Attachment 730907 Details for Bug 1025084

[patch] complete patch proposal with backward compatibility for getrandom

auth-entropy-fix-full.patch (text/plain), 5.18 KB, created by Matthias Gerstner on 2017-06-30 15:31:10 UTC

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Creator: Matthias Gerstner

Created: 2017-06-30 15:31:10 UTC

Size: 5.18 KB

patch

obsolete

>Index: xserver/configure.ac
>===================================================================
>--- xserver.orig/configure.ac
>+++ xserver/configure.ac
>@@ -132,7 +132,7 @@ AM_CONDITIONAL(SPECIAL_DTRACE_OBJECTS, [
> AC_HEADER_DIRENT
> AC_HEADER_STDC
> AC_CHECK_HEADERS([fcntl.h stdlib.h string.h unistd.h dlfcn.h stropts.h \
>- fnmatch.h sys/mkdev.h sys/sysmacros.h sys/utsname.h])
>+ fnmatch.h sys/mkdev.h sys/sysmacros.h sys/utsname.h sys/syscall.h])
> 
> dnl Checks for typedefs, structures, and compiler characteristics.
> AC_C_CONST
>@@ -164,7 +164,7 @@ AC_REPLACE_FUNCS([reallocarray strcasecm
> AM_CONDITIONAL(POLL, [test "x$ac_cv_func_poll" = "xyes"])
> 
> AC_CHECK_LIB([bsd], [arc4random_buf])
>-AC_CHECK_FUNCS([arc4random_buf])
>+AC_CHECK_FUNCS([arc4random_buf getentropy])
> 
> AC_CHECK_DECLS([program_invocation_short_name], [], [], [[#include <errno.h>]])
> 
>Index: xserver/include/dix-config.h.in
>===================================================================
>--- xserver.orig/include/dix-config.h.in
>+++ xserver/include/dix-config.h.in
>@@ -164,6 +164,9 @@
> /* Define to 1 if you have the `arc4random_buf' function. */
> #undef HAVE_ARC4RANDOM_BUF
> 
>+/* Define to 1 if you have the `getentropy' function. */
>+#undef HAVE_GETENTROPY
>+
> /* Define to use libc SHA1 functions */
> #undef HAVE_SHA1_IN_LIBC
> 
>@@ -241,6 +244,9 @@
> /* Define to 1 if you have the <sys/utsname.h> header file. */
> #undef HAVE_SYS_UTSNAME_H
> 
>+/* Define to 1 if you have the <sys/syscall.h> header file. */
>+#undef HAVE_SYS_SYSCALL_H
>+
> /* Define to 1 if you have the `timingsafe_memcmp' function. */
> #undef HAVE_TIMINGSAFE_MEMCMP
> 
>Index: xserver/os/auth.c
>===================================================================
>--- xserver.orig/os/auth.c
>+++ xserver/os/auth.c
>@@ -48,6 +48,10 @@ from The Open Group.
> #ifdef HAVE_LIBBSD
> #include   <bsd/stdlib.h>       /* for arc4random_buf() */
> #endif
>+#include   <errno.h>
>+#ifdef HAVE_SYS_SYSCALL_H
>+#include   <syscall.h>
>+#endif
> 
> struct protocol {
>     unsigned short name_length;
>@@ -302,18 +306,136 @@ GenerateAuthorization(unsigned name_leng
>     return -1;
> }
> 
>+#if ! defined(HAVE_ARC4RANDOM_BUF)
>+
>+// fallback function to get random data directly from /dev/urandom
>+
>+static int
>+GetUrandom ( char *buffer, size_t length )
>+{
>+    int random_fd = -1;
>+    int res = -1;
>+    size_t filled = 0;
>+
>+    // larger requests are typically rejected by getentropy() / getrandom()
>+    // because they could block or return partially filled buffers
>+    if( length > 256 ) {
>+        errno = EIO;
>+        return -1;
>+    }
>+
>+    random_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
>+
>+    if( random_fd == -1 ) {
>+        return -1;
>+    }
>+
>+    while( filled < length ) {
>+        res = read(random_fd, (char*)buffer + filled, length - filled);
>+
>+        if( res == -1 ) {
>+            // shouldn't actually happen acc. to man(4) random,
>+            // but you never know
>+            if( errno == EINTR ) {
>+                continue;
>+            }
>+
>+            return -1;
>+        }
>+        else if( res == 0 ) {
>+            // no more bytes available? should not happen
>+            errno = EIO;
>+            return -1;
>+        }
>+
>+        filled += res;
>+    }
>+
>+    return 0;
>+}
>+
>+#endif // ! defined(HAVE_ARC4RANDOM_BUF)
>+
>+#if !defined(HAVE_GETENTROPY) && defined(HAVE_SYS_SYSCALL_H) && defined(SYS_getrandom)
>+#    define TRY_GETRANDOM
>+#endif
>+
>+#ifdef TRY_GETRANDOM
>+
>+/*
>+ * wrapper for the getrandom() syscall which was for a long time implemented
>+ * in the Linux kernel, but not wrapped in glibc
>+ */
>+static int
>+GetRandom ( char *buffer, size_t length )
>+{
>+    int res;
>+    size_t filled = 0;
>+
>+    // larger requests are typically rejected by getentropy() / getrandom()
>+    // because they could block or return partially filled buffers
>+    if( length > 256 )
>+    {
>+        errno = EIO;
>+        return -1;
>+    }
>+
>+    while( filled < length )
>+    {
>+        /*
>+         * glibc does not contain a syscall wrapper for this in older
>+         * versions
>+         */
>+        res = syscall(SYS_getrandom, (char*)buffer + filled, length - filled, 0);
>+
>+        if( res == -1 )
>+        {
>+            if( errno == EINTR ) {
>+                continue;
>+            }
>+
>+            return -1;
>+        }
>+        else if( res == 0 )
>+        {
>+            // no more bytes available? should not happen
>+            errno = EIO;
>+            return -1;
>+        }
>+
>+        filled += res;
>+    }
>+
>+    return 0;
>+}
>+
>+#endif /* TRY_GETRANDOM */
>+
> void
> GenerateRandomData(int len, char *buf)
> {
> #ifdef HAVE_ARC4RANDOM_BUF
>     arc4random_buf(buf, len);
> #else
>-    int fd;
>+    int ret = -1;
>+#   ifdef HAVE_GETENTROPY
>+    /* use getentropy instead */
>+    ret = getentropy (auth, len);
>+#   elif defined(TRY_GETRANDOM)
>+    /* try getrandom() wrapper */
>+    ret = GetRandom(buf, len);
>+#   endif
>+
>+    if( ret == -1 ) {
>+        // fallback to manual reading of /dev/urandom
>+        ret = GetUrandom(buf, len);
>+    }
> 
>-    fd = open("/dev/urandom", O_RDONLY);
>-    read(fd, buf, len);
>-    close(fd);
>-#endif
>+    if( ret == -1 ) {
>+        // no error return possible, rather abort than have security problems
>+        OsAbort();
>+    }
>+#endif // HAVE_ARC4RANDOM_BUF
> }
> 
> #endif                          /* XCSECURITY */

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Attachments on bug 1025084: 730759 | 730907 | 731000 | 732617