string safe functions

NTDEV
1

I am having trouble with the string safe functions.

i am testing out how to use the kernel-mode strcpy and
strncpy functions, but they are giving me buffer
overflow errors (C0000005).

i am experimenting with reading files and copying the
file contents to a character buffer.

so I open a file for reading, get the file size
information and store that to a variable (ULONG
fileoffsetsize). i allocate memory of size
(fileoffsetsize + 1) using ExAllocatePool and i read
the file contents and store them into a character
buffer declared as (UCHAR *ReadBuffer)…

now i want to try to do a kernel-mode strcpy and store
ReadBuffer to another char buffer, let’s call it
(UCHAR *TempBuffer)…

i allocate memory of the same size(FileOffsetSize + 1)
for TempBuffer, and try the following

status = RtlStringCbCopyA(TempBuffer, FileOffsetSize,
ReadBuffer);

and I am getting C0000005 errors
(status_buffer_overflow)…

can anybody help me with this one?

-SA

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2

I am having trouble with the string safe functions.

i am testing out how to use the kernel-mode strcpy and
strncpy functions, but they are giving me buffer
overflow errors (C0000005).

i am experimenting with reading files and copying the
file contents to a character buffer.

so I open a file for reading, get the file size
information and store that to a variable (ULONG
fileoffsetsize). i allocate memory of size
(fileoffsetsize + 1) using ExAllocatePool and i read
the file contents and store them into a character
buffer declared as (UCHAR *ReadBuffer)…

now i want to try to do a kernel-mode strcpy and store
ReadBuffer to another char buffer, let’s call it
(UCHAR *TempBuffer)…

i allocate memory of the same size(FileOffsetSize + 1)
for TempBuffer, and try the following

status = RtlStringCbCopyA(TempBuffer, FileOffsetSize,
ReadBuffer);

and I am getting C0000005 errors
(status_buffer_overflow)…

can anybody help me with this one?

-SA

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3

FileOffsetSize should be the size of the destination buffer, which has
to accommodate the terminating NUL. Your string has FileOffsetSize
bytes of data + a NUL. Your buffer can only hold FileOffsetSize bytes
of data. RtlStringCbCopyA wants to terminate the string and you’re not
leaving enough space, so it reports an overflow.

Use FileOffsetSize+1 for the buffer length and you should be fine.

-p

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Steven Aumack
Sent: Monday, January 10, 2005 2:03 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] string safe functions

I am having trouble with the string safe functions.

i am testing out how to use the kernel-mode strcpy and
strncpy functions, but they are giving me buffer overflow
errors (C0000005).

i am experimenting with reading files and copying the file
contents to a character buffer.

so I open a file for reading, get the file size information
and store that to a variable (ULONG fileoffsetsize). i
allocate memory of size (fileoffsetsize + 1) using
ExAllocatePool and i read the file contents and store them
into a character buffer declared as (UCHAR *ReadBuffer)…

now i want to try to do a kernel-mode strcpy and store
ReadBuffer to another char buffer, let’s call it (UCHAR
*TempBuffer)…

i allocate memory of the same size(FileOffsetSize + 1) for
TempBuffer, and try the following

status = RtlStringCbCopyA(TempBuffer, FileOffsetSize, ReadBuffer);

and I am getting C0000005 errors
(status_buffer_overflow)…

can anybody help me with this one?

-SA

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4

" cbDest - size of destination buffer in bytes.
length must be = ((_tcslen(src) + 1) * sizeof(TCHAR))
to
hold all of the source including the null terminator"

See the header file ntstrsafe.h. You are one byte short of a big enough
buffer.

=====================
Mark Roddy

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Steven Aumack
Sent: Monday, January 10, 2005 5:03 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] string safe functions

I am having trouble with the string safe functions.

i am testing out how to use the kernel-mode strcpy and strncpy functions,
but they are giving me buffer overflow errors (C0000005).

i am experimenting with reading files and copying the file contents to a
character buffer.

so I open a file for reading, get the file size information and store that
to a variable (ULONG fileoffsetsize). i allocate memory of size
(fileoffsetsize + 1) using ExAllocatePool and i read the file contents and
store them into a character buffer declared as (UCHAR *ReadBuffer)…

now i want to try to do a kernel-mode strcpy and store ReadBuffer to another
char buffer, let’s call it (UCHAR *TempBuffer)…

i allocate memory of the same size(FileOffsetSize + 1) for TempBuffer, and
try the following

status = RtlStringCbCopyA(TempBuffer, FileOffsetSize, ReadBuffer);

and I am getting C0000005 errors
(status_buffer_overflow)…

can anybody help me with this one?

-SA

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http://www.osronline.com/article.cfm?id=256

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5

Another really cool benefit of strsafe functions is that you can use the
inline version of them and step through the implementation since it is
embedded in the header itself.

d

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Roddy, Mark
Sent: Monday, January 10, 2005 5:18 PM
To: Windows System Software Devs Interest List
Subject: RE: [ntdev] string safe functions

" cbDest - size of destination buffer in bytes.
length must be = ((_tcslen(src) + 1) *
sizeof(TCHAR))
to
hold all of the source including the null
terminator"

See the header file ntstrsafe.h. You are one byte short of a big enough
buffer.

=====================
Mark Roddy

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Steven Aumack
Sent: Monday, January 10, 2005 5:03 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] string safe functions

I am having trouble with the string safe functions.

i am testing out how to use the kernel-mode strcpy and strncpy
functions,
but they are giving me buffer overflow errors (C0000005).

i am experimenting with reading files and copying the file contents to a
character buffer.

so I open a file for reading, get the file size information and store
that
to a variable (ULONG fileoffsetsize). i allocate memory of size
(fileoffsetsize + 1) using ExAllocatePool and i read the file contents
and
store them into a character buffer declared as (UCHAR *ReadBuffer)…

now i want to try to do a kernel-mode strcpy and store ReadBuffer to
another
char buffer, let’s call it (UCHAR *TempBuffer)…

i allocate memory of the same size(FileOffsetSize + 1) for TempBuffer,
and
try the following

status = RtlStringCbCopyA(TempBuffer, FileOffsetSize, ReadBuffer);

and I am getting C0000005 errors
(status_buffer_overflow)…

can anybody help me with this one?

-SA

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Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

You are currently subscribed to ntdev as: xxxxx@stratus.com To
unsubscribe send a blank email to xxxxx@lists.osr.com

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

You are currently subscribed to ntdev as: xxxxx@windows.microsoft.com
To unsubscribe send a blank email to xxxxx@lists.osr.com