…

.gitignore

@@ -0,0 +1,3 @@
+src/secretkey.h
+src/secretkey.bin
+src/keygen

src/exim4encrypt.c

@@ -1,8 +1,49 @@
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
 #include "exim4encrypt.h"
+#include "secretkey.h"
 
-__attribute__((constructor)) static void init() {
-    sodium_init();
+int kitencrypt(uschar **yield, int argc, uschar *argv[]) {
+	int sinit;
+	size_t inputlen;
+	unsigned char * input;
+
+	sinit = sodium_init();
+	if (sinit == -1 ) {
+		*yield = string_sprintf("Unable to initialize libsodium");
+		return ERROR;
+	}
+	if (argc != 1) {
+		*yield = string_sprintf("Wrong number of arguments (got %i, expected 1)", argc);
+		return ERROR;
 	}
 
-int dlfunction(uschar **yield, int argc, uschar *argv[]) {
+	input = argv[0];
+	inputlen = strlen(input);
+
+	unsigned char nonce[crypto_secretbox_NONCEBYTES];
+	randombytes_buf(nonce, sizeof nonce);
+
+	unsigned int cipherlen = inputlen + crypto_secretbox_MACBYTES;
+	unsigned char * ciphertext = malloc(cipherlen);
+	explicit_bzero(ciphertext, cipherlen);
+
+	crypto_secretbox_easy(ciphertext, input, inputlen, nonce, key);
+
+	unsigned int outputsize = sodium_base64_ENCODED_LEN(cipherlen, sodium_base64_VARIANT_URLSAFE);
+	unsigned char * outstring = malloc(outputsize);
+	explicit_bzero(outstring, outputsize);
+
+	sodium_bin2base64(outstring, outputsize,
+			ciphertext, cipherlen,
+			sodium_base64_VARIANT_URLSAFE);
+
+	free(ciphertext);
+
+	*yield = string_sprintf(outstring);
+
+	free(outstring);
+
+	return OK;
 }

src/genkey.c

@@ -0,0 +1,49 @@
+#include <sodium.h>
+
+void dumpkey(FILE* f, unsigned char * name, unsigned char * key, unsigned int keylen) {
+	fprintf(f, "const unsigned char %s[] = { ", name);
+	for(int i=0; i < keylen; i++) {
+		fprintf(f, "0x%02X", key[i]);
+		if (i < keylen-1) {
+			fprintf(f, ", ");
+		}
+	}
+	fprintf(f, " };\n");
+}
+
+int main(void)
+{
+	if (sodium_init() < 0) {
+		fputs("Unable to initialize libsodium", stderr);
+		exit(128);
+	}
+
+	unsigned char key[crypto_secretbox_KEYBYTES];
+	crypto_secretbox_keygen(key);
+
+	FILE *keyfile = fopen("secretkey.h", "w+");
+	if (keyfile == NULL) {
+		fputs("Unable to open secretkey.h", stderr);
+		exit(129);
+	}
+
+	fputs("#ifndef EXIM4ENCRYPTSECRETKEY_H\n#define EXIM4ENCRYPTSECRETKEY_H\n\n", keyfile);
+	dumpkey(keyfile, "key", key, crypto_secretbox_KEYBYTES);
+	fprintf(keyfile, "unsigned int keylen = %u;\n", crypto_secretbox_KEYBYTES);
+	fputs("#endif // EXIM4ENCRYPTSECRETKEY_H\n", keyfile);
+
+	fclose(keyfile);
+
+	FILE *keyfilebin = fopen("secretkey.bin", "w+");
+	if (keyfilebin == NULL) {
+		fputs("Unable to open secretkey.bin", stderr);
+		exit(129);
+	}
+
+	fwrite(key, sizeof(key[0]), crypto_secretbox_KEYBYTES, keyfilebin);
+
+	fclose(keyfilebin);
+
+	exit(EXIT_SUCCESS);
+}
+