I’m trying to do online encrypt/decrypt via filter driver.
The problem I have is, that when I want to read a file (for example with
notepad), there is no read request IRP_MJ_READ or FastIoRead (using
filemon). So I’m not able to decrypt the data.
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This question seems to have been asked hundred times. But most people do not
know, and those who know will not tell.
At 08:51 PM 11/26/01, you wrote:
I’m trying to do online encrypt/decrypt via filter driver.
The problem I have is, that when I want to read a file (for example with
notepad), there is no read request IRP_MJ_READ or FastIoRead (using
filemon). So I’m not able to decrypt the data.
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Memory mapped IO results in no IO stack activity if the pages are
resident in memory.
As I believe another poster already responded, do the work to decide
access at create time. If the user has access to the file the system
assumes access to the bytes and permits creation of the mapping.
Notepad is the classic test case since it uses memory maps for access
the file. You will only see paging reads for the data of the file.
–
This posting is provided “AS IS” with no warranties, and confers no
rights. You assume all risk for your use.
-----Original Message-----
From: Basudeb [mailto:xxxxx@giascl01.vsnl.net.in]
Sent: Monday, November 26, 2001 7:44 PM
To: File Systems Developers
Subject: [ntfsd] Re: encrypt/decrypt filter driver
This question seems to have been asked hundred times. But most people do
not
know, and those who know will not tell.
At 08:51 PM 11/26/01, you wrote:
I’m trying to do online encrypt/decrypt via filter driver.
The problem I have is, that when I want to read a file (for example
with
notepad), there is no read request IRP_MJ_READ or FastIoRead (using
filemon). So I’m not able to decrypt the data.
You are currently subscribed to ntfsd as: xxxxx@giascl01.vsnl.net.in
To unsubscribe send a blank email to leave-ntfsd-$subst(‘Recip.MemberIDChar’)@lists.osr.com
You are currently subscribed to ntfsd as: xxxxx@windows.microsoft.com
To unsubscribe send a blank email to leave-ntfsd-$subst(‘Recip.MemberIDChar’)@lists.osr.com
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Yes - I believe the poster’s problem is that he was probably not
tracking the paging reads.
Notice you’ll have to leave the data in cache unencrypted for memory
mapped access to occur.
You can fail creation of mapped sections in Windows XP if you use the
FsRtlRegisterFileSystemFilterCallbacks() mechanizm.
However, I recommend Dan’s suggestion either way. Create is the right
place to determine access to the file.
This posting is provided “AS IS” with no warranties, and confers no
rights. You assume all risk for your use.
-----Original Message-----
From: Daniel Lovinger
Sent: Monday, November 26, 2001 7:24 PM
To: File Systems Developers
Subject: [ntfsd] Re: encrypt/decrypt filter driver
Memory mapped IO results in no IO stack activity if the pages are
resident in memory.
As I believe another poster already responded, do the work to decide
access at create time. If the user has access to the file the system
assumes access to the bytes and permits creation of the mapping.
Notepad is the classic test case since it uses memory maps for access
the file. You will only see paging reads for the data of the file.
–
This posting is provided “AS IS” with no warranties, and confers no
rights. You assume all risk for your use.
-----Original Message-----
From: Basudeb [mailto:xxxxx@giascl01.vsnl.net.in]
Sent: Monday, November 26, 2001 7:44 PM
To: File Systems Developers
Subject: [ntfsd] Re: encrypt/decrypt filter driver
This question seems to have been asked hundred times. But most people do
not know, and those who know will not tell.
At 08:51 PM 11/26/01, you wrote:
I’m trying to do online encrypt/decrypt via filter driver.
The problem I have is, that when I want to read a file (for example
with
notepad), there is no read request IRP_MJ_READ or FastIoRead (using
filemon). So I’m not able to decrypt the data.
You are currently subscribed to ntfsd as: xxxxx@giascl01.vsnl.net.in
To unsubscribe send a blank email to leave-ntfsd-$subst(‘Recip.MemberIDChar’)@lists.osr.com
You are currently subscribed to ntfsd as: xxxxx@windows.microsoft.com To
unsubscribe send a blank email to leave-ntfsd-$subst(‘Recip.MemberIDChar’)@lists.osr.com
You are currently subscribed to ntfsd as: xxxxx@windows.microsoft.com
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