Handling large ASN.1 objects such as encrypted CMS files will require
the ability to use the asn1_enter() and asn1_skip() family of
functions on partial object cursors, where a defined additional length
is known to exist after the end of the data buffer pointed to by the
ASN.1 object cursor.
We already have support for partial object cursors in the underlying
asn1_start() operation used by both asn1_enter() and asn1_skip(), and
this is used by the DER image probe routine to check that the
potential DER file comprises a single ASN.1 SEQUENCE object.
Add asn1_enter_partial() to formalise the process of entering an ASN.1
partial object, and refactor the DER image probe routine to use this
instead of open-coding calls to the underlying asn1_start() operation.
There is no need for an equivalent asn1_skip_partial() function, since
only objects that are wholly contained within the partial cursor may
be successfully skipped.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Calling asn1_skip_if_exists() on a malformed ASN.1 object may
currently leave the cursor in a partially-updated state, where the tag
byte and one of the length bytes have been stripped. The cursor is
left with a valid data pointer and length and so no out-of-bounds
access can arise, but the cursor no longer points to the start of an
ASN.1 object.
Ensure that each ASN.1 cursor manipulation code path leads to the
cursor being either fully updated, left unmodified, or invalidated,
and update the function descriptions to reflect this.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Successfully reaching the end of a well-formed ASN.1 object list is
arguably not an error, but the current code (dating back to the
original ASN.1 commit in 2007) will explicitly check for and report
this as an error condition.
Remove the explicit check for reaching the end of a well-formed ASN.1
object list, and instead return success along with a zero-length (and
hence implicitly invalidated) cursor.
Almost every existing caller of asn1_skip() or asn1_skip_if_exists()
currently ignores the return value anyway. Skipped objects are (by
definition) not of interest to the caller, and the invalidation
behaviour of asn1_skip() ensures that any errors will be safely caught
on a subsequent attempt to actually use the ASN.1 object content.
Since these existing callers ignore the return value, they cannot be
affected by this change.
There is one existing caller of asn1_skip_if_exists() that does check
the return value: in asn1_skip() itself, an error returned from
asn1_skip_if_exists() will cause the cursor to be invalidated. In the
case of an error indicating only that the cursor length is already
zero, invalidation is a no-op, and so this change affects only the
return value propagated from asn1_skip().
This leaves only a single call site within ocsp_request() where the
return value from asn1_skip() is currently checked. The return status
here is moot since there is no way for the code in question to fail
(absent a bug in the ASN.1 construction or parsing code).
There are therefore no callers of asn1_skip() or asn1_skip_if_exists()
that rely on an error being returned for successfully reaching the end
of a well-formed ASN.1 object list. Simplify the code by redefining
this as a successful outcome.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Enable both IMAGE_DER and IMAGE_PEM by default, and drag in the
relevant objects only when image_asn1() is present in the binary.
This allows "imgverify" to transparently use either DER or PEM
signature files.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow code to create a partial ASN.1 cursor containing only the type
and length bytes, so that asn1_start() may be used to determine the
length of a large ASN.1 blob without first allocating memory to hold
the entire blob.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The assumption in asn1_type() that an ASN.1 cursor will always contain
a type byte is incorrect. A cursor that has been cleanly invalidated
via asn1_invalidate_cursor() will contain a type byte, but there are
other ways in which to arrive at a zero-length cursor.
Fix by explicitly checking the cursor length in asn1_type(). This
allows asn1_invalidate_cursor() to be reduced to simply zeroing the
length field.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
asn1_skip() will return an error on reaching the end of an object, and
so should not be used as the basis for asn1_shrink().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The concept of an OID-identified algorithm as defined in X.509 is used
in some other standards (e.g. PKCS#7). Generalise this functionality
and provide it as part of the ASN.1 core.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The version field of an X.509 certificate appears to be optional.
Reported-by: Sebastiano Manusia <Sebastiano.Manusia@chuv.ch>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Access to the gpxe.org and etherboot.org domains and associated
resources has been revoked by the registrant of the domain. Work
around this problem by renaming project from gPXE to iPXE, and
updating URLs to match.
Also update README, LOG and COPYRIGHTS to remove obsolete information.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown
Michael Brown