GSS_INIT_SEC_CONTEXT(3) FreeBSD Library Functions Manual (prm)
NAME
gss_init_sec_context - Initiate a security context with a peer
application
SYNOPSIS
#include <gssapi/gssapi.h>
OM_uint32
gss_init_sec_context(OM_uint32 *minor_status,
const gss_cred_id_t initiator_cred_handle,
gss_ctx_id_t *context_handle, const gss_name_t target_name,
const gss_OID mech_type, OM_uint32 req_flags, OM_uint32 time_req,
const gss_channel_bindings_t input_chan_bindings,
const gss_buffer_t input_token, gss_OID *actual_mech_type,
gss_buffer_t output_token, OM_uint32 *ret_flags,
OM_uint32 *time_rec);
DESCRIPTION
Initiates the establishment of a security context between the application
and a remote peer. Initially, the input_token parameter should be
specified either as GSS_C_NO_BUFFER, or as a pointer to a gss_buffer_desc
object whose length field contains the value zero. The routine may
return a output_token which should be transferred to the peer
application, where the peer application will present it to
gss_accept_sec_context(3). If no token need be sent,
gss_init_sec_context() will indicate this by setting the length field of
the output_token argument to zero. To complete the context establishment,
one or more reply tokens may be required from the peer application; if
so, gss_init_sec_context() will return a status containing the
supplementary information bit GSS_S_CONTINUE_NEEDED. In this case,
gss_init_sec_context() should be called again when the reply token is
received from the peer application, passing the reply token to
gss_init_sec_context() via the input_token parameters.
Portable applications should be constructed to use the token length and
return status to determine whether a token needs to be sent or waited
for. Thus a typical portable caller should always invoke
gss_init_sec_context() within a loop:
int context_established = 0;
gss_ctx_id_t context_hdl = GSS_C_NO_CONTEXT;
...
input_token->length = 0;
while (!context_established) {
maj_stat = gss_init_sec_context(&min_stat,
cred_hdl,
&context_hdl,
target_name,
desired_mech,
desired_services,
desired_time,
input_bindings,
input_token,
&actual_mech,
output_token,
&actual_services,
&actual_time);
if (GSS_ERROR(maj_stat)) {
report_error(maj_stat, min_stat);
};
if (output_token->length != 0) {
send_token_to_peer(output_token);
gss_release_buffer(&min_stat, output_token)
};
if (GSS_ERROR(maj_stat)) {
if (context_hdl != GSS_C_NO_CONTEXT)
gss_delete_sec_context(&min_stat,
&context_hdl,
GSS_C_NO_BUFFER);
break;
};
if (maj_stat & GSS_S_CONTINUE_NEEDED) {
receive_token_from_peer(input_token);
} else {
context_established = 1;
};
};
Whenever the routine returns a major status that includes the value
GSS_S_CONTINUE_NEEDED, the context is not fully established and the
following restrictions apply to the output parameters:
• The value returned via the time_rec parameter is undefined Unless the
accompanying ret_flags parameter contains the bit
GSS_C_PROT_READY_FLAG, indicating that per-message services may be
applied in advance of a successful completion status, the value
returned via the actual_mech_type parameter is undefined until the
routine returns a major status value of GSS_S_COMPLETE.
• The values of the GSS_C_DELEG_FLAG, GSS_C_MUTUAL_FLAG,
GSS_C_REPLAY_FLAG, GSS_C_SEQUENCE_FLAG, GSS_C_CONF_FLAG,
GSS_C_INTEG_FLAG and GSS_C_ANON_FLAG bits returned via the ret_flags
parameter should contain the values that the implementation expects
would be valid if context establishment were to succeed. In
particular, if the application has requested a service such as
delegation or anonymous authentication via the req_flags argument,
and such a service is unavailable from the underlying mechanism,
gss_init_sec_context() should generate a token that will not provide
the service, and indicate via the ret_flags argument that the service
will not be supported. The application may choose to abort the
context establishment by calling gss_delete_sec_context(3) (if it
cannot continue in the absence of the service), or it may choose to
transmit the token and continue context establishment (if the service
was merely desired but not mandatory).
• The values of the GSS_C_PROT_READY_FLAG and GSS_C_TRANS_FLAG bits
within ret_flags should indicate the actual state at the time
gss_init_sec_context() returns, whether or not the context is fully
established.
• GSS-API implementations that support per-message protection are
encouraged to set the GSS_C_PROT_READY_FLAG in the final ret_flags
returned to a caller (i.e. when accompanied by a GSS_S_COMPLETE
status code). However, applications should not rely on this behavior
as the flag was not defined in Version 1 of the GSS-API. Instead,
applications should determine what per-message services are available
after a successful context establishment according to the
GSS_C_INTEG_FLAG and GSS_C_CONF_FLAG values.
• All other bits within the ret_flags argument should be set to zero.
If the initial call of gss_init_sec_context() fails, the implementation
should not create a context object, and should leave the value of the
context_handle parameter set to GSS_C_NO_CONTEXT to indicate this. In
the event of a failure on a subsequent call, the implementation is
permitted to delete the "half-built" security context (in which case it
should set the context_handle parameter to GSS_C_NO_CONTEXT ), but the
preferred behavior is to leave the security context untouched for the
application to delete (using gss_delete_sec_context(3) ).
During context establishment, the informational status bits
GSS_S_OLD_TOKEN and GSS_S_DUPLICATE_TOKEN indicate fatal errors, and GSS-
API mechanisms should always return them in association with a routine
error of GSS_S_FAILURE. This requirement for pairing did not exist in
version 1 of the GSS-API specification, so applications that wish to run
over version 1 implementations must special-case these codes.
PARAMETERS
minor_status Mechanism specific status code.
initiator_cred_handle handle for credentials claimed. Supply
GSS_C_NO_CREDENTIAL to act as a default
initiator principal. If no default initiator
is defined, the function will return
GSS_S_NO_CRED.
context_handle context handle for new context. Supply
GSS_C_NO_CONTEXT for first call; use value
returned by first call in continuation calls.
Resources associated with this context-handle
must be released by the application after use
with a call to gss_delete_sec_context().
target_name Name of target
mech_type Object ID of desired mechanism. Supply
GSS_C_NO_OID to obtain an implementation
specific default
req_flags Contains various independent flags, each of
which requests that the context support a
specific service option. Symbolic names are
provided for each flag, and the symbolic names
corresponding to the required flags should be
logically-ORed together to form the bit-mask
value. The flags are:
GSS_C_DELEG_FLAG
True Delegate credentials to remote peer
False Don't delegate
GSS_C_MUTUAL_FLAG
True Request that remote peer
authenticate itself
False Authenticate self to remote peer
only
GSS_C_REPLAY_FLAG
True Enable replay detection for
messages protected with gss_wrap(3)
or gss_get_mic(3)
False Don't attempt to detect replayed
messages
GSS_C_SEQUENCE_FLAG
True Enable detection of out-of-sequence
protected messages
False Don't attempt to detect out-of-
sequence messages
GSS_C_CONF_FLAG
True Request that confidentiality
service be made available (via
gss_wrap(3))
False No per-message confidentiality
service is required.
GSS_C_INTEG_FLAG
True Request that integrity service be
made available (via gss_wrap(3) or
gss_get_mic(3))
False No per-message integrity service is
required.
GSS_C_ANON_FLAG
True Do not reveal the initiator's
identity to the acceptor.
False Authenticate normally.
time_req Desired number of seconds for which context
should remain valid. Supply 0 to request a
default validity period.
input_chan_bindings Application-specified bindings. Allows
application to securely bind channel
identification information to the security
context. Specify GSS_C_NO_CHANNEL_BINDINGS if
channel bindings are not used.
input_token Token received from peer application. Supply
GSS_C_NO_BUFFER, or a pointer to a buffer
containing the value GSS_C_EMPTY_BUFFER on
initial call.
actual_mech_type Actual mechanism used. The OID returned via
this parameter will be a pointer to static
storage that should be treated as read-only;
In particular the application should not
attempt to free it. Specify NULL if not
required.
output_token token to be sent to peer application. If the
length field of the returned buffer is zero,
no token need be sent to the peer application.
Storage associated with this buffer must be
freed by the application after use with a call
to gss_release_buffer(3).
ret_flags Contains various independent flags, each of
which indicates that the context supports a
specific service option. Specify NULL if not
required. Symbolic names are provided for
each flag, and the symbolic names
corresponding to the required flags should be
logically-ANDed with the ret_flags value to
test whether a given option is supported by
the context. The flags are:
GSS_C_DELEG_FLAG
True Credentials were delegated to the
remote peer
False No credentials were delegated
GSS_C_MUTUAL_FLAG
True The remote peer has authenticated
itself.
False Remote peer has not authenticated
itself.
GSS_C_REPLAY_FLAG
True Replay of protected messages will
be detected
False Replayed messages will not be
detected
GSS_C_SEQUENCE_FLAG
True Out-of-sequence protected messages
will be detected
False Out-of-sequence messages will not
be detected
GSS_C_CONF_FLAG
True Confidentiality service may be
invoked by calling gss_wrap(3)
routine
False No confidentiality service (via
gss_wrap(3)) available. gss_wrap(3)
will provide message encapsulation,
data-origin authentication and
integrity services only.
GSS_C_INTEG_FLAG
True Integrity service may be invoked by
calling either gss_get_mic(3) or
gss_wrap(3) routines.
False Per-message integrity service
unavailable.
GSS_C_ANON_FLAG
True The initiator's identity has not
been revealed, and will not be
revealed if any emitted token is
passed to the acceptor.
False The initiator's identity has been
or will be authenticated normally.
GSS_C_PROT_READY_FLAG
True Protection services (as specified
by the states of the
GSS_C_CONF_FLAG and
GSS_C_INTEG_FLAG) are available for
use if the accompanying major
status return value is either
GSS_S_COMPLETE or
GSS_S_CONTINUE_NEEDED.
False Protection services (as specified
by the states of the
GSS_C_CONF_FLAG and
GSS_C_INTEG_FLAG) are available
only if the accompanying major
status return value is
GSS_S_COMPLETE.
GSS_C_TRANS_FLAG
True The resultant security context may
be transferred to other processes
via a call to
gss_export_sec_context().
False The security context is not
transferable.
All other bits should be set to zero.
time_rec Number of seconds for which the context will
remain valid. If the implementation does not
support context expiration, the value
GSS_C_INDEFINITE will be returned. Specify
NULL if not required.
RETURN VALUES
GSS_S_COMPLETE Successful completion
GSS_S_CONTINUE_NEEDED Indicates that a token from the peer
application is required to complete the
context, and that gss_init_sec_context
must be called again with that token.
GSS_S_DEFECTIVE_TOKEN Indicates that consistency checks
performed on the input_token failed
GSS_S_DEFECTIVE_CREDENTIAL Indicates that consistency checks
performed on the credential failed.
GSS_S_NO_CRED The supplied credentials were not valid
for context initiation, or the credential
handle did not reference any credentials.
GSS_S_CREDENTIALS_EXPIRED The referenced credentials have expired
GSS_S_BAD_BINDINGS The input_token contains different channel
bindings to those specified via the
input_chan_bindings parameter
GSS_S_BAD_SIG The input_token contains an invalid MIC,
or a MIC that could not be verified
GSS_S_OLD_TOKEN The input_token was too old. This is a
fatal error during context establishment
GSS_S_DUPLICATE_TOKEN The input_token is valid, but is a
duplicate of a token already processed.
This is a fatal error during context
establishment.
GSS_S_NO_CONTEXT Indicates that the supplied context handle
did not refer to a valid context
GSS_S_BAD_NAMETYPE The provided target_name parameter
contained an invalid or unsupported type
of name
GSS_S_BAD_NAME The provided target_name parameter was
ill-formed.
GSS_S_BAD_MECH The specified mechanism is not supported
by the provided credential, or is
unrecognized by the implementation.
SEE ALSO
gss_accept_sec_context(3), gss_delete_sec_context(3), gss_get_mic(3),
gss_release_buffer(3), gss_wrap(3)
STANDARDS
RFC 2743 Generic Security Service Application Program Interface
Version 2, Update 1
RFC 2744 Generic Security Service API Version 2 : C-bindings
HISTORY
The gss_init_sec_context function first appeared in FreeBSD 7.0.
AUTHORS
John Wray, Iris Associates
COPYRIGHT
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FreeBSD 13.1-RELEASE-p6 January 26, 2010 FreeBSD 13.1-RELEASE-p6
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