Avoid undefined behavior with unaligned accesses

Fixes: #4983

[extended tests]

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/6074)

2 files changed, 22 insertions, 20 deletions

diff --git a/crypto/ec/ecp_nistp224.c b/crypto/ec/ecp_nistp224.c
index 1808c4c76c..2b665842c7 100644
--- a/crypto/ec/ecp_nistp224.c
+++ b/crypto/ec/ecp_nistp224.c
@@ -75,6 +75,7 @@ typedef uint64_t u64;
  */
 
 typedef uint64_t limb;
+typedef uint64_t limb_aX __attribute((__aligned__(1)));
 typedef uint128_t widelimb;
 
 typedef limb felem[4];
@@ -311,10 +312,10 @@ const EC_METHOD *EC_GFp_nistp224_method(void)
  */
 static void bin28_to_felem(felem out, const u8 in[28])
 {
-    out[0] = *((const uint64_t *)(in)) & 0x00ffffffffffffff;
-    out[1] = (*((const uint64_t *)(in + 7))) & 0x00ffffffffffffff;
-    out[2] = (*((const uint64_t *)(in + 14))) & 0x00ffffffffffffff;
-    out[3] = (*((const uint64_t *)(in+20))) >> 8;
+    out[0] = *((const limb *)(in)) & 0x00ffffffffffffff;
+    out[1] = (*((const limb_aX *)(in + 7))) & 0x00ffffffffffffff;
+    out[2] = (*((const limb_aX *)(in + 14))) & 0x00ffffffffffffff;
+    out[3] = (*((const limb_aX *)(in + 20))) >> 8;
 }
 
 static void felem_to_bin28(u8 out[28], const felem in)
diff --git a/crypto/ec/ecp_nistp521.c b/crypto/ec/ecp_nistp521.c
index 28e048ede9..0e7f1dae3b 100644
--- a/crypto/ec/ecp_nistp521.c
+++ b/crypto/ec/ecp_nistp521.c
@@ -131,6 +131,7 @@ static const felem_bytearray nistp521_curve_params[5] = {
 #define NLIMBS 9
 
 typedef uint64_t limb;
+typedef limb limb_aX __attribute((__aligned__(1)));
 typedef limb felem[NLIMBS];
 typedef uint128_t largefelem[NLIMBS];
 
@@ -144,14 +145,14 @@ static const limb bottom58bits = 0x3ffffffffffffff;
 static void bin66_to_felem(felem out, const u8 in[66])
 {
     out[0] = (*((limb *) & in[0])) & bottom58bits;
-    out[1] = (*((limb *) & in[7]) >> 2) & bottom58bits;
-    out[2] = (*((limb *) & in[14]) >> 4) & bottom58bits;
-    out[3] = (*((limb *) & in[21]) >> 6) & bottom58bits;
-    out[4] = (*((limb *) & in[29])) & bottom58bits;
-    out[5] = (*((limb *) & in[36]) >> 2) & bottom58bits;
-    out[6] = (*((limb *) & in[43]) >> 4) & bottom58bits;
-    out[7] = (*((limb *) & in[50]) >> 6) & bottom58bits;
-    out[8] = (*((limb *) & in[58])) & bottom57bits;
+    out[1] = (*((limb_aX *) & in[7]) >> 2) & bottom58bits;
+    out[2] = (*((limb_aX *) & in[14]) >> 4) & bottom58bits;
+    out[3] = (*((limb_aX *) & in[21]) >> 6) & bottom58bits;
+    out[4] = (*((limb_aX *) & in[29])) & bottom58bits;
+    out[5] = (*((limb_aX *) & in[36]) >> 2) & bottom58bits;
+    out[6] = (*((limb_aX *) & in[43]) >> 4) & bottom58bits;
+    out[7] = (*((limb_aX *) & in[50]) >> 6) & bottom58bits;
+    out[8] = (*((limb_aX *) & in[58])) & bottom57bits;
 }
 
 /*
@@ -162,14 +163,14 @@ static void felem_to_bin66(u8 out[66], const felem in)
 {
     memset(out, 0, 66);
     (*((limb *) & out[0])) = in[0];
-    (*((limb *) & out[7])) |= in[1] << 2;
-    (*((limb *) & out[14])) |= in[2] << 4;
-    (*((limb *) & out[21])) |= in[3] << 6;
-    (*((limb *) & out[29])) = in[4];
-    (*((limb *) & out[36])) |= in[5] << 2;
-    (*((limb *) & out[43])) |= in[6] << 4;
-    (*((limb *) & out[50])) |= in[7] << 6;
-    (*((limb *) & out[58])) = in[8];
+    (*((limb_aX *) & out[7])) |= in[1] << 2;
+    (*((limb_aX *) & out[14])) |= in[2] << 4;
+    (*((limb_aX *) & out[21])) |= in[3] << 6;
+    (*((limb_aX *) & out[29])) = in[4];
+    (*((limb_aX *) & out[36])) |= in[5] << 2;
+    (*((limb_aX *) & out[43])) |= in[6] << 4;
+    (*((limb_aX *) & out[50])) |= in[7] << 6;
+    (*((limb_aX *) & out[58])) = in[8];
 }
 
 /* BN_to_felem converts an OpenSSL BIGNUM into an felem */