[edk2-devel] [PATCH 3/6] NetworkPkg/IScsiDxe: distinguish "maximum" and "selected" CHAP digest sizes

Laszlo Ersek posted 6 patches 4 years, 8 months ago
There is a newer version of this series
[edk2-devel] [PATCH 3/6] NetworkPkg/IScsiDxe: distinguish "maximum" and "selected" CHAP digest sizes
Posted by Laszlo Ersek 4 years, 8 months ago
IScsiDxe uses the ISCSI_CHAP_RSP_LEN macro for expressing the size of the
digest (16) that it solely supports at this point (MD5).
ISCSI_CHAP_RSP_LEN is used for both (a) *allocating* digest-related
buffers (binary buffers and hex encodings alike), and (b) *processing*
binary digest buffers (comparing them, filling them, reading them).

In preparation for adding other hash algorithms, split purpose (a) from
purpose (b). For purpose (a) -- buffer allocation --, introduce
ISCSI_CHAP_MAX_DIGEST_SIZE. For purpose (b) -- processing --, rely on
MD5_DIGEST_SIZE from <BaseCryptLib.h>.

Distinguishing these purposes is justified because purpose (b) --
processing -- must depend on the hashing algorithm negotiated between
initiator and target, while for purpose (a) -- allocation --, using the
maximum supported digest size is suitable. For now, because only MD5 is
supported, introduce ISCSI_CHAP_MAX_DIGEST_SIZE *as* MD5_DIGEST_SIZE.

Note that the argument for using the digest size as the size of the
outgoing challenge (in case mutual authentication is desired by the
initiator) remains in place. Because of this, the above two purposes are
distinguished for the "ISCSI_CHAP_AUTH_DATA.OutChallenge" field as well.

This patch is functionally a no-op, just yet.

Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3355
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 NetworkPkg/IScsiDxe/IScsiCHAP.h | 17 +++++++++------
 NetworkPkg/IScsiDxe/IScsiCHAP.c | 22 ++++++++++----------
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/NetworkPkg/IScsiDxe/IScsiCHAP.h b/NetworkPkg/IScsiDxe/IScsiCHAP.h
index d6a90fc27fc3..b8811b7580f0 100644
--- a/NetworkPkg/IScsiDxe/IScsiCHAP.h
+++ b/NetworkPkg/IScsiDxe/IScsiCHAP.h
@@ -1,86 +1,91 @@
 /** @file
   The header file of CHAP configuration.
 
 Copyright (c) 2004 - 2018, Intel Corporation. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
 #ifndef _ISCSI_CHAP_H_
 #define _ISCSI_CHAP_H_
 
 #define ISCSI_AUTH_METHOD_CHAP                    "CHAP"
 
 #define ISCSI_KEY_CHAP_ALGORITHM                  "CHAP_A"
 #define ISCSI_KEY_CHAP_IDENTIFIER                 "CHAP_I"
 #define ISCSI_KEY_CHAP_CHALLENGE                  "CHAP_C"
 #define ISCSI_KEY_CHAP_NAME                       "CHAP_N"
 #define ISCSI_KEY_CHAP_RESPONSE                   "CHAP_R"
 
+//
+// Identifiers of supported CHAP hash algorithms:
+// https://www.iana.org/assignments/ppp-numbers/ppp-numbers.xhtml#ppp-numbers-9
+//
 #define ISCSI_CHAP_ALGORITHM_MD5                  5
 
-///
-/// MD5_HASHSIZE
-///
-#define ISCSI_CHAP_RSP_LEN                        16
+//
+// Byte count of the largest digest over the above-listed
+// ISCSI_CHAP_ALGORITHM_* hash algorithms.
+//
+#define ISCSI_CHAP_MAX_DIGEST_SIZE                MD5_DIGEST_SIZE
 
 #define ISCSI_CHAP_STEP_ONE                       1
 #define ISCSI_CHAP_STEP_TWO                       2
 #define ISCSI_CHAP_STEP_THREE                     3
 #define ISCSI_CHAP_STEP_FOUR                      4
 
 
 #pragma pack(1)
 
 typedef struct _ISCSI_CHAP_AUTH_CONFIG_NVDATA {
   UINT8 CHAPType;
   CHAR8 CHAPName[ISCSI_CHAP_NAME_STORAGE];
   CHAR8 CHAPSecret[ISCSI_CHAP_SECRET_STORAGE];
   CHAR8 ReverseCHAPName[ISCSI_CHAP_NAME_STORAGE];
   CHAR8 ReverseCHAPSecret[ISCSI_CHAP_SECRET_STORAGE];
 } ISCSI_CHAP_AUTH_CONFIG_NVDATA;
 
 #pragma pack()
 
 ///
 /// ISCSI CHAP Authentication Data
 ///
 typedef struct _ISCSI_CHAP_AUTH_DATA {
   ISCSI_CHAP_AUTH_CONFIG_NVDATA *AuthConfig;
   UINT32                        InIdentifier;
   UINT8                         InChallenge[1024];
   UINT32                        InChallengeLength;
   //
   // Calculated CHAP Response (CHAP_R) value.
   //
-  UINT8                         CHAPResponse[ISCSI_CHAP_RSP_LEN];
+  UINT8                         CHAPResponse[ISCSI_CHAP_MAX_DIGEST_SIZE];
 
   //
   // Auth-data to be sent out for mutual authentication.
   //
   // While the challenge size is technically independent of the hashing
   // algorithm, it is good practice to avoid hashing *fewer bytes* than the
   // digest size. In other words, it's good practice to feed *at least as many
   // bytes* to the hashing algorithm as the hashing algorithm will output.
   //
   UINT32                        OutIdentifier;
-  UINT8                         OutChallenge[ISCSI_CHAP_RSP_LEN];
+  UINT8                         OutChallenge[ISCSI_CHAP_MAX_DIGEST_SIZE];
 } ISCSI_CHAP_AUTH_DATA;
 
 /**
   This function checks the received iSCSI Login Response during the security
   negotiation stage.
 
   @param[in] Conn             The iSCSI connection.
 
   @retval EFI_SUCCESS          The Login Response passed the CHAP validation.
   @retval EFI_OUT_OF_RESOURCES Failed to allocate memory.
   @retval EFI_PROTOCOL_ERROR   Some kind of protocol error occurred.
   @retval Others               Other errors as indicated.
 
 **/
 EFI_STATUS
 IScsiCHAPOnRspReceived (
   IN ISCSI_CONNECTION  *Conn
   );
 /**
diff --git a/NetworkPkg/IScsiDxe/IScsiCHAP.c b/NetworkPkg/IScsiDxe/IScsiCHAP.c
index bb84f4359d35..744824e63d23 100644
--- a/NetworkPkg/IScsiDxe/IScsiCHAP.c
+++ b/NetworkPkg/IScsiDxe/IScsiCHAP.c
@@ -96,90 +96,90 @@ IScsiCHAPCalculateResponse (
 
   @param[in]   AuthData             iSCSI CHAP authentication data.
   @param[in]   TargetResponse       The response from target.
 
   @retval EFI_SUCCESS               The response from target passed
                                     authentication.
   @retval EFI_SECURITY_VIOLATION    The response from target was not expected
                                     value.
   @retval Others                    Other errors as indicated.
 
 **/
 EFI_STATUS
 IScsiCHAPAuthTarget (
   IN  ISCSI_CHAP_AUTH_DATA  *AuthData,
   IN  UINT8                 *TargetResponse
   )
 {
   EFI_STATUS  Status;
   UINT32      SecretSize;
-  UINT8       VerifyRsp[ISCSI_CHAP_RSP_LEN];
+  UINT8       VerifyRsp[ISCSI_CHAP_MAX_DIGEST_SIZE];
 
   Status      = EFI_SUCCESS;
 
   SecretSize  = (UINT32) AsciiStrLen (AuthData->AuthConfig->ReverseCHAPSecret);
   Status = IScsiCHAPCalculateResponse (
              AuthData->OutIdentifier,
              AuthData->AuthConfig->ReverseCHAPSecret,
              SecretSize,
              AuthData->OutChallenge,
-             ISCSI_CHAP_RSP_LEN,                      // ChallengeLength
+             MD5_DIGEST_SIZE,                         // ChallengeLength
              VerifyRsp
              );
 
-  if (CompareMem (VerifyRsp, TargetResponse, ISCSI_CHAP_RSP_LEN) != 0) {
+  if (CompareMem (VerifyRsp, TargetResponse, MD5_DIGEST_SIZE) != 0) {
     Status = EFI_SECURITY_VIOLATION;
   }
 
   return Status;
 }
 
 
 /**
   This function checks the received iSCSI Login Response during the security
   negotiation stage.
 
   @param[in] Conn             The iSCSI connection.
 
   @retval EFI_SUCCESS          The Login Response passed the CHAP validation.
   @retval EFI_OUT_OF_RESOURCES Failed to allocate memory.
   @retval EFI_PROTOCOL_ERROR   Some kind of protocol error occurred.
   @retval Others               Other errors as indicated.
 
 **/
 EFI_STATUS
 IScsiCHAPOnRspReceived (
   IN ISCSI_CONNECTION  *Conn
   )
 {
   EFI_STATUS                  Status;
   ISCSI_SESSION               *Session;
   ISCSI_CHAP_AUTH_DATA        *AuthData;
   CHAR8                       *Value;
   UINT8                       *Data;
   UINT32                      Len;
   LIST_ENTRY                  *KeyValueList;
   UINTN                       Algorithm;
   CHAR8                       *Identifier;
   CHAR8                       *Challenge;
   CHAR8                       *Name;
   CHAR8                       *Response;
-  UINT8                       TargetRsp[ISCSI_CHAP_RSP_LEN];
+  UINT8                       TargetRsp[ISCSI_CHAP_MAX_DIGEST_SIZE];
   UINT32                      RspLen;
   UINTN                       Result;
 
   ASSERT (Conn->CurrentStage == ISCSI_SECURITY_NEGOTIATION);
   ASSERT (Conn->RspQue.BufNum != 0);
 
   Session     = Conn->Session;
   AuthData    = &Session->AuthData.CHAP;
   Len         = Conn->RspQue.BufSize;
   Data        = AllocateZeroPool (Len);
   if (Data == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }
   //
   // Copy the data in case the data spans over multiple PDUs.
   //
   NetbufQueCopy (&Conn->RspQue, 0, Len, Data);
 
   //
@@ -324,41 +324,41 @@ IScsiCHAPOnRspReceived (
 
   case ISCSI_CHAP_STEP_FOUR:
     ASSERT (AuthData->AuthConfig->CHAPType == ISCSI_CHAP_MUTUAL);
     //
     // The forth step, CHAP_N=<N> CHAP_R=<R> is received from Target.
     //
     Name = IScsiGetValueByKeyFromList (KeyValueList, ISCSI_KEY_CHAP_NAME);
     if (Name == NULL) {
       goto ON_EXIT;
     }
 
     Response = IScsiGetValueByKeyFromList (
                  KeyValueList,
                  ISCSI_KEY_CHAP_RESPONSE
                  );
     if (Response == NULL) {
       goto ON_EXIT;
     }
 
-    RspLen = ISCSI_CHAP_RSP_LEN;
+    RspLen = MD5_DIGEST_SIZE;
     Status = IScsiHexToBin (TargetRsp, &RspLen, Response);
-    if (EFI_ERROR (Status) || RspLen != ISCSI_CHAP_RSP_LEN) {
+    if (EFI_ERROR (Status) || RspLen != MD5_DIGEST_SIZE) {
       Status = EFI_PROTOCOL_ERROR;
       goto ON_EXIT;
     }
 
     //
     // Check the CHAP Name and Response replied by Target.
     //
     Status = IScsiCHAPAuthTarget (AuthData, TargetRsp);
     break;
 
   default:
     break;
   }
 
 ON_EXIT:
 
   if (KeyValueList != NULL) {
     IScsiFreeKeyValueList (KeyValueList);
   }
@@ -395,45 +395,45 @@ IScsiCHAPToSendReq (
   ISCSI_CHAP_AUTH_DATA        *AuthData;
   CHAR8                       *Value;
   CHAR8                       ValueStr[256];
   CHAR8                       *Response;
   UINT32                      RspLen;
   CHAR8                       *Challenge;
   UINT32                      ChallengeLen;
   EFI_STATUS                  BinToHexStatus;
 
   ASSERT (Conn->CurrentStage == ISCSI_SECURITY_NEGOTIATION);
 
   Session     = Conn->Session;
   AuthData    = &Session->AuthData.CHAP;
   LoginReq    = (ISCSI_LOGIN_REQUEST *) NetbufGetByte (Pdu, 0, 0);
   if (LoginReq == NULL) {
     return EFI_PROTOCOL_ERROR;
   }
   Status      = EFI_SUCCESS;
 
-  RspLen      = 2 * ISCSI_CHAP_RSP_LEN + 3;
+  RspLen      = 2 * ISCSI_CHAP_MAX_DIGEST_SIZE + 3;
   Response    = AllocateZeroPool (RspLen);
   if (Response == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }
 
-  ChallengeLen  = 2 * ISCSI_CHAP_RSP_LEN + 3;
+  ChallengeLen  = 2 * ISCSI_CHAP_MAX_DIGEST_SIZE + 3;
   Challenge     = AllocateZeroPool (ChallengeLen);
   if (Challenge == NULL) {
     FreePool (Response);
     return EFI_OUT_OF_RESOURCES;
   }
 
   switch (Conn->AuthStep) {
   case ISCSI_AUTH_INITIAL:
     //
     // It's the initial Login Request. Fill in the key=value pairs mandatory
     // for the initial Login Request.
     //
     IScsiAddKeyValuePair (
       Pdu,
       ISCSI_KEY_INITIATOR_NAME,
       mPrivate->InitiatorName
       );
     IScsiAddKeyValuePair (Pdu, ISCSI_KEY_SESSION_TYPE, "Normal");
     IScsiAddKeyValuePair (
@@ -466,59 +466,59 @@ IScsiCHAPToSendReq (
 
   case ISCSI_CHAP_STEP_THREE:
     //
     // Third step, send the Login Request with CHAP_N=<N> CHAP_R=<R> or
     // CHAP_N=<N> CHAP_R=<R> CHAP_I=<I> CHAP_C=<C> if target authentication is
     // required too.
     //
     // CHAP_N=<N>
     //
     IScsiAddKeyValuePair (
       Pdu,
       ISCSI_KEY_CHAP_NAME,
       (CHAR8 *) &AuthData->AuthConfig->CHAPName
       );
     //
     // CHAP_R=<R>
     //
     BinToHexStatus = IScsiBinToHex (
                        (UINT8 *) AuthData->CHAPResponse,
-                       ISCSI_CHAP_RSP_LEN,
+                       MD5_DIGEST_SIZE,
                        Response,
                        &RspLen
                        );
     ASSERT_EFI_ERROR (BinToHexStatus);
     IScsiAddKeyValuePair (Pdu, ISCSI_KEY_CHAP_RESPONSE, Response);
 
     if (AuthData->AuthConfig->CHAPType == ISCSI_CHAP_MUTUAL) {
       //
       // CHAP_I=<I>
       //
       IScsiGenRandom ((UINT8 *) &AuthData->OutIdentifier, 1);
       AsciiSPrint (ValueStr, sizeof (ValueStr), "%d", AuthData->OutIdentifier);
       IScsiAddKeyValuePair (Pdu, ISCSI_KEY_CHAP_IDENTIFIER, ValueStr);
       //
       // CHAP_C=<C>
       //
-      IScsiGenRandom ((UINT8 *) AuthData->OutChallenge, ISCSI_CHAP_RSP_LEN);
+      IScsiGenRandom ((UINT8 *) AuthData->OutChallenge, MD5_DIGEST_SIZE);
       BinToHexStatus = IScsiBinToHex (
                          (UINT8 *) AuthData->OutChallenge,
-                         ISCSI_CHAP_RSP_LEN,
+                         MD5_DIGEST_SIZE,
                          Challenge,
                          &ChallengeLen
                          );
       ASSERT_EFI_ERROR (BinToHexStatus);
       IScsiAddKeyValuePair (Pdu, ISCSI_KEY_CHAP_CHALLENGE, Challenge);
 
       Conn->AuthStep = ISCSI_CHAP_STEP_FOUR;
     }
     //
     // Set the stage transition flag.
     //
     ISCSI_SET_FLAG (LoginReq, ISCSI_LOGIN_REQ_PDU_FLAG_TRANSIT);
     break;
 
   default:
     Status = EFI_PROTOCOL_ERROR;
     break;
   }
 
-- 
2.19.1.3.g30247aa5d201




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Re: [edk2-devel] [PATCH 3/6] NetworkPkg/IScsiDxe: distinguish "maximum" and "selected" CHAP digest sizes
Posted by Philippe Mathieu-Daudé 4 years, 8 months ago
Hi Laszlo,

On 6/8/21 3:06 PM, Laszlo Ersek wrote:
> IScsiDxe uses the ISCSI_CHAP_RSP_LEN macro for expressing the size of the
> digest (16) that it solely supports at this point (MD5).
> ISCSI_CHAP_RSP_LEN is used for both (a) *allocating* digest-related
> buffers (binary buffers and hex encodings alike), and (b) *processing*
> binary digest buffers (comparing them, filling them, reading them).
> 
> In preparation for adding other hash algorithms, split purpose (a) from
> purpose (b). For purpose (a) -- buffer allocation --, introduce
> ISCSI_CHAP_MAX_DIGEST_SIZE. For purpose (b) -- processing --, rely on
> MD5_DIGEST_SIZE from <BaseCryptLib.h>.

Matter of taste probably, I'd rather see this patch split in 2, as you
identified. (b) first then (a). Regardless:
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

> Distinguishing these purposes is justified because purpose (b) --
> processing -- must depend on the hashing algorithm negotiated between
> initiator and target, while for purpose (a) -- allocation --, using the
> maximum supported digest size is suitable. For now, because only MD5 is
> supported, introduce ISCSI_CHAP_MAX_DIGEST_SIZE *as* MD5_DIGEST_SIZE.
> 
> Note that the argument for using the digest size as the size of the
> outgoing challenge (in case mutual authentication is desired by the
> initiator) remains in place. Because of this, the above two purposes are
> distinguished for the "ISCSI_CHAP_AUTH_DATA.OutChallenge" field as well.
> 
> This patch is functionally a no-op, just yet.
> 
> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Siyuan Fu <siyuan.fu@intel.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3355
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
>  NetworkPkg/IScsiDxe/IScsiCHAP.h | 17 +++++++++------
>  NetworkPkg/IScsiDxe/IScsiCHAP.c | 22 ++++++++++----------
>  2 files changed, 22 insertions(+), 17 deletions(-)



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Re: [edk2-devel] [PATCH 3/6] NetworkPkg/IScsiDxe: distinguish "maximum" and "selected" CHAP digest sizes
Posted by Laszlo Ersek 4 years, 8 months ago
On 06/09/21 12:43, Philippe Mathieu-Daudé wrote:
> Hi Laszlo,
> 
> On 6/8/21 3:06 PM, Laszlo Ersek wrote:
>> IScsiDxe uses the ISCSI_CHAP_RSP_LEN macro for expressing the size of the
>> digest (16) that it solely supports at this point (MD5).
>> ISCSI_CHAP_RSP_LEN is used for both (a) *allocating* digest-related
>> buffers (binary buffers and hex encodings alike), and (b) *processing*
>> binary digest buffers (comparing them, filling them, reading them).
>>
>> In preparation for adding other hash algorithms, split purpose (a) from
>> purpose (b). For purpose (a) -- buffer allocation --, introduce
>> ISCSI_CHAP_MAX_DIGEST_SIZE. For purpose (b) -- processing --, rely on
>> MD5_DIGEST_SIZE from <BaseCryptLib.h>.
> 
> Matter of taste probably, I'd rather see this patch split in 2, as you
> identified. (b) first then (a). Regardless:
> Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

Interesting; I thought that showing all uses of ISCSI_CHAP_RSP_LEN in
one patch, and classifying each use one way or another at once, was the
best for reviewer understanding. Basically it's a single "mental loop"
over all uses, and in the "loop body", we have an "if" (classification)
-- allocation vs. processing.

What you propose is basically "two loops". In that approach, in the
first patch (= the first "mental loop"), only "processing" uses would be
updated; the "allocation sites" wouldn't be shown at all. I feel that
this approach is counter-intuitive:

From the body of the first patch,

- the reviewer can check the *correctness* of the patch (that is,
whether everything that I converted is indeed "processing"),

- but they can't check the *completeness* of the patch (that is, whether
there is a "processing" site that I should have converted, but missed).

For the reviewer to verify the completeness of the first patch, they
have to apply it (or check out the branch at that stage), and go over
all the *remaining* ISCSI_CHAP_RSP_LEN instances, to see if I missed
something. And, if the reviewer has to check every single instance of
ISCSI_CHAP_RSP_LEN right after the first patch, they end up doing the
same work as if they had just reviewed this particular patch.

I think your approach boils down to the following idea:

  The completeness of the first patch would be proved by the correctness
  of the second patch.

That is, *after* you reviewed the second patch (and see that every site
converted is indeed an allocation site, and that the ISCSI_CHAP_RSP_LEN
macro definition is being removed, so no other ISCSI_CHAP_RSP_LEN
instance remains), you could be sure that no processing site was missed
in the first patch.

Technically / mathematically, this is entirely true; I just prefer
avoiding situations where you have to review patch (N+X) to see the
validity (completeness) of patch (N). I quite dislike jumping between
patches during review.

Does my explanation make sense?

If you still prefer the split, I'm OK to do it.

Thanks!
Laszlo

> 
>> Distinguishing these purposes is justified because purpose (b) --
>> processing -- must depend on the hashing algorithm negotiated between
>> initiator and target, while for purpose (a) -- allocation --, using the
>> maximum supported digest size is suitable. For now, because only MD5 is
>> supported, introduce ISCSI_CHAP_MAX_DIGEST_SIZE *as* MD5_DIGEST_SIZE.
>>
>> Note that the argument for using the digest size as the size of the
>> outgoing challenge (in case mutual authentication is desired by the
>> initiator) remains in place. Because of this, the above two purposes are
>> distinguished for the "ISCSI_CHAP_AUTH_DATA.OutChallenge" field as well.
>>
>> This patch is functionally a no-op, just yet.
>>
>> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
>> Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
>> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Cc: Siyuan Fu <siyuan.fu@intel.com>
>> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3355
>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
>> ---
>>  NetworkPkg/IScsiDxe/IScsiCHAP.h | 17 +++++++++------
>>  NetworkPkg/IScsiDxe/IScsiCHAP.c | 22 ++++++++++----------
>>  2 files changed, 22 insertions(+), 17 deletions(-)
> 



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Re: [edk2-devel] [PATCH 3/6] NetworkPkg/IScsiDxe: distinguish "maximum" and "selected" CHAP digest sizes
Posted by Maciej Rabeda 4 years, 8 months ago
To cut to the chase on this patch:
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>

On 09-Jun-21 15:46, Laszlo Ersek wrote:
> On 06/09/21 12:43, Philippe Mathieu-Daudé wrote:
>> Hi Laszlo,
>>
>> On 6/8/21 3:06 PM, Laszlo Ersek wrote:
>>> IScsiDxe uses the ISCSI_CHAP_RSP_LEN macro for expressing the size of the
>>> digest (16) that it solely supports at this point (MD5).
>>> ISCSI_CHAP_RSP_LEN is used for both (a) *allocating* digest-related
>>> buffers (binary buffers and hex encodings alike), and (b) *processing*
>>> binary digest buffers (comparing them, filling them, reading them).
>>>
>>> In preparation for adding other hash algorithms, split purpose (a) from
>>> purpose (b). For purpose (a) -- buffer allocation --, introduce
>>> ISCSI_CHAP_MAX_DIGEST_SIZE. For purpose (b) -- processing --, rely on
>>> MD5_DIGEST_SIZE from <BaseCryptLib.h>.
>> Matter of taste probably, I'd rather see this patch split in 2, as you
>> identified. (b) first then (a). Regardless:
>> Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
> Interesting; I thought that showing all uses of ISCSI_CHAP_RSP_LEN in
> one patch, and classifying each use one way or another at once, was the
> best for reviewer understanding. Basically it's a single "mental loop"
> over all uses, and in the "loop body", we have an "if" (classification)
> -- allocation vs. processing.
>
> What you propose is basically "two loops". In that approach, in the
> first patch (= the first "mental loop"), only "processing" uses would be
> updated; the "allocation sites" wouldn't be shown at all. I feel that
> this approach is counter-intuitive:
>
>  From the body of the first patch,
>
> - the reviewer can check the *correctness* of the patch (that is,
> whether everything that I converted is indeed "processing"),
>
> - but they can't check the *completeness* of the patch (that is, whether
> there is a "processing" site that I should have converted, but missed).
>
> For the reviewer to verify the completeness of the first patch, they
> have to apply it (or check out the branch at that stage), and go over
> all the *remaining* ISCSI_CHAP_RSP_LEN instances, to see if I missed
> something. And, if the reviewer has to check every single instance of
> ISCSI_CHAP_RSP_LEN right after the first patch, they end up doing the
> same work as if they had just reviewed this particular patch.
>
> I think your approach boils down to the following idea:
>
>    The completeness of the first patch would be proved by the correctness
>    of the second patch.
>
> That is, *after* you reviewed the second patch (and see that every site
> converted is indeed an allocation site, and that the ISCSI_CHAP_RSP_LEN
> macro definition is being removed, so no other ISCSI_CHAP_RSP_LEN
> instance remains), you could be sure that no processing site was missed
> in the first patch.
>
> Technically / mathematically, this is entirely true; I just prefer
> avoiding situations where you have to review patch (N+X) to see the
> validity (completeness) of patch (N). I quite dislike jumping between
> patches during review.
>
> Does my explanation make sense?
>
> If you still prefer the split, I'm OK to do it.
>
> Thanks!
> Laszlo
>
>>> Distinguishing these purposes is justified because purpose (b) --
>>> processing -- must depend on the hashing algorithm negotiated between
>>> initiator and target, while for purpose (a) -- allocation --, using the
>>> maximum supported digest size is suitable. For now, because only MD5 is
>>> supported, introduce ISCSI_CHAP_MAX_DIGEST_SIZE *as* MD5_DIGEST_SIZE.
>>>
>>> Note that the argument for using the digest size as the size of the
>>> outgoing challenge (in case mutual authentication is desired by the
>>> initiator) remains in place. Because of this, the above two purposes are
>>> distinguished for the "ISCSI_CHAP_AUTH_DATA.OutChallenge" field as well.
>>>
>>> This patch is functionally a no-op, just yet.
>>>
>>> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
>>> Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
>>> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> Cc: Siyuan Fu <siyuan.fu@intel.com>
>>> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3355
>>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
>>> ---
>>>   NetworkPkg/IScsiDxe/IScsiCHAP.h | 17 +++++++++------
>>>   NetworkPkg/IScsiDxe/IScsiCHAP.c | 22 ++++++++++----------
>>>   2 files changed, 22 insertions(+), 17 deletions(-)



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