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author | Zack Weinberg <zackw@panix.com> | 2018-06-29 16:53:37 +0200 |
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committer | Florian Weimer <fweimer@redhat.com> | 2018-06-29 16:53:37 +0200 |
commit | 841785bad14dfad81a0af94900310141c59f26a4 (patch) | |
tree | 9fba8a7c16596dcb9652576f9322c810eb0cf682 /ChangeLog | |
parent | 6ab902e4decd89c1a9206497d14ddba7680bfc37 (diff) | |
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manual: Revise crypt.texi.
This is a major rewrite of the description of 'crypt', 'getentropy',
and 'getrandom'.
A few highlights of the content changes:
- Throughout the manual, public headers, and user-visible messages,
I replaced the term "password" with "passphrase", the term
"password database" with "user database", and the term
"encrypt(ion)" with "(one-way) hashing" whenever it was applied to
passphrases. I didn't bother making this change in internal code
or tests. The use of the term "password" in ruserpass.c survives,
because that refers to a keyword in netrc files, but it is adjusted
to make this clearer.
There is a note in crypt.texi explaining that they were
traditionally called passwords but single words are not good enough
anymore, and a note in users.texi explaining that actual passphrase
hashes are found in a "shadow" database nowadays.
- There is a new short introduction to the "Cryptographic Functions"
section, explaining how we do not intend to be a general-purpose
cryptography library, and cautioning that there _are_, or have
been, legal restrictions on the use of cryptography in many
countries, without getting into any kind of detail that we can't
promise to keep up to date.
- I added more detail about what a "one-way function" is, and why
they are used to obscure passphrases for storage. I removed the
paragraph saying that systems not connected to a network need no
user authentication, because that's a pretty rare situation
nowadays. (It still says "sometimes it is necessary" to
authenticate the user, though.)
- I added documentation for all of the hash functions that glibc
actually supports, but not for the additional hash functions
supported by libxcrypt. If we're going to keep this manual section
around after the transition is more advanced, it would probably
make sense to add them then.
- There is much more detailed discussion of how to generate a salt,
and the failure behavior for crypt is documented. (Returning an
invalid hash on failure is what libxcrypt does; Solar Designer's
notes say that this was done "for compatibility with old programs
that assume crypt can never fail".)
- As far as I can tell, the header 'crypt.h' is entirely a GNU
invention, and never existed on any other Unix lineage. The
function 'crypt', however, was in Issue 1 of the SVID and is now
in the XSI component of POSIX. I tried to make all of the
@standards annotations consistent with this, but I'm not sure I got
them perfectly right.
- The genpass.c example has been improved to use getentropy instead
of the current time to generate the salt, and to use a SHA-256 hash
instead of MD5. It uses more random bytes than is strictly
necessary because I didn't want to complicate the code with proper
base64 encoding.
- The testpass.c example has three hardwired hashes now, to
demonstrate that different one-way functions produce different
hashes for the same input. It also demonstrates how DES hashing
only pays attention to the first eight characters of the input.
- There is new text explaining in more detail how a CSPRNG differs
from a regular random number generator, and how
getentropy/getrandom are not exactly a CSPRNG. I tried not to make
specific falsifiable claims here. I also tried to make the
blocking/cancellation/error behavior of both getentropy and
getrandom clearer.
Diffstat (limited to 'ChangeLog')
-rw-r--r-- | ChangeLog | 26 |
1 files changed, 26 insertions, 0 deletions
@@ -1,5 +1,31 @@ 2018-06-29 Zack Weinberg <zackw@panix.com> + * crypt/crypt.h, posix/unistd.h: Update comments and + prototypes for crypt and crypt_r. + + * manual/crypt.texi (Cryptographic Functions): New initial + exposition. + (crypt): Section renamed to 'Passphrase Storage'. Full rewrite. + (Unpredictable Bytes): Improve initial exposition. Clarify error + behavior of getentropy and getrandom. + * manual/examples/genpass.c: Generate a salt using getentropy + instead of the current time. Use hash $5$ (SHA-2-256). + * manual/examples/testpass.c: Demonstrate validation against + hashes generated with three different one-way functions. + + * manual/intro.texi: crypt.texi does not need an overview + anymore. + + * manual/nss.texi, manual/memory.texi, manual/socket.texi + * manual/terminal.texi: Consistently refer to "passphrases" + * instead of "passwords", and to the "user database" instead + * of the "password database". + * manual/users.texi: Similarly. Add notes about how actual + passphrase hashes are now stored in the shadow database. + Remove 20-year-old junk todo note. + +2018-06-29 Zack Weinberg <zackw@panix.com> + * manual/crypt.texi: Use a normal top-level @node declaration. Move most of the introductory text to the 'crypt' section. Move the example programs below the @deftypefun for 'crypt_r'. |