resolv: Move __res_context_hostalias into its own file and into libc

And reformat it to GNU style.  Remove the unecessary setbuf call.
Use __fgets_unlocked for PLT avoidance; no locking is required here.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

5 files changed, 135 insertions, 42 deletions

diff --git a/resolv/Makefile b/resolv/Makefile
index 83ba39cb52..bfcca70f26 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -48,6 +48,7 @@ routines := \
   res-close \
   res-name-checking \
   res-state \
+  res_context_hostalias \
   res_get_nsaddr \
   res_hconf \
   res_init \
diff --git a/resolv/Versions b/resolv/Versions
index 5bbda96230..b084660dde 100644
--- a/resolv/Versions
+++ b/resolv/Versions
@@ -85,6 +85,7 @@ libc {
     __ns_name_skip;
     __ns_name_uncompress;
     __ns_name_unpack;
+    __res_context_hostalias;
     __res_get_nsaddr;
     __res_iclose;
     __resolv_context_get;
@@ -192,7 +193,6 @@ libresolv {
   GLIBC_PRIVATE {
     __ns_get16;
     __ns_get32;
-    __res_context_hostalias;
     __res_context_query;
     __res_context_search;
   }
diff --git a/resolv/res_context_hostalias.c b/resolv/res_context_hostalias.c
new file mode 100644
index 0000000000..b4dc1763db
--- /dev/null
+++ b/resolv/res_context_hostalias.c
@@ -0,0 +1,132 @@
+/* HOSTALIASES-based name resolution.  Internal function.
+   Copyright (C) 2015-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/*
+ * Copyright (c) 1988, 1993
+ *    The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Portions Copyright (c) 1993 by Digital Equipment Corporation.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies, and that
+ * the name of Digital Equipment Corporation not be used in advertising or
+ * publicity pertaining to distribution of the document or software without
+ * specific, written prior permission.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
+ * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
+ * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/*
+ * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+#include <arpa/nameser.h>
+#include <ctype.h>
+#include <resolv-internal.h>
+#include <resolv_context.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+const char *
+__res_context_hostalias (struct resolv_context *ctx,
+                         const char *name, char *dst, size_t siz)
+{
+  char *file, *cp1, *cp2;
+  char buf[BUFSIZ];
+  FILE *fp;
+
+  if (ctx->resp->options & RES_NOALIASES)
+    return NULL;
+  file = getenv ("HOSTALIASES");
+  if (file == NULL || (fp = fopen (file, "rce")) == NULL)
+    return NULL;
+  buf[sizeof (buf) - 1] = '\0';
+  while (__fgets_unlocked (buf, sizeof (buf), fp))
+    {
+      for (cp1 = buf; *cp1 && !isspace (*cp1); ++cp1)
+        ;
+      if (!*cp1)
+        break;
+      *cp1 = '\0';
+      if (__libc_ns_samename (buf, name) == 1)
+        {
+          while (isspace (*++cp1))
+            ;
+          if (!*cp1)
+            break;
+          for (cp2 = cp1 + 1; *cp2 && !isspace (*cp2); ++cp2)
+            ;
+          *cp2 = '\0';
+          strncpy (dst, cp1, siz - 1);
+          dst[siz - 1] = '\0';
+          fclose (fp);
+          return dst;
+        }
+    }
+  fclose (fp);
+  return NULL;
+}
+libc_hidden_def (__res_context_hostalias)
diff --git a/resolv/res_query.c b/resolv/res_query.c
index 5b51af8451..45c591ae27 100644
--- a/resolv/res_query.c
+++ b/resolv/res_query.c
@@ -635,46 +635,6 @@ res_querydomain (const char *name, const char *domain, int class, int type,
     (__resolv_context_get (), name, domain, class, type, answer, anslen);
 }
 
-const char *
-__res_context_hostalias (struct resolv_context *ctx,
-			 const char *name, char *dst, size_t siz)
-{
-	char *file, *cp1, *cp2;
-	char buf[BUFSIZ];
-	FILE *fp;
-
-	if (ctx->resp->options & RES_NOALIASES)
-		return (NULL);
-	file = getenv("HOSTALIASES");
-	if (file == NULL || (fp = fopen(file, "rce")) == NULL)
-		return (NULL);
-	setbuf(fp, NULL);
-	buf[sizeof(buf) - 1] = '\0';
-	while (fgets(buf, sizeof(buf), fp)) {
-		for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
-			;
-		if (!*cp1)
-			break;
-		*cp1 = '\0';
-		if (__libc_ns_samename(buf, name) == 1) {
-			while (isspace(*++cp1))
-				;
-			if (!*cp1)
-				break;
-			for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
-				;
-			*cp2 = '\0';
-			strncpy(dst, cp1, siz - 1);
-			dst[siz - 1] = '\0';
-			fclose(fp);
-			return (dst);
-		}
-	}
-	fclose(fp);
-	return (NULL);
-}
-libresolv_hidden_def (__res_context_hostalias)
-
 /* Common part of res_hostalias and hostalias.  */
 static const char *
 context_hostalias_common (struct resolv_context *ctx,
diff --git a/resolv/resolv-internal.h b/resolv/resolv-internal.h
index c18b1d0472..7d37817232 100644
--- a/resolv/resolv-internal.h
+++ b/resolv/resolv-internal.h
@@ -79,7 +79,7 @@ int __res_context_send (struct resolv_context *, const unsigned char *, int,
 /* Internal function similar to res_hostalias.  */
 const char *__res_context_hostalias (struct resolv_context *,
                                      const char *, char *, size_t);
-libresolv_hidden_proto (__res_context_hostalias);
+libc_hidden_proto (__res_context_hostalias);
 
 /* Add an OPT record to a DNS query.  */
 int __res_nopt (struct resolv_context *, int n0,