From 10750020fcfa62b6948b4ec2aea0611d13dddf45 Mon Sep 17 00:00:00 2001
From: Andrei Litvin <andrei@andy314.com>
Date: Thu, 18 Nov 2021 10:47:32 -0500
Subject: [PATCH] Cleanup darwin usage of strtok and strncpy in DNS
 implementation (#11934)

* Update DnssdImpl for darwin

* Replace one more instance of strncpy with copystring

* Restyle fixes

* Use platform namespace prefix for CopyString

* Use a memcpy for sometthing that is not a string

* add a limit to  valuelen on txt records

* Validate value lenght - 0 size value should not copy anything

* Restyle fixes

* Fix off by one memcpy
---
 src/platform/Darwin/DnssdImpl.cpp | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/platform/Darwin/DnssdImpl.cpp b/src/platform/Darwin/DnssdImpl.cpp
index 8915c3d1d340e4..8cb8d609e74f41 100644
--- a/src/platform/Darwin/DnssdImpl.cpp
+++ b/src/platform/Darwin/DnssdImpl.cpp
@@ -312,19 +312,22 @@ void OnBrowseAdd(BrowseContext * context, const char * name, const char * type,
 
     VerifyOrReturn(strcmp(kLocalDot, domain) == 0);
 
-    char * tokens  = strdup(type);
-    char * regtype = strtok(tokens, ".");
-    free(tokens);
-
     DnssdService service = {};
     service.mInterface   = interfaceId;
     service.mProtocol    = context->protocol;
 
-    strncpy(service.mName, name, sizeof(service.mName));
-    service.mName[Common::kInstanceNameMaxLength] = 0;
+    Platform::CopyString(service.mName, name);
+    Platform::CopyString(service.mType, type);
 
-    strncpy(service.mType, regtype, sizeof(service.mType));
-    service.mType[kDnssdTypeMaxSize] = 0;
+    // only the first token after '.' should be included in the type
+    for (char * p = service.mType; *p != '\0'; p++)
+    {
+        if (*p == '.')
+        {
+            *p = '\0';
+            break;
+        }
+    }
 
     context->services.push_back(service);
 }
@@ -426,7 +429,12 @@ static CHIP_ERROR GetAddrInfo(void * context, DnssdResolveCallback callback, uin
         err = TXTRecordGetItemAtIndex(txtLen, txtRecord, i, kDnssdKeyMaxSize, key, &valueLen, &valuePtr);
         VerifyOrReturnError(CheckForSuccess(sdCtx, __func__, err, true), CHIP_ERROR_INTERNAL);
 
-        strncpy(value, reinterpret_cast<const char *>(valuePtr), valueLen);
+        if (valueLen >= sizeof(value))
+        {
+            // Truncation, but nothing better we can do
+            valueLen = sizeof(value) - 1;
+        }
+        memcpy(value, valuePtr, valueLen);
         value[valueLen] = 0;
 
         sdCtx->textEntries.push_back(TextEntry{ strdup(key), reinterpret_cast<const uint8_t *>(strdup(value)), valueLen });