From 20d96999a4c7fe7e2cdf5056b8a293e266564f4a Mon Sep 17 00:00:00 2001
From: Hiroki Sato <hrs@FreeBSD.org>
Date: Thu, 15 Mar 2018 13:46:28 +0000
Subject: [PATCH] Make getnameinfo(3) salen requirement less strict and
 document details of salen in getnameinfo(3) manual page.

getnameinfo(3) returned EAI_FAIL when salen was not equal to
the length corresponding to the value specified by sa->sa_family.
However, POSIX or RFC 3493 does not require it and RFC 4038
Sec.6.2.3 shows an example passing sizeof(struct sockaddr_storage)
to salen.

This change makes the requirement less strict by accepting
salen up to sizeof(struct sockaddr_storage).  It also includes
two more changes: one is to fix return values because both SUSv4
and RFC 3493 require EAI_FAMILY when the address length is invalid,
another is to fix sa_len dependency in PF_LOCAL.

Pointed out by:	Christophe Beauval
Reviewed by:	ae
Differential Revision:	https://reviews.freebsd.org/D14585
---
 lib/libc/net/getnameinfo.3 | 16 +++++++++++++++-
 lib/libc/net/getnameinfo.c | 26 ++++++++++++++++++--------
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/lib/libc/net/getnameinfo.3 b/lib/libc/net/getnameinfo.3
index 9e49eaccf3f1..5d5719c010c7 100644
--- a/lib/libc/net/getnameinfo.3
+++ b/lib/libc/net/getnameinfo.3
@@ -18,7 +18,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 28, 2016
+.Dd March 15, 2018
 .Dt GETNAMEINFO 3
 .Os
 .Sh NAME
@@ -80,6 +80,20 @@ or UNIX-domain respectively
 that is
 .Fa salen
 bytes long.
+If
+.Fa salen
+is shorter than the length corresponding to the specified
+address family or longer than
+.Fn sizeof "struct sockaddr_storage" ,
+it returns
+.Er EAI_FAMILY .
+Note that
+.Va sa->sa_len
+should be consistent with
+.Fa salen
+though the value of
+.Va sa->sa_len
+is not directly used in this function.
 .Pp
 The host and service names associated with
 .Fa sa
diff --git a/lib/libc/net/getnameinfo.c b/lib/libc/net/getnameinfo.c
index b3788534c7dc..a07355fac6f9 100644
--- a/lib/libc/net/getnameinfo.c
+++ b/lib/libc/net/getnameinfo.c
@@ -124,26 +124,36 @@ getnameinfo(const struct sockaddr *sa, socklen_t salen,
 	afd = find_afd(sa->sa_family);
 	if (afd == NULL)
 		return (EAI_FAMILY);
+	/*
+	 * getnameinfo() accepts an salen of sizeof(struct sockaddr_storage)
+	 * at maximum as shown in RFC 4038 Sec.6.2.3.
+	 */
+	if (salen > sizeof(struct sockaddr_storage))
+		return (EAI_FAMILY);
+
 	switch (sa->sa_family) {
 	case PF_LOCAL:
 		/*
-		 * PF_LOCAL uses variable sa->sa_len depending on the
+		 * PF_LOCAL uses variable salen depending on the
 		 * content length of sun_path.  Require 1 byte in
 		 * sun_path at least.
 		 */
-		if (salen > afd->a_socklen ||
-		    salen <= afd->a_socklen -
+		if (salen <= afd->a_socklen -
 			sizeofmember(struct sockaddr_un, sun_path))
-			return (EAI_FAIL);
+			return (EAI_FAMILY);
+		else if (salen > afd->a_socklen)
+			salen = afd->a_socklen;
 		break;
 	case PF_LINK:
 		if (salen <= afd->a_socklen -
 			sizeofmember(struct sockaddr_dl, sdl_data))
-			return (EAI_FAIL);
+			return (EAI_FAMILY);
 		break;
 	default:
-		if (salen != afd->a_socklen)
-			return (EAI_FAIL);
+		if (salen < afd->a_socklen)
+			return (EAI_FAMILY);
+		else
+			salen = afd->a_socklen;
 		break;
 	}
 
@@ -517,7 +527,7 @@ getnameinfo_un(const struct afd *afd,
 	if (serv != NULL && servlen > 0)
 		*serv = '\0';
 	if (host != NULL && hostlen > 0) {
-		pathlen = sa->sa_len - afd->a_off;
+		pathlen = salen - afd->a_off;
 
 		if (pathlen + 1 > hostlen) {
 			*host = '\0';