SRI hashes (https://www.w3.org/TR/SRI/) combine the hash algorithm and
a base-64 hash. This allows more concise and standard hash
specifications. For example, instead of
import <nix/fetchurl.nl> {
url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
};
you can write
import <nix/fetchurl.nl> {
url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
};
In fixed-output derivations, the outputHashAlgo is no longer mandatory
if outputHash specifies the hash (either as an SRI or in the old
"<type>:<hash>" format).
'nix hash-{file,path}' now print hashes in SRI format by default. I
also reverted them to use SHA-256 by default because that's what we're
using most of the time in Nixpkgs.
Suggested by @zimbatm.
In structured-attributes derivations, you can now specify per-output
checks such as:
outputChecks."out" = {
# The closure of 'out' must not be larger than 256 MiB.
maxClosureSize = 256 * 1024 * 1024;
# It must not refer to C compiler or to the 'dev' output.
disallowedRequisites = [ stdenv.cc "dev" ];
};
outputChecks."dev" = {
# The 'dev' output must not be larger than 128 KiB.
maxSize = 128 * 1024;
};
Also fixed a bug in allowedRequisites that caused it to ignore
self-references.
The current usage technically works by putting multiple different
repos in to the same git directory. However, it is very slow as
Git tries very hard to find common commits between the two
repositories. If the two repositories are large (like Nixpkgs and
another long-running project,) it is maddeningly slow.
This change busts the cache for existing deployments, but users
will be promptly repaid in per-repository performance.
In EvalState::checkSourcePath, the path is checked against the list of
allowed paths first and later it's checked again *after* resolving
symlinks.
The resolving of the symlinks is done via canonPath, which also strips
out "../" and "./". However after the canonicalisation the error message
pointing out that the path is not allowed prints the symlink target in
the error message.
Even if we'd suppress the message, symlink targets could still be leaked
if the symlink target doesn't exist (in this case the error is thrown in
canonPath).
So instead, we now do canonPath() without symlink resolving first before
even checking against the list of allowed paths and then later do the
symlink resolving and checking the allowed paths again.
The first call to canonPath() should get rid of all the "../" and "./",
so in theory the only way to leak a symlink if the attacker is able to
put a symlink in one of the paths allowed by restricted evaluation mode.
For the latter I don't think this is part of the threat model, because
if the attacker can write to that path, the attack vector is even
larger.
Signed-off-by: aszlig <aszlig@nix.build>
Allow global config settings to be defined in multiple Config
classes. For example, this means that libutil can have settings and
evaluator settings can be moved out of libstore. The Config classes
are registered in a new GlobalConfig class to which config files
etc. are applied.
Relevant to https://github.com/NixOS/nix/issues/2009 in that it
removes the need for ad hoc handling of useCaseHack, which was the
underlying cause of that issue.
Flex's regexes have an annoying feature: the dot matches everything
except a newline. This causes problems for expressions like:
"${0}\
"
where the backslash-newline combination matches this rule instead of the
intended one mentioned in the comment:
<STRING>\$|\\|\$\\ {
/* This can only occur when we reach EOF, otherwise the above
(...|\$[^\{\"\\]|\\.|\$\\.)+ would have triggered.
This is technically invalid, but we leave the problem to the
parser who fails with exact location. */
return STR;
}
However, the parser actually accepts the resulting token sequence
('"' DOLLAR_CURLY 0 '}' STR '"'), which is a problem because the lexer
rule didn't assign anything to yylval. Ultimately this leads to a crash
when dereferencing a NULL pointer in ExprConcatStrings::bindVars().
The fix does change the syntax of the language in some corner cases
but I think it's only turning previously invalid (or crashing) syntax
to valid syntax. E.g.
"a\
b"
and
''a''\
b''
were previously syntax errors but now both result in "a\nb".
Found by afl-fuzz.
Otherwise, running e.g.
nix-instantiate --eval -E --strict 'builtins.replaceStrings [""] ["X"] "abc"'
would just hang in an infinite loop.
Found by afl-fuzz.
First attempt of this was reverted in e2d71bd186 because it caused
another infinite loop, which is fixed now and a test added.
Otherwise, running e.g.
nix-instantiate --eval -E --strict 'builtins.replaceStrings [""] ["X"] "abc"'
would just hang in an infinite loop.
Found by afl-fuzz.
Samuel Dionne-Riel
Linus Heckemann