If we have a device tree available (e.g. because the user has
explicitly downloaded a device tree using the "fdt" command), then
provide it to the booted operating system as an EFI configuration
table.
Since x86 does not typically use device trees, we create weak symbols
for efi_fdt_install() and efi_fdt_uninstall() to avoid dragging FDT
support into all x86 UEFI binaries.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide fdt_create() to create a device tree to be passed to a booted
operating system. The device tree will be created from the FDT image
(if present), falling back to the system device tree (if present).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
EFI configuration tables may be freed at any time, and there is no way
to be notified when the table becomes invalidated. Create a copy of
the system flattened device tree (if present), so that we do not risk
being left with an invalid pointer.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow for parsing device trees where an external factor (such as a
downloaded image length) determines the maximum length, which must be
validated against the length within the device tree header.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
When running on a platform that uses FDT as its hardware description
mechanism, we are likely to have multiple device tree structures. At
a minimum, there will be the device tree passed to us from the
previous boot stage (e.g. OpenSBI), and the device tree that we
construct to be passed to the booted operating system.
Update the internal FDT API to include an FDT pointer in all function
parameter lists.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Define the concept of an "FDT" image, representing a Flattened Device
Tree blob that has been downloaded in order to be provided to a kernel
or other executable image. FDT images are represented using an image
tag (as with other special-purpose images such as the UEFI shim), and
are similarly marked as hidden so that they will not be included in a
generated magic initrd or show up in a virtual filesystem directory
listing.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide wrapper macros to allow efi_open() and related functions to
accept a pointer to any pointer type as the "interface" argument, in
order to allow a substantial amount of type adjustment boilerplate to
be removed.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The UEFI model for opening and closing protocols is broken by design
and cannot be repaired.
Calling OpenProtocol() to obtain a protocol interface pointer does
not, in general, provide any guarantees about the lifetime of that
pointer. It is theoretically possible that the pointer has already
become invalid by the time that OpenProtocol() returns the pointer to
its caller. (This can happen when a USB device is physically removed,
for example.)
Various UEFI design flaws make it occasionally necessary to hold on to
a protocol interface pointer despite the total lack of guarantees that
the pointer will remain valid.
The UEFI driver model overloads the semantics of OpenProtocol() to
accommodate the use cases of recording a driver attachment (which is
modelled as opening a protocol with EFI_OPEN_PROTOCOL_BY_DRIVER
attributes) and recording the existence of a related child controller
(which is modelled as opening a protocol with
EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER attributes).
The parameters defined for CloseProtocol() are not sufficient to allow
the implementation to precisely identify the matching call to
OpenProtocol(). While the UEFI model appears to allow for matched
open and close pairs, this is merely an illusion. Calling
CloseProtocol() will delete *all* matching records in the protocol
open information tables.
Since the parameters defined for CloseProtocol() do not include the
attributes passed to OpenProtocol(), this means that a matched
open/close pair using EFI_OPEN_PROTOCOL_GET_PROTOCOL can inadvertently
end up deleting the record that defines a driver attachment or the
existence of a child controller. This in turn can cause some very
unexpected side effects, such as allowing other UEFI drivers to start
controlling hardware to which iPXE believes it has exclusive access.
This rarely ends well.
To prevent this kind of inadvertent deletion, we establish a
convention for four different types of protocol opening:
- ephemeral opens: always opened with ControllerHandle = NULL
- unsafe opens: always opened with ControllerHandle = AgentHandle
- by-driver opens: always opened with ControllerHandle = Handle
- by-child opens: always opened with ControllerHandle != Handle
This convention ensures that the four types of open never overlap
within the set of parameters defined for CloseProtocol(), and so a
close of one type cannot inadvertently delete the record corresponding
to a different type.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
In preparation for formalising the way that EFI protocols are opened
across the codebase, remove the efipci_open() wrapper.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
When DEBUG=efi_wrap is enabled, we construct a patched copy of the
boot services table and patch the global system table to point to this
copy. This ensures that any subsequently loaded EFI binaries will
call our wrappers.
Previously loaded EFI binaries will typically have cached the boot
services table pointer (in the gBS variable used by EDK2 code), and
therefore will not pick up the updated pointer and so will not call
our wrappers. In most cases, this is what we want to happen: we are
interested in tracing the calls issued by the newly loaded binary and
we do not want to be distracted by the high volume of boot services
calls issued by existing UEFI drivers.
In some circumstances (such as when a badly behaved OEM driver is
causing the system to lock up during the ExitBootServices() call), it
can be very useful to be able to patch the global boot services table
in situ, so that we can trace calls issued by existing drivers.
Restructure the wrapping code to allow wrapping to be enabled or
disabled at any time, and to allow for patching the global boot
services table in situ.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
UEFI's built-in HTTPS boot mechanism requires the trusted CA
certificates to be provided via the TlsCaCertificates variable.
(There is no equivalent of the iPXE cross-signing mechanism, so it is
not possible for UEFI to automatically use public CA certificates.)
Users who have configured UEFI HTTPS boot to use a custom root of
trust (e.g. a private CA certificate) may find it useful to have iPXE
automatically pick up and use this same root of trust, so that iPXE
can seamlessly fetch files via HTTPS from the same servers that were
trusted by UEFI HTTPS boot, in addition to servers that iPXE can
validate through other means such as cross-signed certificates.
Parse the TlsCaCertificates variable at startup, add any certificates
to the certificate store, and mark these certificates as trusted.
There are no access restrictions on modifying the TlsCaCertificates
variable: anybody with access to write UEFI variables is permitted to
change the root of trust. The UEFI security model assumes that anyone
with access to run code prior to ExitBootServices() or with access to
modify UEFI variables from within a loaded operating system is
supposed to be able to change the system's root of trust for TLS.
Any certificates parsed from TlsCaCertificates will show up in the
output of "certstat", and may be discarded using "certfree" if
unwanted.
Support for parsing TlsCaCertificates is enabled by default in EFI
builds, but may be disabled in config/general.h if needed.
As with the ${trust} setting, the contents of the TlsCaCertificates
variable will be ignored if iPXE has been compiled with an explicit
root of trust by specifying TRUST=... on the build command line.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add the TlsAuthentication.h header from EDK2's NetworkPkg, along with
a GUID definition for EFI_TLS_CA_CERTIFICATE_GUID.
It is unclear whether or not the TlsCaCertificate variable is intended
to be a UEFI standard. Its presence in NetworkPkg (rather than
MdePkg) suggests not, but the choice of EFI_TLS_CA_CERTIFICATE_GUID
(rather than e.g. EDKII_TLS_CA_CERTIFICATE_GUID) suggests that it is
intended to be included in future versions of the standard.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add support for the EFI signature list image format (as produced by
tools such as efisecdb).
The parsing code does not require any EFI boot services functions and
so may be enabled even in non-EFI builds. We default to enabling it
only for EFI builds.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently provide pem_asn1() to allow for parsing of PEM data that
is not necessarily contained in an image. Provide an equivalent
function der_asn1() to allow for similar parsing of DER data.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The UsbHostController.h header has been removed from the EDK2 codebase
since it was never defined in a released UEFI specification. However,
we may still encounter it in the wild and so it is useful to retain
the GUID and the corresponding protocol name for debug messages.
Add an iPXE include guard to this file so that the EDK2 header import
script will no longer attempt to import it from the EDK2 tree.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
iPXE allows individual raw files to be automatically wrapped with
suitable CPIO headers and injected into the magic initrd image as
exposed to a booted Linux kernel. This feature is currently limited
to placing files within directories that already exist in the initrd
filesystem.
Remove this limitation by adding the ability for iPXE to construct
CPIO headers for parent directories as needed, under control of the
"mkdir=<n>" command-line argument. For example:
initrd config.ign /usr/share/oem/config.ign mkdir=1
will create CPIO headers for the "/usr/share/oem" directory as well as
for the "/usr/share/oem/config.ign" file itself.
This simplifies the process of booting operating systems such as
Flatcar Linux, which otherwise require the single "config.ign" file to
be manually wrapped up as a CPIO archive solely in order to create the
relevant parent directory entries.
The value <n> may be used to control the number of parent directory
entries that are created. For example, "mkdir=2" would cause up to
two parent directories to be created (i.e. "/usr/share" and
"/usr/share/oem" in the above example). A negative value such as
"mkdir=-1" may be used to create all parent directories up to the root
of the tree.
Do not create any parent directory entries by default, since doing so
would potentially cause the modes and ownership information for
existing directories to be overwritten.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow the "--retimeout" option to be used to specify a timeout value
that will be (re)applied after each keypress activity. This allows
script authors to ensure that a single (potentially accidental)
keypress will not pause the boot process indefinitely.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The ANS X9.82 specification implicitly assumes that the RBG_Startup
function will be called before it is needed, and includes checks to
make sure that Generate_function fails if this has not happened.
However, there is no well-defined point at which the RBG_Startup
function is to be called: it's just assumed that this happens as part
of system startup.
We currently call RBG_Startup to instantiate the DRBG as an iPXE
startup function, with the corresponding shutdown function
uninstantiating the DRBG. This works for most use cases, and avoids
an otherwise unexpected user-visible delay when a caller first
attempts to use the DRBG (e.g. by attempting an HTTPS download).
The download of autoexec.ipxe for UEFI is triggered by the EFI root
bus probe in efi_probe(). Both the root bus probe and the RBG startup
function run at STARTUP_NORMAL, so there is no defined ordering
between them. If the base URI for autoexec.ipxe uses HTTPS, then this
may cause random bits to be requested before the RBG has been started.
Extend the logic in rbg_generate() to automatically start up the RBG
if startup has not already been attempted. If startup fails
(e.g. because the entropy source is broken), then do not automatically
retry since this could result in extremely long delays waiting for
entropy that will never arrive.
Reported-by: Michael Niehaus <niehaus@live.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The only remaining use case for direct reduction (outside of the unit
tests) is in calculating the constant R^2 mod N used during Montgomery
multiplication.
The current implementation of direct reduction requires a writable
copy of the modulus (to allow for shifting), and both the modulus and
the result buffer must be padded to be large enough to hold (R^2 - N),
which is twice the size of the actual values involved.
For the special case of reducing R^2 mod N (or any power of two mod
N), we can run the same algorithm without needing either a writable
copy of the modulus or a padded result buffer. The working state
required is only two bits larger than the result buffer, and these
additional bits may be held in local variables instead.
Rewrite bigint_reduce() to handle only this use case, and remove the
no longer necessary uses of double-sized big integers.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
When allocating memory with a non-zero alignment offset, the free
memory block structure following the allocation may end up improperly
aligned.
Ensure that free memory blocks always remain aligned to the size of
the free memory block structure.
Ensure that the initial heap is also correctly aligned, thereby
allowing the logic for leaking undersized free memory blocks to be
omitted.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The NIST elliptic curves are Weierstrass curves and have the form
y^2 = x^3 + ax + b
with each curve defined by its field prime, the constants "a" and "b",
and a generator base point.
Implement a constant-time algorithm for point addition, based upon
Algorithm 1 from "Complete addition formulas for prime order elliptic
curves" (Joost Renes, Craig Costello, and Lejla Batina), and use this
as a Montgomery ladder commutative operation to perform constant-time
point multiplication.
The code for point addition is implemented using a custom bytecode
interpreter with 16-bit instructions, since this results in
substantially smaller code than compiling the somewhat lengthy
sequence of arithmetic operations directly. Values are calculated
modulo small multiples of the field prime in order to allow for the
use of relaxed Montgomery reduction.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The Montgomery ladder may be used to perform any operation that is
isomorphic to exponentiation, i.e. to compute the result
r = g^e = g * g * g * g * .... * g
for an arbitrary commutative operation "*", base or generator "g", and
exponent "e".
Implement a generic Montgomery ladder for use by both modular
exponentiation and elliptic curve point multiplication (both of which
are isomorphic to exponentiation).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The elliptic curve point representation for the x25519 curve includes
only the X value, since the curve is designed such that the Montgomery
ladder does not need to ever know or calculate a Y value. There is no
curve point format byte: the public key data is simply the X value.
The pre-master secret is also simply the X value of the shared secret
curve point.
The point representation for the NIST curves includes both X and Y
values, and a single curve point format byte that must indicate that
the format is uncompressed. The pre-master secret for the NIST curves
does not include both X and Y values: only the X value is used.
Extend the definition of an elliptic curve to allow the point size to
be specified separately from the key size, and extend the definition
of a TLS named curve to include an optional curve point format byte
and a pre-master secret length.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Split out the portion of tls_send_client_key_exchange_ecdhe() that
actually performs the elliptic curve key exchange into a separate
function ecdhe_key().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
In debug messages, big integers are currently printed as hex dumps.
This is quite verbose and cumbersome to check against external
sources.
Add bigint_ntoa() to transcribe big integers into a static buffer
(following the model of inet_ntoa(), eth_ntoa(), uuid_ntoa(), etc).
Abbreviate big integers that will not fit within the static buffer,
showing both the most significant and least significant digits in the
transcription. This is generally the most useful form when visually
comparing against external sources (such as test vectors, or results
produced by high-level languages).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Calculating the Montgomery constant (R^2 mod N) is done in our
implementation by zeroing the double-width representation of N,
subtracting N once to give (R^2 - N) in order to obtain a positive
value, then reducing this value modulo N.
Extract this logic from bigint_mod_exp() to a separate function
bigint_reduce_supremum(), to allow for reuse by other code.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Classic Montgomery reduction involves a single conditional subtraction
to ensure that the result is strictly less than the modulus.
When performing chains of Montgomery multiplications (potentially
interspersed with additions and subtractions), it can be useful to
work with values that are stored modulo some small multiple of the
modulus, thereby allowing some reductions to be elided. Each addition
and subtraction stage will increase this running multiple, and the
following multiplication stages can be used to reduce the running
multiple since the reduction carried out for multiplication products
is generally strong enough to absorb some additional bits in the
inputs. This approach is already used in the x25519 code, where
multiplication takes two 258-bit inputs and produces a 257-bit output.
Split out the conditional subtraction from bigint_montgomery() and
provide a separate bigint_montgomery_relaxed() for callers who do not
require immediate reduction to within the range of the modulus.
Modular exponentiation could potentially make use of relaxed
Montgomery multiplication, but this would require R>4N, i.e. that the
two most significant bits of the modulus be zero. For both RSA and
DHE, this would necessitate extending the modulus size by one element,
which would negate any speed increase from omitting the conditional
subtractions. We therefore retain the use of classic Montgomery
reduction for modular exponentiation, apart from the final conversion
out of Montgomery form.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Reduce the number of parameters passed to bigint_montgomery() by
calculating the inverse of the modulus modulo the element size on
demand. Cache the result, since Montgomery reduction will be used
repeatedly with the same modulus value.
In all currently supported algorithms, the modulus is a public value
(or a fixed value defined by specification) and so this non-constant
timing does not leak any private information.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
There is no further need for a standalone modular multiplication
primitive, since the only consumer is modular exponentiation (which
now uses Montgomery multiplication instead).
Remove the now obsolete bigint_mod_multiply().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Speed up modular exponentiation by using Montgomery reduction rather
than direct modular reduction.
Montgomery reduction in base 2^n requires the modulus to be coprime to
2^n, which would limit us to requiring that the modulus is an odd
number. Extend the implementation to include support for
exponentiation with even moduli via Garner's algorithm as described in
"Montgomery reduction with even modulus" (Koç, 1994).
Since almost all use cases for modular exponentation require a large
prime (and hence odd) modulus, the support for even moduli could
potentially be removed in future.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Montgomery reduction is substantially faster than direct reduction,
and is better suited for modular exponentiation operations.
Add bigint_montgomery() to perform the Montgomery reduction operation
(often referred to as "REDC"), along with some test vectors.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Montgomery reduction requires only the least significant element of an
inverse modulo 2^k, which in turn depends upon only the least
significant element of the invertend.
Use the inverse size (rather than the invertend size) as the effective
size for bigint_mod_invert(). This eliminates around 97% of the loop
iterations for a typical 2048-bit RSA modulus.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
With a slight modification to the algorithm to ignore bits of the
residue that can never contribute to the result, it is possible to
reuse the as-yet uncalculated portions of the inverse to hold the
residue. This removes the requirement for additional temporary
working space.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Direct modular reduction is expected to be used in situations where
there is no requirement to retain the original (unreduced) value.
Modify the API for bigint_reduce() to reduce the value in place,
(removing the separate result buffer), impose a constraint that the
modulus and value have the same size, and require the modulus to be
passed in writable memory (to allow for scaling in place). This
removes the requirement for additional temporary working space.
Reverse the order of arguments so that the constant input is first,
to match the usage pattern for bigint_add() et al.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Expose the effective carry (or borrow) out flag from big integer
addition and subtraction, and use this to elide an explicit bit test
when performing x25519 reduction.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add a dedicated bigint_msb_is_set() to reduce the amount of open
coding required in the common case of testing the sign of a two's
complement big integer.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown