[xmlsec] xmlSecDSigCtxVerify fails

[Aleksey Sanin]

See my answers inline.

Aleksey


On 2/3/2010 10:15 PM, mahendra N wrote:
> Hi Aleksey,
>              In /xmlSecDSigCtxVerify/ there are calls to two functions
> /xmlSecDSigCtxProcessSignatureNode/ and /xmlSecTransformVerifyNodeContent/
> / After the call to x/mlSecDSigCtxProcessSignatureNode /there is a check
> placed for /
> /      dSigCtx->status!=xmlSecDSigStatusUnknown .If there is a success
> then the function returns 0. Is this check absolutely necessary at that
> point in the code?. Because when we comment the check and proceed
> further, then /xmlSecTransformVerifyNodeContent /returns -1 for any XML
> file that is tampered./

[Aleksey] The check there returns -1 if the status is NOT equal to
xmlSecDSigStatusUnknown. This is a check to make sure that we don't
have unexpected state in the signature. One of the possible cases where
it might happen is if you are re-using the *same* xmlDsigCtx for
multiple signatures w/o calling xmlSecDSigCtxFinalize().


> /
> /
> /
> /
> /And I tried with purify tool, there was no memory corruption reported/
> /./
> /Aleksey the system where this error is reproduced is a 64-bit, MIPS
> architecture ,Windriver linux/
> /
> /
> /.Are there any specific compiler flags to be set for the above
> mentioned configuration./
> /
[Aleksey] No idea. Never used such a setup.

> /
> /
> /
> Some more investigation that was done:
> (i) The unpredictable behaviour  is due to mismatch of memory location
> of status member of the structure struct xmlSecDSigCtx.
> (ii) I tried to get the adress of each of the member variable of
> structure xmlSecDSigCtx. Please find it below.
> Inside the ImplLibXml(our local file)
>
>   dsigCtx Address ( 4832286288) + size (8)
> Address of userData(4832286288) + size(8)
> Address of flags(4832286296) + size(4)
> Address of flags2(4832286300) + size(4)
> Address of keyInfoReadCtx(4832286304) + size(368)
> Address of keyInfoWriteCtx(4832286672) + size(368)
> Address of transformCtx(4832287040) + size(136)
> Address of enabledReferenceUris(4832287176) + size(4)
> Address of enabledReferenceTransforms(4832287184) + size(8)
> Address of referencePreExecuteCallback(4832287192) + size(8)
> Address of defSignMethodId(4832287200) + size(8)
> Address of defC14NMethodId(4832287208) + size(8)
> Address of defDigestMethodId(4832287216) + size(8)
> Address of signKey(4832287224) + size(8)
> Address of operation(4832287232) + size(4)
> Address of result(4832287240) + size(8)
> Address of status(4832287248) + size(4)
> Address of signMethod(4832287256) + size(8)
> Address of preSignMemBufMethod(4832287272) + size(8)
> Address of signValueNode(4832287280) + size(8)
> Address of id(4832287288) + size(8)
> Address of signedInfoReferences(4832287296) + size(40)
> Address of manifestReferences(4832287336) + size(40)
> Address of reserved0(4832287376) + size(8)
> Address of reserved1(4832287384) + size(8)
>
> ImplLibXml **END**
>
> Inside xmlsec
>
> dsigCtx Address ( 4832286288) + size (8)
> Address of userData(4832286288) + size(8)
> Address of flags(4832286296) + size(4)
> Address of flags2(4832286300) + size(4)
> Address of keyInfoReadCtx(4832286304) + size(344)
> Address of keyInfoWriteCtx(4832286648) + size(344)
> Address of transformCtx(4832286992) + size(128)
> Address of enabledReferenceUris(4832287120) + size(4)
> Address of enabledReferenceTransforms(4832287128) + size(8)
> Address of referencePreExecuteCallback(4832287136) + size(8)
> Address of defSignMethodId(4832287144) + size(8)
> Address of defC14NMethodId(4832287152) + size(8)
> Address of defDigestMethodId(4832287160) + size(8)
> Address of signKey(4832287168) + size(8)
> Address of operation(4832287176) + size(4)
> Address of result(4832287184) + size(8)
> Address of status(4832287192) + size(4)
> Address of signMethod(4832287200) + size(8)
> Address of preSignMemBufMethod(4832287216) + size(8)
> Address of signValueNode(4832287224) + size(8)
> Address of id(4832287232) + size(8)
> Address of signedInfoReferences(4832287240) + size(32)
> Address of manifestReferences(4832287272) + size(32)
> Address of reserved0(4832287304) + size(8)
> Address of reserved1(4832287312) + size(8)
>
> xmlSecDSigCtxVerify****************END**********
>
> Please observe that the main culprit for mismatch of memory location are
> three user defined data members
> Address of keyInfoReadCtx(4832286304) + size(368) -- more 24 bytes
> Address of keyInfoWriteCtx(4832286672) + size(368) -- more 24 bytes
> Address of transformCtx(4832287040) + size(136)     -- more 8 bytes.
>
> But I find the consistency in case of status member is that the
> difference of location (i.e. between the status member in xmlsec and in
> ImplLibXml )is always 56 bytes as above the memory difference is also 56
> bytes.I feel issue on MIPS is somehow related to memory mapping issues.
>

[Aleksey] Bingo! As I said, it feels like you have a problem
with compiler flags. Check data alignment related flags for xmlsec
compilation vs. your program compilation. This obviously explains
why you can't reproduce this problem with xmlsec command line tool.