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Every GSS-API routine returns two distinct values to report status information to the caller: GSS status codes and Mechanism status codes.
GSS-API routines return GSS status codes as their OM_uint32
function value. These codes indicate errors that are independent of
the underlying mechanism(s) used to provide the security service. The
errors that can be indicated via a GSS status code are either generic
API routine errors (errors that are defined in the GSS-API
specification) or calling errors (errors that are specific to these
language bindings).
A GSS status code can indicate a single fatal generic API error from the routine and a single calling error. In addition, supplementary status information may be indicated via the setting of bits in the supplementary info field of a GSS status code.
These errors are encoded into the 32-bit GSS status code as follows:
MSB LSB |------------------------------------------------------------| | Calling Error | Routine Error | Supplementary Info | |------------------------------------------------------------| Bit 31 24 23 16 15 0
Hence if a GSS-API routine returns a GSS status code whose upper 16 bits contain a non-zero value, the call failed. If the calling error field is non-zero, the invoking application’s call of the routine was erroneous. Calling errors are defined in table 3-1. If the routine error field is non-zero, the routine failed for one of the routine- specific reasons listed below in table 3-2. Whether or not the upper 16 bits indicate a failure or a success, the routine may indicate additional information by setting bits in the supplementary info field of the status code. The meaning of individual bits is listed below in table 3-3.
Table 3-1 Calling Errors Name Value in field Meaning ---- -------------- ------- GSS_S_CALL_INACCESSIBLE_READ 1 A required input parameter could not be read GSS_S_CALL_INACCESSIBLE_WRITE 2 A required output parameter could not be written. GSS_S_CALL_BAD_STRUCTURE 3 A parameter was malformed
Table 3-2 Routine Errors Name Value in field Meaning ---- -------------- ------- GSS_S_BAD_MECH 1 An unsupported mechanism was requested GSS_S_BAD_NAME 2 An invalid name was supplied GSS_S_BAD_NAMETYPE 3 A supplied name was of an unsupported type GSS_S_BAD_BINDINGS 4 Incorrect channel bindings were supplied GSS_S_BAD_STATUS 5 An invalid status code was supplied GSS_S_BAD_MIC GSS_S_BAD_SIG 6 A token had an invalid MIC GSS_S_NO_CRED 7 No credentials were supplied, or the credentials were unavailable or inaccessible. GSS_S_NO_CONTEXT 8 No context has been established GSS_S_DEFECTIVE_TOKEN 9 A token was invalid GSS_S_DEFECTIVE_CREDENTIAL 10 A credential was invalid GSS_S_CREDENTIALS_EXPIRED 11 The referenced credentials have expired GSS_S_CONTEXT_EXPIRED 12 The context has expired GSS_S_FAILURE 13 Miscellaneous failure (see text) GSS_S_BAD_QOP 14 The quality-of-protection requested could not be provided GSS_S_UNAUTHORIZED 15 The operation is forbidden by local security policy GSS_S_UNAVAILABLE 16 The operation or option is unavailable GSS_S_DUPLICATE_ELEMENT 17 The requested credential element already exists GSS_S_NAME_NOT_MN 18 The provided name was not a mechanism name
Table 3-3 Supplementary Status Bits Name Bit Number Meaning ---- ---------- ------- GSS_S_CONTINUE_NEEDED 0 (LSB) Returned only by gss_init_sec_context or gss_accept_sec_context. The routine must be called again to complete its function. See routine documentation for detailed description GSS_S_DUPLICATE_TOKEN 1 The token was a duplicate of an earlier token GSS_S_OLD_TOKEN 2 The token's validity period has expired GSS_S_UNSEQ_TOKEN 3 A later token has already been processed GSS_S_GAP_TOKEN 4 An expected per-message token was not received
The routine documentation also uses the name GSS_S_COMPLETE, which is a zero value, to indicate an absence of any API errors or supplementary information bits.
All GSS_S_xxx symbols equate to complete OM_uint32 status
codes, rather than to bitfield values. For example, the actual value
of the symbol GSS_S_BAD_NAMETYPE (value 3 in the routine error
field) is 3<<16. The macros GSS_CALLING_ERROR,
GSS_ROUTINE_ERROR and GSS_SUPPLEMENTARY_INFO are
provided, each of which takes a GSS status code and removes all but
the relevant field. For example, the value obtained by applying
GSS_ROUTINE_ERROR to a status code removes the calling errors
and supplementary info fields, leaving only the routine errors field.
The values delivered by these macros may be directly compared with a
GSS_S_xxx symbol of the appropriate type. The macro
GSS_ERROR is also provided, which when applied to a GSS status
code returns a non-zero value if the status code indicated a calling
or routine error, and a zero value otherwise. All macros defined by
GSS-API evaluate their argument(s) exactly once.
A GSS-API implementation may choose to signal calling errors in a platform-specific manner instead of, or in addition to the routine value; routine errors and supplementary info should be returned via major status values only.
The GSS major status code GSS_S_FAILURE is used to indicate
that the underlying mechanism detected an error for which no specific
GSS status code is defined. The mechanism-specific status code will
provide more details about the error.
In addition to the explicit major status codes for each API function,
the code GSS_S_FAILURE may be returned by any routine,
indicating an implementation-specific or mechanism-specific error
condition, further details of which are reported via the
minor_status parameter.
GSS-API routines return a minor_status parameter, which is used to
indicate specialized errors from the underlying security mechanism.
This parameter may contain a single mechanism-specific error,
indicated by a OM_uint32 value.
The minor_status parameter will always be set by a GSS-API routine,
even if it returns a calling error or one of the generic API errors
indicated above as fatal, although most other output parameters may
remain unset in such cases. However, output parameters that are
expected to return pointers to storage allocated by a routine must
always be set by the routine, even in the event of an error, although
in such cases the GSS-API routine may elect to set the returned
parameter value to NULL to indicate that no storage was actually
allocated. Any length field associated with such pointers (as in a
gss_buffer_desc structure) should also be set to zero in such cases.
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