3 files changed, 72 insertions, 0 deletions
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0d33524
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,4 @@
+CCOPTS = --std=c99 -Wall -Werror -O2
+
+all:
+	cc $(CCOPTS) -o kcpasswd main.c
diff --git a/README.rst b/README.rst
new file mode 100644
index 0000000..6122cb7
--- /dev/null
+++ b/README.rst
@@ -0,0 +1,15 @@
+README
+======
+
+The MacOS ``/etc/kcpassword`` file controls logins
+
+Usage
+-----
+
+To encrypt a password::
+
+  kcpasswd <password>
+
+To decrypt a kcpassword file::
+
+  kcpasswd /path/to/file
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..c065116
--- /dev/null
+++ b/main.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <string.h>
+
+#define MAXLEN 256
+
+int readfile(char* path, char* buf) {
+  FILE* fd;
+  fd = fopen(path, "r");
+  if(!fd)
+    return -1;
+  fgets(buf, MAXLEN, fd);
+  fclose(fd);
+  return 0;
+}
+
+void applexor(char* msg, char* out) {
+  int keys[] = {125, 137, 82, 35, 210, 188, 221, 234, 163, 185, 31};
+  int i = 0;
+
+  // Encrypt/decrypt (xor)
+  for(i=0; msg[i] != '\0'; i++)
+    out[i] = msg[i] ^ keys[i % 11];
+
+  // If the previous char wasn't a null byte, we are likely encrypting not
+  // decrypting, so add a null byte.
+  if(out[i-1] != '\0') {
+    out[i] = '\0' ^ keys[i % 11];
+    i++;
+  }
+
+  // Append until we hit a multiple of 12
+  for(; i%12 != 0; i++)
+    out[i] = msg[i%strlen(msg)] ^ keys[i % 11];
+  out[i] = '\0' ;
+}
+
+int main(int argc, char* argv[]) {
+  char in[MAXLEN];
+  char out[MAXLEN];
+  if(argc == 1) {
+    printf("Must provide path to file or a password to encrypt\n");
+    return 1;
+  }
+
+  // If the file can't be opened, try to use the "path" as a password
+  if(readfile(argv[1], in) == -1)
+    strcpy(in, argv[1]);
+
+  applexor(in, out);
+
+  printf("%s\n", out);
+  return 0;
+}