This is fixed in Debian Sid (version 1.8.10.0).

Blacklisted for both Metad and Parkes in rev. 212.

In asterisk_1.6.2.9.orig.tar.gz

From the comment on main/sha1.c it looks like you can add comments to the file but otherwise not modify it?

• This document and translations of it may be copied and furnished to
• others, and derivative works that comment on or otherwise explain it
• or assist in its implementation may be prepared, copied, published
• and distributed, in whole or in part, without restriction of any
• kind, provided that the above copyright notice and this paragraph are
• included on all such copies and derivative works. However, this
• document itself may not be modified in any way, such as by removing
• the copyright notice or references to the Internet Society or other
• Internet organizations, except as needed for the purpose of
• developing Internet standards in which case the procedures for
• copyrights defined in the Internet Standards process must be
• followed, or as required to translate it into languages other than
• English.