From 4cca7923992a13f6b753782f469ee944da2db796 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Wed, 8 Jan 2020 23:24:02 +0100 Subject: [PATCH] NetworkPkg/HttpDxe: fix 32-bit truncation in HTTPS download When downloading over TLS, each TLS message ("APP packet") is returned as a (decrypted) fragment table by EFI_TLS_PROTOCOL.ProcessPacket(). The TlsProcessMessage() function in "NetworkPkg/HttpDxe/HttpsSupport.c" linearizes the fragment table into a single contiguous data block. The resultant flat data block contains both TLS headers and data. The HttpsReceive() function parses the actual application data -- in this case: decrypted HTTP data -- out of the flattened TLS data block, peeling off the TLS headers. The HttpResponseWorker() function in "NetworkPkg/HttpDxe/HttpImpl.c" propagates this HTTP data outwards, implementing the EFI_HTTP_PROTOCOL.Response() function. Now consider the following documentation for EFI_HTTP_PROTOCOL.Response(), quoted from "MdePkg/Include/Protocol/Http.h": > It is the responsibility of the caller to allocate a buffer for Body and > specify the size in BodyLength. If the remote host provides a response > that contains a content body, up to BodyLength bytes will be copied from > the receive buffer into Body and BodyLength will be updated with the > amount of bytes received and copied to Body. This allows the client to > download a large file in chunks instead of into one contiguous block of > memory. Note that, if the caller-allocated buffer is larger than the server-provided chunk, then the transfer length is limited by the latter. This is in fact the dominant case when downloading a huge file (for which UefiBootManagerLib allocated a huge contiguous RAM Disk buffer) in small TLS messages. For adjusting BodyLength as described above -- i.e., to the application data chunk that has been extracted from the TLS message --, the HttpResponseWorker() function employs the following assignment: HttpMsg->BodyLength = MIN (Fragment.Len, (UINT32) HttpMsg->BodyLength); The (UINT32) cast is motivated by the MIN() requirement -- in "MdePkg/Include/Base.h" -- that both arguments be of the same type. "Fragment.Len" (NET_FRAGMENT.Len) has type UINT32, and "HttpMsg->BodyLength" (EFI_HTTP_MESSAGE.BodyLength) has type UINTN. Therefore a cast is indeed necessary. Unfortunately, the cast is done in the wrong direction. Consider the following circumstances: - "Fragment.Len" happens to be consistently 16KiB, dictated by the HTTPS Server's TLS stack, - the size of the file to download is 4GiB + N*16KiB, where N is a positive integer. As the download progresses, each received 16KiB application data chunk brings the *next* input value of BodyLength closer down to 4GiB. The cast in MIN() always masks off the high-order bits from the input value of BodyLength, but this is no problem because the low-order bits are nonzero, therefore the MIN() always permits progress. However, once BodyLength reaches 4GiB exactly on input, the MIN() invocation produces a zero value. HttpResponseWorker() adjusts the output value of BodyLength to zero, and then passes it to HttpParseMessageBody(). HttpParseMessageBody() (in "NetworkPkg/Library/DxeHttpLib/DxeHttpLib.c") rejects the zero BodyLength with EFI_INVALID_PARAMETER, which is fully propagated outwards, and aborts the HTTPS download. HttpBootDxe writes the message "Error: Unexpected network error" to the UEFI console. For example, a file with size (4GiB + 197MiB) terminates after downloading just 197MiB. Invert the direction of the cast: widen "Fragment.Len" to UINTN. Cc: Jiaxin Wu Cc: Maciej Rabeda Cc: Siyuan Fu Signed-off-by: Laszlo Ersek Reviewed-by: Philippe Mathieu-Daude Reviewed-by: Siyuan Fu Reviewed-by: Maciej Rabeda --- NetworkPkg/HttpDxe/HttpImpl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/NetworkPkg/HttpDxe/HttpImpl.c b/NetworkPkg/HttpDxe/HttpImpl.c index 6b877314bd..1acbb60d10 100644 --- a/NetworkPkg/HttpDxe/HttpImpl.c +++ b/NetworkPkg/HttpDxe/HttpImpl.c @@ -1348,7 +1348,7 @@ HttpResponseWorker ( // // Process the received the body packet. // - HttpMsg->BodyLength = MIN (Fragment.Len, (UINT32) HttpMsg->BodyLength); + HttpMsg->BodyLength = MIN ((UINTN) Fragment.Len, HttpMsg->BodyLength); CopyMem (HttpMsg->Body, Fragment.Bulk, HttpMsg->BodyLength); -- 2.39.2