Randomness and stack protection!!

kernel/Makefile

@@ -8,7 +8,7 @@ CXX := x86_64-elf-g++
 AS := x86_64-elf-as
 NASM := nasm
 
-CFLAGS := -Wall -Wextra -Werror -Os -ffreestanding -mno-red-zone -mno-mmx -mno-sse -mno-sse2 -fshort-wchar -mcmodel=kernel -I$(MOON_DIR)/include -isystem $(MOON_DIR)/include/std
+CFLAGS := -Wall -Wextra -Werror -Os -ffreestanding -fstack-protector-all -mno-red-zone -mno-mmx -mno-sse -mno-sse2 -fshort-wchar -mcmodel=kernel -I$(MOON_DIR)/include -isystem $(MOON_DIR)/include/std
 CXXFLAGS := -fno-rtti -fno-exceptions
 NASMFLAGS := -felf64
 ASFLAGS :=
@@ -40,6 +40,14 @@ $(MOON_OBJ)/interrupts/handlers.cpp.o: $(MOON_SRC)/interrupts/handlers.cpp
 	@mkdir -p $(@D)
 	$(CXX) $(CFLAGS) -mgeneral-regs-only $(CXXFLAGS) -o $@ -c $^
 
+$(MOON_OBJ)/main.cpp.o: $(MOON_SRC)/main.cpp
+	@mkdir -p $(@D)
+	$(CXX) $(CFLAGS) -fno-stack-protector $(CXXFLAGS) -o $@ -c $^
+
+$(MOON_OBJ)/init/Init.cpp.o: $(MOON_SRC)/init/Init.cpp
+	@mkdir -p $(@D)
+	$(CXX) $(CFLAGS) -fno-stack-protector $(CXXFLAGS) -o $@ -c $^
+
 $(MOON_OBJ)/%.cpp.o: $(MOON_SRC)/%.cpp
 	@mkdir -p $(@D)
 	$(CXX) $(CFLAGS) $(CXXFLAGS) -o $@ -c $^

kernel/include/assert.h

@@ -12,3 +12,5 @@
     } while (0)
 
 #define TODO(message) __call_assert_fail("TODO at %s, line %d: %s", __FILE__, __LINE__, message)
+
+#define PANIC(message) __call_assert_fail("PANIC at %s, line %d: %s", __FILE__, __LINE__, message)

kernel/include/rand/Init.h

@@ -0,0 +1,7 @@
+#pragma once
+
+namespace Mersenne
+{
+    void init();
+    void reseed();
+}

kernel/include/rand/Mersenne.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <stdint.h>
+
+namespace Mersenne
+{
+    void seed(uint64_t);
+    uint64_t get();
+}

kernel/src/init/Init.cpp

@@ -7,12 +7,16 @@
 #include "memory/RangeAllocator.h"
 #include "memory/VMM.h"
 #include "panic/hang.h"
+#include "rand/Init.h"
+#include "rand/Mersenne.h"
 #include "render/Framebuffer.h"
 #include "render/TextRenderer.h"
 #include <string.h>
 
 extern BOOTBOOT bootboot;
 
+uintptr_t __stack_chk_guard = 0xfeff34;
+
 void Init::check_magic()
 {
     ASSERT(strncmp((char*)bootboot.magic, BOOTBOOT_MAGIC, 4) == 0);
@@ -35,4 +39,8 @@ void Init::early_init()
 
     kernelPMM.init_from_mmap();
     kernelVMM.init();
+
+    Mersenne::init();
+
+    __stack_chk_guard = Mersenne::get();
 }

kernel/src/interrupts/IRQ.cpp

@@ -1,6 +1,7 @@
 #include "interrupts/IRQ.h"
 #include "io/IO.h"
 #include "io/PIC.h"
+#include "rand/Init.h"
 #include "scheduling/PIT.h"
 #include "std/stdio.h"
 
@@ -16,6 +17,7 @@ void IRQ::interrupt_handler(SavedContext* context)
     }
     default: printf("Unhandled IRQ: %ld", context->irq_number); break;
     }
+    Mersenne::reseed();
     PIC::send_eoi(context->irq_number);
     return;
 }

kernel/src/main.cpp

@@ -18,6 +18,7 @@
 #include "memory/RangeAllocator.h"
 #include "panic/hang.h"
 #include "power/reboot.h"
+#include "rand/Mersenne.h"
 #include "render/Framebuffer.h"
 #include "render/TextRenderer.h"
 #include "scheduling/PIT.h"

kernel/src/rand/Init.asm

@@ -0,0 +1,10 @@
+global _test_rdseed
+
+_test_rdseed:
+    mov eax, 7
+    mov ecx, 0
+    cpuid
+    shr ebx, 18
+    and ebx, 1
+    mov eax, ebx
+    ret

kernel/src/rand/Init.cpp

@@ -0,0 +1,66 @@
+#define MODULE "rand"
+
+#include "rand/Init.h"
+#include "config.h"
+#include "cpu/CPU.h"
+#include "io/IO.h"
+#include "log/Log.h"
+#include "rand/Mersenne.h"
+
+static uint64_t state = 0xf5026f5ae96319e9;
+
+extern "C" int _test_rdseed();
+
+static uint64_t rdtsc()
+{
+    uint64_t result1;
+    uint64_t result2;
+    asm volatile("rdtsc" : "=a"(result1), "=d"(result2));
+    return result2 << 32 | result1;
+}
+
+static uint64_t rdseed()
+{
+    uint64_t result;
+    asm volatile("rdseed %0" : "=r"(result));
+    return result;
+}
+
+static uint64_t rdrand()
+{
+    uint64_t result;
+    asm volatile("rdrand %0" : "=r"(result));
+    return result;
+}
+
+void Mersenne::init()
+{
+    state ^= (0x45fe1024UL + MOON_MAJOR) * (MOON_MINOR ^ 200UL);
+
+    state ^= 0xe0e4f5332ea75b;
+
+    reseed();
+
+    state ^= Mersenne::get() * 0xffe3;
+
+    state ^= rdtsc();
+
+    Mersenne::seed(state);
+}
+
+void Mersenne::reseed()
+{
+    state ^= rdtsc();
+
+    if (CPU::has_feature(CPU::Features::RDRAND)) { state ^= rdrand(); }
+
+    if (_test_rdseed()) { state ^= rdseed(); }
+
+    state ^= rdtsc();
+
+    state ^= IO::inb(0x40);
+
+    state ^= rdtsc();
+
+    Mersenne::seed(state);
+}

kernel/src/rand/Mersenne.cpp

@@ -0,0 +1,62 @@
+#define MODULE "rand"
+
+#include "rand/Mersenne.h"
+#include "assert.h"
+#include <stddef.h>
+
+typedef uint64_t word_t;
+
+static const int STATE_SIZE = 312;
+static const int MIDDLE = 156;
+static const int INIT_SHIFT = 62;
+static const uint64_t TWIST_MASK = 0xb5026f5aa96619e9;
+static const uint64_t INIT_FACT = 6364136223846793005;
+static const int SHIFT1 = 29;
+static const uint64_t MASK1 = 0x5555555555555555;
+static const int SHIFT2 = 17;
+static const uint64_t MASK2 = 0x71d67fffeda60000;
+static const int SHIFT3 = 37;
+static const uint64_t MASK3 = 0xfff7eee000000000;
+static const int SHIFT4 = 43;
+
+static const word_t LOWER_MASK = 0x7fffffff;
+static const word_t UPPER_MASK = (~(word_t)LOWER_MASK);
+
+static word_t state[STATE_SIZE];
+static size_t index = STATE_SIZE + 1;
+
+void Mersenne::seed(uint64_t s)
+{
+    index = STATE_SIZE;
+    state[0] = s;
+    for (size_t i = 1; i < STATE_SIZE; i++) state[i] = (INIT_FACT * (state[i - 1] ^ (state[i - 1] >> INIT_SHIFT))) + i;
+}
+
+static void twist()
+{
+    for (size_t i = 0; i < STATE_SIZE; i++)
+    {
+        word_t x = (state[i] & UPPER_MASK) | (state[(i + 1) % STATE_SIZE] & LOWER_MASK);
+        x = (x >> 1) ^ (x & 1 ? TWIST_MASK : 0);
+        state[i] = state[(i + MIDDLE) % STATE_SIZE] ^ x;
+    }
+    index = 0;
+}
+
+uint64_t Mersenne::get()
+{
+    if (index >= STATE_SIZE)
+    {
+        ASSERT(index == STATE_SIZE && "Mersenne generator was never seeded");
+        twist();
+    }
+
+    word_t y = state[index];
+    y ^= (y >> SHIFT1) & MASK1;
+    y ^= (y << SHIFT2) & MASK2;
+    y ^= (y << SHIFT3) & MASK3;
+    y ^= y >> SHIFT4;
+
+    index++;
+    return y;
+}

kernel/src/stack.cpp

@@ -0,0 +1,7 @@
+#include "assert.h"
+#include <stdint.h>
+
+extern "C" void __stack_chk_fail()
+{
+    PANIC("Stack smashing detected");
+}