[edk2-devel] [PUBLIC edk2 PATCH v2 10/10] NetworkPkg/IScsiDxe: check IScsiHexToBin() return values

[Laszlo Ersek]

IScsiDxe (that is, the initiator) receives two hex-encoded strings from
the iSCSI target:

- CHAP_C, where the target challenges the initiator,

- CHAP_R, where the target answers the challenge from the initiator (in
  case the initiator wants mutual authentication).

Accordingly, we have two IScsiHexToBin() call sites:

- At the CHAP_C decoding site, check whether the decoding succeeds. The
  decoded buffer ("AuthData->InChallenge") can accommodate 1024 bytes,
  which is a permissible restriction on the target, per
  <https://tools.ietf.org/html/rfc7143#section-12.1.3>. Shorter challenges
  from the target are acceptable.

- At the CHAP_R decoding site, enforce that the decoding both succeed, and
  provide exactly ISCSI_CHAP_RSP_LEN bytes. CHAP_R contains the digest
  calculated by the target, therefore it must be of fixed size. We may
  only call IScsiCHAPAuthTarget() if "TargetRsp" has been fully populated.

Cc: Jiaxin Wu <jiaxin.wu at intel.com>
Cc: Maciej Rabeda <maciej.rabeda at linux.intel.com>
Cc: Philippe Mathieu-Daudé <philmd at redhat.com>
Cc: Siyuan Fu <siyuan.fu at intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3356
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd at redhat.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda at linux.intel.com>
---
 NetworkPkg/IScsiDxe/IScsiCHAP.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/NetworkPkg/IScsiDxe/IScsiCHAP.c b/NetworkPkg/IScsiDxe/IScsiCHAP.c
index dbe3c8ef46f9..7e930c0d1eab 100644
--- a/NetworkPkg/IScsiDxe/IScsiCHAP.c
+++ b/NetworkPkg/IScsiDxe/IScsiCHAP.c
@@ -274,43 +274,47 @@ IScsiCHAPOnRspReceived (
 
     Challenge = IScsiGetValueByKeyFromList (
                   KeyValueList,
                   ISCSI_KEY_CHAP_CHALLENGE
                   );
     if (Challenge == NULL) {
       goto ON_EXIT;
     }
     //
     // Process the CHAP identifier and CHAP Challenge from Target.
     // Calculate Response value.
     //
     Result = IScsiNetNtoi (Identifier);
     if (Result > 0xFF) {
       goto ON_EXIT;
     }
 
     AuthData->InIdentifier      = (UINT32) Result;
     AuthData->InChallengeLength = (UINT32) sizeof (AuthData->InChallenge);
-    IScsiHexToBin (
-      (UINT8 *) AuthData->InChallenge,
-      &AuthData->InChallengeLength,
-      Challenge
-      );
+    Status = IScsiHexToBin (
+               (UINT8 *) AuthData->InChallenge,
+               &AuthData->InChallengeLength,
+               Challenge
+               );
+    if (EFI_ERROR (Status)) {
+      Status = EFI_PROTOCOL_ERROR;
+      goto ON_EXIT;
+    }
     Status = IScsiCHAPCalculateResponse (
                AuthData->InIdentifier,
                AuthData->AuthConfig->CHAPSecret,
                (UINT32) AsciiStrLen (AuthData->AuthConfig->CHAPSecret),
                AuthData->InChallenge,
                AuthData->InChallengeLength,
                AuthData->CHAPResponse
                );
 
     //
     // Transit to next step.
     //
     Conn->AuthStep = ISCSI_CHAP_STEP_THREE;
     break;
 
   case ISCSI_CHAP_STEP_THREE:
     //
     // One way CHAP authentication and the target would like to
     // authenticate us.
@@ -321,39 +325,43 @@ 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;
-    IScsiHexToBin (TargetRsp, &RspLen, Response);
+    Status = IScsiHexToBin (TargetRsp, &RspLen, Response);
+    if (EFI_ERROR (Status) || RspLen != ISCSI_CHAP_RSP_LEN) {
+      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);
   }
 
   FreePool (Data);
 
-- 
2.19.1.3.g30247aa5d201



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