From fa9e0ecb219000e07eaf694f50679a8edfb5dc9e Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@systemlinux.org>
Date: Wed, 4 Jan 2012 21:46:11 +0100
Subject: [PATCH] Send and receive challenge via sideband.

If both server and client support sideband connections, the challenge
is now sent as a sideband packet using the dedicated SBD_CHALLENGE
designator.
---
 client_common.c | 37 ++++++++++++++++++++++++++++---------
 command.c       | 22 ++++++++++++++++------
 2 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/client_common.c b/client_common.c
index ba4c2699..f3cea05d 100644
--- a/client_common.c
+++ b/client_common.c
@@ -299,14 +299,33 @@ static void client_post_select(struct sched *s, struct task *t)
 		/* the SHA1 of the decrypted challenge */
 		unsigned char challenge_hash[HASH_SIZE];
 
-		ret = client_recv_buffer(ct, &s->rfds, buf, sizeof(buf), &n);
-		if (ret < 0 || n == 0)
-			goto out;
-		PARA_INFO_LOG("<-- [challenge] (%zu bytes)\n", n);
-		ret = priv_decrypt(ct->key_file, crypt_buf,
-			(unsigned char *)buf, n);
-		if (ret < 0)
-			goto out;
+		if (ct->use_sideband) {
+			struct sb_buffer sbb;
+			ret = recv_sb(ct, &s->rfds, &sbb);
+			if (ret <= 0)
+				goto out;
+			if (sbb.band != SBD_CHALLENGE) {
+				ret = -E_BAD_BAND;
+				free(sbb.iov.iov_base);
+					goto out;
+			}
+			n = sbb.iov.iov_len;
+			PARA_INFO_LOG("<-- [challenge] (%zu bytes)\n", n);
+			ret = priv_decrypt(ct->key_file, crypt_buf,
+				sbb.iov.iov_base, n);
+			free(sbb.iov.iov_base);
+			if (ret < 0)
+				goto out;
+		} else {
+			ret = client_recv_buffer(ct, &s->rfds, buf, sizeof(buf), &n);
+			if (ret < 0 || n == 0)
+				goto out;
+			PARA_INFO_LOG("<-- [challenge] (%zu bytes)\n", n);
+			ret = priv_decrypt(ct->key_file, crypt_buf,
+				(unsigned char *)buf, n);
+			if (ret < 0)
+				goto out;
+		}
 		hash_function((char *)crypt_buf, CHALLENGE_SIZE, challenge_hash);
 		ct->scc.send = sc_new(crypt_buf + CHALLENGE_SIZE, SESSION_KEY_LEN);
 		ct->scc.recv = sc_new(crypt_buf + CHALLENGE_SIZE + SESSION_KEY_LEN,
@@ -417,7 +436,7 @@ static void client_post_select(struct sched *s, struct task *t)
 out:
 	t->error = ret;
 	if (ret < 0) {
-		if (ret != -E_SERVER_EOF && ret != -E_BTR_EOF)
+		if (ret != -E_SERVER_EOF && ret != -E_BTR_EOF && ret != -E_EOF)
 			PARA_ERROR_LOG("%s\n", para_strerror(-t->error));
 		btr_remove_node(btrn);
 	}
diff --git a/command.c b/command.c
index 9cf1967f..5790f11d 100644
--- a/command.c
+++ b/command.c
@@ -854,6 +854,8 @@ out:
 	return ret;
 }
 
+#define HANDSHAKE_BUFSIZE 4096
+
 /**
  * Perform user authentication and execute a command.
  *
@@ -884,10 +886,9 @@ out:
 __noreturn void handle_connect(int fd, const char *peername)
 {
 	int ret;
-	char buf[4096];
 	unsigned char rand_buf[CHALLENGE_SIZE + 2 * SESSION_KEY_LEN];
 	unsigned char challenge_hash[HASH_SIZE];
-	char *p, *command = NULL;
+	char *p, *command = NULL, *buf = para_malloc(HANDSHAKE_BUFSIZE) /* must be on the heap */;
 	size_t numbytes;
 	struct command_context cc_struct = {.peer = peername}, *cc = &cc_struct;
 
@@ -905,7 +906,7 @@ __noreturn void handle_connect(int fd, const char *peername)
 	if (ret < 0)
 		goto net_err;
 	/* recv auth request line */
-	ret = recv_buffer(fd, buf, sizeof(buf));
+	ret = recv_buffer(fd, buf, HANDSHAKE_BUFSIZE);
 	if (ret < 0)
 		goto net_err;
 	ret = parse_auth_request(buf, ret, &cc->u, &cc->use_sideband);
@@ -932,9 +933,17 @@ __noreturn void handle_connect(int fd, const char *peername)
 	}
 	PARA_DEBUG_LOG("sending %u byte challenge + rc4 keys (%zu bytes)\n",
 		CHALLENGE_SIZE, numbytes);
-	ret = write_all(fd, buf, numbytes);
-	if (ret < 0)
-		goto net_err;
+	if (cc->use_sideband) {
+		ret = send_sb(&cc->scc, buf, numbytes, SBD_CHALLENGE, false);
+		buf = NULL;
+		if (ret < 0)
+			goto net_err;
+		buf = para_malloc(HANDSHAKE_BUFSIZE);
+	} else {
+		ret = write_all(fd, buf, numbytes);
+		if (ret < 0)
+			goto net_err;
+	}
 	/* recv challenge response */
 	ret = recv_bin_buffer(fd, buf, HASH_SIZE);
 	if (ret < 0)
@@ -995,6 +1004,7 @@ err_out:
 net_err:
 	PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
 out:
+	free(buf);
 	free(command);
 	sc_free(cc->scc.recv);
 	sc_free(cc->scc.send);
-- 
2.39.5