Blame SOURCES/edk2-NetworkPkg-IScsiDxe-clean-up-ISCSI_CHAP_AUTH_DATA.Ou.patch

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From fca7e61fa3ba21cbf6e89d75b23fea03af5d517e Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Tue, 8 Jun 2021 14:12:52 +0200
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Subject: [PATCH 03/10] NetworkPkg/IScsiDxe: clean up
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 "ISCSI_CHAP_AUTH_DATA.OutChallengeLength"
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Laszlo Ersek <lersek@redhat.com>
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RH-MergeRequest: 5: NetworkPkg/IScsiDxe: fix IScsiHexToBin() security and functionality bugs [rhel-8.5.0, post-rebase]
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RH-Commit: [3/10] cc7118399f64979f2d81fe9fc381ed22c3815f9e
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RH-Bugzilla: 1956408
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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The "ISCSI_CHAP_AUTH_DATA.OutChallenge" field is declared as a UINT8 array
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with ISCSI_CHAP_AUTH_MAX_LEN (1024) elements. However, when the challenge
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is generated and formatted, only ISCSI_CHAP_RSP_LEN (16) octets are used
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in the array.
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Change the array size to ISCSI_CHAP_RSP_LEN, and remove the (now unused)
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ISCSI_CHAP_AUTH_MAX_LEN macro.
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Remove the "ISCSI_CHAP_AUTH_DATA.OutChallengeLength" field, which is
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superfluous too.
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Most importantly, explain in a new comment *why* tying the challenge size
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to the digest size (ISCSI_CHAP_RSP_LEN) has always made sense. (See also
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Linux kernel commit 19f5f88ed779, "scsi: target: iscsi: tie the challenge
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length to the hash digest size", 2019-11-06.) For sure, the motivation
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that the new comment now explains has always been there, and has always
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been the same, for IScsiDxe; it's just that now we spell it out too.
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No change in peer-visible behavior.
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Cc: Jiaxin Wu <jiaxin.wu@intel.com>
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Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
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Cc: Philippe Mathieu-Daud <philmd@redhat.com>
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Cc: Siyuan Fu <siyuan.fu@intel.com>
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Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3356
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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Reviewed-by: Philippe Mathieu-Daud <philmd@redhat.com>
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Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>
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Message-Id: <20210608121259.32451-4-lersek@redhat.com>
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(cherry picked from commit 95616b866187b00355042953efa5c198df07250f)
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---
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 NetworkPkg/IScsiDxe/IScsiCHAP.c | 3 +--
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 NetworkPkg/IScsiDxe/IScsiCHAP.h | 9 ++++++---
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 2 files changed, 7 insertions(+), 5 deletions(-)
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diff --git a/NetworkPkg/IScsiDxe/IScsiCHAP.c b/NetworkPkg/IScsiDxe/IScsiCHAP.c
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index df3c2eb120..9e192ce292 100644
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--- a/NetworkPkg/IScsiDxe/IScsiCHAP.c
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+++ b/NetworkPkg/IScsiDxe/IScsiCHAP.c
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@@ -122,7 +122,7 @@ IScsiCHAPAuthTarget (
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              AuthData->AuthConfig->ReverseCHAPSecret,
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              SecretSize,
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              AuthData->OutChallenge,
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-             AuthData->OutChallengeLength,
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+             ISCSI_CHAP_RSP_LEN,                      // ChallengeLength
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              VerifyRsp
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              );
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@@ -490,7 +490,6 @@ IScsiCHAPToSendReq (
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       // CHAP_C=<C>
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       //
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       IScsiGenRandom ((UINT8 *) AuthData->OutChallenge, ISCSI_CHAP_RSP_LEN);
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-      AuthData->OutChallengeLength = ISCSI_CHAP_RSP_LEN;
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       IScsiBinToHex (
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         (UINT8 *) AuthData->OutChallenge,
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         ISCSI_CHAP_RSP_LEN,
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diff --git a/NetworkPkg/IScsiDxe/IScsiCHAP.h b/NetworkPkg/IScsiDxe/IScsiCHAP.h
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index 1fc1d96ea3..35d5d6ec29 100644
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--- a/NetworkPkg/IScsiDxe/IScsiCHAP.h
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+++ b/NetworkPkg/IScsiDxe/IScsiCHAP.h
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@@ -19,7 +19,6 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
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 #define ISCSI_CHAP_ALGORITHM_MD5  5
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-#define ISCSI_CHAP_AUTH_MAX_LEN   1024
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 ///
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 /// MD5_HASHSIZE
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 ///
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@@ -59,9 +58,13 @@ typedef struct _ISCSI_CHAP_AUTH_DATA {
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   //
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   // Auth-data to be sent out for mutual authentication.
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   //
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+  // While the challenge size is technically independent of the hashing
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+  // algorithm, it is good practice to avoid hashing *fewer bytes* than the
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+  // digest size. In other words, it's good practice to feed *at least as many
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+  // bytes* to the hashing algorithm as the hashing algorithm will output.
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+  //
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   UINT32                        OutIdentifier;
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-  UINT8                         OutChallenge[ISCSI_CHAP_AUTH_MAX_LEN];
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-  UINT32                        OutChallengeLength;
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+  UINT8                         OutChallenge[ISCSI_CHAP_RSP_LEN];
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 } ISCSI_CHAP_AUTH_DATA;
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 /**
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-- 
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2.27.0
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