[PATCH] Fix carry overflow in Stribog in 512-bit addition

[Dmitry Eremin-Solenikov]

* cipher/stribog.c (transform_bits): properly calculate carry flag
* tests/basic.c (check_digests): add two more test cases

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov at gmail.com>
---
 cipher/stribog.c | 12 +++++++-----
 tests/basic.c    | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/cipher/stribog.c b/cipher/stribog.c
index 3eb0773564ef..267872474fb1 100644
--- a/cipher/stribog.c
+++ b/cipher/stribog.c
@@ -1223,7 +1223,7 @@ static void
 transform_bits (STRIBOG_CONTEXT *hd, const unsigned char *data, unsigned count)
 {
   u64 M[8];
-  u64 l;
+  u64 l, cf;
   int i;
 
   for (i = 0; i < 8; i++)
@@ -1243,11 +1243,13 @@ transform_bits (STRIBOG_CONTEXT *hd, const unsigned char *data, unsigned count)
     }
 
   hd->Sigma[0] += M[0];
+  cf = 0;
   for (i = 1; i < 8; i++)
-    if (hd->Sigma[i-1] < M[i-1])
-      hd->Sigma[i] += M[i] + 1;
-    else
-      hd->Sigma[i] += M[i];
+    {
+      if (hd->Sigma[i-1] != M[i-1])
+	cf = (hd->Sigma[i-1] < M[i-1]);
+      hd->Sigma[i] += M[i] + cf;
+    }
 }
 
 static unsigned int
diff --git a/tests/basic.c b/tests/basic.c
index 3efd3744a34a..55a8b72f2731 100644
--- a/tests/basic.c
+++ b/tests/basic.c
@@ -9168,6 +9168,33 @@ check_digests (void)
         "\x20\xc8\xe3\xee\xf0\xe5\xe2\xfb",
         "\x9d\xd2\xfe\x4e\x90\x40\x9e\x5d\xa8\x7f\x53\x97\x6d\x74\x05\xb0"
         "\xc0\xca\xc6\x28\xfc\x66\x9a\x74\x1d\x50\x06\x3c\x55\x7e\x8f\x50" },
+      /* Special tests for carry flag in addition */
+      { GCRY_MD_STRIBOG512,
+        "\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE"
+	"\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE"
+	"\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE"
+	"\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE\xEE"
+	"\x16\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11"
+	"\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11"
+	"\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11"
+	"\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x11\x16",
+	"\x8b\x06\xf4\x1e\x59\x90\x7d\x96\x36\xe8\x92\xca\xf5\x94\x2f\xcd"
+	"\xfb\x71\xfa\x31\x16\x9a\x5e\x70\xf0\xed\xb8\x73\x66\x4d\xf4\x1c"
+	"\x2c\xce\x6e\x06\xdc\x67\x55\xd1\x5a\x61\xcd\xeb\x92\xbd\x60\x7c"
+	"\xc4\xaa\xca\x67\x32\xbf\x35\x68\xa2\x3a\x21\x0d\xd5\x20\xfd\x41" },
+      { GCRY_MD_STRIBOG512,
+        "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+	"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff",
+	"\x90\xa1\x61\xd1\x2a\xd3\x09\x49\x8d\x3f\xe5\xd4\x82\x02\xd8\xa4"
+	"\xe9\xc4\x06\xd6\xa2\x64\xae\xab\x25\x8a\xc5\xec\xc3\x7a\x79\x62"
+	"\xaa\xf9\x58\x7a\x5a\xbb\x09\xb6\xbb\x81\xec\x4b\x37\x52\xa3\xff"
+	"\x5a\x83\x8e\xf1\x75\xbe\x57\x72\x05\x6b\xc5\xfe\x54\xfc\xfc\x7e" },
 #include "./sha3-224.h"
 #include "./sha3-256.h"
 #include "./sha3-384.h"
-- 
2.20.1