BaseTools: Update Stack Cookie Logic

This patch updates the GenC logic to generate a random stack cookie value
for the stack check libraries. These random values improve security
for modules which cannot update the global intrinsics.

If the stack cookie value is randomized in the AutoGen.h file each
build, the build system will determine the module/library must be
rebuilt causing effectively a clean build every time. This also makes
binary reproducibility impossible.

This patch updates the early build scripts to create 32 and 64-bit JSON
files in the build output directory which each contain 100 randomized
stack cookie values for each bitwidth. If the JSON files are already
present, then they are not recreated which allows them to be stored and
moved to other builds for binary reproducibility. Because they are in
the build directory, a clean build will cause the values to be
regenerated.

The logic which creates AutoGen.h will read these JSON files and use a
hash of the module GUID (the hash seed is fixed in Basetools) to index
into the array of stack cookie values for the module bitwidth. This
model is necessary because there isn't thread-consistent data so we
cannot use a locking mechanism to ensure only one thread is writing to
the stack cookie files at a time. With this model, the build threads
only need to read from the files.

Signed-off-by: Oliver Smith-Denny <osde@linux.microsoft.com>

BaseTools/Source/Python/AutoGen/GenC.py

@@ -21,6 +21,9 @@ from .StrGather import *
 from .GenPcdDb import CreatePcdDatabaseCode
 from .IdfClassObject import *
 
+import json
+import secrets
+
 ## PCD type string
 gItemTypeStringDatabase  = {
     TAB_PCDS_FEATURE_FLAG       :   TAB_PCDS_FIXED_AT_BUILD,
@@ -2039,6 +2042,34 @@ def CreateFooterCode(Info, AutoGenC, AutoGenH):
 def CreateCode(Info, AutoGenC, AutoGenH, StringH, UniGenCFlag, UniGenBinBuffer, StringIdf, IdfGenCFlag, IdfGenBinBuffer):
     CreateHeaderCode(Info, AutoGenC, AutoGenH)
 
+    # The only 32 bit archs we have are IA32 and ARM, everything else is 64 bit
+    Bitwidth = 32 if Info.Arch == 'IA32' or Info.Arch == 'ARM' else 64
+
+    if GlobalData.gStackCookieValues64 == [] and os.path.exists(os.path.join(Info.PlatformInfo.BuildDir, "StackCookieValues64.json")):
+        with open (os.path.join(Info.PlatformInfo.BuildDir, "StackCookieValues64.json"), "r") as file:
+            GlobalData.gStackCookieValues64 = json.load(file)
+    if GlobalData.gStackCookieValues32 == [] and os.path.exists(os.path.join(Info.PlatformInfo.BuildDir, "StackCookieValues32.json")):
+        with open (os.path.join(Info.PlatformInfo.BuildDir, "StackCookieValues32.json"), "r") as file:
+            GlobalData.gStackCookieValues32 = json.load(file)
+
+    try:
+        if Bitwidth == 32:
+            CookieValue = int(GlobalData.gStackCookieValues32[hash(Info.Guid) % len(GlobalData.gStackCookieValues32)])
+        else:
+            CookieValue = int(GlobalData.gStackCookieValues64[hash(Info.Guid) % len(GlobalData.gStackCookieValues64)])
+    except:
+        EdkLogger.warn("build", "Failed to get Stack Cookie Value List! Generating random value.", ExtraData="[%s]" % str(Info))
+        if Bitwidth == 32:
+            CookieValue = secrets.randbelow (0xFFFFFFFF)
+        else:
+            CookieValue = secrets.randbelow (0xFFFFFFFFFFFFFFFF)
+
+    AutoGenH.Append((
+        '#define STACK_COOKIE_VALUE 0x%XULL\n' % CookieValue
+        if Bitwidth == 64 else
+        '#define STACK_COOKIE_VALUE 0x%X\n' % CookieValue
+    ))
+
     CreateGuidDefinitionCode(Info, AutoGenC, AutoGenH)
     CreateProtocolDefinitionCode(Info, AutoGenC, AutoGenH)
     CreatePpiDefinitionCode(Info, AutoGenC, AutoGenH)

BaseTools/Source/Python/Common/GlobalData.py

@@ -122,4 +122,5 @@ gEnableGenfdsMultiThread = True
 gSikpAutoGenCache = set()
 # Common lock for the file access in multiple process AutoGens
 file_lock = None
-
+gStackCookieValues32 = []
+gStackCookieValues64 = []

BaseTools/Source/Python/build/build.py

@@ -28,6 +28,8 @@ import threading
 from linecache import getlines
 from subprocess import Popen,PIPE, STDOUT
 from collections import OrderedDict, defaultdict
+import json
+import secrets
 
 from AutoGen.PlatformAutoGen import PlatformAutoGen
 from AutoGen.ModuleAutoGen import ModuleAutoGen
@@ -282,6 +284,22 @@ def LaunchCommand(Command, WorkingDir,ModuleAuto = None):
         iau.CreateDepsTarget()
     return "%dms" % (int(round((time.time() - BeginTime) * 1000)))
 
+def GenerateStackCookieValues():
+    if GlobalData.gBuildDirectory == "":
+        return
+
+    # Check if the 32 bit values array needs to be created
+    if not os.path.exists(os.path.join(GlobalData.gBuildDirectory, "StackCookieValues32.json")):
+        StackCookieValues32 = [secrets.randbelow(0xFFFFFFFF) for _ in range(0, 100)]
+        with open (os.path.join(GlobalData.gBuildDirectory, "StackCookieValues32.json"), "w") as file:
+            json.dump(StackCookieValues32, file)
+
+    # Check if the 64 bit values array needs to be created
+    if not os.path.exists(os.path.join(GlobalData.gBuildDirectory, "StackCookieValues64.json")):
+        StackCookieValues64 = [secrets.randbelow(0xFFFFFFFFFFFFFFFF) for _ in range(0, 100)]
+        with open (os.path.join(GlobalData.gBuildDirectory, "StackCookieValues64.json"), "w") as file:
+            json.dump(StackCookieValues64, file)
+
 ## The smallest unit that can be built in multi-thread build mode
 #
 # This is the base class of build unit. The "Obj" parameter must provide
@@ -1794,6 +1812,7 @@ class Build():
                         self.UniFlag,
                         self.Progress
                         )
+                GenerateStackCookieValues()
                 self.Fdf = Wa.FdfFile
                 self.LoadFixAddress = Wa.Platform.LoadFixAddress
                 self.BuildReport.AddPlatformReport(Wa)
@@ -1897,6 +1916,7 @@ class Build():
                         self.Progress,
                         self.ModuleFile
                         )
+                GenerateStackCookieValues()
                 self.Fdf = Wa.FdfFile
                 self.LoadFixAddress = Wa.Platform.LoadFixAddress
                 Wa.CreateMakeFile(False)
@@ -2147,6 +2167,7 @@ class Build():
                 self.UniFlag,
                 self.Progress
                 )
+        GenerateStackCookieValues()
         self.Fdf = Wa.FdfFile
         self.LoadFixAddress = Wa.Platform.LoadFixAddress
         self.BuildReport.AddPlatformReport(Wa)