Coverity reports a spurious potential null pointer dereference in
cms_decrypt(), since the null pointer check takes place after the
pointer has already been dereferenced. The pointer can never be null,
since it is initialised to point to cipher_null at the point that the
containing structure is allocated.
Remove the redundant null pointer check, and for symmetry ensure that
the digest and public-key algorithm pointers are similarly initialised
at the point of allocation.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Almost all image consumers do not need to modify the content of the
image. Now that the image data is a pointer type (rather than the
opaque userptr_t type), we can rely on the compiler to enforce this at
build time.
Change the .data field to be a const pointer, so that the compiler can
verify that image consumers do not modify the image content. Provide
a transparent .rwdata field for consumers who have a legitimate (and
now explicit) reason to modify the image content.
We do not attempt to impose any runtime restriction on checking
whether or not an image is writable. The only existing instances of
genuinely read-only images are the various unit test images, and it is
acceptable for defective test cases to result in a segfault rather
than a runtime error.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Simplify the CMS code by assuming that all content is fully accessible
via pointer dereferences. This avoids the need to use fragment loops
for calculating digests and decrypting (or reencrypting) data.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add support for decrypting images containing detached encrypted data
using a cipher key obtained from a separate CMS envelope image (in DER
or PEM format).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Reduce the number of dynamic allocations required to parse a CMS
message by retaining the ASN.1 cursor returned from image_asn1() for
the lifetime of the CMS message. This allows embedded ASN.1 cursors
to be used for parsed objects within the message, such as embedded
signatures.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Instances of cipher and digest algorithms tend to get called
repeatedly to process substantial amounts of data. This is not true
for public-key algorithms, which tend to get called only once or twice
for a given key.
Simplify the public-key algorithm API so that there is no reusable
algorithm context. In particular, this allows callers to omit the
error handling currently required to handle memory allocation (or key
parsing) errors from pubkey_init(), and to omit the cleanup calls to
pubkey_final().
This change does remove the ability for a caller to distinguish
between a verification failure due to a memory allocation failure and
a verification failure due to a bad signature. This difference is not
material in practice: in both cases, for whatever reason, the caller
was unable to verify the signature and so cannot proceed further, and
the cause of the error will be visible to the user via the return
status code.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Asymmetric keys are invariably encountered within ASN.1 structures
such as X.509 certificates, and the various large integers within an
RSA key are themselves encoded using ASN.1.
Simplify all code handling asymmetric keys by passing keys as a single
ASN.1 cursor, rather than separate data and length pointers.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
There is some exploitable similarity between the data structures used
for representing CMS signatures and CMS encryption keys. In both
cases, the CMS message fundamentally encodes a list of participants
(either message signers or message recipients), where each participant
has an associated certificate and an opaque octet string representing
the signature or encrypted cipher key. The ASN.1 structures are not
identical, but are sufficiently similar to be worth exploiting: for
example, the SignerIdentifier and RecipientIdentifier data structures
are defined identically.
Rename data structures and functions, and add the concept of a CMS
message type.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The cms_signature() and cms_verify() functions currently accept raw
data pointers. This will not be possible for cms_decrypt(), which
will need the ability to extract fragments of ASN.1 data from a
potentially large image.
Change cms_signature() and cms_verify() to accept an image as an input
parameter, and move the responsibility for setting the image trust
flag within cms_verify() since that now becomes a more natural fit.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Centralise all current mechanisms for identifying an X.509 certificate
(by raw content, by subject, by issuer and serial number, and by
matching public key), and remove the certstore-specific and
CMS-specific variants of these functions.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
There is nothing OID-specific about the ASN1_OID_CURSOR macro. Rename
to allow it to be used for constructing ASN.1 cursors with arbitrary
contents.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Expand the concept of the X.509 cache to provide the functionality of
a certificate store. Certificates in the store will be automatically
used to complete certificate chains where applicable.
The certificate store may be prepopulated at build time using the
CERT=... build command line option. For example:
make bin/ipxe.usb CERT=mycert1.crt,mycert2.crt
Certificates within the certificate store are not implicitly trusted;
the trust list is specified using TRUST=... as before. For example:
make bin/ipxe.usb CERT=root.crt TRUST=root.crt
This can be used to embed the full trusted root certificate within the
iPXE binary, which is potentially useful in an HTTPS-only environment
in which there is no HTTP server from which to automatically download
cross-signed certificates or other certificate chain fragments.
This usage of CERT= extends the existing use of CERT= to specify the
client certificate. The client certificate is now identified
automatically by checking for a match against the private key. For
example:
make bin/ipxe.usb CERT=root.crt,client.crt TRUST=root.crt KEY=client.key
Signed-off-by: Michael Brown <mcb30@ipxe.org>
iPXE currently allocates a copy the certificate's common name as a
string. This string is used by the TLS and CMS code to check
certificate names against an expected name, and also appears in
debugging messages.
Provide a function x509_check_name() to centralise certificate name
checking (in preparation for adding subjectAlternativeName support),
and a function x509_name() to provide a name to be used in debugging
messages, and remove the dynamically allocated string.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
CMS includes an unordered certificate set, from which certificates
must be extracted in order by matching up issuers with subjects. We
will use the same functionality as part of the automatic download of
cross-signing certificates. Generalise cms_find_subject() to
x509_find_subject(), and create x509_auto_append().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
At present, certificate chain validation is treated as an
instantaneous process that can be carried out using only data that is
already in memory. This model does not allow for validation to
include non-instantaneous steps, such as downloading a cross-signing
certificate, or determining certificate revocation status via OCSP.
Redesign the internal representation of certificate chains to allow
chains to outlive the scope of the original source of certificates
(such as a TLS Certificate record).
Allow for certificates to be cached, so that each certificate needs to
be validated only once.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The Cryptographic Message Syntax (PKCS#7) provides a format for
encapsulating digital signatures of arbitrary binary blobs. A
signature can be generated using
openssl cms -sign -in <file to sign> -binary -noattr \
-signer <signer>.crt -inkey <signer>.key -certfile <CA>.crt \
-outform DER -out <signature>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
