Implemented basic user program ASLR

3 files changed, 21 insertions, 11 deletions

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();