Verify TLS certificate before downloading binaries

The --insecure flag to curl tells curl not to bother checking if the TLS
certificate presented by the server actually matches the hostname
requested, and actually is issued by a trusted CA chain.  This almost
entirely negates any benefit from using TLS in the first place.

This removes the --insecure flag to ensure we actually have a secure
connection to the intended hostname before downloading binaries.

Manually tested locally within a dev-shell; was able to download
binaries from https://cache.nixos.org without issue.

[Note: --insecure was only used for fetching NARs, whose integrity is
verified by Nix anyway using the hash from the .narinfo. But if we can
fetch the .narinfo without --insecure, we can also fetch the .nar, so
there is not much point to using --insecure. --Eelco]

2 files changed, 2 insertions, 3 deletions

diff --git a/scripts/download-from-binary-cache.pl.in b/scripts/download-from-binary-cache.pl.in
index 60f7f9aef..a4f858610 100644
--- a/scripts/download-from-binary-cache.pl.in
+++ b/scripts/download-from-binary-cache.pl.in
@@ -566,7 +566,7 @@ sub downloadBinary {
         die if $requireSignedBinaryCaches && !defined $info->{signedBy};
         print STDERR "\n*** Downloading ‘$url’ ", ($requireSignedBinaryCaches ? "(signed by ‘$info->{signedBy}’) " : ""), "to ‘$storePath’...\n";
         checkURL $url;
-        if (system("$Nix::Config::curl --fail --location --insecure --connect-timeout $curlConnectTimeout -A '$userAgent' '$url' $decompressor | $Nix::Config::binDir/nix-store --restore $destPath") != 0) {
+        if (system("$Nix::Config::curl --fail --location --connect-timeout $curlConnectTimeout -A '$userAgent' '$url' $decompressor | $Nix::Config::binDir/nix-store --restore $destPath") != 0) {
             warn "download of ‘$url’ failed" . ($! ? ": $!" : "") . "\n";
             next;
         }
diff --git a/scripts/download-using-manifests.pl.in b/scripts/download-using-manifests.pl.in
index 591cd6b43..ffc49f8ff 100755
--- a/scripts/download-using-manifests.pl.in
+++ b/scripts/download-using-manifests.pl.in
@@ -17,8 +17,7 @@ my $logFile = "$Nix::Config::logDir/downloads";
 # estimating the expected download size.
 my $fast = 1;
 
-# ‘--insecure’ is fine because Nix verifies the hash of the result.
-my $curl = "$Nix::Config::curl --fail --location --insecure";
+my $curl = "$Nix::Config::curl --fail --location";
 
 
 # Open the manifest cache and update it if necessary.