aboutsummaryrefslogtreecommitdiffstats
path: root/doc/crypto/hmac.pod
diff options
context:
space:
mode:
Diffstat (limited to 'doc/crypto/hmac.pod')
-rw-r--r--doc/crypto/hmac.pod3
1 files changed, 2 insertions, 1 deletions
diff --git a/doc/crypto/hmac.pod b/doc/crypto/hmac.pod
index 2c8f20a20188..ca9798af62c3 100644
--- a/doc/crypto/hmac.pod
+++ b/doc/crypto/hmac.pod
@@ -38,7 +38,8 @@ B<key_len> bytes long.
It places the result in B<md> (which must have space for the output of
the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes).
If B<md> is NULL, the digest is placed in a static array. The size of
-the output is placed in B<md_len>, unless it is B<NULL>.
+the output is placed in B<md_len>, unless it is B<NULL>. Note: passing a NULL
+value for B<md> to use the static array is not thread safe.
B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.