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FreeBSD 11.0 - man page for gss_accept_sec_context (freebsd section 3)

GSS_ACCEPT_SEC_CONTEXT(3)					Programmer's Manual					 GSS_ACCEPT_SEC_CONTEXT(3)

gss_accept_sec_context -- Accept a security context initiated by a peer application
#include <gssapi/gssapi.h> OM_uint32 gss_accept_sec_context(OM_uint32 *minor_status, gss_ctx_id_t *context_handle, const gss_cred_id_t acceptor_cred_handle, const gss_buffer_t input_token_buffer, const gss_channel_bindings_t input_chan_bindings, const gss_name_t *src_name, gss_OID *mech_type, gss_buffer_t output_token, OM_uint32 *ret_flags, OM_uint32 *time_rec, gss_cred_id_t *delegated_cred_handle);
Allows a remotely initiated security context between the application and a remote peer to be established. The routine may return a output_token which should be transferred to the peer application, where the peer application will present it to gss_init_sec_context(3). If no token need be sent, gss_accept_sec_context() will indicate this by setting the length field of the output_token argument to zero. To com- plete the context establishment, one or more reply tokens may be required from the peer application; if so, gss_accept_sec_context() will return a status flag of GSS_S_CONTINUE_NEEDED, in which case it should be called again when the reply token is received from the peer appli- cation, passing the token to gss_accept_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_accept_sec_context() within a loop: gss_ctx_id_t context_hdl = GSS_C_NO_CONTEXT; do { receive_token_from_peer(input_token); maj_stat = gss_accept_sec_context(&min_stat, &context_hdl, cred_hdl, input_token, input_bindings, &client_name, &mech_type, output_token, &ret_flags, &time_rec, &deleg_cred); 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; }; } while (maj_stat & GSS_S_CONTINUE_NEEDED); Whenever the routine returns a major status that includes the value GSS_S_CONTINUE_NEEDED, the context is not fully established and the fol- lowing 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 mech_type parameter may be 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. 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_accept_sec_context() returns, whether or not the context is fully established. Although this requires that GSS-API implementations 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), applications should not rely on this behavior as the flag was not defined in Version 1 of the GSS-API. Instead, applications should be prepared to use per-message services 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. While the routine returns GSS_S_CONTINUE_NEEDED, the values returned via the ret_flags argument indicate the services that the implementation expects to be available from the established context. If the initial call of gss_accept_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 (and the context_handle parameter) 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 ver- sion 1 of the GSS-API specification, so applications that wish to run over version 1 implementations must special-case these codes.
context_handle Context handle for new context. Supply GSS_C_NO_CONTEXT for first call; use value returned in subsequent calls. Once gss_accept_sec_context() has returned a value via this parameter, resources have been assigned to the corresponding con- text, and must be freed by the application after use with a call to gss_delete_sec_context(3). acceptor_cred_handle Credential handle claimed by context acceptor. Specify GSS_C_NO_CREDENTIAL to accept the context as a default princi- pal. If GSS_C_NO_CREDENTIAL is specified, but no default acceptor principal is defined, GSS_S_NO_CRED will be returned. input_token_buffer Token obtained from remote application. input_chan_bindings Application-specified bindings. Allows application to securely bind channel identification information to the security context. If channel bindings are not used, specify GSS_C_NO_CHANNEL_BINDINGS. src_name Authenticated name of context initiator. After use, this name should be deallocated by passing it to gss_release_name(3). If not required, specify NULL. mech_type Security mechanism used. The returned OID value will be a pointer into static storage, and should be treated as read- only by the caller (in particular, it does not need to be freed). If not required, specify NULL. output_token Token to be passed to peer application. If the length field of the returned token buffer is 0, then no token need be passed to the peer application. If a non-zero length field is returned, the associated storage must be freed after use by the application 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. If not needed, specify NULL. 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 Delegated credentials are available via the delegated_cred_handle parameter False No credentials were delegated GSS_C_MUTUAL_FLAG True Remote peer asked for mutual authentication False Remote peer did not ask for mutual authentication 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 the 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 does not wish to be authenticated; the src_name parameter (if requested) contains an anonymous internal name. False The initiator has been 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 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(3). 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. Specify NULL if not required. delegated_cred_handle Credential handle for credentials received from context initiator. Only valid if GSS_C_DELEG_FLAG in ret_flags is true, in which case an explicit credential handle (i.e. not GSS_C_NO_CREDENTIAL) will be returned; if false, gss_accept_context() will set this parameter to GSS_C_NO_CREDENTIAL. If a credential handle is returned, the associated resources must be released by the application after use with a call to gss_release_cred(3). Specify NULL if not required. minor_status Mechanism specific status code.
GSS_S_CONTINUE_NEEDED Indicates that a token from the peer application is required to complete the context, and that gss_accept_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 acceptance, 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_NO_CONTEXT Indicates that the supplied context handle did not refer to a valid context. GSS_S_BAD_SIG The input_token contains an invalid MIC. 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_BAD_MECH The received token specified a mechanism that is not supported by the implementation or the provided credential.
gss_delete_sec_context(3), gss_export_sec_context(3), gss_get_mic(3), gss_init_sec_context(3), gss_release_buffer(3), gss_release_cred(3), gss_release_name(3), gss_wrap(3)
RFC 2743 Generic Security Service Application Program Interface Version 2, Update 1 RFC 2744 Generic Security Service API Version 2 : C-bindings
The gss_accept_sec_context function first appeared in FreeBSD 7.0.
John Wray, Iris Associates
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January 26, 2010 BSD