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authorDaniel Kahn Gillmor <dkg@fifthhorseman.net>2009-02-04 00:27:35 -0500
committerDaniel Kahn Gillmor <dkg@fifthhorseman.net>2009-02-04 00:27:35 -0500
commit325baae0ae5e78fa0a4e9895270d2cd71757f869 (patch)
tree0940659de6ebe65ee04303f2a4f98bf7bc450c3b /src/keytrans
parentbc8f6439a96dbae1e0c58d6ac0032f4b043ee692 (diff)
ensure that the output of modular multiplicative inverse is positive.
Diffstat (limited to 'src/keytrans')
-rwxr-xr-xsrc/keytrans/pem2openpgp17
1 files changed, 15 insertions, 2 deletions
diff --git a/src/keytrans/pem2openpgp b/src/keytrans/pem2openpgp
index 9dead77..7abe52c 100755
--- a/src/keytrans/pem2openpgp
+++ b/src/keytrans/pem2openpgp
@@ -185,12 +185,18 @@ sub modular_multi_inverse {
my $a = shift;
my $b = shift;
+
+ my $origdivisor = $b->copy();
+
my $ctx = Crypt::OpenSSL::Bignum::CTX->new();
my $x = Crypt::OpenSSL::Bignum->zero();
my $y = Crypt::OpenSSL::Bignum->one();
my $lastx = Crypt::OpenSSL::Bignum->one();
my $lasty = Crypt::OpenSSL::Bignum->zero();
+ my $finalquotient;
+ my $finalremainder;
+
while (! $b->is_zero()) {
my ($quotient, $remainder) = $a->div($b, $ctx);
@@ -210,7 +216,12 @@ sub modular_multi_inverse {
die "did this math wrong.\n";
}
- return $lastx;
+ # let's make sure that we return a positive value because RFC 4880,
+ # section 3.2 only allows unsigned values:
+
+ ($finalquotient, $finalremainder) = $lastx->add($origdivisor)->div($origdivisor, $ctx);
+
+ return $finalremainder;
}
@@ -287,10 +298,12 @@ sub make_rsa_sec_key_body {
# we're not using $a and $b, but we need them to get to $c.
my ($n, $e, $d, $p, $q) = $key->get_key_parameters();
+ my $c3 = modular_multi_inverse($p, $q);
+
my $secret_material = mpi_pack($d).
mpi_pack($p).
mpi_pack($q).
- mpi_pack(modular_multi_inverse($p, $q));
+ mpi_pack($c3);
# according to Crypt::OpenSSL::RSA, the closest value we can get out
# of get_key_parameters is 1/q mod p; but according to sec 5.5.3 of