Added code that extracts ELF binary stored in define value of the compiled binary

1 files changed, 57 insertions, 0 deletions

diff --git a/extract_decoded_executable/extractor.c b/extract_decoded_executable/extractor.c
new file mode 100644
index 0000000..3a53536
--- /dev/null
+++ b/extract_decoded_executable/extractor.c
@@ -0,0 +1,57 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+
+void extract_contained_binary(){
+	double bin_hex_div = (double)strlen((const char*)BIN_HEX) / 2;
+	if ( bin_hex_div == 0.5 ){
+		fputs( "Error: binary hex is uneven number of characters\n", stderr );
+		return;
+	}
+	size_t hex_byte_count = (size_t)bin_hex_div;
+	unsigned char *decoded_bytes = (unsigned char*)calloc( hex_byte_count + 1, sizeof(unsigned char) );
+	if ( decoded_bytes == NULL ){
+		fprintf( stderr, "Error: failed to allocate memory for decoding: %s\n", strerror(errno) );
+		return;
+	}
+	const char *bin_hex = (const char*)BIN_HEX;
+	size_t byte_pos = 0;
+	size_t dec_byte_pos = 0;
+	char c_byte[2];
+	memset( (void*)&c_byte, 0, sizeof(c_byte) );
+	unsigned char decoded_byte = '\0';
+	for ( ; dec_byte_pos < hex_byte_count; byte_pos += 2, dec_byte_pos++ ){
+		memmove( (void*)&c_byte, (const void*)&bin_hex[byte_pos], 2 );
+		decoded_byte = (unsigned char)strtoul( (const char*)&c_byte, NULL, 16 );
+		if ( errno != 0 ){
+			fprintf( stderr, "Error: failed to decode byte: %s\n", strerror(errno) );
+			free( decoded_bytes );
+			return;
+		}
+		decoded_bytes[dec_byte_pos] = decoded_byte;
+	}
+	int out_fd = open( "/tmp/test_output_binary", O_RDWR | O_CREAT, 0755 );
+	if ( out_fd == -1 ){
+		fprintf( stderr, "Error: failed to open /tmp/test_output_binary for writing: %s\n", strerror(errno) );
+		free( decoded_bytes );
+		return;
+	}
+	if ( write(out_fd, (const void*)decoded_bytes, hex_byte_count + 1) == -1 ){
+		fprintf( stderr, "Error: failed to write /tmp/test_output_binary: %s\n", strerror(errno) );
+		free( decoded_bytes );
+		close( out_fd );
+		return;
+	}
+	close( out_fd );
+	free( decoded_bytes );
+	fputs( "Binary extracted, check /tmp for test_output_binary\n", stdout );
+	return;
+}
+
+int main( int argc, char *const *args ){
+	extract_contained_binary();
+	return 0;
+}