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Date: Wed, 21 Oct 2015 15:27:14 +0100
From: David Howells <dhowells@...hat.com>
To: keyrings@...r.kernel.org
Cc: dhowells@...hat.com, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 4/6] KEYS: Provide a script to extract the sys cert list
from a vmlinux file
The supplied script takes a vmlinux file - and if necessary a System.map
file - locates the system certificates list and extracts it to the named
file.
Call as:
./scripts/extract-sys-certs vmlinux certs
if vmlinux contains symbols and:
./scripts/extract-sys-certs -s System.map vmlinux certs
if it does not.
It prints something like the following to stdout:
Have 27 sections
No symbols in vmlinux, trying System.map
Have 80088 symbols
Have 1346 bytes of certs at VMA 0xffffffff8201c540
Certificate list in section .init.data
Certificate list at file offset 0x141c540
If vmlinux contains symbols then that is used rather than System.map - even
if one is given.
Signed-off-by: David Howells <dhowells@...hat.com>
---
scripts/extract-sys-certs.pl | 144 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 144 insertions(+)
create mode 100755 scripts/extract-sys-certs.pl
diff --git a/scripts/extract-sys-certs.pl b/scripts/extract-sys-certs.pl
new file mode 100755
index 000000000000..d476e7d1fd88
--- /dev/null
+++ b/scripts/extract-sys-certs.pl
@@ -0,0 +1,144 @@
+#!/usr/bin/perl -w
+#
+use strict;
+use Math::BigInt;
+use Fcntl "SEEK_SET";
+
+die "Format: $0 [-s <systemmap-file>] <vmlinux-file> <keyring-file>\n"
+ if ($#ARGV != 1 && $#ARGV != 3 ||
+ $#ARGV == 3 && $ARGV[0] ne "-s");
+
+my $sysmap = "";
+if ($#ARGV == 3) {
+ shift;
+ $sysmap = $ARGV[0];
+ shift;
+}
+
+my $vmlinux = $ARGV[0];
+my $keyring = $ARGV[1];
+
+#
+# Parse the vmlinux section table
+#
+open FD, "objdump -h $vmlinux |" || die $vmlinux;
+my @lines = <FD>;
+close(FD) || die $vmlinux;
+
+my @sections = ();
+
+foreach my $line (@lines) {
+ chomp($line);
+ if ($line =~ /\s*([0-9]+)\s+(\S+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+([0-9a-f]+)\s+2[*][*]([0-9]+)/
+ ) {
+ my $seg = $1;
+ my $name = $2;
+ my $len = Math::BigInt->new("0x" . $3);
+ my $vma = Math::BigInt->new("0x" . $4);
+ my $lma = Math::BigInt->new("0x" . $5);
+ my $foff = Math::BigInt->new("0x" . $6);
+ my $align = 2 ** $7;
+
+ push @sections, { name => $name,
+ vma => $vma,
+ len => $len,
+ foff => $foff };
+ }
+}
+
+print "Have $#sections sections\n";
+
+#
+# Try and parse the vmlinux symbol table. If the vmlinux file has been created
+# from a vmlinuz file with extract-vmlinux then the symbol table will be empty.
+#
+open FD, "nm $vmlinux 2>/dev/null |" || die $vmlinux;
+@...es = <FD>;
+close(FD) || die $vmlinux;
+
+my %symbols = ();
+my $nr_symbols = 0;
+
+sub parse_symbols(@) {
+ foreach my $line (@_) {
+ chomp($line);
+ if ($line =~ /([0-9a-f]+)\s([a-zA-Z])\s(\S+)/
+ ) {
+ my $addr = "0x" . $1;
+ my $type = $2;
+ my $name = $3;
+
+ $symbols{$name} = $addr;
+ $nr_symbols++;
+ }
+ }
+}
+parse_symbols(@lines);
+
+if ($nr_symbols == 0 && $sysmap ne "") {
+ print "No symbols in vmlinux, trying $sysmap\n";
+
+ open FD, "<$sysmap" || die $sysmap;
+ @lines = <FD>;
+ close(FD) || die $sysmap;
+ parse_symbols(@lines);
+}
+
+die "No symbols available\n"
+ if ($nr_symbols == 0);
+
+print "Have $nr_symbols symbols\n";
+
+die "Can't find system certificate list"
+ unless (exists($symbols{"__cert_list_start"}) &&
+ exists($symbols{"__cert_list_end"}));
+
+my $start = Math::BigInt->new($symbols{"__cert_list_start"});
+my $end = Math::BigInt->new($symbols{"__cert_list_end"});
+my $size = $end - $start;
+
+printf "Have %u bytes of certs at VMA 0x%x\n", $size, $start;
+
+my $s = undef;
+foreach my $sec (@sections) {
+ my $s_name = $sec->{name};
+ my $s_vma = $sec->{vma};
+ my $s_len = $sec->{len};
+ my $s_foff = $sec->{foff};
+ my $s_vend = $s_vma + $s_len;
+
+ next unless ($start >= $s_vma);
+ next if ($start >= $s_vend);
+
+ die "Cert object partially overflows section $s_name\n"
+ if ($end > $s_vend);
+
+ die "Cert object in multiple sections: ", $s_name, " and ", $s->{name}, "\n"
+ if ($s);
+ $s = $sec;
+}
+
+die "Cert object not inside a section\n"
+ unless ($s);
+
+print "Certificate list in section ", $s->{name}, "\n";
+
+my $foff = $start - $s->{vma} + $s->{foff};
+
+printf "Certificate list at file offset 0x%x\n", $foff;
+
+open FD, "<$vmlinux" || die $vmlinux;
+binmode(FD);
+die $vmlinux if (!defined(sysseek(FD, $foff, SEEK_SET)));
+my $buf = "";
+my $len = sysread(FD, $buf, $size);
+die "$vmlinux" if (!defined($len));
+die "Short read on $vmlinux\n" if ($len != $size);
+close(FD) || die $vmlinux;
+
+open FD, ">$keyring" || die $keyring;
+binmode(FD);
+$len = syswrite(FD, $buf, $size);
+die "$keyring" if (!defined($len));
+die "Short write on $keyring\n" if ($len != $size);
+close(FD) || die $keyring;
--
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