From b476dc856431436ac0f3e0179f8a25302421a0cc Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Mon, 5 Apr 2021 00:22:15 +0200
Subject: Added new randomization features

---
 libs/libc/crt/crt0.c   | 22 ++++++++++++++++------
 libs/libc/inc/random.h |  1 +
 libs/libc/inc/sys.h    |  2 --
 libs/libc/random.c     | 32 ++++++++++++++++++++++++--------
 libs/libc/sanitize.c   |  4 ----
 libs/libc/sys.c        |  5 -----
 6 files changed, 41 insertions(+), 25 deletions(-)

(limited to 'libs')

diff --git a/libs/libc/crt/crt0.c b/libs/libc/crt/crt0.c
index 6c38474..3bd413f 100644
--- a/libs/libc/crt/crt0.c
+++ b/libs/libc/crt/crt0.c
@@ -1,18 +1,28 @@
 // MIT License, Copyright (c) 2021 Marvin Borner
 
+#include <assert.h>
 #include <def.h>
+#include <random.h>
 #include <sys.h>
 
 #ifdef USER
 
-extern int main(int, char **);
+extern u32 __stack_chk_guard;
+u32 __stack_chk_guard;
 
-void _start(void);
-void _start(void)
+int main(int, char **);
+
+int _start(int argc, char **argv);
+int _start(int argc, char **argv)
 {
-	exit(main(0, NULL));
-	while (1)
-		;
+	u32 stamp = 0;
+	assert(read("/dev/rtc", &stamp, 0, sizeof(stamp)) == sizeof(stamp) && stamp);
+	srand(stamp);
+	rand_fill(&__stack_chk_guard, sizeof(__stack_chk_guard));
+
+	exit(main(argc, argv));
+
+	return 1;
 }
 
 #endif
diff --git a/libs/libc/inc/random.h b/libs/libc/inc/random.h
index 6360625..1b41df5 100644
--- a/libs/libc/inc/random.h
+++ b/libs/libc/inc/random.h
@@ -9,6 +9,7 @@
 
 void srand(u32 seed);
 u32 rand(void);
+void rand_fill(void *buf, u32 size);
 char *randstr(u32 size);
 
 #endif
diff --git a/libs/libc/inc/sys.h b/libs/libc/inc/sys.h
index b435899..58d7969 100644
--- a/libs/libc/inc/sys.h
+++ b/libs/libc/inc/sys.h
@@ -28,7 +28,6 @@ enum sys {
 	SYS_EXIT, // Exit current process
 	SYS_BOOT, // Boot functions (e.g. reboot/shutdown)
 	SYS_YIELD, // Switch to next process
-	SYS_TIME, // Get kernel time
 	/* SYS_NET_OPEN, // Open network socket */
 	/* SYS_NET_CLOSE, // Close network socket */
 	/* SYS_NET_CONNECT, // Connect to destination */
@@ -75,7 +74,6 @@ res poll(const char **files) NONNULL;
 res exec(const char *path, ...) ATTR((nonnull(1))) SENTINEL;
 res yield(void);
 res boot(u32 cmd);
-u32 time(void);
 
 res sys_alloc(u32 size, u32 *addr) NONNULL;
 res sys_free(void *ptr) NONNULL;
diff --git a/libs/libc/random.c b/libs/libc/random.c
index 983357f..2cd7f93 100644
--- a/libs/libc/random.c
+++ b/libs/libc/random.c
@@ -15,36 +15,52 @@ void srand(u32 seed)
 	g_seed = seed;
 }
 
-static u32 default_rand(void)
+static u32 rand_default(void)
 {
 	g_seed = g_seed * 1103515245 + 12345;
 	return (g_seed >> 16) & 0x7FFF;
 }
 
-u32 rand(void)
+static u32 rand_once(void)
 {
 #ifdef KERNEL
-	u32 rd;
+	u32 val = 0;
 	if (cpu_extended_features.ebx & CPUID_EXT_FEAT_EBX_RDSEED) {
 		__asm__ volatile("1:\n"
 				 "rdseed %0\n"
 				 "jnc 1b\n"
-				 : "=r"(rd));
+				 : "=r"(val));
 	} else if (cpu_features.ecx & CPUID_FEAT_ECX_RDRND) {
 		__asm__ volatile("1:\n"
 				 "rdrand %0\n"
 				 "jnc 1b\n"
-				 : "=r"(rd));
+				 : "=r"(val));
 	} else {
-		rd = default_rand();
+		val = rand_default();
 	}
 
-	return rd;
+	return val;
 #else
-	return default_rand();
+	return rand_default();
 #endif
 }
 
+u32 rand(void)
+{
+	u32 ret = 0;
+	ret |= (rand_once() & (0xffu << 0));
+	ret |= (rand_once() & (0xffu << 8));
+	ret |= (rand_once() & (0xffu << 16));
+	ret |= (rand_once() & (0xffu << 24));
+	return ret;
+}
+
+void rand_fill(void *buf, u32 size)
+{
+	for (u32 i = 0; i < size; i++)
+		((u8 *)buf)[i] = rand_once() & 0xff;
+}
+
 char *randstr(u32 size)
 {
 	if (!size)
diff --git a/libs/libc/sanitize.c b/libs/libc/sanitize.c
index 415b790..d31c20c 100644
--- a/libs/libc/sanitize.c
+++ b/libs/libc/sanitize.c
@@ -8,10 +8,6 @@
  * Stack protector
  */
 
-#define STACK_CHK_GUARD 0xdeadbeef
-
-u32 __stack_chk_guard = STACK_CHK_GUARD;
-
 void __stack_chk_fail(void);
 NORETURN void __stack_chk_fail(void)
 {
diff --git a/libs/libc/sys.c b/libs/libc/sys.c
index 15a9669..139f523 100644
--- a/libs/libc/sys.c
+++ b/libs/libc/sys.c
@@ -170,11 +170,6 @@ res boot(u32 cmd)
 	return sys2(SYS_BOOT, SYS_BOOT_MAGIC, cmd);
 }
 
-u32 time(void)
-{
-	return (u32)sys0(SYS_TIME);
-}
-
 /**
  * At exit
  */
-- 
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