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Key rollover: rewrite the PGP keys manual appendix.

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This gives pride of place to the new set of keys we've recently
generated, and relegates the old ones to an afterthought.

(cherry picked from commit bb68baf53bacfc71bb0144780cf0b2b63bd76f98)
This commit is contained in:
Simon Tatham 2015-09-02 18:24:39 +01:00
parent eb319f9b6e
commit a063e52297
2 changed files with 131 additions and 76 deletions
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5
doc/index.but
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@ -843,8 +843,9 @@ saved sessions from
\IM{version of PuTTY} version, of PuTTY
\IM{PGP signatures} PGP signatures, of PuTTY binaries
\IM{PGP signatures} signatures, of PuTTY binaries
\IM{GPG signatures} PGP signatures, of PuTTY binaries
\IM{GPG signatures} GPG signatures, of PuTTY binaries
\IM{GPG signatures} signatures, of PuTTY binaries
\IM{logical host name} logical host name
\IM{logical host name} host name, logical

202
doc/pgpkeys.but
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@ -2,7 +2,7 @@
\cfg{winhelp-topic}{pgpfingerprints}
\I{verifying new versions}We create \i{PGP signatures} for all the PuTTY
\I{verifying new versions}We create \i{GPG signatures} for all the PuTTY
files distributed from our web site, so that users can be confident
that the files have not been tampered with. Here we identify
our public keys, and explain our signature policy so you can have an
@ -22,40 +22,49 @@ the origin of files distributed by the PuTTY team.)
\H{pgpkeys-pubkey} Public keys
We supply two complete sets of keys. We supply a set of RSA keys,
compatible with both \W{http://www.gnupg.org/}{GnuPG} and PGP2,
and also a set of DSA keys compatible with GnuPG.
We maintain a set of three keys, stored with different levels of
security due to being used in different ways. See \k{pgpkeys-security}
below for details.
In each format, we have three keys:
The three keys we provide are:
\b A Development Snapshots key, used to sign the nightly builds.
\dt Snapshot Key
\b A Releases key, used to sign actual releases.
\dd Used to sign routine development builds of PuTTY: nightly
snapshots, pre-releases, and sometimes also custom diagnostic builds
we send to particular users.
\b A Master Key. The Master Key is used to sign the other two keys, and
they sign it in return.
\dt Release Key
Therefore, we have six public keys in total:
\dd Used to sign manually released versions of PuTTY.
\b RSA:
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-rsa.asc}{Master Key},
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-rsa.asc}{Release key},
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-rsa.asc}{Snapshot key}
\dt Master Key
\lcont{
Master Key: 1024-bit; \I{PGP key fingerprint}fingerprint:
\cw{8F\_15\_97\_DA\_25\_30\_AB\_0D\_\_88\_D1\_92\_54\_11\_CF\_0C\_4C}
}
\dd Used to tie the other two keys into the GPG web of trust. The
Master Key signs the other two keys, and other GPG users have signed
it in turn.
\b DSA:
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-dsa.asc}{Master Key},
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-dsa.asc}{Release key},
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-dsa.asc}{Snapshot key}
The current issue of those three keys are available for download from
the PuTTY website, and are also available on PGP keyservers using the
key IDs listed below.
\lcont{
Master Key: 1024-bit; fingerprint:
\cw{313C\_3E76\_4B74\_C2C5\_F2AE\_\_83A8\_4F5E\_6DF5\_6A93\_B34E}
}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-2015.asc}{\s{Master Key}}
\dd RSA, 4096-bit. Key ID: \cw{4096R/04676F7C} (long version:
\cw{4096R/AB585DC604676F7C}). Fingerprint:
\cw{440D\_E3B5\_B7A1\_CA85\_B3CC\_\_1718\_AB58\_5DC6\_0467\_6F7C}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-2015.asc}{\s{Release Key}}
\dd RSA, 2048-bit. Key ID: \cw{2048R/B43434E4} (long version:
\cw{2048R/9DFE2648B43434E4}). Fingerprint:
\cw{0054\_DDAA\_8ADA\_15D2\_768A\_\_6DE7\_9DFE\_2648\_B434\_34E4}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-2015.asc}{\s{Snapshot Key}}
\dd RSA, 2048-bit. Key ID: \cw{2048R/D15F7E8A} (long version:
\cw{2048R/EEF20295D15F7E8A}). Fingerprint:
\cw{0A3B\_0048\_FE49\_9B67\_A234\_\_FEB6\_EEF2\_0295\_D15F\_7E8A}
\H{pgpkeys-security} Security details
@ -63,77 +72,122 @@ The various keys have various different security levels. This
section explains what those security levels are, and how far you can
expect to trust each key.
\S{pgpkeys-snapshot} The Development Snapshots keys
\S{pgpkeys-snapshot} The Development Snapshots key
These keys are stored \e{without passphrases}. This is
necessary, because the snapshots are generated every night without
human intervention, so nobody would be able to type a passphrase.
The Development Snapshots private key is stored \e{without a
passphrase}. This is necessary, because the snapshots are generated
every night without human intervention, so nobody would be able to
type a passphrase.
The actual snapshots are built on a team member's home Windows box.
The keys themselves are stored on an independently run Unix box
(the same one that hosts our Git repository). After
being built, the binaries are uploaded to this Unix box and then
signed automatically.
The snapshots are built and signed on a team member's home computers,
before being uploaded to the web server from which you download them.
Therefore, a signature from one of the Development Snapshots keys
\e{DOES} protect you against:
Therefore, a signature from the Development Snapshots key \e{DOES}
protect you against:
\b People tampering with the PuTTY binaries between the PuTTY web site
and you.
\b The maintainers of our web server attempting to abuse their root
privilege to tamper with the binaries.
But it \e{DOES NOT} protect you against:
\b People tampering with the binaries before they are uploaded to the
independent Unix box.
\b People tampering with the binaries before they are uploaded to our
download servers.
\b The sysadmin of the independent Unix box using his root privilege to
steal the private keys and abuse them, or tampering with the
binaries before they are signed.
\b People tampering with the build machines so that the next set of
binaries they build will be malicious in some way.
\b Somebody getting root on the Unix box.
\b People stealing the unencrypted private key from the build machine
it lives on.
Of course, we don't believe any of those things is very likely. We
know our sysadmin personally and trust him (both to be competent and
to be non-malicious), and we take all reasonable precautions to
guard the build machine. But when you see a signature, you should
always be certain of precisely what it guarantees and precisely what
it does not.
Of course, we take all reasonable precautions to guard the build
machines. But when you see a signature, you should always be certain
of precisely what it guarantees and precisely what it does not.
\S{pgpkeys-release} The Releases keys
\S{pgpkeys-release} The Releases key
The Release keys have passphrases and we can be more careful about
how we use them.
The Releases key is more secure: because it is only used at release
time, to sign each release by hand, we can store it encrypted.
The Release keys are kept safe on the developers' own local
machines, and only used to sign releases that have been built by
hand. A signature from a Release key protects you from almost any
plausible attack.
(Some of the developers' machines have cable modem connections and
might in theory be crackable, but of course the private keys are
still encrypted, so the crack would have to go unnoticed for long
enough to steal a passphrase.)
The Releases private key is kept encrypted on the developers' own
local machines. So an attacker wanting to steal it would have to also
steal the passphrase.
\S{pgpkeys-master} The Master Keys
The Master Keys sign almost nothing. Their purpose is to bind the
other keys together and certify that they are all owned by the same
people and part of the same integrated setup. The only signatures
produced by the Master Keys, \e{ever}, should be the signatures
on the other keys.
The Master Key signs almost nothing. Its purpose is to bind the other
keys together and certify that they are all owned by the same people
and part of the same integrated setup. The only signatures produced by
the Master Key, \e{ever}, should be the signatures on the other keys.
We intend to arrange for the Master Keys to sign each other, to
certify that the DSA keys and RSA keys are part of the same setup.
We have not yet got round to this at the time of writing.
The Master Key is especially long, and its private key and passphrase
are stored with special care.
We have collected a few third-party signatures on the Master Keys,
in order to increase the chances that you can find a suitable trust
path to them. We intend to collect more. (Note that the keys on the
keyservers appear to have also collected some signatures from people
who haven't performed any verification of the Master Keys.)
We have collected some third-party signatures on the Master Key, in
order to increase the chances that you can find a suitable trust path
to them.
We have uploaded our various keys to public keyservers, so that
even if you don't know any of the people who have signed our
keys, you can still be reasonably confident that an attacker would
find it hard to substitute fake keys on all the public keyservers at
once.
\H{pgpkeys-rollover} Key rollover
Our current three keys were generated in September 2015. Prior to
that, we had a much older set of keys generated in 2000. For each of
the three key types above, we provided both an RSA key \e{and} a DSA
key (because at the time we generated them, RSA was not in practice
available to everyone, due to export restrictions).
The new Master Key is signed with both of the old ones, to show that
it really is owned by the same people and not substituted by an
attacker. Also, we have retrospectively signed the old Release Keys
with the new Master Key, in case you're trying to verify the
signatures on a release prior to the rollover and can find a chain of
trust to those keys from any of the people who have signed our new
Master Key.
Future releases will be signed with the up-to-date keys shown above.
Releases prior to the rollover are signed with the old Release Keys.
For completeness, those old keys are given here:
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-rsa.asc}{\s{Master Key} (original RSA)}
\dd RSA, 1024-bit. Key ID: \cw{1024R/1E34AC41} (long version:
\cw{1024R/9D5877BF1E34AC41}). Fingerprint:
\cw{8F\_15\_97\_DA\_25\_30\_AB\_0D\_\_88\_D1\_92\_54\_11\_CF\_0C\_4C}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-rsa.asc}{\s{Master Key} (original DSA)}
\dd DSA, 1024-bit. Key ID: \cw{1024D/6A93B34E} (long version:
\cw{1024D/4F5E6DF56A93B34E}). Fingerprint:
\cw{313C\_3E76\_4B74\_C2C5\_F2AE\_\_83A8\_4F5E\_6DF5\_6A93\_B34E}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-rsa.asc}{\s{Release Key} (original RSA)}
\dd RSA, 1024-bit. Key ID: \cw{1024R/B41CAE29} (long version:
\cw{1024R/EF39CCC0B41CAE29}). Fingerprint:
\cw{AE\_65\_D3\_F7\_85\_D3\_18\_E0\_\_3B\_0C\_9B\_02\_FF\_3A\_81\_FE}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-rsa.asc}{\s{Release Key} (original DSA)}
\dd DSA, 1024-bit. Key ID: \cw{1024D/08B0A90B} (long version:
\cw{1024D/FECD6F3F08B0A90B}). Fingerprint:
\cw{00B1\_1009\_38E6\_9800\_6518\_\_F0AB\_FECD\_6F3F\_08B0\_A90B}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-rsa.asc}{\s{Snapshot Key} (original RSA)}
\dd RSA, 1024-bit. Key ID: \cw{1024R/32B903A9} (long version:
\cw{1024R/FAAED21532B903A9}). Fingerprint:
\cw{86\_8B\_1F\_79\_9C\_F4\_7F\_BD\_\_8B\_1B\_D7\_8E\_C6\_4E\_4C\_03}
\dt \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-rsa.asc}{\s{Snapshot Key} (original DSA)}
\dd DSA, 1024-bit. Key ID: \cw{1024D/7D3E4A00} (long version:
\cw{1024D/165E56F77D3E4A00}). Fingerprint:
\cw{63DD\_8EF8\_32F5\_D777\_9FF0\_\_2947\_165E\_56F7\_7D3E\_4A00}