exim-encrypt-dlfunc/src/libexim-kitencrypt-dlfunc.c

#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sodium.h>

/* Local encryption key */
#include "secretkey.h"

/* Exim4 dlfunc API header */
#include <local_scan.h>

int kitencrypt(uschar **yield, int argc, uschar *argv[]) {
	int sinit;
	size_t inputlen;
	unsigned char * input;

	sinit = sodium_init();
	if (sinit == -1 ) {
		*yield = string_copy(US"Unable to initialize libsodium");
		return ERROR;
	}
	if (argc != 1) {
		*yield = string_sprintf("Wrong number of arguments (got %i, expected 1)", argc);
		return ERROR;
	}

	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_copy(outstring);

	free(outstring);

	return OK;
}