From 3782dfda5fc4f45a19b1ce1b01ecf7206a3d304a Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Wed, 25 May 2022 10:09:53 +0200
Subject: [PATCH 1/3] fopen: add Curl_fopen() for better overwriting of files

---
 lib/Makefile.inc |   2 +
 lib/cookie.c     |  19 ++-------
 lib/fopen.c      | 106 +++++++++++++++++++++++++++++++++++++++++++++++
 lib/fopen.h      |  28 +++++++++++++
 4 files changed, 140 insertions(+), 15 deletions(-)
 create mode 100644 lib/fopen.c
 create mode 100644 lib/fopen.h

Index: curl-7.81.0/lib/Makefile.inc
===================================================================
--- curl-7.81.0.orig/lib/Makefile.inc
+++ curl-7.81.0/lib/Makefile.inc
@@ -131,6 +131,7 @@ LIB_CFILES =         \
   escape.c           \
   file.c             \
   fileinfo.c         \
+  fopen.c            \
   formdata.c         \
   ftp.c              \
   ftplistparser.c    \
@@ -263,6 +264,7 @@ LIB_HFILES =         \
   escape.h           \
   file.h             \
   fileinfo.h         \
+  fopen.h            \
   formdata.h         \
   ftp.h              \
   ftplistparser.h    \
Index: curl-7.81.0/lib/cookie.c
===================================================================
--- curl-7.81.0.orig/lib/cookie.c
+++ curl-7.81.0/lib/cookie.c
@@ -96,8 +96,8 @@ Example set of cookies:
 #include "curl_get_line.h"
 #include "curl_memrchr.h"
 #include "parsedate.h"
-#include "rand.h"
 #include "rename.h"
+#include "fopen.h"
 
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
@@ -1612,20 +1612,9 @@ static CURLcode cookie_output(struct Cur
     use_stdout = TRUE;
   }
   else {
-    unsigned char randsuffix[9];
-
-    if(Curl_rand_hex(data, randsuffix, sizeof(randsuffix)))
-      return 2;
-
-    tempstore = aprintf("%s.%s.tmp", filename, randsuffix);
-    if(!tempstore)
-      return CURLE_OUT_OF_MEMORY;
-
-    out = fopen(tempstore, FOPEN_WRITETEXT);
-    if(!out) {
-      error = CURLE_WRITE_ERROR;
+    error = Curl_fopen(data, filename, &out, &tempstore);
+    if(error)
       goto error;
-    }
   }
 
   fputs("# Netscape HTTP Cookie File\n"
@@ -1672,7 +1661,7 @@ static CURLcode cookie_output(struct Cur
   if(!use_stdout) {
     fclose(out);
     out = NULL;
-    if(Curl_rename(tempstore, filename)) {
+    if(tempstore && Curl_rename(tempstore, filename)) {
       unlink(tempstore);
       error = CURLE_WRITE_ERROR;
       goto error;
Index: curl-7.81.0/lib/fopen.c
===================================================================
--- /dev/null
+++ curl-7.81.0/lib/fopen.c
@@ -0,0 +1,106 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#if !defined(CURL_DISABLE_COOKIES) || !defined(CURL_DISABLE_ALTSVC) ||  \
+  !defined(CURL_DISABLE_HSTS)
+
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+
+#include "urldata.h"
+#include "rand.h"
+#include "fopen.h"
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+/*
+ * Curl_fopen() opens a file for writing with a temp name, to be renamed
+ * to the final name when completed. If there is an existing file using this
+ * name at the time of the open, this function will clone the mode from that
+ * file.  if 'tempname' is non-NULL, it needs a rename after the file is
+ * written.
+ */
+CURLcode Curl_fopen(struct Curl_easy *data, const char *filename,
+                    FILE **fh, char **tempname)
+{
+  CURLcode result = CURLE_WRITE_ERROR;
+  unsigned char randsuffix[9];
+  char *tempstore = NULL;
+  struct_stat sb, nsb;
+  int fd = -1;
+  *tempname = NULL;
+
+  if(stat(filename, &sb) == -1 || !S_ISREG(sb.st_mode)) {
+    /* a non-regular file, fallback to direct fopen() */
+    *fh = fopen(filename, FOPEN_WRITETEXT);
+    if(*fh)
+      return CURLE_OK;
+    goto fail;
+  }
+
+  result = Curl_rand_hex(data, randsuffix, sizeof(randsuffix));
+  if(result)
+    goto fail;
+
+  tempstore = aprintf("%s.%s.tmp", filename, randsuffix);
+  if(!tempstore) {
+    result = CURLE_OUT_OF_MEMORY;
+    goto fail;
+  }
+
+  result = CURLE_WRITE_ERROR;
+  fd = open(tempstore, O_WRONLY | O_CREAT | O_EXCL, 0600);
+  if(fd == -1)
+    goto fail;
+
+  if((fstat(fd, &nsb) != -1) &&
+     (nsb.st_uid == sb.st_uid) && (nsb.st_gid == sb.st_gid)) {
+    /* if the user and group are the same, clone the original mode */
+    if(fchmod(fd, sb.st_mode) == -1)
+      goto fail;
+  }
+
+  *fh = fdopen(fd, FOPEN_WRITETEXT);
+  if(!*fh)
+    goto fail;
+
+  *tempname = tempstore;
+  return CURLE_OK;
+
+fail:
+  if(fd != -1) {
+    close(fd);
+    unlink(tempstore);
+  }
+
+  free(tempstore);
+
+  *tempname = NULL;
+  return result;
+}
+
+#endif /* ! disabled */
Index: curl-7.81.0/lib/fopen.h
===================================================================
--- /dev/null
+++ curl-7.81.0/lib/fopen.h
@@ -0,0 +1,28 @@
+#ifndef HEADER_CURL_FOPEN_H
+#define HEADER_CURL_FOPEN_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+CURLcode Curl_fopen(struct Curl_easy *data, const char *filename,
+                    FILE **fh, char **tempname);
+
+#endif
Index: curl-7.81.0/lib/altsvc.c
===================================================================
--- curl-7.81.0.orig/lib/altsvc.c
+++ curl-7.81.0/lib/altsvc.c
@@ -34,7 +34,7 @@
 #include "parsedate.h"
 #include "sendf.h"
 #include "warnless.h"
-#include "rand.h"
+#include "fopen.h"
 #include "rename.h"
 
 /* The last 3 #include files should be in this order */
@@ -329,8 +329,7 @@ CURLcode Curl_altsvc_save(struct Curl_ea
   struct Curl_llist_element *n;
   CURLcode result = CURLE_OK;
   FILE *out;
-  char *tempstore;
-  unsigned char randsuffix[9];
+  char *tempstore = NULL;
 
   if(!altsvc)
     /* no cache activated */
@@ -344,17 +343,8 @@ CURLcode Curl_altsvc_save(struct Curl_ea
     /* marked as read-only, no file or zero length file name */
     return CURLE_OK;
 
-  if(Curl_rand_hex(data, randsuffix, sizeof(randsuffix)))
-    return CURLE_FAILED_INIT;
-
-  tempstore = aprintf("%s.%s.tmp", file, randsuffix);
-  if(!tempstore)
-    return CURLE_OUT_OF_MEMORY;
-
-  out = fopen(tempstore, FOPEN_WRITETEXT);
-  if(!out)
-    result = CURLE_WRITE_ERROR;
-  else {
+  result = Curl_fopen(data, file, &out, &tempstore);
+  if(!result) {
     fputs("# Your alt-svc cache. https://curl.se/docs/alt-svc.html\n"
           "# This file was generated by libcurl! Edit at your own risk.\n",
           out);
@@ -366,10 +356,10 @@ CURLcode Curl_altsvc_save(struct Curl_ea
         break;
     }
     fclose(out);
-    if(!result && Curl_rename(tempstore, file))
+    if(!result && tempstore && Curl_rename(tempstore, file))
       result = CURLE_WRITE_ERROR;
 
-    if(result)
+    if(result && tempstore)
       unlink(tempstore);
   }
   free(tempstore);
Index: curl-7.81.0/lib/hsts.c
===================================================================
--- curl-7.81.0.orig/lib/hsts.c
+++ curl-7.81.0/lib/hsts.c
@@ -35,7 +35,7 @@
 #include "sendf.h"
 #include "strtoofft.h"
 #include "parsedate.h"
-#include "rand.h"
+#include "fopen.h"
 #include "rename.h"
 #include "strtoofft.h"
 
@@ -334,8 +334,7 @@ CURLcode Curl_hsts_save(struct Curl_easy
   struct Curl_llist_element *n;
   CURLcode result = CURLE_OK;
   FILE *out;
-  char *tempstore;
-  unsigned char randsuffix[9];
+  char *tempstore = NULL;
 
   if(!h)
     /* no cache activated */
@@ -349,17 +348,8 @@ CURLcode Curl_hsts_save(struct Curl_easy
     /* marked as read-only, no file or zero length file name */
     goto skipsave;
 
-  if(Curl_rand_hex(data, randsuffix, sizeof(randsuffix)))
-    return CURLE_FAILED_INIT;
-
-  tempstore = aprintf("%s.%s.tmp", file, randsuffix);
-  if(!tempstore)
-    return CURLE_OUT_OF_MEMORY;
-
-  out = fopen(tempstore, FOPEN_WRITETEXT);
-  if(!out)
-    result = CURLE_WRITE_ERROR;
-  else {
+  result = Curl_fopen(data, file, &out, &tempstore);
+  if(!result) {
     fputs("# Your HSTS cache. https://curl.se/docs/hsts.html\n"
           "# This file was generated by libcurl! Edit at your own risk.\n",
           out);
@@ -371,10 +361,10 @@ CURLcode Curl_hsts_save(struct Curl_easy
         break;
     }
     fclose(out);
-    if(!result && Curl_rename(tempstore, file))
+    if(!result && tempstore && Curl_rename(tempstore, file))
       result = CURLE_WRITE_ERROR;
 
-    if(result)
+    if(result && tempstore)
       unlink(tempstore);
   }
   free(tempstore);
