From 7846299adb4d52342f0ec2da3cca7165b3946cf7 Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Fri, 7 Jun 2019 16:38:28 +0200
Subject: [PATCH] Fix misuse of signed ints in the HAVEGE module

The elements of the HAVEGE state are manipulated with bitwise
operations, with the expectations that the elements are 32-bit
unsigned integers (or larger). But they are declared as int, and so
the code has undefined behavior. Clang with Asan correctly points out
some shifts that reach the sign bit.

Since these are supposed to be 32-bit unsigned integers, declare them
as uint32_t.

This is technically an API break, since the type mbedtls_havege_state
is exposed in a public header. However normal applications should not
be affected.
---
 include/mbedtls/havege.h |  7 ++++---
 library/havege.c         | 22 ++++++++++++----------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/include/mbedtls/havege.h b/include/mbedtls/havege.h
index 4c1c86087..749257a36 100644
--- a/include/mbedtls/havege.h
+++ b/include/mbedtls/havege.h
@@ -31,6 +31,7 @@
 #endif
 
 #include <stddef.h>
+#include <stdint.h>
 
 #define MBEDTLS_HAVEGE_COLLECT_SIZE 1024
 
@@ -43,9 +44,9 @@ extern "C" {
  */
 typedef struct mbedtls_havege_state
 {
-    int PT1, PT2, offset[2];
-    int pool[MBEDTLS_HAVEGE_COLLECT_SIZE];
-    int WALK[8192];
+    uint32_t PT1, PT2, offset[2];
+    uint32_t pool[MBEDTLS_HAVEGE_COLLECT_SIZE];
+    uint32_t WALK[8192];
 }
 mbedtls_havege_state;
 
diff --git a/library/havege.c b/library/havege.c
index 54f897c6e..a9dded1cf 100644
--- a/library/havege.c
+++ b/library/havege.c
@@ -38,6 +38,7 @@
 #include "mbedtls/timing.h"
 #include "mbedtls/platform_util.h"
 
+#include <stdint.h>
 #include <string.h>
 
 /* ------------------------------------------------------------------------
@@ -54,7 +55,7 @@
  * ------------------------------------------------------------------------
  */
 
-#define SWAP(X,Y) { int *T = (X); (X) = (Y); (Y) = T; }
+#define SWAP(X,Y) { uint32_t *T = (X); (X) = (Y); (Y) = T; }
 
 #define TST1_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
 #define TST2_ENTER if( PTEST & 1 ) { PTEST ^= 3; PTEST >>= 1;
@@ -77,7 +78,7 @@
     PTX = (PT1 >> 18) & 7;                              \
     PT1 &= 0x1FFF;                                      \
     PT2 &= 0x1FFF;                                      \
-    CLK = (int) mbedtls_timing_hardclock();                            \
+    CLK = (uint32_t) mbedtls_timing_hardclock();        \
                                                         \
     i = 0;                                              \
     A = &WALK[PT1    ]; RES[i++] ^= *A;                 \
@@ -100,7 +101,7 @@
                                                         \
     IN = (*A >> (5)) ^ (*A << (27)) ^ CLK;              \
     *A = (*B >> (6)) ^ (*B << (26)) ^ CLK;              \
-    *B = IN; CLK = (int) mbedtls_timing_hardclock();                   \
+    *B = IN; CLK = (uint32_t) mbedtls_timing_hardclock();       \
     *C = (*C >> (7)) ^ (*C << (25)) ^ CLK;              \
     *D = (*D >> (8)) ^ (*D << (24)) ^ CLK;              \
                                                         \
@@ -158,10 +159,11 @@
  */
 static void havege_fill( mbedtls_havege_state *hs )
 {
-    int i, n = 0;
-    int  U1,  U2, *A, *B, *C, *D;
-    int PT1, PT2, *WALK, RES[16];
-    int PTX, PTY, CLK, PTEST, IN;
+    size_t n = 0;
+    unsigned i;
+    uint32_t  U1,  U2, *A, *B, *C, *D;
+    uint32_t PT1, PT2, *WALK, RES[16];
+    uint32_t PTX, PTY, CLK, PTEST, IN;
 
     WALK = hs->WALK;
     PT1  = hs->PT1;
@@ -212,7 +214,7 @@ void mbedtls_havege_free( mbedtls_havege_state *hs )
  */
 int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
 {
-    int val;
+    uint32_t val;
     size_t use_len;
     mbedtls_havege_state *hs = (mbedtls_havege_state *) p_rng;
     unsigned char *p = buf;
@@ -220,8 +222,8 @@ int mbedtls_havege_random( void *p_rng, unsigned char *buf, size_t len )
     while( len > 0 )
     {
         use_len = len;
-        if( use_len > sizeof(int) )
-            use_len = sizeof(int);
+        if( use_len > sizeof( val ) )
+            use_len = sizeof( val );
 
         if( hs->offset[1] >= MBEDTLS_HAVEGE_COLLECT_SIZE )
             havege_fill( hs );