Re: [pve-devel] [PATCH v7 common 1/1] tools: add download_file_from_url

[Lorenz Stechauner <l.stechauner@proxmox.com>]

adds a common function to download arbitrary files from urls.

security notice: this function does not perform any permission checking.
the calling function and/or api endpoint has to make sure, that only 
authorized users may use this function.

caution: This function is able to download files from internal networks 
(which would not be visible/accessible from outside).

On 14.06.21 11:05, Lorenz Stechauner wrote:
> code is based on
> manager:PVE/API2/Nodes.pm:aplinfo
>
> Signed-off-by: Lorenz Stechauner <l.stechauner@proxmox.com>
> ---
>   src/PVE/Tools.pm | 124 +++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 124 insertions(+)
>
> diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
> index 16ae3d2..7b82e00 100644
> --- a/src/PVE/Tools.pm
> +++ b/src/PVE/Tools.pm
> @@ -1829,4 +1829,128 @@ sub safe_compare {
>       return $cmp->($left, $right);
>   }
>   
> +
> +# opts
> +#  -> hash_required
> +#       if 1, at least one checksum has to be specified otherwise an error will be thrown
> +#  -> http_proxy
> +#  -> https_proxy
> +#  -> verify_certificates
> +#  -> sha(1|224|256|384|512)sum
> +#  -> md5sum
> +sub download_file_from_url {
> +    my ($dest, $url, $opts) = @_;
> +
> +    my $tmpdest = "$dest.tmp.$$";
> +
> +    my $algorithm;
> +    my $expected;
> +
> +    for ('sha512', 'sha384', 'sha256', 'sha224', 'sha1', 'md5') {
> +	if (defined($opts->{"${_}sum"})) {
> +	    $algorithm = $_;
> +	    $expected = $opts->{"${_}sum"};
> +	    last;
> +	}
> +    }
> +
> +    die "checksum required but not specified\n" if ($opts->{hash_required} && !$algorithm);
> +
> +    my $worker = sub  {
> +	my $upid = shift;
> +
> +	print "downloading $url to $dest\n";
> +
> +	eval {
> +	    if (-f $dest && $algorithm) {
> +		print "calculating checksum of existing file...\n";
> +		my $correct = check_file_hash($algorithm, $expected, $dest);
> +
> +		if ($correct) {
> +		    print "file already exists, no need to download\n";
> +		    return;
> +		} else {
> +		    print "mismatch, downloading\n";
> +		}
> +	    }
> +
> +	    my @cmd = ('/usr/bin/wget', '--progress=dot:mega', '-O', $tmpdest, $url);
> +
> +	    local %ENV;
> +	    if ($opts->{http_proxy}) {
> +		$ENV{http_proxy} = $opts->{http_proxy};
> +	    }
> +	    if ($opts->{https_proxy}) {
> +		$ENV{https_proxy} = $opts->{https_proxy};
> +	    }
> +
> +	    my $verify = $opts->{verify_certificates} // 1;
> +	    if (!$verify) {
> +		push @cmd, '--no-check-certificate';
> +	    }
> +
> +	    if (run_command([[@cmd]]) != 0) {
> +		die "download failed: $!\n";
> +	    }
> +
> +	    if ($algorithm) {
> +		print "calculating checksum...\n";
> +
> +		my $correct = check_file_hash($algorithm, $expected, $tmpdest);
> +
> +		if ($correct) {
> +		    print "checksum verified\n";
> +		} else {
> +		    die "checksum mismatch\n";
> +		}
> +	    } else {
> +		print "no checksum for verification specified\n";
> +	    }
> +
> +	    if (!rename($tmpdest, $dest)) {
> +		die "unable to save file: $!\n";
> +	    }
> +	};
> +	my $err = $@;
> +
> +	unlink $tmpdest;
> +
> +	if ($err) {
> +	    print "\n";
> +	    die $err;
> +	}
> +
> +	print "download finished\n";
> +    };
> +
> +    my $rpcenv = PVE::RPCEnvironment::get();
> +    my $user = $rpcenv->get_user();
> +
> +    (my $filename = $dest) =~ s!.*/([^/]*)$!$1!;
> +
> +    return $rpcenv->fork_worker('download', $filename, $user, $worker);
> +}
> +
> +sub check_file_hash {
> +    my ($algorithm, $expected, $filename) = @_;
> +
> +    my $algorithm_map = {
> +	'md5' => sub { Digest::MD5->new },
> +	'sha1' => sub { Digest::SHA->new(1) },
> +	'sha224' => sub { Digest::SHA->new(224) },
> +	'sha256' => sub { Digest::SHA->new(256) },
> +	'sha384' => sub { Digest::SHA->new(384) },
> +	'sha512' => sub { Digest::SHA->new(512) },
> +    };
> +
> +    my $digester = $algorithm_map->{$algorithm}->() or die "unknown algorithm '$algorithm'\n";
> +
> +    open(my $fh, '<', $filename) or die "unable to open '$filename': $!\n";
> +    binmode($fh);
> +
> +    my $digest = $digester->addfile($fh)->hexdigest;
> +
> +    return lc($digest) eq lc($expected);
> +}
> +
>   1;