NAR info files in binary caches can now have a cryptographic signature
that Nix will verify before using the corresponding NAR file.
To create a private/public key pair for signing and verifying a binary
cache, do:
$ openssl genrsa -out ./cache-key.sec 2048
$ openssl rsa -in ./cache-key.sec -pubout > ./cache-key.pub
You should also come up with a symbolic name for the key, such as
"cache.example.org-1". This will be used by clients to look up the
public key. (It's a good idea to number keys, in case you ever need
to revoke/replace one.)
To create a binary cache signed with the private key:
$ nix-push --dest /path/to/binary-cache --key ./cache-key.sec --key-name cache.example.org-1
The public key (cache-key.pub) should be distributed to the clients.
They should have a nix.conf should contain something like:
signed-binary-caches = *
binary-cache-public-key-cache.example.org-1 = /path/to/cache-key.pub
If all works well, then if Nix fetches something from the signed
binary cache, you will see a message like:
*** Downloading ‘http://cache.example.org/nar/7dppcj5sc1nda7l54rjc0g5l1hamj09j-subversion-1.7.11’ (signed by ‘cache.example.org-1’) to ‘/nix/store/7dppcj5sc1nda7l54rjc0g5l1hamj09j-subversion-1.7.11’...
On the other hand, if the signature is wrong, you get a message like
NAR info file `http://cache.example.org/7dppcj5sc1nda7l54rjc0g5l1hamj09j.narinfo' has an invalid signature; ignoring
Signatures are implemented as a single line appended to the NAR info
file, which looks like this:
Signature: 1;cache.example.org-1;HQ9Xzyanq9iV...muQ==
Thus the signature has 3 fields: a version (currently "1"), the ID of
key, and the base64-encoded signature of the SHA-256 hash of the
contents of the NAR info file up to but not including the Signature
line.
Issue #75.
Ever since SQLite in Nixpkgs was updated to 3.8.0.2, Nix has randomly
segfaulted on Darwin:
http://hydra.nixos.org/build/6175515http://hydra.nixos.org/build/6611038
It turns out that this is because the binary cache substituter somehow
ends up loading two versions of SQLite: the one in Nixpkgs and the
other from /usr/lib/libsqlite3.dylib. It's not exactly clear why the
latter is loaded, but it appears to be because WWW::Curl indirectly loads
/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation,
which in turn seems to load /usr/lib/libsqlite3.dylib. This leads to
a segfault when Perl exits:
#0 0x00000001010375f4 in sqlite3_finalize ()
#1 0x000000010125806e in sqlite_st_destroy ()
#2 0x000000010124bc30 in XS_DBD__SQLite__st_DESTROY ()
#3 0x00000001001c8155 in XS_DBI_dispatch ()
...
#14 0x0000000100023224 in perl_destruct ()
#15 0x0000000100000d6a in main ()
...
The workaround is to explicitly load DBD::SQLite before WWW::Curl.
For instance, it's pointless to keep copy-from-other-stores running if
there are no other stores, or download-using-manifests if there are no
manifests. This also speeds things up because we don't send queries
to those substituters.
read the manifest just to check the version and print the number of
paths. This makes nix-pull very fast for the cached cache (speeding
up nixos-rebuild without the ‘--no-pull’ or ‘--fast’ options).
