diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..821590e
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,53 @@
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "common.h"
+
+char * read_first_line(const char * filename) {
+    int fd;
+    char *endptr;
+    char *cipherstring;
+
+    // open file
+    fd = open(filename, O_RDONLY, (mode_t)0600);
+    if (fd == -1) {
+        perror("Error opening file");
+        exit(EXIT_FAILURE);
+    }
+    // get length
+    struct stat fileInfo = {0};
+    if (fstat(fd, &fileInfo) == -1) {
+        perror("Error getting the file size");
+        exit(EXIT_FAILURE);
+    }
+    if (fileInfo.st_size == 0) {
+        fprintf(stderr, "Error: File is empty, nothing to do\n");
+        exit(EXIT_FAILURE);
+    }
+    // mmap file
+    char *map = mmap(0, fileInfo.st_size, PROT_READ, MAP_SHARED, fd, 0);
+    if (map == MAP_FAILED)
+    {
+        close(fd);
+        perror("Error mmapping the file");
+        exit(EXIT_FAILURE);
+    }
+    // find first line
+    endptr = strchrnul(map, 0x0a);
+
+    size_t cipherstring_len = endptr - map;
+    cipherstring = malloc(cipherstring_len+1);
+    strncpy(cipherstring, map, cipherstring_len);
+
+    // munmap and close file
+    if (munmap(map, fileInfo.st_size) == -1)
+    {
+        close(fd);
+        perror("Error un-mmapping the file");
+        exit(EXIT_FAILURE);
+    }
+    close(fd);
+
+    return cipherstring;
+}
\ No newline at end of file
diff --git a/src/common.h b/src/common.h
new file mode 100644
index 0000000..8987394
--- /dev/null
+++ b/src/common.h
@@ -0,0 +1,10 @@
+//
+// Created by sprawl on 08/09/2021.
+//
+
+#ifndef EXIM_ENCRYPT_DLFUNC_COMMON_H
+#define EXIM_ENCRYPT_DLFUNC_COMMON_H
+
+char * read_first_line(const char *);
+
+#endif //EXIM_ENCRYPT_DLFUNC_COMMON_H
diff --git a/src/libexim-encrypt-dlfunc-decrypt-secretbox.c b/src/libexim-encrypt-dlfunc-decrypt-secretbox.c
index d9d2a75..1ab7779 100644
--- a/src/libexim-encrypt-dlfunc-decrypt-secretbox.c
+++ b/src/libexim-encrypt-dlfunc-decrypt-secretbox.c
@@ -3,11 +3,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <getopt.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <unistd.h>
 #include <sodium.h>
+#include "common.c"
 
 #define ENVVAR_PASSWORD_NAME "LIBEXIM_PASSWORD"
 
@@ -38,8 +35,6 @@ int main(int argc, char *argv[]) {
     size_t pwlen;
     char *b64password;
     char *password_env;
-    int fd;
-    char *endptr;
 
     seen_args mode = NONE;
     seen_args input = NONE;
@@ -73,6 +68,7 @@ int main(int argc, char *argv[]) {
                 password_env = getenv(ENVVAR_PASSWORD_NAME);
                 if (password_env == NULL) {
                     fprintf(stderr, "[ERROR] Environment variable %s is undefined.\n\n", ENVVAR_PASSWORD_NAME);
+                    exit(EXIT_FAILURE);
                 }
                 pwlen = strlen(password_env);
                 b64password = malloc(pwlen+1);
@@ -80,46 +76,7 @@ int main(int argc, char *argv[]) {
                 mode |= PASSENV;
                 break;
             case 'f':
-                // open file
-                fd = open(optarg, O_RDONLY, (mode_t)0600);
-                if (fd == -1) {
-                    perror("Error opening file");
-                    exit(EXIT_FAILURE);
-                }
-                // get length
-                struct stat fileInfo = {0};
-                if (fstat(fd, &fileInfo) == -1) {
-                    perror("Error getting the file size");
-                    exit(EXIT_FAILURE);
-                }
-                if (fileInfo.st_size == 0) {
-                    fprintf(stderr, "Error: File is empty, nothing to do\n");
-                    exit(EXIT_FAILURE);
-                }
-                // mmap file
-                char *map = mmap(0, fileInfo.st_size, PROT_READ, MAP_SHARED, fd, 0);
-                if (map == MAP_FAILED)
-                {
-                    close(fd);
-                    perror("Error mmapping the file");
-                    exit(EXIT_FAILURE);
-                }
-                // find first line
-                endptr = strchrnul(map, 0x0a);
-
-                size_t cipherstring_len = endptr - map;
-                cipherstring = malloc(cipherstring_len+1);
-                strncpy(cipherstring, map, cipherstring_len);
-
-                // munmap and close file
-                if (munmap(map, fileInfo.st_size) == -1)
-                {
-                    close(fd);
-                    perror("Error un-mmapping the file");
-                    exit(EXIT_FAILURE);
-                }
-                close(fd);
-
+                cipherstring = read_first_line(optarg);
                 input |= INFILE;
                 break;
         }
@@ -132,18 +89,30 @@ int main(int argc, char *argv[]) {
             exit(EXIT_FAILURE);
     }
 
-    // read first non-option argument as ciphertext
+    // read first non-option argument as ciphertext if present
     if (optind < argc) {
         size_t cipherstring_len = strlen(argv[optind])+1;
         cipherstring = malloc(cipherstring_len+1);
         strncpy(cipherstring, argv[optind], cipherstring_len);
         input |= INSTRING;
     }
-
+    // fail if neither argument nor filename is present
     if (input == NONE) {
             fprintf(stderr, "[ERROR] Please specify a ciphertext source.\n\n");
             print_usage(prog_basename);
             exit(EXIT_FAILURE);
     }
-    printf("»%s«\n", cipherstring);
+
+    // base64-decode password
+    size_t password_len = strlen(b64password) / 4 * 3;
+    unsigned char * password = malloc(password_len);
+    int b64err = sodium_base642bin(password, password_len,
+                                   (const char *) b64password, strlen(b64password),
+                                   NULL, &password_len, NULL, sodium_base64_VARIANT_ORIGINAL);
+    if (b64err != 0) {
+        fprintf(stderr, "[ERROR] Unable to base64-decode the password\n");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("»%s«\n", password);
 }
\ No newline at end of file