1 files changed, 53 insertions, 0 deletions
diff --git a/crypto/xdmauth.c b/crypto/xdmauth.c
new file mode 100644
index 00000000..86339b85
--- /dev/null
+++ b/crypto/xdmauth.c
@@ -0,0 +1,53 @@
+/*
+ * Convenience functions to encrypt and decrypt the cookies used in
+ * XDM-AUTHORIZATION-1. 
+ */
+
+#include "ssh.h"
+
+static ssh_cipher *des_xdmauth_cipher(const void *vkeydata)
+{
+    /*
+     * XDM-AUTHORIZATION-1 uses single-DES, but packs the key into 7
+     * bytes, so here we have to repack it manually into the canonical
+     * form where it occupies 8 bytes each with the low bit unused.
+     */
+    const unsigned char *keydata = (const unsigned char *)vkeydata;
+    unsigned char key[8];
+    int i, nbits, j;
+    unsigned int bits;
+
+    bits = 0;
+    nbits = 0;
+    j = 0;
+    for (i = 0; i < 8; i++) {
+        if (nbits < 7) {
+            bits = (bits << 8) | keydata[j];
+            nbits += 8;
+            j++;
+        }
+        key[i] = (bits >> (nbits - 7)) << 1;
+        bits &= ~(0x7F << (nbits - 7));
+        nbits -= 7;
+    }
+
+    ssh_cipher *c = ssh_cipher_new(&ssh_des);
+    ssh_cipher_setkey(c, key);
+    smemclr(key, sizeof(key));
+    ssh_cipher_setiv(c, key);
+    return c;
+}
+
+void des_encrypt_xdmauth(const void *keydata, void *blk, int len)
+{
+    ssh_cipher *c = des_xdmauth_cipher(keydata);
+    ssh_cipher_encrypt(c, blk, len);
+    ssh_cipher_free(c);
+}
+
+void des_decrypt_xdmauth(const void *keydata, void *blk, int len)
+{
+    ssh_cipher *c = des_xdmauth_cipher(keydata);
+    ssh_cipher_decrypt(c, blk, len);
+    ssh_cipher_free(c);
+}