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rpcsec_gss - security flavor incorporating GSS-API protections

cc [ flag... ] file... -lnsl [ library... ]
#include <rpc/rpcsec_gss.h>

RPCSEC_GSS is a security flavor which sits "on top" of the GSS-API (Generic Security Service API) for network transmissions. Applications using RPCSEC_GSS can take advantage of GSS-API security features; moreover, they can use any security mechanism (such as RSA public key or Kerberos) that works with the GSS-API.

The GSS-API offers two security services beyond the traditional authentication services (AUTH_DH, AUTH_SYS, and AUTH_KERB): integrity and privacy. With integrity, the system uses cryptographic checksumming to ensure the authenticity of a message (authenticity of originator, recipient, and data); privacy provides additional security by encrypting data. Applications using RPCSEC_GSS specify which service they wish to use. Type of security service is mechanism-independent.

Before exchanging data with a peer, an application must establish a context for the exchange. RPCSEC_GSS provides a single function for this purpose, rpc_gss_seccreate(), which allows the application to specify the security mechanism, Quality of Protection (QOP), and type of service at context creation. (The QOP parameter sets the cryptographic algorithms to be used with integrity or privacy, and is mechanism-dependent.) Once a context is established, applications can reset the QOP and type of service for each data unit exchanged, if desired.

Valid mechanisms and QOPs may be obtained from configuration files or from the name service. Each mechanism has a default QOP.

Contexts are destroyed with the usual RPC auth_destroy() call.

Some of the data structures used by the RPCSEC_GSS package are shown below.

This enum defines the types of security services the context may have. rpc_gss_seccreate() takes this as one argument when setting the service type for a session.

typedef enum {
 rpc_gss_svc_default = 0,
 rpc_gss_svc_none = 1,
 rpc_gss_svc_integrity = 2,
 rpc_gss_svc_privacy = 3
} rpc_gss_service_t ;

Structure containing options passed directly through to the GSS-API. rpc_gss_seccreate() takes this as an argument when creating a context.

typedef struct {
 int req_flags; /*GSS request bits */
 int time_req; /*requested credential lifetime */
 gss_cred_id_t my_cred; /*GSS credential struct*/
 gss_channel_bindings_t;
 input_channel_bindings;
} rpc_gss_options_req_t ;

This data type is used by in-kernel RPC routines, and thus is mentioned here for informational purposes only.

typedef struct {
 u_int length; 
 void *elements 
} *rpc_gss_OID;

Structure containing GSS-API options returned to the calling function, rpc_gss_seccreate(). MAX_GSS_MECH is defined as 128.

typedef struct {
 int major_status;
 int minor_status;
 u_int rpcsec_version /*vers. of RPCSEC_GSS */
 int ret_flags
 int time_req
 gss_ctx_id_t gss_context;
 char actual_mechanism[MAX_GSS_MECH]; /*mechanism used*/
} rpc_gss_options_ret_t;

The (mechanism-dependent, opaque) client principal type. Used as an argument to the rpc_gss_get_principal_name() function, and in the gsscred table. Also referenced by the rpc_gss_rawcred_t structure for raw credentials (see below).

typedef struct {
 int len; 
 char name[1]; 
} *rpc_gss_principal_t;

Structure for raw credentials. Used by rpc_gss_getcred() and rpc_gss_set_callback().

typedef struct {
 u_int version; /*RPC version # */
 char *mechanism; /*security mechanism*/
 char *qop; /*Quality of Protection*/
 rpc_gss_principal_t client_principal; /*client name*/
 char *svc_principal; /*server name*/
 rpc_gss_service_t service; /*service (integrity, etc.)*/
} rpc_gss_rawcred_t;

Structure for UNIX credentials. Used by rpc_gss_getcred() as an alternative to rpc_gss_rawcred_t.

typedef struct {
 uid_t uid; /*user ID*/
 gid_t gid; /*group ID*/
 short gidlen; 
 git_t *gidlist; /*list of groups*/
} rpc_gss_ucred_t;

Callback structure used by rpc_gss_set_callback().

typedef struct {
 u_int program; /*RPC program #*/
 u_int version; /*RPC version #*/
 bool_t (*callback)(); /*user-defined callback routine*/
} rpc_gss_callback_t;

Structure used by a callback routine to enforce a particular QOP and service for a session. The locked field is normally set to FALSE; the server sets it to TRUE in order to lock the session. (A locked context will reject all requests having different QOP and service values than those found in the raw_cred structure.) For more information, see the rpc_gss_set_callback(3NSL) man page.

typedef struct {
 bool_t locked;
 rpc_gss_rawcred_t *raw_cred;
} rpc_gss_lock_t;

Structure used by rpc_gss_get_error() to fetch an error code when a RPCSEC_GSS routine fails.

typedef struct {
 int rpc_gss_error;
 int system_error; /*same as errno*/
} rpc_gss_error_t;

The following lists RPCSEC_GSS routines and the manual reference pages on which they are described. An (S) indicates it is a server-side function: Routine (Manual Page)

rpc_gss_seccreate(3NSL) rpc_gss_set_defaults(3NSL) rpc_gss_max_data_length(3NSL) rpc_gss_set_svc_name(3NSL) rpc_gss_getcred(3NSL) rpc_gss_set_callback(3NSL) rpc_gss_get_principal_name(3NSL) rpc_gss_svc_max_data_length(3NSL) rpc_gss_get_error(3NSL) rpc_gss_get_mechanisms(3NSL) rpc_gss_get_mech_info(3NSL) rpc_gss_get_versions(3NSL) rpc_gss_is_installed(3NSL) rpc_gss_mech_to_oid(3NSL) rpc_gss_qop_to_num(3NSL)

The gsscred utility manages the gsscred table, which contains mappings of principal names between network and local credentials. See gsscred(8).

/etc/gss/mech /etc/gss/qop

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE

MT-Level MT-Safe

rpc (3NSL), rpc_clnt_auth (3NSL), xdr (3NSL), attributes (7), environ (7), gsscred (8)

ONC+ Developer's Guide