1 files changed, 57 insertions, 0 deletions
diff --git a/contrib/ntp/libntp/authparity.c b/contrib/ntp/libntp/authparity.c
new file mode 100644
index 000000000000..32fde586c00f
--- /dev/null
+++ b/contrib/ntp/libntp/authparity.c
@@ -0,0 +1,57 @@
+/*
+ * auth_parity - set parity on a key/check for odd parity
+ */
+#include "ntp_stdlib.h"
+
+int
+DESauth_parity(
+	u_int32 *key
+	)
+{
+	u_int32 mask;
+	int parity_err;
+	int bitcount;
+	int half;
+	int byte;
+	int i;
+
+	/*
+	 * Go through counting bits in each byte.  Check to see if
+	 * each parity bit was set correctly.  If not, note the error
+	 * and set it right.
+	 */
+	parity_err = 0;
+	for (half = 0; half < 2; half++) {		/* two halves of key */
+		mask = 0x80000000;
+		for (byte = 0; byte < 4; byte++) {	/* 4 bytes per half */
+			bitcount = 0;
+			for (i = 0; i < 7; i++) {	/* 7 data bits / byte */
+				if (key[half] & mask)
+				    bitcount++;
+				mask >>= 1;
+			}
+
+			/*
+			 * If bitcount is even, parity must be set.  If
+			 * bitcount is odd, parity must be clear.
+			 */
+			if ((bitcount & 0x1) == 0) {
+				if (!(key[half] & mask)) {
+					parity_err++;
+					key[half] |= mask;
+				}
+			} else {
+				if (key[half] & mask) {
+					parity_err++;
+					key[half] &= ~mask;
+				}
+			}
+			mask >>= 1;
+		}
+	}
+
+	/*
+	 * Return the result of the parity check.
+	 */
+	return (parity_err == 0);
+}