[openssl-commits] [openssl] master update

[Dr. Stephen Henson]

The branch master has been updated
       via  bd19d1aa04d14233c037386a2c969b0164c2cc37 (commit)
      from  3770b877ea7b7fa08e88395e8c472c102f9e707e (commit)


- Log -----------------------------------------------------------------
commit bd19d1aa04d14233c037386a2c969b0164c2cc37
Author: Dr. Stephen Henson <steve at openssl.org>
Date:   Tue Jul 19 18:40:14 2016 +0100

    Clarify digest change in HMAC_Init_ex()
    
    RT#4603
    
    Reviewed-by: Rich Salz <rsalz at openssl.org>

-----------------------------------------------------------------------

Summary of changes:
 doc/crypto/HMAC.pod | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/doc/crypto/HMAC.pod b/doc/crypto/HMAC.pod
index fdafec8..91d0bdc 100644
--- a/doc/crypto/HMAC.pod
+++ b/doc/crypto/HMAC.pod
@@ -79,13 +79,17 @@ function B<evp_md> and the key B<key> which is B<key_len> bytes
 long. It is deprecated and only included for backward compatibility
 with OpenSSL 0.9.6b.
 
-HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use
-the function B<evp_md> and key B<key>. Either can be NULL, in which
-case the existing one will be reused. B<ctx> must have been created
-with HMAC_CTX_new() before the first use of an B<HMAC_CTX> in this
-function. B<N.B. HMAC_Init() had this undocumented behaviour in
-previous versions of OpenSSL - failure to switch to HMAC_Init_ex() in
-programs that expect it will cause them to stop working>.
+HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use the hash
+function B<evp_md> and key B<key>. If both are NULL (or B<evp_md> is the same
+as the previous digest used by B<ctx> and B<key> is NULL) the existing key is
+reused. B<ctx> must have been created with HMAC_CTX_new() before the first use
+of an B<HMAC_CTX> in this function. B<N.B. HMAC_Init() had this undocumented
+behaviour in previous versions of OpenSSL - failure to switch to HMAC_Init_ex()
+in programs that expect it will cause them to stop working>.
+
+B<NB: if HMAC_Init_ex() is called with B<key> NULL and B<evp_md> is not the
+same as the previous digest used by B<ctx> then an error is returned
+because reuse of an existing key with a different digest is not supported.>
 
 HMAC_Update() can be called repeatedly with chunks of the message to
 be authenticated (B<len> bytes at B<data>).