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182 lines
4.4 KiB
Plaintext
182 lines
4.4 KiB
Plaintext
A Hacker's Guide to GNUPG
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================================
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(Some notes on GNUPG internals.)
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===> Under construction <=======
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CVS Access
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==========
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Anonymous read-only CVS access is available:
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cvs -z6 -d :pserver:anonymous@ftp.guug.de:/home/koch/cvs login
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use the password "anonymous". To check out the the complete
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archive use:
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cvs -z6 -d :pserver:anonymous@ftp.guug.de:/home/koch/cvs checkout gnupg
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This service is provided to help you in hunting bugs and not to deliver
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stable snapshots; it may happen that it even does not compile, so please
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don't complain. CVS may put a high load on a server, so please don't poll
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poll for new updates but wait for an announcement; to receive this you may
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want to subscribe to:
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gnupg-commit-watchers@isil.d.shuttle.de
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by sending a mail with "subscribe" in the body to
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gnupg-commit-watchers-request@isil.d.shuttle.de
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Please run scripts/autogen.sh to create some required files.
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RFCs
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====
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1423 Privacy Enhancement for Internet Electronic Mail:
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Part III: Algorithms, Modes, and Identifiers.
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1489 Registration of a Cyrillic Character Set.
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1750 Randomness Recommendations for Security.
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1991 PGP Message Exchange Formats.
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2015 MIME Security with Pretty Good Privacy (PGP).
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2144 The CAST-128 Encryption Algorithm.
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2279 UTF-8, a transformation format of ISO 10646.
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2440 OpenPGP.
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Debug Flags
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-----------
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Use the option "--debug n" to output debug information. This option
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can be used multiple times, all values are ORed; n maybe prefixed with
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0x to use hex-values.
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value used for
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----- ----------------------------------------------
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1 packet reading/writing
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2 MPI details
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4 ciphers and primes (may reveal sensitive data)
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8 iobuf filter functions
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16 iobuf stuff
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32 memory allocation stuff
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64 caching
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128 show memory statistics at exit
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256 trust verification stuff
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Directory Layout
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----------------
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./ Readme, configure
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./scripts Scripts needed by configure and others
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./doc Documentation
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./util General purpose utility function
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./mpi Multi precision integer library
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./cipher Cryptographic functions
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./g10 GnuPG application
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./tools Some helper and demo programs
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./keybox The keybox library
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./gcrypt Stuff needed to build libgcrypt
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Memory allocation
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-----------------
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Use only the functions:
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m_alloc()
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m_alloc_clear()
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m_strdup()
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m_free()
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If you want to store a passphrase or some other sensitive data you may
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want to use m_alloc_secure() instead of m_alloc(), as this puts the data
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into a memory region which is protected from swapping (on some platforms).
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m_free() works for both. This functions will not return if there is not
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enough memory available.
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Logging
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-------
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Option parsing
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---------------
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GNUPG does not use getopt or GNU getopt but functions of it's own. See
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util/argparse.c for details. The advantage of these functions is that
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it is more easy to display and maintain the help texts for the options.
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The same option table is also used to parse resource files.
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What is an iobuf
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----------------
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This is the data structure used for most I/O of gnupg. It is similar
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to System V Streams but much simpler. It should be replaced by a cleaner
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and faster implementation. We are doing to much copying and the semantics
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of "filter" removing are not very clean. EOF handling is also a problem.
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How to use the message digest functions
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---------------------------------------
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cipher/md.c implements an interface to hash (message digest functions).
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a) If you have a common part of data and some variable parts
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and you need to hash of the concatenated parts, you can use this:
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md = md_open(...)
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md_write( md, common_part )
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md1 = md_copy( md )
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md_write(md1, part1)
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md_final(md1);
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digest1 = md_read(md1)
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md2 = md_copy( md )
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md_write(md2, part2)
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md_final(md2);
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digest2 = md_read(md2)
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An example are key signatures; the key packet is the common part
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and the user-id packets are the variable parts.
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b) If you need a running digest you should use this:
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md = md_open(...)
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md_write( md, part1 )
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digest_of_part1 = md_digest( md );
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md_write( md, part2 )
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digest_of_part1_cat_part2 = md_digest( md );
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....
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Both methods may be combined. [Please see the source for the real syntax]
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How to use the cipher functions
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-------------------------------
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How to use the public key functions
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-----------------------------------
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