postfix-2.5.4

postfix/HISTORY

@@ -14411,3 +14411,22 @@ Apologies for any names omitted.
 	by the recipient. Requested by Sebastian Krahmer, SuSE.
 	Specify "strict_mailbox_ownership=no" to ignore ownership
 	discrepancies.  Files: local/mailbox.c, virtual/mailbox.c.
+
+20080804
+
+	Bugfix: dangling pointer in vstring_sprintf_prepend().
+	File: util/vstring.c.
+
+20080814
+
+	Security: some systems have changed their link() semantics,
+	and will hardlink a symlink, contrary to POSIX and XPG4.
+	Sebastian Krahmer, SuSE. File: util/safe_open.c.
+
+	The solution introduces the following incompatible change:
+	when the target of mail delivery is a symlink, the parent
+	directory of that symlink must now be writable by root only
+	(in addition to the already existing requirement that the
+	symlink itself is owned by root).  This change will break
+	legitimate configurations that deliver mail to a symbolic
+	link in a directory with less restrictive permissions.

postfix/src/global/mail_version.h

@@ -20,8 +20,8 @@
   * Patches change both the patchlevel and the release date. Snapshots have no
   * patchlevel; they change the release date only.
   */
-#define MAIL_RELEASE_DATE	"20080726"
+#define MAIL_RELEASE_DATE	"20080814"
-#define MAIL_VERSION_NUMBER	"2.5.3"
+#define MAIL_VERSION_NUMBER	"2.5.4"
 
 #ifdef SNAPSHOT
 # define MAIL_VERSION_DATE	"-" MAIL_RELEASE_DATE

postfix/src/util/safe_open.c

@@ -83,6 +83,7 @@
 #include <msg.h>
 #include <vstream.h>
 #include <vstring.h>
+#include <stringops.h>
 #include <safe_open.h>
 
 /* safe_open_exist - open existing file */
@@ -138,13 +139,29 @@ static VSTREAM *safe_open_exist(const char *path, int flags,
      * for symlinks owned by root. NEVER, NEVER, make exceptions for symlinks
      * owned by a non-root user. This would open a security hole when
      * delivering mail to a world-writable mailbox directory.
+     * 
+     * Sebastian Krahmer of SuSE brought to my attention that some systems have
+     * changed their semantics of link(symlink, newpath), such that the
+     * result is a hardlink to the symlink. For this reason, we now also
+     * require that the symlink's parent directory is writable only by root.
      */
     else if (lstat(path, &lstat_st) < 0) {
 	vstring_sprintf(why, "file status changed unexpectedly: %m");
 	errno = EPERM;
     } else if (S_ISLNK(lstat_st.st_mode)) {
-	if (lstat_st.st_uid == 0)
+	if (lstat_st.st_uid == 0) {
-	    return (fp);
+	    VSTRING *parent_buf = vstring_alloc(100);
+	    const char *parent_path = sane_dirname(parent_buf, path);
+	    struct stat parent_st;
+	    int     parent_ok;
+
+	    parent_ok = (stat(parent_path, &parent_st) == 0	/* not lstat */
+			 && parent_st.st_uid == 0
+			 && (parent_st.st_mode & (S_IWGRP | S_IWOTH)) == 0);
+	    vstring_free(parent_buf);
+	    if (parent_ok)
+		return (fp);
+	}
 	vstring_sprintf(why, "file is a symbolic link");
 	errno = EPERM;
     } else if (fstat_st->st_dev != lstat_st.st_dev

postfix/src/util/vstring.c

@@ -624,6 +624,7 @@ VSTRING *vstring_sprintf_prepend(VSTRING *vp, const char *format,...)
     result_len = VSTRING_LEN(vp);
 
     /* Construct: old|new|old|free */
+    VSTRING_SPACE(vp, old_len);
     vstring_memcat(vp, vstring_str(vp), old_len);
 
     /* Construct: new|old|free */