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Include a PGP keyring containing the public keys required to perform module
verification in the kernel image during build and create a special keyring
during boot which is then populated with keys of crypto type holding the public
keys found in the PGP keyring.
These can be seen by root:
[root@andromeda ~]# cat /proc/keys
07ad4ee0 I----- 1 perm 3f010000 0 0 crypto modsign.0: RSA 87b9b3bd []
15c7f8c3 I----- 1 perm 1f030000 0 0 keyring .module_sign: 1/4
...
It is probably worth permitting root to invalidate these keys, resulting in
their removal and preventing further modules from being loaded with that key.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Automatically generate keys for module signing if they're absent so that
allyesconfig doesn't break. The builder should consider generating their own
key and certificate, however, so that the keys are appropriately named.
The private key for the module signer should be placed in signing_key.priv
(unencrypted!) and the public key in an X.509 certificate as signing_key.x509.
If a transient key is desired for signing the modules, a config file for
'openssl req' can be placed in x509.genkey, looking something like the
following:
[ req ]
default_bits = 4096
distinguished_name = req_distinguished_name
prompt = no
x509_extensions = myexts
[ req_distinguished_name ]
O = Magarathea
CN = Glacier signing key
emailAddress = slartibartfast@magrathea.h2g2
[ myexts ]
basicConstraints=critical,CA:FALSE
keyUsage=digitalSignature
subjectKeyIdentifier=hash
authorityKeyIdentifier=hash
The build process will use this to configure:
openssl req -new -nodes -utf8 -sha1 -days 36500 -batch \
-x509 -config x509.genkey \
-outform DER -out signing_key.x509 \
-keyout signing_key.priv
to generate the key.
Note that it is required that the X.509 certificate have a subjectKeyIdentifier
and an authorityKeyIdentifier. Without those, the certificate will be
rejected. These can be used to check the validity of a certificate.
Note that 'make distclean' will remove signing_key.{priv,x509} and x509.genkey,
whether or not they were generated automatically.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Provide kernel configuration options for module signing.
The following configuration options are added:
CONFIG_MODULE_SIG_SHA1
CONFIG_MODULE_SIG_SHA224
CONFIG_MODULE_SIG_SHA256
CONFIG_MODULE_SIG_SHA384
CONFIG_MODULE_SIG_SHA512
These select the cryptographic hash used to digest the data prior to signing.
Additionally, the crypto module selected will be built into the kernel as it
won't be possible to load it as a module without incurring a circular
dependency when the kernel tries to check its signature.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Provide gitignore and make clean rules for extra files to hide and clean up the
extra files produced by module signing stuff once it is added. Also add a
clean up rule for the module content extractor program used to extract the data
to be signed.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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If we're in FIPS mode, we should panic if we fail to verify the signature on a
module or we're asked to load an unsigned module in signature enforcing mode.
Possibly FIPS mode should automatically enable enforcing mode.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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We do a very simple search for a particular string appended to the module
(which is cache-hot and about to be SHA'd anyway). There's both a config
option and a boot parameter which control whether we accept or fail with
unsigned modules and modules that are signed with an unknown key.
If module signing is enabled, the kernel will be tainted if a module is
loaded that is unsigned or has a signature for which we don't have the
key.
(Useful feedback and tweaks by David Howells <dhowells@redhat.com>)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Add a crypto key parser for binary (DER) encoded X.509 certificates. The
certificate is parsed and, if possible, the signature is verified.
An X.509 key can be added like this:
# keyctl padd crypto bar @s </tmp/x509.cert
15768135
and displayed like this:
# cat /proc/keys
00f09a47 I--Q--- 1 perm 39390000 0 0 asymmetri bar: X509.RSA e9fd6d08 []
Note that this only works with binary certificates. PEM encoded certificates
are ignored by the parser.
Note also that the X.509 key ID is not congruent with the PGP key ID, but for
the moment, they will match.
If a NULL or "" name is given to add_key(), then the parser will generate a key
description from the CertificateSerialNumber and Name fields of the
TBSCertificate:
00aefc4e I--Q--- 1 perm 39390000 0 0 asymmetri bfbc0cd76d050ea4:/C=GB/L=Cambridge/O=Red Hat/CN=kernel key: X509.RSA 0c688c7b []
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Provide a function to read raw data of a predetermined size into an MPI rather
than expecting the size to be encoded within the data. The data is assumed to
represent an unsigned integer, and the resulting MPI will be positive.
The function looks like this:
MPI mpi_read_raw_data(const void *, size_t);
This is useful for reading ASN.1 integer primitives where the length is encoded
in the ASN.1 metadata.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Add an ASN.1 BER/DER/CER decoder. This uses the bytecode from the ASN.1
compiler in the previous patch to inform it as to what to expect to find in the
encoded byte stream. The output from the compiler also tells it what functions
to call on what tags, thus allowing the caller to retrieve information.
The decoder is called as follows:
int asn1_decoder(const struct asn1_decoder *decoder,
void *context,
const unsigned char *data,
size_t datalen);
The decoder argument points to the bytecode from the ASN.1 compiler. context
is the caller's context and is passed to the action functions. data and
datalen define the byte stream to be decoded.
Note that the decoder is currently limited to datalen being less than 64K.
This reduces the amount of stack space used by the decoder because ASN.1 is a
nested construct. Similarly, the decoder is limited to a maximum of 10 levels
of constructed data outside of a leaf node also in an effort to keep stack
usage down.
These restrictions can be raised if necessary.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Add a simple ASN.1 grammar compiler. This produces a bytecode output that can
be fed to a decoder to inform the decoder how to interpret the ASN.1 stream it
is trying to parse.
Action functions can be specified in the grammar by interpolating:
({ foo })
after a type, for example:
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING ({ do_key_data })
}
The decoder is expected to call these after matching this type and parsing the
contents if it is a constructed type.
The grammar compiler does not currently support the SET type (though it does
support SET OF) as I can't see a good way of tracking which members have been
encountered yet without using up extra stack space.
Currently, the grammar compiler will fail if more than 256 bytes of bytecode
would be produced or more than 256 actions have been specified as it uses
8-bit jump values and action indices to keep space usage down.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Add a pair of utility functions to render OIDs as strings. The first takes an
encoded OID and turns it into a "a.b.c.d" form string:
int sprint_oid(const void *data, size_t datasize,
char *buffer, size_t bufsize);
The second takes an OID enum index and calls the first on the data held
therein:
int sprint_OID(enum OID oid, char *buffer, size_t bufsize);
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Implement a simple static OID registry that allows the mapping of an encoded
OID to an enum value for ease of use.
The OID registry index enum appears in the:
linux/oid_registry.h
header file. A script generates the registry from lines in the header file
that look like:
<sp*>OID_foo,<sp*>/*<sp*>1.2.3.4<sp*>*/
The actual OID is taken to be represented by the numbers with interpolated
dots in the comment.
All other lines in the header are ignored.
The registry is queries by calling:
OID look_up_oid(const void *data, size_t datasize);
This returns a number from the registry enum representing the OID if found or
OID__NR if not.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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gpg can produce a signature file where length of signature is less than the
modulus size because the amount of space an MPI takes up is kept as low as
possible by discarding leading zeros. This regularly happens for several
modules during the build.
Fix it by relaxing check in RSA verification code.
Thanks to Tomas Mraz and Miloslav Trmac for help.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Implement RSA public key cryptography [PKCS#1 / RFC3447]. At this time, only
the signature verification algorithm is supported. This uses the asymmetric
public key subtype to hold its key data.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Reinstate and export mpi_cmp() and mpi_cmp_ui() from the MPI library for use by
RSA signature verification as per RFC3447 section 5.2.2 step 1.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Provide signature verification using an asymmetric-type key to indicate the
public key to be used.
The API is a single function that can be found in crypto/public_key.h:
int verify_signature(const struct key *key,
const struct public_key_signature *sig)
The first argument is the appropriate key to be used and the second argument
is the parsed signature data:
struct public_key_signature {
u8 *digest;
u16 digest_size;
enum pkey_hash_algo pkey_hash_algo : 8;
union {
MPI mpi[2];
struct {
MPI s; /* m^d mod n */
} rsa;
struct {
MPI r;
MPI s;
} dsa;
};
};
This should be filled in prior to calling the function. The hash algorithm
should already have been called and the hash finalised and the output should
be in a buffer pointed to by the 'digest' member.
Any extra data to be added to the hash by the hash format (eg. PGP) should
have been added by the caller prior to finalising the hash.
It is assumed that the signature is made up of a number of MPI values. If an
algorithm becomes available for which this is not the case, the above structure
will have to change.
It is also assumed that it will have been checked that the signature algorithm
matches the key algorithm.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Add a subtype for supporting asymmetric public-key encryption algorithms such
as DSA (FIPS-186) and RSA (PKCS#1 / RFC1337).
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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The instantiation data passed to the asymmetric key type are expected to be
formatted in some way, and there are several possible standard ways to format
the data.
The two obvious standards are OpenPGP keys and X.509 certificates. The latter
is especially useful when dealing with UEFI, and the former might be useful
when dealing with, say, eCryptfs.
Further, it might be desirable to provide formatted blobs that indicate
hardware is to be accessed to retrieve the keys or that the keys live
unretrievably in a hardware store, but that the keys can be used by means of
the hardware.
From userspace, the keys can be loaded using the keyctl command, for example,
an X.509 binary certificate:
keyctl padd asymmetric foo @s <dhowells.pem
or a PGP key:
keyctl padd asymmetric bar @s <dhowells.pub
or a pointer into the contents of the TPM:
keyctl add asymmetric zebra "TPM:04982390582905f8" @s
Inside the kernel, pluggable parsers register themselves and then get to
examine the payload data to see if they can handle it. If they can, they get
to:
(1) Propose a name for the key, to be used it the name is "" or NULL.
(2) Specify the key subtype.
(3) Provide the data for the subtype.
The key type asks the parser to do its stuff before a key is allocated and thus
before the name is set. If successful, the parser stores the suggested data
into the key_preparsed_payload struct, which will be either used (if the key is
successfully created and instantiated or updated) or discarded.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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Create a key type that can be used to represent an asymmetric key type for use
in appropriate cryptographic operations, such as encryption, decryption,
signature generation and signature verification.
The key type is "asymmetric" and can provide access to a variety of
cryptographic algorithms.
Possibly, this would be better as "public_key" - but that has the disadvantage
that "public key" is an overloaded term.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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David Howells
Rusty Russell