git: 933893771344 - main - tftpd: Add missing bounds checks

The branch main has been updated by des:

URL: https://cgit.FreeBSD.org/src/commit/?id=933893771344e1647eeda152016b938fdc30ccdc

commit 933893771344e1647eeda152016b938fdc30ccdc
Author:     Dag-Erling Smørgrav <des@FreeBSD.org>
AuthorDate: 2026-05-22 17:57:31 +0000
Commit:     Dag-Erling Smørgrav <des@FreeBSD.org>
CommitDate: 2026-05-22 17:57:31 +0000

    tftpd: Add missing bounds checks
    
    In send_[rw]rq(), we were using strlcpy() to avoid overflowing our
    packet buffer, then failing to check the result and blithely advancing
    our pointer by the full length.
    
    Luckily, this code is only ever used by tftp(1), not tftpd(8).
    
    MFC after:      1 week
    Reviewed by:    markj
    Differential Revision:  https://reviews.freebsd.org/D57075
---
 libexec/tftpd/tftp-io.c | 62 +++++++++++++++++++++++++++----------------------
 1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/libexec/tftpd/tftp-io.c b/libexec/tftpd/tftp-io.c
index 50102e652d2f..3384071d6df2 100644
--- a/libexec/tftpd/tftp-io.c
+++ b/libexec/tftpd/tftp-io.c
@@ -173,11 +173,11 @@ send_error(int peer, int error)
 int
 send_wrq(int peer, char *filename, char *mode)
 {
-	int n;
+	char buf[MAXPKTSIZE];
 	struct tftphdr *tp;
 	char *bp;
-	char buf[MAXPKTSIZE];
-	int size;
+	size_t len;
+	int n, size;
 
 	if (debug & DEBUG_PACKETS)
 		tftp_log(LOG_DEBUG, "Sending WRQ: filename: '%s', mode '%s'",
@@ -191,17 +191,17 @@ send_wrq(int peer, char *filename, char *mode)
 	size = offsetof(struct tftphdr, th_stuff);
 
 	bp = tp->th_stuff;
-	strlcpy(bp, filename, sizeof(buf) - size);
-	bp += strlen(filename);
-	*bp = 0;
-	bp++;
-	size += strlen(filename) + 1;
-
-	strlcpy(bp, mode, sizeof(buf) - size);
-	bp += strlen(mode);
-	*bp = 0;
-	bp++;
-	size += strlen(mode) + 1;
+	len = strlcpy(bp, filename, sizeof(buf) - size);
+	if (len >= sizeof(buf) - size)
+		goto overflow;
+	bp += len + 1;
+	size += len + 1;
+
+	len = strlcpy(bp, mode, sizeof(buf) - size);
+	if (len >= sizeof(buf) - size)
+		goto overflow;
+	bp += len + 1;
+	size += len + 1;
 
 	if (options_rfc_enabled)
 		size += make_options(peer, bp, sizeof(buf) - size);
@@ -213,6 +213,9 @@ send_wrq(int peer, char *filename, char *mode)
 		return (1);
 	}
 	return (0);
+overflow:
+	tftp_log(LOG_ERR, "%s: file name too long", __func__);
+	return (1);
 }
 
 /*
@@ -221,11 +224,11 @@ send_wrq(int peer, char *filename, char *mode)
 int
 send_rrq(int peer, char *filename, char *mode)
 {
-	int n;
+	char buf[MAXPKTSIZE];
 	struct tftphdr *tp;
 	char *bp;
-	char buf[MAXPKTSIZE];
-	int size;
+	size_t len;
+	int n, size;
 
 	if (debug & DEBUG_PACKETS)
 		tftp_log(LOG_DEBUG, "Sending RRQ: filename: '%s', mode '%s'",
@@ -239,17 +242,17 @@ send_rrq(int peer, char *filename, char *mode)
 	size = offsetof(struct tftphdr, th_stuff);
 
 	bp = tp->th_stuff;
-	strlcpy(bp, filename, sizeof(buf) - size);
-	bp += strlen(filename);
-	*bp = 0;
-	bp++;
-	size += strlen(filename) + 1;
-
-	strlcpy(bp, mode, sizeof(buf) - size);
-	bp += strlen(mode);
-	*bp = 0;
-	bp++;
-	size += strlen(mode) + 1;
+	len = strlcpy(bp, filename, sizeof(buf) - size);
+	if (len >= sizeof(buf) - size)
+		goto overflow;
+	bp += len + 1;
+	size += len + 1;
+
+	len = strlcpy(bp, mode, sizeof(buf) - size);
+	if (len >= sizeof(buf) - size)
+		goto overflow;
+	bp += len + 1;
+	size += len + 1;
 
 	if (options_rfc_enabled) {
 		options_set_request(OPT_TSIZE, "0");
@@ -263,6 +266,9 @@ send_rrq(int peer, char *filename, char *mode)
 		return (1);
 	}
 	return (0);
+overflow:
+	tftp_log(LOG_ERR, "%s: file name too long", __func__);
+	return (1);
 }
 
 /*