. Note that sending such
KRB-CRED is clear exposes crypto keys and tickets and is insecure, make sure the packet is encrypted in the protocol.
krb5_rd_cred(3),
krb5_rd_priv(3),
krb5_rd_safe(3),
krb5_mk_priv(3) and
krb5_mk_safe(3). Setting this flag requires that parameter to be passed to these functions.
The flags
KRB5_AUTH_CONTEXT_DO_TIME also modifies the behavior the function
krb5_get_forwarded_creds() by removing the timestamp in the forward credential message, this have backward compatibility problems since not all versions of the heimdal supports timeless credentional messages. Is very useful since it always the sender of the message to cache forward message and thus avoiding a round trip to the KDC for each time a credential is forwarded. The same functionality can be obtained by using address-less tickets.
krb5_auth_con_setaddrs(),
krb5_auth_con_setaddrs_from_fd() and
krb5_auth_con_getaddrs() gets and sets the addresses that are checked when a packet is received. It is mandatory to set an address for the remote host. If the local address is not set, it iss deduced from the underlaying operating system.
krb5_auth_con_getaddrs() will call
krb5_free_address() on any address that is passed in
local_addr or
remote_addr.
krb5_auth_con_setaddr() allows passing in a
NULL pointer as
local_addr and
remote_addr, in that case it will just not set that address.
krb5_auth_con_setaddrs_from_fd() fetches the addresses from a file descriptor.
krb5_auth_con_genaddrs() fetches the address information from the given file descriptor
fd depending on the bitmap argument
flags.
Possible values on
flags are:
KRB5_AUTH_CONTEXT_GENERATE_LOCAL_ADDR
fetches the local address from fd.
KRB5_AUTH_CONTEXT_GENERATE_REMOTE_ADDR
fetches the remote address from fd.
krb5_auth_con_setkey(),
krb5_auth_con_setuserkey() and
krb5_auth_con_getkey() gets and sets the key used for this auth context. The keyblock returned by
krb5_auth_con_getkey() should be freed with
krb5_free_keyblock(). The keyblock send into
krb5_auth_con_setkey() is copied into the
krb5_auth_context, and thus no special handling is needed.
NULL is not a valid keyblock to
krb5_auth_con_setkey().
krb5_auth_con_setuserkey() is only useful when doing user to user authentication.
krb5_auth_con_setkey() is equivalent to
krb5_auth_con_setuserkey().
krb5_auth_con_getlocalsubkey(),
krb5_auth_con_setlocalsubkey(),
krb5_auth_con_getremotesubkey() and
krb5_auth_con_setremotesubkey() gets and sets the keyblock for the local and remote subkey. The keyblock returned by
krb5_auth_con_getlocalsubkey() and
krb5_auth_con_getremotesubkey() must be freed with
krb5_free_keyblock().
krb5_auth_setcksumtype() and
krb5_auth_getcksumtype() sets and gets the checksum type that should be used for this connection.
krb5_auth_con_generatelocalsubkey() generates a local subkey that have the same encryption type as
key.
krb5_auth_getremoteseqnumber()
krb5_auth_setremoteseqnumber(),
krb5_auth_getlocalseqnumber() and
krb5_auth_setlocalseqnumber() gets and sets the sequence-number for the local and remote sequence-number counter.
krb5_auth_setkeytype() and
krb5_auth_getkeytype() gets and gets the keytype of the keyblock in
krb5_auth_context.
krb5_auth_con_getauthenticator() Retrieves the authenticator that was used during mutual authentication. The
authenticator returned should be freed by calling
krb5_free_authenticator().
krb5_auth_con_getrcache() and
krb5_auth_con_setrcache() gets and sets the replay-cache.
krb5_auth_con_initivector() allocates memory for and zeros the initial vector in the
auth_context keyblock.
krb5_auth_con_setivector() sets the i_vector portion of
auth_context to
ivector.
krb5_free_authenticator() free the content of
authenticator and
authenticator itself.