nix/corepkgs/fetchurl.nix
Eelco Dolstra 6024dc1d97
Support SRI hashes
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.
2018-12-13 14:30:52 +01:00

42 lines
1.2 KiB
Nix

{ system ? "" # obsolete
, url
, hash ? "" # an SRI ash
# Legacy hash specification
, md5 ? "", sha1 ? "", sha256 ? "", sha512 ? ""
, outputHash ?
if hash != "" then hash else if sha512 != "" then sha512 else if sha1 != "" then sha1 else if md5 != "" then md5 else sha256
, outputHashAlgo ?
if hash != "" then "" else if sha512 != "" then "sha512" else if sha1 != "" then "sha1" else if md5 != "" then "md5" else "sha256"
, executable ? false
, unpack ? false
, name ? baseNameOf (toString url)
}:
derivation {
builder = "builtin:fetchurl";
# New-style output content requirements.
inherit outputHashAlgo outputHash;
outputHashMode = if unpack || executable then "recursive" else "flat";
inherit name url executable unpack;
system = "builtin";
# No need to double the amount of network traffic
preferLocalBuild = true;
impureEnvVars = [
# We borrow these environment variables from the caller to allow
# easy proxy configuration. This is impure, but a fixed-output
# derivation like fetchurl is allowed to do so since its result is
# by definition pure.
"http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
];
# To make "nix-prefetch-url" work.
urls = [ url ];
}