PRB: Obtaining Maximum Buffer Size for SSL Encryption Operations (262403)
The information in this article applies to:
- Microsoft Windows 2000 Server
- Microsoft Windows 2000 Advanced Server
- Microsoft Windows 2000 Professional
- Microsoft Win32 Application Programming Interface (API)
- Microsoft Windows 98
- Microsoft Windows NT Server 4.0 SP5
- Microsoft Windows NT Server 4.0 SP6
- Microsoft Windows NT Server 4.0 SP6a
- Microsoft Windows NT Workstation 4.0 SP5
- Microsoft Windows NT Workstation 4.0 SP6
- Microsoft Windows NT Workstation 4.0 SP6a
This article was previously published under Q262403 SYMPTOMS
When you use the Security Support Provider Interface (SSPI) to perform Secure Sockets Layer (SSL) or Transport Layer Security (TLS) encryption you can determine the encryption buffer size by using QueryContextAttributes. Use of the cbMaximumMessage value from the SecPkgContext_StreamSizes structure of QueryContextAttributes for specifying the message buffer size to the EncryptMessage or DecryptMessage API might cause the API to fail, with the following error message, on some platforms:
0x80090304 - SEC_E_INTERNAL_ERROR
CAUSE
Differences between SSPI SSL protocol implementations and different properties for a given SSL or TLS connection can result in a variance of the maximum message buffer size limit.
RESOLUTION
To specify a maximum size that is safe in all cases, use the cbMaximumMessage from QueryContextAttributes: (header + trailer).
The following code snippet demonstrates how to set up the security buffers for a call to the EncryptMessage function, with a modified maximum message size.
scRet = QueryContextAttributes(&hContext, SECPKG_ATTR_STREAM_SIZES, &Sizes);
pMsgBuf = (SecPkgContext_StreamSizes*)LocalAlloc(0,Sizes.cbMaximumMessage);
cbMsgBuf = Sizes.cbMaximumMessage - (Sizes.cbHeader + Sizes.cbTrailer);
Buffers[0].pvBuffer = pMsgBuf;
Buffers[0].cbBuffer = Sizes.cbHeader;
Buffers[0].BufferType = SECBUFFER_STREAM_HEADER;
Buffers[1].pvBuffer = pMsgBuf + Sizes.cbHeader;
Buffers[1].cbBuffer = cbMsgBuf;
Buffers[1].BufferType = SECBUFFER_DATA;
Buffers[2].pvBuffer = pMsgBuf + Sizes.cbHeader + cbMsgBuf;
Buffers[2].cbBuffer = Sizes.cbTrailer;
Buffers[2].BufferType = SECBUFFER_STREAM_TRAILER;
Buffers[3].BufferType = SECBUFFER_EMPTY;
scRet = EncryptMessage(&hContext,
0,
&Message,
0);
| Modification Type: | Minor | Last Reviewed: | 12/21/2004 |
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| Keywords: | kbprb KB262403 |
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