Implemented basic user program ASLR

10 files changed, 53 insertions, 51 deletions

diff --git a/apps/Makefile b/apps/Makefile
index c015d18..1afa879 100644
--- a/apps/Makefile
+++ b/apps/Makefile
@@ -6,14 +6,14 @@ LD = ccache ../cross/opt/bin/i686-elf-ld
 OC = ccache ../cross/opt/bin/i686-elf-objcopy
 ST = ccache ../cross/opt/bin/i686-elf-strip
 
-CFLAGS = $(CFLAGS_DEFAULT) -I../libs/ -I../libs/libc/inc/ -DUSER
+CFLAGS = $(CFLAGS_DEFAULT) -I../libs/ -I../libs/libc/inc/ -pie -fPIE -fPIC -DUSER
 
 all: $(COBJS)
 
 %.o: %.c
 	@mkdir -p ../build/apps/
 	@$(CC) -c $(CFLAGS) $< -o $@
-	@$(LD) -o $(@:.o=.elf) --section-start=.text=0x42000000 -L../build/ -static $@ -lgui -ltxt -lc
+	@$(LD) -o $(@:.o=.elf) --section-start=.text=0x42000000 -L../build/ -pie -no-dynamic-linker $@ -lgui -ltxt -lc
 	@cp $(@:.o=.elf) ../build/apps/$(@:.o=)
 #@$(ST) --strip-all ../build/apps/$(@:.o=)
 
diff --git a/kernel/features/load.c b/kernel/features/load.c
index 2b82a44..3dff831 100644
--- a/kernel/features/load.c
+++ b/kernel/features/load.c
@@ -6,12 +6,11 @@
 #include <load.h>
 #include <mem.h>
 #include <mm.h>
+#include <random.h>
 #include <str.h>
 
 #define PROC_STACK_SIZE 0x4000
 
-#include <print.h>
-
 res elf_load(const char *path, struct proc *proc)
 {
 	if (!memory_valid(path))
@@ -45,10 +44,15 @@ res elf_load(const char *path, struct proc *proc)
 			 magic[ELF_IDENT_MAG2] == ELF_MAG2 && magic[ELF_IDENT_MAG3] == ELF_MAG3 &&
 			 magic[ELF_IDENT_CLASS] == ELF_IDENT_CLASS_32 &&
 			 magic[ELF_IDENT_DATA] == ELF_IDENT_DATA_LSB;
-	if (!valid_magic || (header.type != ELF_ETYPE_REL && header.type != ELF_ETYPE_EXEC) ||
+	if (!valid_magic ||
+	    (header.type != ELF_ETYPE_REL && header.type != ELF_ETYPE_EXEC &&
+	     header.type != ELF_ETYPE_DYN) ||
 	    header.version != 1 || header.machine != ELF_MACHINE_386)
 		return -ENOEXEC;
 
+	// ASLR
+	u32 rand_off = (rand() & 0xffff) * PAGE_SIZE;
+
 	// Loop through programs
 	for (u32 i = 0; i < header.phnum; i++) {
 		struct elf_program program = { 0 };
@@ -62,6 +66,9 @@ res elf_load(const char *path, struct proc *proc)
 		}
 		memory_bypass_disable();
 
+		if (program.type == ELF_PROGRAM_TYPE_INTERP)
+			return -ENOEXEC;
+
 		if (program.vaddr == 0 || program.type != ELF_PROGRAM_TYPE_LOAD)
 			continue;
 
@@ -72,13 +79,14 @@ res elf_load(const char *path, struct proc *proc)
 		memory_backup_dir(&prev);
 		memory_switch_dir(proc->page_dir);
 
-		struct memory_range vrange = memory_range_around(program.vaddr, program.memsz);
+		struct memory_range vrange =
+			memory_range_around(program.vaddr + rand_off, program.memsz);
 		struct memory_range prange = physical_alloc(vrange.size);
 		virtual_map(proc->page_dir, prange, vrange.base, MEMORY_CLEAR | MEMORY_USER);
 
 		memory_bypass_enable();
-		if ((u32)vfs_read(proc->name, (void *)program.vaddr, program.offset,
-				  program.filesz) != program.filesz) {
+		if ((u32)vfs_read(proc->name, (void *)((u32)program.vaddr + rand_off),
+				  program.offset, program.filesz) != program.filesz) {
 			memory_bypass_disable();
 			memory_switch_dir(prev);
 			return -ENOEXEC;
@@ -133,7 +141,8 @@ res elf_load(const char *path, struct proc *proc)
 
 		// Remap readonly sections
 		if (!(section.flags & ELF_SECTION_FLAG_WRITE)) {
-			struct memory_range range = memory_range_around(section.addr, section.size);
+			struct memory_range range =
+				memory_range_around(section.addr + rand_off, section.size);
 			virtual_remap_readonly(proc->page_dir, range);
 		}
 	}
@@ -152,8 +161,9 @@ res elf_load(const char *path, struct proc *proc)
 
 	proc->regs.ebp = stack + PROC_STACK_SIZE;
 	proc->regs.useresp = stack + PROC_STACK_SIZE;
-	proc->regs.eip = header.entry;
-	proc->entry = header.entry;
+	proc->regs.eip = header.entry + rand_off;
+	proc->entry = header.entry + rand_off;
+
 	clac();
 
 	memory_switch_dir(prev);
diff --git a/kernel/features/mm.c b/kernel/features/mm.c
index 67a5abf..76049ef 100644
--- a/kernel/features/mm.c
+++ b/kernel/features/mm.c
@@ -464,7 +464,7 @@ res memory_sys_alloc(struct page_dir *dir, u32 size, u32 *addr, u32 *id, u8 shar
 		return -ENOMEM;
 
 	struct memory_object *obj = zalloc(sizeof(*obj));
-	obj->id = rdrand() + 1;
+	obj->id = rand() + 1;
 	obj->prange = memory_range(virtual_to_physical(dir, vaddr), size);
 	obj->refs = 1;
 	obj->shared = shared;
diff --git a/kernel/main.c b/kernel/main.c
index 14a3555..6752fcf 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -31,7 +31,7 @@ void kernel_main(struct mem_info *mem_info, struct vid_info *vid_info)
 
 	cpu_enable_features();
 	cpu_print();
-	srand(rdseed());
+	srand(rand());
 
 	// Install drivers
 	vfs_install();
diff --git a/libs/libc/Makefile b/libs/libc/Makefile
index 24970d8..cc1b836 100644
--- a/libs/libc/Makefile
+++ b/libs/libc/Makefile
@@ -1,7 +1,8 @@
 # MIT License, Copyright (c) 2020 Marvin Borner
 
 # TODO: Remove cpu from libc?
-COBJS = sanitize.o \
+COBJS = crt/crt0.o \
+	sanitize.o \
 	errno.o \
 	str.o \
 	alloc.o \
@@ -26,11 +27,12 @@ ASFLAGS = -f elf32
 %.o: %.c
 	@$(CC) -c $(CFLAGS) $< -o $@
 
-libc: CFLAGS += -DUSER
+libc: CFLAGS += -pie -fPIE -fPIC -DUSER
 libc: $(COBJS)
-	@$(AS) $(ASFLAGS) crt/crt0.asm -o crt0.o
 	@mkdir -p ../../build/
-	@$(AR) rcs ../../build/libc.a crt0.o $+
+	@$(AS) $(ASFLAGS) crt/crti.asm -o ../../build/crti.o
+	@$(AS) $(ASFLAGS) crt/crtn.asm -o ../../build/crtn.o
+	@$(AR) rcs ../../build/libc.a ../../build/crti.o ../../build/crti.o $+
 
 libk: CFLAGS += -DKERNEL -ffreestanding -I../../kernel/inc/ $(CFLAGS_EXTRA)
 libk: $(COBJS)
diff --git a/libs/libc/inc/random.h b/libs/libc/inc/random.h
index a82524c..6360625 100644
--- a/libs/libc/inc/random.h
+++ b/libs/libc/inc/random.h
@@ -5,9 +5,9 @@
 
 #include <def.h>
 
+#define rand_range(min, max) (rand() % ((max) + 1 - (min)) + (min))
+
 void srand(u32 seed);
-u32 rdrand(void);
-u32 rdseed(void);
 u32 rand(void);
 char *randstr(u32 size);
 
diff --git a/libs/libc/random.c b/libs/libc/random.c
index 6296407..983357f 100644
--- a/libs/libc/random.c
+++ b/libs/libc/random.c
@@ -15,46 +15,36 @@ void srand(u32 seed)
 	g_seed = seed;
 }
 
-u32 rdrand(void)
+static u32 default_rand(void)
 {
-#ifdef KERNEL
-	if (!(cpu_features.ecx & CPUID_FEAT_ECX_RDRND))
-		return rand();
-
-	u32 rd;
-	__asm__ volatile("1:\n"
-			 "rdrand %0\n"
-			 "jnc 1b\n"
-			 : "=r"(rd));
-	return rd;
-#else
-	return rand();
-#endif
+	g_seed = g_seed * 1103515245 + 12345;
+	return (g_seed >> 16) & 0x7FFF;
 }
 
-u32 rdseed(void)
+u32 rand(void)
 {
 #ifdef KERNEL
-	if (!(cpu_extended_features.ebx & CPUID_EXT_FEAT_EBX_RDSEED))
-		return rand();
-
 	u32 rd;
-	__asm__ volatile("1:\n"
-			 "rdseed %0\n"
-			 "jnc 1b\n"
-			 : "=r"(rd));
+	if (cpu_extended_features.ebx & CPUID_EXT_FEAT_EBX_RDSEED) {
+		__asm__ volatile("1:\n"
+				 "rdseed %0\n"
+				 "jnc 1b\n"
+				 : "=r"(rd));
+	} else if (cpu_features.ecx & CPUID_FEAT_ECX_RDRND) {
+		__asm__ volatile("1:\n"
+				 "rdrand %0\n"
+				 "jnc 1b\n"
+				 : "=r"(rd));
+	} else {
+		rd = default_rand();
+	}
+
 	return rd;
 #else
-	return rand();
+	return default_rand();
 #endif
 }
 
-u32 rand(void)
-{
-	g_seed = g_seed * 1103515245 + 12345;
-	return (g_seed >> 16) & 0x7FFF;
-}
-
 char *randstr(u32 size)
 {
 	if (!size)
diff --git a/libs/libgui/Makefile b/libs/libgui/Makefile
index e04b703..47e2556 100644
--- a/libs/libgui/Makefile
+++ b/libs/libgui/Makefile
@@ -10,7 +10,7 @@ CC = ccache ../../cross/opt/bin/i686-elf-gcc
 LD = ccache ../../cross/opt/bin/i686-elf-ld
 AR = ccache ../../cross/opt/bin/i686-elf-ar
 
-CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -DUSER
+CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -pie -fPIE -fPIC -DUSER
 
 all: libgui
 
diff --git a/libs/libnet/Makefile b/libs/libnet/Makefile
index 69c899d..7094875 100644
--- a/libs/libnet/Makefile
+++ b/libs/libnet/Makefile
@@ -5,7 +5,7 @@ CC = ccache ../../cross/opt/bin/i686-elf-gcc
 LD = ccache ../../cross/opt/bin/i686-elf-ld
 AR = ccache ../../cross/opt/bin/i686-elf-ar
 
-CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -DUSER
+CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -pie -fPIE -fPIC -DUSER
 
 all: libtxt
 
diff --git a/libs/libtxt/Makefile b/libs/libtxt/Makefile
index 6d06502..38fe01f 100644
--- a/libs/libtxt/Makefile
+++ b/libs/libtxt/Makefile
@@ -5,7 +5,7 @@ CC = ccache ../../cross/opt/bin/i686-elf-gcc
 LD = ccache ../../cross/opt/bin/i686-elf-ld
 AR = ccache ../../cross/opt/bin/i686-elf-ar
 
-CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -DUSER
+CFLAGS = $(CFLAGS_DEFAULT) -I../ -I../libc/inc/ -pie -fPIE -fPIC -DUSER
 
 all: libtxt