commit 3fe030c5e0903a3bce3ed499d8ed3898bc7cbc38
from: Omar Polo <op@omarpolo.com>
date: Fri Jul 30 18:18:14 2021 UTC

log on protocol violations to aid debug

commit - 9ebb95a72ab30c47e0c1e37626b79f75e2d9c4e2
commit + 3fe030c5e0903a3bce3ed499d8ed3898bc7cbc38
blob - aaf97758e6406fad4916feafe973c1a3cb7c8b90
blob + a81736d696625086f75ceab40a35c8f7baaf8ee2
--- client.c
+++ client.c
@@ -610,8 +610,11 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	}
 
 	/* fid[4] afid[4] uname[s] aname[s] */
-	if (len < 4 + 4 + 2 + 2)
+	if (len < 12) {		/* minimal case, uname and aname both "" */
+		log_warnx("%s: expecting at least %d bytes; got %zu",
+		    __func__, 12, len);
 		goto err;
+	}
 
 	memcpy(&fid, data, sizeof(fid));
 	data += sizeof(fid);
@@ -627,8 +630,11 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	len -= sizeof(size);
 	size = le16toh(size);
 
-	if (len < size + 2)
+	if (len < size + 2) {
+		log_warnx("%s: expecting at least %d bytes for "
+		    "uname and aname; got %zu", __func__, size + 2, len);
 		goto err;
+	}
 
 	data += size;
 	len -= size;
@@ -638,8 +644,12 @@ tattach(struct np_msg_header *hdr, const uint8_t *data
 	len -= sizeof(size);
 	size = le16toh(size);
 
-	if (len != size)
+	if (len != size) {
+		log_warnx("%s: expecting %d bytes for aname, got %zu",
+		    __func__, size, len);
 		goto err;
+	}
+
 	if (len > sizeof(aname)-1) {
 		np_error(hdr->tag, "name too long");
 		return;