ptunnel-ng:

	* this is now an autotools project (added/renamed required files e.g. AUTHORS, COPYING)
	* removed user defined ip header (buggy; not useful anymore)

1 files changed, 56 insertions, 0 deletions

diff --git a/src/challenge.c b/src/challenge.c
new file mode 100644
index 0000000..4d8bf65
--- /dev/null
+++ b/src/challenge.c
@@ -0,0 +1,56 @@
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+
+#include "challenge.h"
+#include "options.h"
+#include "md5.h"
+
+/* generate_challenge: Generates a random challenge, incorporating the current
+ * local timestamp to avoid replay attacks.
+ */
+challenge_t* generate_challenge(void) {
+	struct timeval  tt;
+	challenge_t     *c;
+	int             i;
+
+	c = (challenge_t *) calloc(1, sizeof(challenge_t));
+	gettimeofday(&tt, 0);
+	c->sec      = tt.tv_sec;
+	c->usec_rnd = tt.tv_usec + rand();
+	for (i=0;i<6;i++)
+		c->random[i] = rand();
+
+	return c;
+}
+
+/* generate_response: Generates a response to the given challenge. The response
+ * is generated by combining the concatenating the challenge data with the
+ * md5 digest of the password, and then calculating the MD5 digest of the
+ * entire buffer. The result is stored in the passed-in challenge, overwriting
+ * the challenge data.
+ */
+void generate_response(challenge_t *challenge) {
+	md5_byte_t  buf[sizeof(challenge_t)+kMD5_digest_size];
+	md5_state_t state;
+
+	memcpy(buf, challenge, sizeof(challenge_t));
+	memcpy(&buf[sizeof(challenge_t)], opts.password_digest, kMD5_digest_size);
+	memset(challenge, 0, sizeof(challenge_t));
+	md5_init(&state);
+	md5_append(&state, buf, sizeof(challenge_t)+kMD5_digest_size);
+	md5_finish(&state, (md5_byte_t*)challenge);
+}
+
+/* validate_challenge: Checks whether a given response matches the expected
+ * response, returning 1 if validation succeeded, and 0 otherwise. Note that
+ * overwriting the local challenge with the challenge result is not a problem,
+ * as the data will not be used again anyway (authentication either succeeds,
+ * or the connection is closed down).
+ */
+int validate_challenge(challenge_t *local, challenge_t *remote) {
+	generate_response(local);
+	if (memcmp(local, remote, sizeof(challenge_t)) == 0)
+		return 1;
+	return 0;
+}