On systems where we do not have BN_ULLONG defined (most 64-bit systems),

BN_mod_word() can return incorrect results if the supplied modulus is
too big, so we need to fall back to BN_div_word.

Now that BN_mod_word may fail, handle errors properly update the man page.

Thanks to Brian Smith for pointing out these fixes from BoringSSL:

https://boringssl.googlesource.com/boringssl/+/67cb49d045f04973ddba0f92fe8a8ad483c7da89
https://boringssl.googlesource.com/boringssl/+/44bedc348d9491e63c7ed1438db100a4b8a830be

ok beck@

1 files changed, 3 insertions, 2 deletions

diff --git a/src/lib/libcrypto/man/BN_add_word.3 b/src/lib/libcrypto/man/BN_add_word.3
index 930aae4d32..16f2a17eb5 100644
--- a/src/lib/libcrypto/man/BN_add_word.3
+++ b/src/lib/libcrypto/man/BN_add_word.3
@@ -1,4 +1,4 @@
-.Dd $Mdocdate: February 23 2015 $
+.Dd $Mdocdate: July 5 2016 $
 .Dt BN_ADD_WORD 3
 .Os
 .Sh NAME
@@ -75,7 +75,8 @@ returns the remainder of
 .Fa a
 divided by
 .Fa w
-.Pq Li a%w .
+.Pq Li a%w
+or (BN_ULONG)-1 on error.
 .Pp
 For
 .Fn BN_div_word