Coverity spotted me copying an uninitialised variable into it, which
made me wonder how I hadn't noticed. The answer is that nothing
actually _uses_ that variable - it's written, but never read. I must
have put it in during development, thinking I was going to need it for
something, and then didn't end up using it after all.
My experimental build with clang-cl at -Wall did show up a few things
that are safe enough to fix right now. One was this list of missing
includes, which was causing a lot of -Wmissing-prototype warnings, and
is a real risk because it means the declarations in headers weren't
being type-checked against the actual function definitions.
Happily, no actual mismatches.
We already have the ability to start a subprocess and hook it up to a
Socket, for running local proxy commands. Now the same facility is
available as an auxiliary feature, so that a backend can start another
subcommand for a different purpose, and make a separate Socket to
communicate with it.
Just like the local proxy system, this facility captures the
subprocess's stderr, and passes it back to the caller via plug_log. To
make that not look silly, I had to add a system where the "proxy:"
prefix on the usual plug_log messages is reconfigurable, and when you
call platform_start_subprocess(), you get to pass the prefix you want
to use in this case.
I made a specific subdirectory 'stubs' to keep all the link-time stub
modules in, like notiming.c. And I put _one_ run-time stub in it,
namely nullplug.c. But the rest of the runtime stubs went into utils.
I think it's better to keep all the stubs together, so I've moved all
the null*.c in utils into stubs (with the exception of nullstrcmp.c,
which means the 'null' in a different sense). Also, fiddled with the
naming to be a bit more consistent, and stated in the new CMakeLists
the naming policy that distinguishes no-*.c from null-*.c.
This provides a convenient hook to be called between SSH messages, for
the crypto components to do any per-message processing like
incrementing a sequence number.
This patch fixes a few other whitespace and formatting issues which
were pointed out by the bulk-reindent or which I spotted in passing,
some involving manual editing to break lines more nicely.
I think the weirdest hunk in here is the one in windows/window.c
TranslateKey() where _half_ of an assignment statement inside an 'if'
was on the same line as the trailing paren of the if condition. No
idea at all how that one managed to happen!
I think a lot of these were inserted by a prior run through GNU indent
many years ago. I noticed in a more recent experiment that that tool
doesn't always correctly distinguish which instances of 'id * id' are
pointer variable declarations and which are multiplications, so it
spaces some of the former as if they were the latter.
My bulk indentation check also turned up a lot of cases where a run-on
function call or if statement didn't have its later lines aligned
correctly relative to the open paren.
I think this is quite easy to do by getting things out of
sync (editing the first line of the function call and forgetting to
update the rest, perhaps even because you never _saw_ the rest during
a search-replace). But a few didn't quite fit into that pattern, in
particular an outright misleading case in unix/askpass.c where the
second line of a call was aligned neatly below the _wrong_ one of the
open parens on the opening line.
Restored as many alignments as I could easily find.
The test in the Pageant list box code for whether we should display
the bit count of a key was done by checking specifically for ssh_rsa
or ssh_dsa, which of course meant that it didn't catch the certified
versions of those keys.
Now there's yet another footling ssh_keyalg method that asks the
question 'is it worth displaying the bit count?', to which RSA and DSA
answer yes, and the opensshcert family delegates to its base key type,
so that RSA and DSA certified keys also answer yes.
(This isn't the same as ssh_key_public_bits(alg, blob) >= 0. All
supported public key algorithms _can_ display a bit count if called
on. But only in RSA and DSA is it configurable, and therefore worth
bothering to print in the list box.)
Also in this commit, I've fixed a bug in the certificate
implementation of public_bits, which was passing a wrongly formatted
public blob to the underlying key. (Done by factoring out the code
from opensshcert_new_shared which constructed the _correct_ public
blob, and reusing it in public_bits to do the same job.)
The text of the host key warnings was replicated in three places: the
Windows rc file, the GTK dialog setup function, and the console.c
shared between both platforms' CLI tools. Now it lives in just one
place, namely ssh/common.c where the rest of the centralised host-key
checking is done, so it'll be easier to adjust the wording in future.
This comes with some extra automation. Paragraph wrapping is no longer
done by hand in any version of these prompts. (Previously we let GTK
do the wrapping on GTK, but on Windows the resource file contained a
bunch of pre-wrapped LTEXT lines, and console.c had pre-wrapped
terminal messages.) And the dialog heights in Windows are determined
automatically based on the amount of stuff in the window.
The main idea of all this is that it'll be easier to set up more
elaborate kinds of host key prompt that deal with certificates (if,
e.g., a server sends us a certified host key which we don't trust the
CA for). But there are side benefits of this refactoring too: each
tool now reliably inserts its own appname in the prompts, and also, on
Windows the entire prompt text is copy-pastable.
Details of implementation: there's a new type SeatDialogText which
holds a set of (type, string) pairs describing the contents of a
prompt. Type codes distinguish ordinary text paragraphs, paragraphs to
be displayed prominently (like key fingerprints), the extra-bold scary
title at the top of the 'host key changed' version of the dialog, and
the various information that lives in the subsidiary 'more info' box.
ssh/common.c constructs this, and passes it to the Seat to present the
actual prompt.
In order to deal with the different UI for answering the prompt, I've
added an extra Seat method 'prompt_descriptions' which returns some
snippets of text to interpolate into the messages. ssh/common.c calls
that while it's still constructing the text, and incorporates the
resulting snippets into the SeatDialogText.
For the moment, this refactoring only affects the host key prompts.
The warnings about outmoded crypto are still done the old-fashioned
way; they probably ought to be similarly refactored to use this new
SeatDialogText system, but it's not immediately critical for the
purpose I have right now.
Partly, this just seems more sensible, since it may well vary per
platform beyond the ability of intorptr to specify. But more
immediately it means the definition of the HELPCTX macro doesn't have
to use the P() function from dialog.h, which isn't defined in any
circumstances outside the config subsystem. And I'm about to want to
put a help context well outside that subsystem.
This replaces the previous placeholder scheme of having a list of
hostname wildcards with implicit logical-OR semantics (if any wildcard
matched then the certificate would be trusted to sign for that host).
That scheme didn't allow for exceptions within a domain ('everything
in example.com except extra-high-security-machine.example.com'), and
also had no way to specify port numbers.
In the new system, you can still write a hostname wildcard by itself
in the simple case, but now those are just atomic subexpressions in a
boolean-logic domain-specific language I've made up. So if you want
multiple wildcards, you can separate them with || in a single longer
expression, and also you can use && and ! to impose exceptions on top
of that.
Full details of the expression language are in the comment at the top
of utils/cert-expr.c. It'll need documenting properly before release,
of course.
For the sake of backwards compatibility for early adopters who've
already set up configuration in the old system, I've put in some code
that will read the old MatchHosts configuration and automatically
translate it into the equivalent boolean expression (by simply
stringing together the list of wildcards with || between them).
These make a good storage format for mostly-textual data in
configuration, if it can't afford to reserve any character as a
delimiter. Assuming very few characters need to be escaped, the space
cost is lower than base64, and also you can read it by eye.
ptrlen_contains and ptrlen_contains_only are useful for checking that
a string is composed entirely of certain characters, or avoids them.
ptrlen_end makes a pointer to the byte just past the end of the
specified string. And it can be used with make_ptrlen_startend, which
makes a ptrlen out of two pointers instead of a pointer and a length.
Instead of maintaining a single sparse table mapping Unicode to the
currently selected code page, we now maintain a collection of such
tables mapping Unicode to any code page we've so far found a need to
work with, and we add code pages to that list as necessary, and never
throw them away (since there are a limited number of them).
This means that the wc_to_mb family of functions are effectively
stateless: they no longer depend on a 'struct unicode_data'
corresponding to the current terminal settings. So I've removed that
parameter from all of them.
This fills in the missing piece of yesterday's commit a216d86106:
now wc_to_mb too should be able to handle internally-implemented
character sets, by hastily making their reverse mapping table if it
doesn't already have it.
(That was only a _latent_ bug, because the only use of wc_to_mb in the
cross-platform or Windows code _did_ want to convert to the currently
selected code page, so the old strategy worked in that case. But there
was no protection against an unworkable use of it being added later.)
When the user provides a password on the PuTTY command line, via -pw
or -pwfile, the flag 'tried_once' inside cmdline_get_passwd_input() is
intended to arrange that we only try sending that password once, and
after we've sent it, we don't try again.
But this plays badly with the 'Restart Session' operation. If the
connection is lost and then restarted at user request, we _do_ want to
send that password again!
So this commit moves that static variable out into a small state
structure held by the client of cmdline_get_passwd_input. Each client
can decide how to manage that state itself.
Clients that support 'Restart Session' - i.e. just GUI PuTTY itself -
will initialise the state at the same time as instantiating the
backend, so that every time the session is restarted, we return
to (correctly) believing that we _haven't_ yet tried the password
provided on the command line.
But clients that don't support 'Restart Session' - i.e. Plink and file
transfer tools - can do the same thing that cmdline.c was doing
before: just keep the state in a static variable.
This also means that the GUI login tools will now retain the
command-line password in memory, whereas previously they'd have wiped
it out once it was used. But the other tools will still wipe and free
the password, because I've also added a 'bool restartable' flag to
cmdline_get_passwd_input to let it know when it _is_ allowed to do
that.
In the GUI tools, I don't see any way to get round that, because if
the session is restarted you _have_ to still have the password to use
again. (And you can't infer that that will never happen from the
CONF_close_on_exit setting, because that too could be changed in
mid-session.) On the other hand, I think it's not all that worrying,
because the use of either -pw or -pwfile means that a persistent copy
of your password is *already* stored somewhere, so another one isn't
too big a stretch.
(Due to the change of -pw policy in 0.77, the effect of this bug was
that an attempt to reconnect in a session set up this way would lead
to "Configured password was not accepted". In 0.76, the failure mode
was different: PuTTY would interactively prompt for the password,
having wiped it out of memory after it was used the first time round.)
Various alignments I want to do in the host CA box have shown up
deficiencies in this system, so I've reworked it a bit.
Firstly, you can now specify more than two controls to be tied
together with an align_next_to (e.g. multiple checkboxes alongside
something else).
Secondly, as well as forcing the controls to be the same height as
each other, the layout algorithm will also move the later controls
further _downward_, so that their top y positions also line up. Until
now that hasn't been necessary, because they lined up already.
In the GTK implementation of this via the Columns class, I've renamed
'columns_force_same_height' to 'columns_align_next_to', and similarly
for some of the internal fields, since the latter change makes the
previous names a misnomer.
In the Windows implementation, I found it most convenient to set this
up by following a linked list of align_next_to fields backwards. But
it won't always be convenient to initialise them that way, so I've
also written a crude normaliser that will rewrite those links into a
canonical form. But I only call that on Windows; it's unnecessary in
GTK, where the Columns class provides plenty of per-widget extra
storage so I just keep each alignment class as a circular list.
As distinct from the type of signature generated by the SSH server
itself from the host key, this lets you exclude (and by default does
exclude) the old "ssh-rsa" SHA-1 signature type from the signature of
the CA on the certificate.
This will allow the central host_ca_new function to pre-populate the
structure with default values for the fields, so that once I add more
options to CA configuration they can take their default values when
loading a saved record from a previous PuTTY version.
Now we offer the OpenSSH certificate key types in our KEXINIT host key
algorithm list, so that if the server has a certificate, they can send
it to us.
There's a new storage.h abstraction for representing a list of trusted
host CAs, and which ones are trusted to certify hosts for what
domains. This is stored outside the normal saved session data, because
the whole point of host certificates is to avoid per-host faffing.
Configuring this set of trusted CAs is done via a new GUI dialog box,
separate from the main PuTTY config box (because it modifies a single
set of settings across all saved sessions), which you can launch by
clicking a button in the 'Host keys' pane. The GUI is pretty crude for
the moment, and very much at a 'just about usable' stage right now. It
will want some polishing.
If we have no CA configured that matches the hostname, we don't offer
to receive certified host keys in the first place. So for existing
users who haven't set any of this up yet, nothing will immediately
change.
Currently, if we do offer to receive certified host keys and the
server presents one signed by a CA we don't trust, PuTTY will bomb out
unconditionally with an error, instead of offering a confirmation box.
That's an unfinished part which I plan to fix before this goes into a
release.
Certificate keys don't work the same as normal keys, so the rest of
the code is going to have to pay attention to whether a key is a
certificate, and if so, treat it differently and do cert-specific
stuff to it. So here's a collection of methods for that purpose.
With one exception, these methods of ssh_key are not expected to be
implemented at all in non-certificate key types: they should only ever
be called once you already know you're dealing with a certificate. So
most of the new method pointers can be left out of the ssh_keyalg
initialisers.
The exception is the base_key method, which retrieves the base key of
a certificate - the underlying one with the certificate stripped off.
It's convenient for non-certificate keys to implement this too, and
just return a pointer to themselves. So I've added an implementation
in nullkey.c doing that. (The returned pointer doesn't transfer
ownership; you have to use the new ssh_key_clone() if you want to keep
the base key after freeing the certificate key.)
The methods _only_ implemented in certificates:
Query methods to return the public key of the CA (for looking up in a
list of trusted ones), and to return the key id string (which exists
to be written into log files).
Obviously, we need a check_cert() method which will verify the CA's
actual signature, not to mention checking all the other details like
the principal and the validity period.
And there's another fiddly method for dealing with the RSA upgrade
system, called 'related_alg'. This is quite like alternate_ssh_id, in
that its job is to upgrade one key algorithm to a related one with
more modern RSA signing flags (or any other similar thing that might
later reuse the same mechanism). But where alternate_ssh_id took the
actual signing flags as an argument, this takes a pointer to the
upgraded base algorithm. So it answers the question "What is to this
key algorithm as you are to its base?" - if you call it on
opensshcert_ssh_rsa and give it ssh_rsa_sha512, it'll give you back
opensshcert_ssh_rsa_sha512.
(It's awkward to have to have another of these fiddly methods, and in
the longer term I'd like to try to clean up their proliferation a bit.
But I even more dislike the alternative of just going through
all_keyalgs looking for a cert algorithm with, say, ssh_rsa_sha512 as
the base: that approach would work fine now but it would be a lurking
time bomb for when all the -cert-v02@ methods appear one day. This
way, each certificate type can upgrade itself to the appropriately
related version. And at least related_alg is only needed if you _are_
a certificate key type - it's not adding yet another piece of
null-method boilerplate to the rest.)
The low-level functions to handle a single atom of base64 at a time
have been in 'utils' / misc.h for ages, but the higher-level family of
base64_encode functions that handle a whole data block were hidden
away in sshpubk.c, and there was no higher-level decode function at
all.
Now moved both into 'utils' modules and declared them in misc.h rather
than ssh.h. Also, improved the APIs: they all take ptrlen in place of
separate data and length arguments, their naming is more consistent
and more explicit (the previous base64_encode which didn't name its
destination is now base64_encode_fp), and the encode functions now
accept cpl == 0 as a special case meaning that the output base64 data
is wanted in the form of an unbroken single-line string with no
trailing \n.
This makes a second independent copy of an existing ssh_key, for
situations where one piece of code is going to want to keep it after
its current owner frees it.
In order to have it work on an arbitrary ssh_key, whether public-only
or a full public+private key pair, I've had to add an ssh_key query
method to ask whether a private key is known. I'm surprised I haven't
found a need for that before! But I suppose in most situations in an
SSH client you statically know which kind of key you're dealing with.
In this commit, I provide further functions which generate the
existing set of data types:
- key_components_add_text_pl() adds a text component, but takes a
ptrlen rather than a const char *, in case that was what you
happened to have already.
- key_components_add_uint() ends up adding an mp_int to the
structure, but takes it as input in the form of an ordinary C
integer, for the convenience of call sites which will want to do
that a lot and don't enjoy repeating the mp_int construction
boilerplate
- key_components_add_copy() takes a pointer to one of the
key_component sub-structs in an existing key_components, and copies
it into the output key_components under a new name, handling
whatever type it turns out to have.
This stores its data in the same format as the existing KCT_TEXT, but
it displays differently in puttygen --dump, expecting that the data
will be full of horrible control characters, invalid UTF-8, etc.
The displayed data is of the form b64("..."), so you get a hint about
what the encoding is, and can still paste into Python by defining the
identifier 'b64' to be base64.b64decode or equivalent.
Having recently pulled it out into its own file, I think it could also
do with a bit of tidying. In this rework:
- the substructure for a single component now has a globally visible
struct tag, so you can make a variable pointing at it, saving
verbiage in every piece of code looping over a key_components
- the 'is_mp_int' flag has been replaced with a type enum, so that
more types can be added without further upheaval
- the printing loop in cmdgen.c for puttygen --dump has factored out
the initial 'name=' prefix on each line so that it isn't repeated
per component type
- the storage format for text components is now a strbuf rather than
a plain char *, which I think is generally more useful.
Previously, the fact that "ssh-rsa" sometimes comes with two subtypes
"rsa-sha2-256" and "rsa-sha2-512" was known to three different parts
of the code - two in userauth and one in transport. Now the knowledge
of what those ids are, which one goes with which signing flags, and
which key types have subtypes at all, is centralised into a method of
the key algorithm, and all those locations just query it.
This will enable the introduction of further key algorithms that have
a parallel upgrade system.
It's a class method rather than an object method, so it doesn't allow
keys with the same algorithm to make different choices about what
flags they support. But that's not what I wanted it for: the real
purpose is to allow one key algorithm to delegate supported_flags to
another, by having its method implementation call the one from the
delegate class.
(If only C's compile/link model permitted me to initialise a field of
one global const struct variable to be a copy of that of another, I
wouldn't need the runtime overhead of this method! But object file
formats don't let you even specify that.)
Most key algorithms support no flags at all, so they all want to use
the same implementation of this method. So I've started a file of
stubs utils/nullkey.c to contain the common stub version.
If you already have a string (of potentially-binary data) in the form
of a ptrlen reference to somewhere else, and you want to keep a copy
somewhere, it's useful to copy it into a strbuf. But it takes a couple
of lines of faff to do that, and it's nicer to wrap that up into a
tiny helper function.
This commit adds that helper function strbuf_dup, and its non-movable
sibling strbuf_dup_nm for secret data. Also, gone through the existing
code and found a bunch of cases where this makes things less verbose.
We call setlocale() at the start of the function to get the current
LC_CTYPE locale, then set it to what we need during the function, and
then call setlocale() at the end to put it back again. But the middle
call is allowed to invalidate the pointer returned from the first, so
we have to save it in our own allocated storage until the end of the
function.
This bit me during development just now, and I was surprised that it
hadn't come up before! But I suppose this is one of those things
that's only _allowed_ to fail, and need not in all circumstances -
perhaps it depends on what your LC_CTYPE was set to before.
bool is dangerous in a time-safe context, because C compilers might
insert a control flow divergence to implement the implicit
normalisation of nonzero integers to 1 when you assign to a bool.
Everywhere else time-safe, I avoid using it; but smemeq has been an
exception until now, because the response to smemeq returning failure
was to do an obvious protocol-level divergence _anyway_ (like
disconnecting due to MAC mismatch).
But I'm about to want to use smemeq in a context where I use the
result _subtly_ and don't want to give away what it is, so now it's
time to get rid of that bool and have smemeq return unsigned.
They're pretty much self-contained, and don't really need to be in the
same module as sshpubk.c (which has other dependencies). Move them out
into a utils module, where pulling them in won't pull in anything else
unwanted.
Visual Studio 2022 is out, and 2019 has added a couple more version
numbers while I wasn't looking.
Also, the main web page that lists the version number mappings now
documents the wrinkle where you sometimes have to disambiguate via
_MSC_FULL_VER (and indeed has added another such case for 16.11), so I
no longer have to link to some unofficial blog post in the comment
explaining that.
(*Also*, if _MSC_FULL_VER is worth checking, then it's worth putting
in the build info!)
All the seat functions that request an interactive prompt of some kind
to the user - both the main seat_get_userpass_input and the various
confirmation dialogs for things like host keys - were using a simple
int return value, with the general semantics of 0 = "fail", 1 =
"proceed" (and in the case of seat_get_userpass_input, answers to the
prompts were provided), and -1 = "request in progress, wait for a
callback".
In this commit I change all those functions' return types to a new
struct called SeatPromptResult, whose primary field is an enum
replacing those simple integer values.
The main purpose is that the enum has not three but _four_ values: the
"fail" result has been split into 'user abort' and 'software abort'.
The distinction is that a user abort occurs as a result of an
interactive UI action, such as the user clicking 'cancel' in a dialog
box or hitting ^D or ^C at a terminal password prompt - and therefore,
there's no need to display an error message telling the user that the
interactive operation has failed, because the user already knows,
because they _did_ it. 'Software abort' is from any other cause, where
PuTTY is the first to know there was a problem, and has to tell the
user.
We already had this 'user abort' vs 'software abort' distinction in
other parts of the code - the SSH backend has separate termination
functions which protocol layers can call. But we assumed that any
failure from an interactive prompt request fell into the 'user abort'
category, which is not true. A couple of examples: if you configure a
host key fingerprint in your saved session via the SSH > Host keys
pane, and the server presents a host key that doesn't match it, then
verify_ssh_host_key would report that the user had aborted the
connection, and feel no need to tell the user what had gone wrong!
Similarly, if a password provided on the command line was not
accepted, then (after I fixed the semantics of that in the previous
commit) the same wrong handling would occur.
So now, those Seat prompt functions too can communicate whether the
user or the software originated a connection abort. And in the latter
case, we also provide an error message to present to the user. Result:
in those two example cases (and others), error messages should no
longer go missing.
Implementation note: to avoid the hassle of having the error message
in a SeatPromptResult being a dynamically allocated string (and hence,
every recipient of one must always check whether it's non-NULL and
free it on every exit path, plus being careful about copying the
struct around), I've instead arranged that the structure contains a
function pointer and a couple of parameters, so that the string form
of the message can be constructed on demand. That way, the only users
who need to free it are the ones who actually _asked_ for it in the
first place, which is a much smaller set.
(This is one of the rare occasions that I regret not having C++'s
extra features available in this code base - a unique_ptr or
shared_ptr to a string would have been just the thing here, and the
compiler would have done all the hard work for me of remembering where
to insert the frees!)
Now it's done using the same code as in write_c_string_literal(), by
means of factoring the latter into a version that targets any old
BinarySink and a convenience wrapper taking a FILE *.
At some point while setting up the utils subdirectory, I apparently
only got half way through renaming miscucs.c to dup_mb_to_wc.c: I
created the new copy of the file, but I didn't delete the old one, I
didn't mention it in utils/CMakeLists.txt, and I didn't change the
comment at the top.
Now done all three, so we now have just one copy of this utility
module.
While I'm in the mood for cleaning up the top-level directory here:
all the 'nostuff.c' files have moved into a new 'stubs' directory, and
I broke up be_misc.c into smaller modules that can live in 'utils'.
Spotted this in passing while I was adding new functions in the same
area. That 'struct strbuf;' must have been there since before I
introduced defs.h to predeclare all the structure tag names and their
typedefs. But marshal.h includes defs.h itself, so it has no reason to
worry about the possibility that the typedef 'strbuf' might not
already exist.
