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Linux/scripts/extract-sys-certs.pl

  1 #!/usr/bin/perl -w
  2 #
  3 use strict;
  4 use Math::BigInt;
  5 use Fcntl "SEEK_SET";
  6 
  7 die "Format: $0 [-s <systemmap-file>] <vmlinux-file> <keyring-file>\n"
  8     if ($#ARGV != 1 && $#ARGV != 3 ||
  9         $#ARGV == 3 && $ARGV[0] ne "-s");
 10 
 11 my $sysmap = "";
 12 if ($#ARGV == 3) {
 13     shift;
 14     $sysmap = $ARGV[0];
 15     shift;
 16 }
 17 
 18 my $vmlinux = $ARGV[0];
 19 my $keyring = $ARGV[1];
 20 
 21 #
 22 # Parse the vmlinux section table
 23 #
 24 open FD, "objdump -h $vmlinux |" || die $vmlinux;
 25 my @lines = <FD>;
 26 close(FD) || die $vmlinux;
 27 
 28 my @sections = ();
 29 
 30 foreach my $line (@lines) {
 31     chomp($line);
 32     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]+)/
 33         ) {
 34         my $seg  = $1;
 35         my $name = $2;
 36         my $len  = Math::BigInt->new("0x" . $3);
 37         my $vma  = Math::BigInt->new("0x" . $4);
 38         my $lma  = Math::BigInt->new("0x" . $5);
 39         my $foff = Math::BigInt->new("0x" . $6);
 40         my $align = 2 ** $7;
 41 
 42         push @sections, { name => $name,
 43                           vma => $vma,
 44                           len => $len,
 45                           foff => $foff };
 46     }
 47 }
 48 
 49 print "Have $#sections sections\n";
 50 
 51 #
 52 # Try and parse the vmlinux symbol table.  If the vmlinux file has been created
 53 # from a vmlinuz file with extract-vmlinux then the symbol table will be empty.
 54 #
 55 open FD, "nm $vmlinux 2>/dev/null |" || die $vmlinux;
 56 @lines = <FD>;
 57 close(FD) || die $vmlinux;
 58 
 59 my %symbols = ();
 60 my $nr_symbols = 0;
 61 
 62 sub parse_symbols(@) {
 63     foreach my $line (@_) {
 64         chomp($line);
 65         if ($line =~ /([0-9a-f]+)\s([a-zA-Z])\s(\S+)/
 66             ) {
 67             my $addr = "0x" . $1;
 68             my $type = $2;
 69             my $name = $3;
 70 
 71             $symbols{$name} = $addr;
 72             $nr_symbols++;
 73         }
 74     }
 75 }
 76 parse_symbols(@lines);
 77 
 78 if ($nr_symbols == 0 && $sysmap ne "") {
 79     print "No symbols in vmlinux, trying $sysmap\n";
 80 
 81     open FD, "<$sysmap" || die $sysmap;
 82     @lines = <FD>;
 83     close(FD) || die $sysmap;
 84     parse_symbols(@lines);
 85 }
 86 
 87 die "No symbols available\n"
 88     if ($nr_symbols == 0);
 89 
 90 print "Have $nr_symbols symbols\n";
 91 
 92 die "Can't find system certificate list"
 93     unless (exists($symbols{"__cert_list_start"}) &&
 94             exists($symbols{"system_certificate_list_size"}));
 95 
 96 my $start = Math::BigInt->new($symbols{"__cert_list_start"});
 97 my $end;
 98 my $size;
 99 my $size_sym = Math::BigInt->new($symbols{"system_certificate_list_size"});
100 
101 open FD, "<$vmlinux" || die $vmlinux;
102 binmode(FD);
103 
104 my $s = undef;
105 foreach my $sec (@sections) {
106     my $s_name = $sec->{name};
107     my $s_vma = $sec->{vma};
108     my $s_len = $sec->{len};
109     my $s_foff = $sec->{foff};
110     my $s_vend = $s_vma + $s_len;
111 
112     next unless ($start >= $s_vma);
113     next if ($start >= $s_vend);
114 
115     die "Certificate list size was not found on the same section\n"
116         if ($size_sym < $s_vma || $size_sym > $s_vend);
117 
118     die "Cert object in multiple sections: ", $s_name, " and ", $s->{name}, "\n"
119         if ($s);
120 
121     my $size_off = $size_sym -$s_vma + $s_foff;
122     my $packed;
123     die $vmlinux if (!defined(sysseek(FD, $size_off, SEEK_SET)));
124     sysread(FD, $packed, 8);
125     $size = unpack 'L!', $packed;
126     $end = $start + $size;
127 
128     printf "Have %u bytes of certs at VMA 0x%x\n", $size, $start;
129 
130     die "Cert object partially overflows section $s_name\n"
131         if ($end > $s_vend);
132 
133     $s = $sec;
134 }
135 
136 die "Cert object not inside a section\n"
137     unless ($s);
138 
139 print "Certificate list in section ", $s->{name}, "\n";
140 
141 my $foff = $start - $s->{vma} + $s->{foff};
142 
143 printf "Certificate list at file offset 0x%x\n", $foff;
144 
145 die $vmlinux if (!defined(sysseek(FD, $foff, SEEK_SET)));
146 my $buf = "";
147 my $len = sysread(FD, $buf, $size);
148 die "$vmlinux" if (!defined($len));
149 die "Short read on $vmlinux\n" if ($len != $size);
150 close(FD) || die $vmlinux;
151 
152 open FD, ">$keyring" || die $keyring;
153 binmode(FD);
154 $len = syswrite(FD, $buf, $size);
155 die "$keyring" if (!defined($len));
156 die "Short write on $keyring\n" if ($len != $size);
157 close(FD) || die $keyring;

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