Questions on gss_verify_mic_iov / KRB5_BAD_MSIZE

[Natalie Li]

On 09/15/15 08:00 AM, Natalie Li wrote:
> 1) Is it intended for supporting GSS_VerifyMICEx() call [support 
> multiple input buffers] mentioned in MS-KILE document as shown below?
>
> https://msdn.microsoft.com/en-us/library/cc233937.aspx
>
> 2) If yes to (1), then can you please confirm the usage of 
> gss_verify_mic_iov() in the following scenario described by MS-RPCE 
> document:
>
> <snippet - MS-RPCE>
> If the client and server Supports Header Signing Flag is TRUE, the 
> party that sends the PDU asks the security provider to apply the 
> following protection to the different PDU segments.
> Authentication level 		| PDU header	| PDU body	|sec_trailer
> -------------------------------------------------------------------------------
> RPC_C_AUTHN_LEVEL_PKT_INTEGRITY |Integrity	|Integrity	| Integrity
>
> :
> :
>      The PDU header, PDU body, and sec_trailer MUST be passed in the
>      input message, in this order, to GSS_WrapEx, GSS_UnwrapEx,
>      GSS_GetMICEx, and GSS_VerifyMICEx. For integrity protection the sign
>      flag for that PDU segment MUST be set to TRUE, else it MUST be set
>      to FALSE.
> <snippet>
>
> where the sign flag is:
>
> <snippet - MS-KILE>
>
> message ORDERED LIST of:
>
>  *
>
>     signed BOOLEAN <-----------------------------
>
>  *
>
>     data OCTET STRING
>
> <snippet>
>
> Based on the MS documentation above where "signed" flag should be set 
> for the various PDU segments, should the iov array be populated as 
> follows:
>
> gss_iov_buffer_desc     iov[4];
>
> /* PDU header */
> iov[0].type = GSS_IOV_BUFFER_TYPE_SIGN_ONLY;
> iov[0].buffer.value = <PDU header of the incoming message>
> iov[0].buffer.length = <PDU header length>
>
> /* PDU body */
> iov[1].type = GSS_IOV_BUFFER_TYPE_SIGN_ONLY;
> iov[1].buffer.value = <PDU body of the incoming message>
> iov[1].buffer.length = <PDU body length>
>
> /* sec_trailer */
> iov[2].type = GSS_IOV_BUFFER_TYPE_SIGN_ONLY;
> iov[2].buffer.value = <sec_trailer of the incoming message>
> iov[2].buffer.length = <sec_trailer length>
>
> /* MIC token */
> iov[3].type = GSS_IOV_BUFFER_TYPE_MIC_TOKEN;
> iov[3].buffer.value = <MIC token in the incoming message to be verified>
> iov[3].buffer.length = <MIC token length>
>
> major = gss_verify_mic_iov(&minor, gss_ctx, &qop_state, iov, 4);
> 3) I've looked at the MIT krb documentation but still not clear on the 
> various GSS_C_BUFFER_TYPE_XXX macros.
>
> a) Is GSS_C_BUFFER_TYPE_TRAILER intended for sec_trailer mentioned in 
> section 2.2.2.11 as shown below?
> https://msdn.microsoft.com/en-us/library/cc243931.aspx
>
> One of the Solaris Kerberos team members suggested that 
> GSS_C_BUFFER_TYPE_TRAILER required due to:
>   -> libgssapi_krb5:kg_verify_checksum_iov_v3(0xd0dee6210, 0x10, 0x10, 
> 0xd0dfe5610, 0x19, 0x7ffe0a607bf0)
>      -> libgssapi_krb5:checksum_iov_v3(0xd0dee6210, 0x10, 0x10, 
> 0xd0dfe5610, 0x19, 0x7ffe0a607bf0)
>           -> libgssapi_krb5:kg_locate_header_iov(0x7ffe0a607bf0, 0x4, 
> 0x101, 0x6, 0x19, 0x7ffe0a607bf0)
>           <- libgssapi_krb5:kg_locate_header_iov() = 0x7ffe0a607c38
>           -> libgssapi_krb5:kg_locate_iov(0x7ffe0a607bf0, 0x4, 0x7, 
> 0x7ffe0a607bd8, 0x19, 0x7ffe0a607bf0)
>          <- libgssapi_krb5:kg_locate_iov() = 0 
> <--GSS_C_BUFFER_TYPE_TRAILER(0x7) not found
>     <- libgssapi_krb5:checksum_iov_v3() = 0x96c73abe
>   <- libgssapi_krb5:kg_verify_checksum_iov_v3() = 0x96c73abe
> <- libgssapi_krb5:gss_krb5int_unseal_v3_iov() = 0x60000
>
> However, added another iov[4] of type TRAILER and the 
> gss_verify_mic_iov() still fail in other place.
To be specific, I'm seeing the following error message in either case:

(GSS major error): A token had an invalid Message Integrity Check (MIC)
(GSS minor error): Message size is incompatible with encryption type

Thanks,

Natalie

>
> b) GSS_C_BUFFER_TYPE_HEADER is not intended for the PDU header (MS-RPC 
> header) mentioned in (2), right? The MIT krb doc suggests that for 
> GSSAPI wrap token header.
> c) Is GSS_C_BUFFER_TYPE_DATA used only for encryption, not for signing?
>
> Thanks,
>
> Natalie
>