Article View: sci.crypt
Article #940Re: pgp2.0 signature security problem
From: Mark Henderson
Date: Mon, 14 Sep 1992 19:17
Date: Mon, 14 Sep 1992 19:17
55 lines
2144 bytes
2144 bytes
In article <1992Sep12.174358.11564@colnet.cmhnet.org> res@colnet.cmhnet.org (Rob Stampfli) writes: >I recently had a chance to play around with pgp2.0 on a sVr2 Unix machine. >There appears to be a big security problem with the signature mechanism: >If you "sign" a file, and then add additional information to the end of >the signed file, pgp includes this additional information as part of what >it says you signed. For instance: > >echo 1 2 3 4 5 | pgp -fs >xyzzy.pgp >echo 6 7 8 9 10 >>xyzzy.pgp >pgp xyzzy.pgp > >pgp now tells me I have signed the phrase: > > 1 2 3 4 5 > 6 7 8 9 10 > >when I have in fact only signed the first line. >-- >Rob Stampfli rob@colnet.cmhnet.org The neat thing about standards: >614-864-9377 HAM RADIO: kd8wk@n8jyv.oh There are so many to choose from. The following may be a fix. I haven't tested it extensively, it may very well screw something else up. Mark *** crypto.c.orig Mon Sep 14 10:31:12 1992 --- crypto.c Mon Sep 14 10:31:48 1992 *************** *** 1494,1505 **** } CONVERSION = (lit_mode == MODE_TEXT) ? EXT_CONV : NO_CONV; #ifdef CANONICAL_TEXT ! copyfile(f,g,-1L); /* copy rest of file from file f to g */ #else if (lit_mode == MODE_BINARY) ! copyfile( f, g, -1L ); else ! copyfile_from_canon( f, g, -1L ); #endif CONVERSION = NO_CONV; --- 1494,1505 ---- } CONVERSION = (lit_mode == MODE_TEXT) ? EXT_CONV : NO_CONV; #ifdef CANONICAL_TEXT ! copyfile(f,g,text_len); /* copy rest of file from file f to g */ #else if (lit_mode == MODE_BINARY) ! copyfile( f, g, text_len ); else ! copyfile_from_canon( f, g, text_len ); #endif CONVERSION = NO_CONV;
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Newsgroups: sci.crypt,alt.security Path: arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!darwin.sura.net!spool.mu.edu!umn.edu!csus.edu!netcom.com!henderso From: henderso@netcom.com (Mark Henderson) Subject: Re: pgp2.0 signature security problem Message-ID: <#yynvxl.henderso@netcom.com> Date: Mon, 14 Sep 92 19:17:32 GMT Organization: Netcom References: <1992Sep12.174358.11564@colnet.cmhnet.org> Lines: 55