From 543e4a3d2ed7c227c69b223116f7ba8c5b126cfe Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 15 Sep 2022 21:18:42 +0200
Subject: [PATCH] pex: move rx header check to callback function

Fixes some length check bugs in the cli code and allows other protocols to be
used on the global PEX port.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 cli.c     | 22 +++++++++++++++-------
 pex-msg.c | 32 +++++++++++++++++++++++---------
 pex-msg.h |  4 +++-
 pex.c     | 21 +++++++++++++--------
 4 files changed, 54 insertions(+), 25 deletions(-)

diff --git a/cli.c b/cli.c
index 34050ff..24a06b3 100644
--- a/cli.c
+++ b/cli.c
@@ -165,12 +165,20 @@ pex_handle_update_request(struct sockaddr_in6 *addr, const uint8_t *id, void *da
 	uloop_end();
 }
 
-static void pex_recv(struct pex_hdr *hdr, struct sockaddr_in6 *addr)
+static void pex_recv(void *msg, size_t msg_len, struct sockaddr_in6 *addr)
 {
-	struct pex_ext_hdr *ehdr = (void *)(hdr + 1);
-	void *data = (void *)(ehdr + 1);
-	uint32_t len = be32_to_cpu(hdr->len);
-	uint64_t *msg_req_id = data;
+	struct pex_hdr *hdr;
+	struct pex_ext_hdr *ehdr;
+	uint64_t *msg_req_id;
+	void *data;
+
+	hdr = pex_rx_accept(msg, msg_len, true);
+	if (!hdr)
+		return;
+
+	ehdr = (void *)(hdr + 1);
+	data = (void *)(ehdr + 1);
+	msg_req_id = data;
 
 	if (hdr->version != 0)
 		return;
@@ -185,12 +193,12 @@ static void pex_recv(struct pex_hdr *hdr, struct sockaddr_in6 *addr)
 		if (cmd != CMD_UPLOAD)
 			break;
 
-		pex_handle_update_request(addr, hdr->id, data, len);
+		pex_handle_update_request(addr, hdr->id, data, hdr->len);
 		break;
 	case PEX_MSG_UPDATE_RESPONSE:
 	case PEX_MSG_UPDATE_RESPONSE_DATA:
 	case PEX_MSG_UPDATE_RESPONSE_NO_DATA:
-		if (len < sizeof(*msg_req_id) || *msg_req_id != req_id)
+		if (hdr->len < sizeof(*msg_req_id) || *msg_req_id != req_id)
 			break;
 
 		if (cmd == CMD_DOWNLOAD &&
diff --git a/pex-msg.c b/pex-msg.c
index 4f0b195..f6cbd71 100644
--- a/pex-msg.c
+++ b/pex-msg.c
@@ -137,7 +137,6 @@ pex_fd_cb(struct uloop_fd *fd, unsigned int events)
 {
 	static struct sockaddr_in6 sin6;
 	static char buf[PEX_RX_BUF_SIZE];
-	struct pex_hdr *hdr = (struct pex_hdr *)buf;
 	ssize_t len;
 
 	while (1) {
@@ -199,14 +198,7 @@ retry:
 			}
 		}
 
-		if (len < sizeof(*hdr) + sizeof(struct pex_ext_hdr))
-			continue;
-
-		hdr->len = ntohs(hdr->len);
-		if (len - sizeof(hdr) - sizeof(struct pex_ext_hdr) < hdr->len)
-			continue;
-
-		pex_recv_cb(hdr, &sin6);
+		pex_recv_cb(buf, len, &sin6);
 	}
 }
 
@@ -666,6 +658,28 @@ error:
 	return NULL;
 }
 
+struct pex_hdr *pex_rx_accept(void *data, size_t len, bool ext)
+{
+	struct pex_hdr *hdr = data;
+	uint16_t hdr_len;
+	size_t min_size;
+
+	min_size = sizeof(*hdr);
+	if (ext)
+		min_size += sizeof(struct pex_ext_hdr);
+
+	if (len < min_size)
+		return NULL;
+
+	hdr_len = ntohs(hdr->len);
+	if (len < min_size + hdr_len)
+		return NULL;
+
+	hdr->len = hdr_len;
+
+	return hdr;
+}
+
 static void
 pex_gc_cb(struct uloop_timeout *t)
 {
diff --git a/pex-msg.h b/pex-msg.h
index e8e4f11..c777a6a 100644
--- a/pex-msg.h
+++ b/pex-msg.h
@@ -94,7 +94,9 @@ struct pex_msg_local_control {
 	int timeout;
 };
 
-typedef void (*pex_recv_cb_t)(struct pex_hdr *hdr, struct sockaddr_in6 *addr);
+struct pex_hdr *pex_rx_accept(void *data, size_t len, bool ext);
+
+typedef void (*pex_recv_cb_t)(void *data, size_t len, struct sockaddr_in6 *addr);
 typedef void (*pex_recv_control_cb_t)(struct pex_msg_local_control *msg, int len);
 
 int pex_open(void *addr, size_t addr_len, pex_recv_cb_t cb, bool server);
diff --git a/pex.c b/pex.c
index 7a76cf7..1f831a0 100644
--- a/pex.c
+++ b/pex.c
@@ -652,11 +652,8 @@ network_pex_fd_cb(struct uloop_fd *fd, unsigned int events)
 		if (!len)
 			continue;
 
-		if (len < sizeof(*hdr))
-			continue;
-
-		hdr->len = ntohs(hdr->len);
-		if (len - sizeof(hdr) < hdr->len)
+		hdr = pex_rx_accept(buf, len, false);
+		if (!hdr)
 			continue;
 
 		peer = pex_msg_peer(net, hdr->id);
@@ -856,15 +853,23 @@ global_pex_set_active(struct network *net, struct sockaddr_in6 *addr)
 }
 
 static void
-global_pex_recv(struct pex_hdr *hdr, struct sockaddr_in6 *addr)
+global_pex_recv(void *msg, size_t msg_len, struct sockaddr_in6 *addr)
 {
-	struct pex_ext_hdr *ehdr = (void *)(hdr + 1);
+	struct pex_hdr *hdr;
+	struct pex_ext_hdr *ehdr;
 	struct network_peer *peer;
 	struct network *net;
-	void *data = (void *)(ehdr + 1);
 	char buf[INET6_ADDRSTRLEN];
+	void *data;
 	int addr_len;
 
+	hdr = pex_rx_accept(msg, msg_len, true);
+	if (!hdr)
+		return;
+
+	ehdr = (void *)(hdr + 1);
+	data = (void *)(ehdr + 1);
+
 	if (hdr->version != 0)
 		return;
 
-- 
2.30.2