From b694b00951eeeb4986387de1179d55dd38643a87 Mon Sep 17 00:00:00 2001
From: Jonathan Hui <jonhui@google.com>
Date: Tue, 18 Jun 2019 11:49:05 -0700
Subject: [PATCH] [tlvs] allow longer length to support forward compatibility
 (#3919)

---
 src/core/meshcop/commissioner.cpp           |  10 +-
 src/core/meshcop/joiner.cpp                 |   3 +-
 src/core/meshcop/leader.cpp                 |   5 +-
 src/core/meshcop/meshcop_tlvs.hpp           | 153 ++++++++++++--------
 src/core/thread/mle.cpp                     |  11 +-
 src/core/thread/mle_tlvs.hpp                |  70 +++++----
 src/core/thread/network_diagnostic.cpp      |   6 -
 src/core/thread/network_diagnostic_tlvs.hpp |  69 ++-------
 src/core/thread/thread_tlvs.hpp             |  14 +-
 9 files changed, 170 insertions(+), 171 deletions(-)

diff --git a/src/core/meshcop/commissioner.cpp b/src/core/meshcop/commissioner.cpp
index 180ad4751..4c423ac86 100644
--- a/src/core/meshcop/commissioner.cpp
+++ b/src/core/meshcop/commissioner.cpp
@@ -224,9 +224,9 @@ otError Commissioner::SendCommissionerSet(void)
     }
 
     // set bloom filter
-    memcpy(dataset.mSteeringData.m8, steeringData.GetValue(), steeringData.GetLength());
-    dataset.mSteeringData.mLength = steeringData.GetLength();
-    dataset.mIsSteeringDataSet    = true;
+    dataset.mSteeringData.mLength = steeringData.GetSteeringDataLength();
+    memcpy(dataset.mSteeringData.m8, steeringData.GetValue(), dataset.mSteeringData.mLength);
+    dataset.mIsSteeringDataSet = true;
 
     SuccessOrExit(error = SendMgmtCommissionerSetRequest(dataset, NULL, 0));
 
@@ -946,9 +946,9 @@ void Commissioner::HandleJoinerFinalize(Coap::Message &aMessage, const Ip6::Mess
 
     if (Tlv::GetTlv(aMessage, Tlv::kProvisioningUrl, sizeof(provisioningUrl), provisioningUrl) == OT_ERROR_NONE)
     {
-        if (provisioningUrl.GetLength() != mProvisioningUrl.GetLength() ||
+        if (provisioningUrl.GetProvisioningUrlLength() != mProvisioningUrl.GetProvisioningUrlLength() ||
             memcmp(provisioningUrl.GetProvisioningUrl(), mProvisioningUrl.GetProvisioningUrl(),
-                   provisioningUrl.GetLength()) != 0)
+                   provisioningUrl.GetProvisioningUrlLength()) != 0)
         {
             state = StateTlv::kReject;
         }
diff --git a/src/core/meshcop/joiner.cpp b/src/core/meshcop/joiner.cpp
index 708c538cf..17ba8d780 100644
--- a/src/core/meshcop/joiner.cpp
+++ b/src/core/meshcop/joiner.cpp
@@ -547,7 +547,6 @@ void Joiner::HandleJoinerEntrust(Coap::Message &aMessage, const Ip6::MessageInfo
     VerifyOrExit(extendedPanId.IsValid(), error = OT_ERROR_PARSE);
 
     SuccessOrExit(error = Tlv::GetTlv(aMessage, Tlv::kNetworkName, sizeof(networkName), networkName));
-    VerifyOrExit(networkName.IsValid(), error = OT_ERROR_PARSE);
 
     SuccessOrExit(error = Tlv::GetTlv(aMessage, Tlv::kActiveTimestamp, sizeof(activeTimestamp), activeTimestamp));
     VerifyOrExit(activeTimestamp.IsValid(), error = OT_ERROR_PARSE);
@@ -560,7 +559,7 @@ void Joiner::HandleJoinerEntrust(Coap::Message &aMessage, const Ip6::MessageInfo
     Get<Mle::MleRouter>().SetMeshLocalPrefix(meshLocalPrefix.GetMeshLocalPrefix());
     Get<Mac::Mac>().SetExtendedPanId(extendedPanId.GetExtendedPanId());
 
-    Get<Mac::Mac>().SetNetworkName(networkName.GetNetworkName(), networkName.GetLength());
+    Get<Mac::Mac>().SetNetworkName(networkName.GetNetworkName(), networkName.GetNetworkNameLength());
 
     otLogInfoMeshCoP("Joiner successful!");
 
diff --git a/src/core/meshcop/leader.cpp b/src/core/meshcop/leader.cpp
index 293515737..fd5ba0e98 100644
--- a/src/core/meshcop/leader.cpp
+++ b/src/core/meshcop/leader.cpp
@@ -82,13 +82,12 @@ void Leader::HandlePetition(Coap::Message &aMessage, const Ip6::MessageInfo &aMe
 
     VerifyOrExit(Get<Mle::MleRouter>().IsRoutingLocator(aMessageInfo.GetPeerAddr()));
     SuccessOrExit(Tlv::GetTlv(aMessage, Tlv::kCommissionerId, sizeof(commissionerId), commissionerId));
-    VerifyOrExit(commissionerId.IsValid());
 
     if (mTimer.IsRunning())
     {
-        VerifyOrExit((commissionerId.GetLength() == mCommissionerId.GetLength()) &&
+        VerifyOrExit((commissionerId.GetCommissionerIdLength() == mCommissionerId.GetCommissionerIdLength()) &&
                      (!strncmp(commissionerId.GetCommissionerId(), mCommissionerId.GetCommissionerId(),
-                               commissionerId.GetLength())));
+                               commissionerId.GetCommissionerIdLength())));
 
         ResignCommissioner();
     }
diff --git a/src/core/meshcop/meshcop_tlvs.hpp b/src/core/meshcop/meshcop_tlvs.hpp
index 03c5a2550..9be06b1eb 100644
--- a/src/core/meshcop/meshcop_tlvs.hpp
+++ b/src/core/meshcop/meshcop_tlvs.hpp
@@ -306,7 +306,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the PAN ID value.
@@ -353,7 +353,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Extended PAN ID value.
@@ -400,7 +400,18 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return true; }
+
+    /**
+     * This method returns the Network Name length.
+     *
+     * @returns The Network Name length.
+     *
+     */
+    uint8_t GetNetworkNameLength(void) const
+    {
+        return GetLength() <= sizeof(mNetworkName) ? GetLength() : sizeof(mNetworkName);
+    }
 
     /**
      * This method returns the Network Name value.
@@ -452,7 +463,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the PSKc value.
@@ -499,7 +510,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Network Master Key value.
@@ -546,7 +557,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Network Key Sequence value.
@@ -593,7 +604,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Mesh Local Prefix value.
@@ -641,19 +652,30 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return ((GetLength() != 0) && (GetLength() <= sizeof(*this) - sizeof(Tlv))); }
+    bool IsValid(void) const { return GetLength() > 0; }
+
+    /**
+     * This method returns the Steering Data length.
+     *
+     * @returns The Steering Data length.
+     *
+     */
+    uint8_t GetSteeringDataLength(void) const
+    {
+        return GetLength() <= sizeof(mSteeringData) ? GetLength() : sizeof(mSteeringData);
+    }
 
     /**
      * This method sets all bits in the Bloom Filter to zero.
      *
      */
-    void Clear(void) { memset(mSteeringData, 0, GetLength()); }
+    void Clear(void) { memset(mSteeringData, 0, GetSteeringDataLength()); }
 
     /**
      * Ths method sets all bits in the Bloom Filter to one.
      *
      */
-    void Set(void) { memset(mSteeringData, 0xff, GetLength()); }
+    void Set(void) { memset(mSteeringData, 0xff, GetSteeringDataLength()); }
 
     /**
      * Ths method indicates whether or not the SteeringData allows all Joiners.
@@ -666,7 +688,7 @@ public:
     {
         bool rval = true;
 
-        for (uint8_t i = 0; i < GetLength(); i++)
+        for (uint8_t i = 0; i < GetSteeringDataLength(); i++)
         {
             if (mSteeringData[i] != 0xff)
             {
@@ -684,7 +706,7 @@ public:
      * @returns The number of bits in the Bloom Filter.
      *
      */
-    uint8_t GetNumBits(void) const { return GetLength() * 8; }
+    uint8_t GetNumBits(void) const { return GetSteeringDataLength() * 8; }
 
     /**
      * This method indicates whether or not bit @p aBit is set.
@@ -695,7 +717,10 @@ public:
      * @retval FALSE  If bit @p aBit is not set.
      *
      */
-    bool GetBit(uint8_t aBit) const { return (mSteeringData[GetLength() - 1 - (aBit / 8)] & (1 << (aBit % 8))) != 0; }
+    bool GetBit(uint8_t aBit) const
+    {
+        return (mSteeringData[GetSteeringDataLength() - 1 - (aBit / 8)] & (1 << (aBit % 8))) != 0;
+    }
 
     /**
      * This method clears bit @p aBit.
@@ -703,7 +728,7 @@ public:
      * @param[in]  aBit  The bit offset.
      *
      */
-    void ClearBit(uint8_t aBit) { mSteeringData[GetLength() - 1 - (aBit / 8)] &= ~(1 << (aBit % 8)); }
+    void ClearBit(uint8_t aBit) { mSteeringData[GetSteeringDataLength() - 1 - (aBit / 8)] &= ~(1 << (aBit % 8)); }
 
     /**
      * This method sets bit @p aBit.
@@ -711,7 +736,7 @@ public:
      * @param[in]  aBit  The bit offset.
      *
      */
-    void SetBit(uint8_t aBit) { mSteeringData[GetLength() - 1 - (aBit / 8)] |= 1 << (aBit % 8); }
+    void SetBit(uint8_t aBit) { mSteeringData[GetSteeringDataLength() - 1 - (aBit / 8)] |= 1 << (aBit % 8); }
 
     /**
      * Ths method indicates whether or not the SteeringData is all zeros.
@@ -759,7 +784,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Border Agent Locator value.
@@ -800,13 +825,15 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns the Commissioner ID length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Commissioner ID length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetCommissionerIdLength(void) const
+    {
+        return GetLength() <= sizeof(mCommissionerId) ? GetLength() : sizeof(mCommissionerId);
+    }
 
     /**
      * This method returns the Commissioner ID value.
@@ -863,7 +890,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Commissioner Session ID value.
@@ -910,7 +937,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Rotation Time value.
@@ -984,7 +1011,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 } OT_TOOL_PACKED_END;
 
 /**
@@ -1012,7 +1039,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the UDP Port value.
@@ -1059,7 +1086,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * State values.
@@ -1117,7 +1144,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the UDP Port value.
@@ -1164,7 +1191,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns a pointer to the Joiner IID.
@@ -1211,7 +1238,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Joiner Router Locator value.
@@ -1258,7 +1285,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns a pointer to the Joiner Router KEK.
@@ -1306,7 +1333,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 } OT_TOOL_PACKED_END;
 
 /**
@@ -1334,7 +1361,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Delay Timer value.
@@ -1657,7 +1684,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Count value.
@@ -1704,7 +1731,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Period value.
@@ -1751,7 +1778,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Scan Duration value.
@@ -1824,14 +1851,16 @@ public:
         SetLength(0);
     }
 
-    /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+    /*
+     * This method returns the Provisioning URL length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Provisioning URL length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetProvisioningUrlLength(void) const
+    {
+        return GetLength() <= sizeof(mProvisioningUrl) ? GetLength() : sizeof(mProvisioningUrl);
+    }
 
     /**
      * This method returns the Provisioning URL value.
@@ -1882,13 +1911,15 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns the Vendor Name length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Vendor Name length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetVendorNameLength(void) const
+    {
+        return GetLength() <= sizeof(mVendorName) ? GetLength() : sizeof(mVendorName);
+    }
 
     /**
      * This method returns the Vendor Name value.
@@ -1944,13 +1975,15 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns the Vendor Model length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Vendor Model length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetVendorModelLength(void) const
+    {
+        return GetLength() <= sizeof(mVendorModel) ? GetLength() : sizeof(mVendorModel);
+    }
 
     /**
      * This method returns the Vendor Model value.
@@ -2006,13 +2039,15 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns the Vendor SW Version length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Vendor SW Version length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetVendorSwVersionLength(void) const
+    {
+        return GetLength() <= sizeof(mVendorSwVersion) ? GetLength() : sizeof(mVendorSwVersion);
+    }
 
     /**
      * This method returns the Vendor SW Version value.
@@ -2068,13 +2103,15 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns the Vendor Data length.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns The Vendor Data length.
      *
      */
-    bool IsValid(void) const { return GetLength() <= sizeof(*this) - sizeof(Tlv); }
+    uint8_t GetVendorDataLength(void) const
+    {
+        return GetLength() <= sizeof(mVendorData) ? GetLength() : sizeof(mVendorData);
+    }
 
     /**
      * This method returns the Vendor Data value.
@@ -2146,7 +2183,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Stack Vendor OUI value.
@@ -2417,7 +2454,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Version value.
@@ -2504,7 +2541,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Version value.
diff --git a/src/core/thread/mle.cpp b/src/core/thread/mle.cpp
index ca3ff80fa..348e27986 100644
--- a/src/core/thread/mle.cpp
+++ b/src/core/thread/mle.cpp
@@ -3349,8 +3349,8 @@ otError Mle::HandleParentResponse(const Message &aMessage, const Ip6::MessageInf
     // Challenge
     SuccessOrExit(error = Tlv::GetTlv(aMessage, Tlv::kChallenge, sizeof(challenge), challenge));
     VerifyOrExit(challenge.IsValid(), error = OT_ERROR_PARSE);
-    memcpy(mChildIdRequest.mChallenge, challenge.GetChallenge(), challenge.GetLength());
-    mChildIdRequest.mChallengeLength = challenge.GetLength();
+    mChildIdRequest.mChallengeLength = challenge.GetChallengeLength();
+    memcpy(mChildIdRequest.mChallenge, challenge.GetChallenge(), mChildIdRequest.mChallengeLength);
 
     mParentCandidate.SetExtAddress(extAddress);
     mParentCandidate.SetRloc16(sourceAddress.GetRloc16());
@@ -3828,9 +3828,8 @@ otError Mle::HandleDiscoveryResponse(const Message &aMessage, const Ip6::Message
 
         case MeshCoP::Tlv::kNetworkName:
             aMessage.Read(offset, sizeof(networkName), &networkName);
-            VerifyOrExit(networkName.IsValid(), error = OT_ERROR_PARSE);
-            memcpy(&result.mNetworkName, networkName.GetNetworkName(), networkName.GetLength());
-            result.mNetworkName.m8[networkName.GetLength()] = '\0';
+            memcpy(&result.mNetworkName, networkName.GetNetworkName(), networkName.GetNetworkNameLength());
+            result.mNetworkName.m8[networkName.GetNetworkNameLength()] = '\0';
             break;
 
         case MeshCoP::Tlv::kSteeringData:
@@ -3844,7 +3843,7 @@ otError Mle::HandleDiscoveryResponse(const Message &aMessage, const Ip6::Message
             }
 
             didCheckSteeringData         = true;
-            result.mSteeringData.mLength = steeringData.GetLength();
+            result.mSteeringData.mLength = steeringData.GetSteeringDataLength();
             memcpy(result.mSteeringData.m8, steeringData.GetValue(), result.mSteeringData.mLength);
 
             break;
diff --git a/src/core/thread/mle_tlvs.hpp b/src/core/thread/mle_tlvs.hpp
index 4e6ddb157..d914a5c80 100644
--- a/src/core/thread/mle_tlvs.hpp
+++ b/src/core/thread/mle_tlvs.hpp
@@ -196,7 +196,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the RLOC16 value.
@@ -243,7 +243,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     enum
     {
@@ -298,7 +298,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Timeout value.
@@ -330,6 +330,7 @@ class ChallengeTlv : public Tlv
 public:
     enum
     {
+        kMinSize = 4, ///< Minimum size in bytes (Thread Specification).
         kMaxSize = 8, ///< Maximum size in bytes (Thread Specification).
     };
 
@@ -350,7 +351,18 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() >= 4 && GetLength() <= 8; }
+    bool IsValid(void) const { return GetLength() >= kMinSize; }
+
+    /**
+     * This method returns the Challenge length.
+     *
+     * @returns The Challenge length.
+     *
+     */
+    uint8_t GetChallengeLength(void) const
+    {
+        return GetLength() <= sizeof(mChallenge) ? GetLength() : sizeof(mChallenge);
+    }
 
     /**
      * This method returns a pointer to the Challenge value.
@@ -366,7 +378,7 @@ public:
      * @param[in]  aChallenge  A pointer to the Challenge value.
      *
      */
-    void SetChallenge(const uint8_t *aChallenge) { memcpy(mChallenge, aChallenge, GetLength()); }
+    void SetChallenge(const uint8_t *aChallenge) { memcpy(mChallenge, aChallenge, GetChallengeLength()); }
 
 private:
     uint8_t mChallenge[kMaxSize];
@@ -382,6 +394,7 @@ class ResponseTlv : public Tlv
 public:
     enum
     {
+        kMinSize = 4, ///< Minimum size in bytes (Thread Specification).
         kMaxSize = 8, ///< Maximum size in bytes (Thread Specification).
     };
 
@@ -398,11 +411,14 @@ public:
     /**
      * This method indicates whether or not the TLV appears to be well-formed.
      *
+     * OpenThread only generates Challenge values with 8-byte length. As a result, a Response value lengths must also
+     * have 8-byte length.
+     *
      * @retval TRUE   If the TLV appears to be well-formed.
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns a pointer to the Response value.
@@ -449,7 +465,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Frame Counter value.
@@ -498,11 +514,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const
-    {
-        return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask) &&
-               GetLength() <= sizeof(*this) - sizeof(Tlv);
-    }
+    bool IsValid(void) const { return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask); }
 
     /**
      * This method returns the Router ID Sequence value.
@@ -674,11 +686,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const
-    {
-        return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask) &&
-               GetLength() <= sizeof(*this) - sizeof(Tlv);
-    }
+    bool IsValid(void) const { return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask); }
 
     /**
      * This method returns the Router ID Sequence value.
@@ -888,7 +896,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Frame Counter value.
@@ -935,7 +943,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the RLOC16 value.
@@ -982,7 +990,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Partition ID value.
@@ -1207,7 +1215,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     enum
     {
@@ -1518,7 +1526,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Link Margin value.
@@ -1565,7 +1573,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * Status values.
@@ -1620,7 +1628,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Version value.
@@ -1762,7 +1770,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the Channel Page value.
@@ -1826,7 +1834,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the PAN ID value.
@@ -1874,7 +1882,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 } OT_TOOL_PACKED_END;
 
 /**
@@ -1902,7 +1910,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the time sync period.
@@ -1966,7 +1974,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 
     /**
      * This method returns the XTAL accuracy.
@@ -2015,7 +2023,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 } OT_TOOL_PACKED_END;
 
 /**
@@ -2044,7 +2052,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(Tlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(Tlv); }
 } OT_TOOL_PACKED_END;
 
 /**
diff --git a/src/core/thread/network_diagnostic.cpp b/src/core/thread/network_diagnostic.cpp
index eae830086..23e106b01 100644
--- a/src/core/thread/network_diagnostic.cpp
+++ b/src/core/thread/network_diagnostic.cpp
@@ -481,8 +481,6 @@ void NetworkDiagnostic::HandleDiagnosticGetQuery(Coap::Message &aMessage, const
 
     VerifyOrExit(networkDiagnosticTlv.GetType() == NetworkDiagnosticTlv::kTypeList, error = OT_ERROR_PARSE);
 
-    VerifyOrExit((static_cast<TypeListTlv *>(&networkDiagnosticTlv)->IsValid()), error = OT_ERROR_PARSE);
-
     // DIAG_GET.qry may be sent as a confirmable message.
     if (aMessage.GetType() == OT_COAP_TYPE_CONFIRMABLE)
     {
@@ -553,8 +551,6 @@ void NetworkDiagnostic::HandleDiagnosticGetRequest(Coap::Message &aMessage, cons
 
     VerifyOrExit(networkDiagnosticTlv.GetType() == NetworkDiagnosticTlv::kTypeList, error = OT_ERROR_PARSE);
 
-    VerifyOrExit((static_cast<TypeListTlv *>(&networkDiagnosticTlv)->IsValid()), error = OT_ERROR_PARSE);
-
     VerifyOrExit((message = Get<Coap::Coap>().NewMessage()) != NULL, error = OT_ERROR_NO_BUFS);
 
     SuccessOrExit(error = message->SetDefaultResponseHeader(aMessage));
@@ -647,8 +643,6 @@ void NetworkDiagnostic::HandleDiagnosticReset(Coap::Message &aMessage, const Ip6
 
     VerifyOrExit(networkDiagnosticTlv.GetType() == NetworkDiagnosticTlv::kTypeList);
 
-    VerifyOrExit((static_cast<TypeListTlv *>(&networkDiagnosticTlv)->IsValid()));
-
     offset = aMessage.GetOffset() + sizeof(NetworkDiagnosticTlv);
 
     for (uint8_t i = 0; i < networkDiagnosticTlv.GetLength(); i++)
diff --git a/src/core/thread/network_diagnostic_tlvs.hpp b/src/core/thread/network_diagnostic_tlvs.hpp
index c98afbede..79723ef66 100644
--- a/src/core/thread/network_diagnostic_tlvs.hpp
+++ b/src/core/thread/network_diagnostic_tlvs.hpp
@@ -179,7 +179,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns a pointer to the Extended MAC Address.
@@ -226,7 +226,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the RLOC16 value.
@@ -273,7 +273,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     enum
     {
@@ -328,7 +328,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the Timeout value.
@@ -377,9 +377,9 @@ public:
      */
     bool IsValid(void) const
     {
-        return (GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv) ||
-                GetLength() ==
-                    sizeof(*this) - sizeof(NetworkDiagnosticTlv) - sizeof(mSedBufferSize) - sizeof(mSedDatagramCount));
+        return ((GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv)) ||
+                (GetLength() ==
+                 sizeof(*this) - sizeof(NetworkDiagnosticTlv) - sizeof(mSedBufferSize) - sizeof(mSedDatagramCount)));
     }
 
     /**
@@ -572,11 +572,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const
-    {
-        return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask) &&
-               GetLength() <= sizeof(*this) - sizeof(NetworkDiagnosticTlv);
-    }
+    bool IsValid(void) const { return GetLength() >= sizeof(mRouterIdSequence) + sizeof(mRouterIdMask); }
 
     /**
      * This method returns the Router ID Sequence value.
@@ -746,7 +742,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the Partition ID value.
@@ -891,11 +887,6 @@ OT_TOOL_PACKED_BEGIN
 class Ip6AddressListTlv : public NetworkDiagnosticTlv
 {
 public:
-    enum
-    {
-        kMaxSize = 8, ///< Maximum size in bytes (Thread Specification).
-    };
-
     /**
      * This method initializes the TLV.
      *
@@ -906,15 +897,6 @@ public:
         SetLength(sizeof(*this) - sizeof(NetworkDiagnosticTlv));
     }
 
-    /**
-     * This method indicates whether or not the TLV appears to be well-formed.
-     *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
-     *
-     */
-    bool IsValid(void) const { return GetLength() <= sizeof(Ip6::Address) * kMaxSize; }
-
     /**
      * This method returns a pointer to the IPv6 address entry.
      *
@@ -955,7 +937,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the IfInUnknownProtos counter.
@@ -1146,7 +1128,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the Status value.
@@ -1193,7 +1175,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the Status value.
@@ -1351,7 +1333,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return (GetLength() % sizeof(ChildTableEntry)) == 0; }
 
     /**
      * This method returns the number of Child Table entries.
@@ -1394,14 +1376,11 @@ public:
     }
 
     /**
-     * This method indicates whether or not the TLV appears to be well-formed.
+     * This method returns a pointer to the list of Channel Pages.
      *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
+     * @returns A pointer to the list of Channel Pages.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
-
     uint8_t *GetChannelPages(void) { return mChannelPages; }
 
 private:
@@ -1425,22 +1404,6 @@ public:
         SetType(kTypeList);
         SetLength(sizeof(*this) - sizeof(NetworkDiagnosticTlv));
     }
-
-    /**
-     * This method indicates whether or not the TLV appears to be well-formed.
-     *
-     * @retval TRUE   If the TLV appears to be well-formed.
-     * @retval FALSE  If the TLV does not appear to be well-formed.
-     *
-     */
-    bool IsValid(void) const { return GetLength() <= OT_NETWORK_DIAGNOSTIC_TYPELIST_MAX_ENTRIES; }
-
-    /**
-     * This method returns a pointer to the Challenge value.
-     *
-     * @returns A pointer to the Challenge value.
-     *
-     */
 } OT_TOOL_PACKED_END;
 
 /**
@@ -1468,7 +1431,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(NetworkDiagnosticTlv); }
 
     /**
      * This method returns the Timeout value.
diff --git a/src/core/thread/thread_tlvs.hpp b/src/core/thread/thread_tlvs.hpp
index 642406fee..a4c795550 100644
--- a/src/core/thread/thread_tlvs.hpp
+++ b/src/core/thread/thread_tlvs.hpp
@@ -138,7 +138,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns a reference to the Target EID.
@@ -185,7 +185,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns a reference to the Extended MAC Address.
@@ -232,7 +232,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns the RLOC16 value.
@@ -279,7 +279,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns a pointer to the ML-EID IID.
@@ -338,7 +338,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * Status values.
@@ -398,7 +398,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns the Last Transaction Time value.
@@ -444,7 +444,7 @@ public:
      * @retval FALSE  If the TLV does not appear to be well-formed.
      *
      */
-    bool IsValid(void) const { return GetLength() == sizeof(*this) - sizeof(ThreadTlv); }
+    bool IsValid(void) const { return GetLength() >= sizeof(*this) - sizeof(ThreadTlv); }
 
     /**
      * This method returns the ID Sequence value.