Add an implementation of the X25519 key exchange algorithm as defined
in RFC7748.
This implementation is inspired by and partially based upon the paper
"Implementing Curve25519/X25519: A Tutorial on Elliptic Curve
Cryptography" by Martin Kleppmann, available for download from
https://www.cl.cam.ac.uk/teaching/2122/Crypto/curve25519.pdf
The underlying modular addition, subtraction, and multiplication
operations are completely redesigned for substantially improved
efficiency compared to the TweetNaCl implementation studied in that
paper (approximately 5x-10x faster and with 70% less memory usage).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add a helper function bigint_swap() that can be used to conditionally
swap a pair of big integers in constant time.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently implement build-time assertions via a mechanism that
generates a call to an undefined external function that will cause the
link to fail unless the compiler can prove that the asserted condition
is true (and thereby eliminate the undefined function call).
This assertion mechanism can be used for conditions that are not
amenable to the use of static_assert(), since static_assert() will not
allow for proofs via dead code elimination.
Add __attribute__((error(...))) to the undefined external function, so
that the error is raised at compile time rather than at link time.
This allows us to provide a more meaningful error message (which will
include the file name and line number, as with any other compile-time
error), and avoids the need for the caller to specify a unique symbol
name for the external function.
Change the name from linker_assert() to build_assert(), since the
assertion now takes place at compile time rather than at link time.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Provide per-source state variables for the repetition count test and
adaptive proportion test, to allow for the situation in which an
entropy source can be enabled but then fails during the startup tests,
thereby requiring an alternative entropy source to be used.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
As noted in commit 3c83843 ("[rng] Check for several functioning RTC
interrupts"), experimentation shows that Hyper-V cannot be trusted to
reliably generate RTC interrupts. (As noted in commit f3ba0fb
("[hyperv] Provide timer based on the 10MHz time reference count
MSR"), Hyper-V appears to suffer from a general problem in reliably
generating any legacy interrupts.) An alternative entropy source is
therefore required for an image that may be used in a Hyper-V Gen1
virtual machine.
The x86 RDRAND instruction provides a suitable alternative entropy
source, but may not be supported by all CPUs. We must therefore allow
for multiple entropy sources to be compiled in, with the single active
entropy source selected only at runtime.
Restructure the internal entropy API to allow a working entropy source
to be detected and chosen at runtime.
Enable the RDRAND entropy source for all x86 builds, since it is
likely to be substantially faster than any other source.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The hash calculation is currently performed incorrectly when
decrypting in place, since the ciphertext will have been overwritten
with the plaintext before being used to update the hash value.
Restructure the code to allow for in-place encryption and decryption.
Choose to optimise for the decryption case, since we are likely to
decrypt much more data than we encrypt.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Reset the accumulated authentication state when cipher_setiv() is
called, to allow the cipher to be reused without resetting the key.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
All existing cipher suites use SHA-256 as the TLSv1.2 and above
handshake digest algorithm (even when using SHA-1 as the MAC digest
algorithm). Some GCM cipher suites use SHA-384 as the handshake
digest algorithm.
Allow the cipher suite to specify the handshake (and PRF) digest
algorithm to be used for TLSv1.2 and above.
This requires some restructuring to allow for the fact that the
ClientHello message must be included within the handshake digest, even
though the relevant digest algorithm is not yet known at the point
that the ClientHello is sent. Fortunately, the ClientHello may be
reproduced verbatim at the point of receiving the ServerHello, so we
rely on reconstructing (rather than storing) this message.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
TLS stream and block ciphers use a MAC with a length equal to the
output length of the digest algorithm in use. For AEAD ciphers there
is no MAC, with the equivalent functionality provided by the cipher
algorithm's authentication tag.
Allow for the existence of AEAD cipher suites by making the MAC length
a parameter of the cipher suite.
Assume that the MAC key length is equal to the MAC length, since this
is true for all currently supported cipher suites.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The GCM cipher mode of operation (in common with other counter-based
modes of operation) has a notion of blocksize that does not neatly
fall into our current abstraction: it does operate in 16-byte blocks
but allows for an arbitrary overall data length (i.e. the final block
may be incomplete).
Model this by adding a concept of alignment size. Each call to
encrypt() or decrypt() must begin at a multiple of the alignment size
from the start of the data stream. This allows us to model GCM by
using a block size of 1 byte and an alignment size of 16 bytes.
As a side benefit, this same concept allows us to neatly model the
fact that raw AES can encrypt only a single 16-byte block, by
specifying an alignment size of zero on this cipher.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
TLS block ciphers always use CBC (as per RFC 5246 section 6.2.3.2)
with a record initialisation vector length that is equal to the cipher
block size, and no fixed initialisation vector.
The initialisation vector for AEAD ciphers such as GCM is less
straightforward, and requires both a fixed and per-record component.
Extend the definition of a cipher suite to include fixed and record
initialisation vector lengths, and generate the fixed portion (if any)
as part of key expansion.
Do not add explicit calls to cipher_setiv() in tls_assemble_block()
and tls_split_block(), since the constraints imposed by RFC 5246 are
specifically chosen to allow implementations to avoid doing so.
(Instead, add a sanity check that the record initialisation vector
length is equal to the cipher block size.)
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some ciphers (such as GCM) support the concept of a tag that can be
used to authenticate the encrypted data. Add a cipher method for
generating an authentication tag.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Add an implementation of the Ephemeral Diffie-Hellman key exchange
algorithm as defined in RFC2631, with test vectors taken from the NIST
Cryptographic Toolkit.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Simplify the internal HMAC API so that the key is provided only at the
point of calling hmac_init(), and the (potentially reduced) key is
stored as part of the context for later use by hmac_final().
This simplifies the calling code, and avoids the need for callers such
as TLS to allocate a potentially variable length block in order to
retain a copy of the unmodified key.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
DNS names are case-insensitive, and RFC 5280 (unlike RFC 3280)
mandates support for case-insensitive name comparison in X.509
certificates.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We surface this debugging information in cases where a cert actually
lacks an issuer, but also in cases where it *has* an issuer, but we
cannot trust it (e.g. due to issues in establishing a trust chain).
Signed-off-by: Josh McSavaney <me@mcsau.cc>
Modified-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Record the root of trust used at the point that a certificate is
validated, redefine validation as checking a certificate against a
specific root of trust, and pass an explicit root of trust when
creating a TLS connection.
This allows a custom TLS connection to be used with a custom root of
trust, without causing any validated certificates to be treated as
valid for normal purposes.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
OCSP currently calls x509_validate() with an empty root certificate
list, on the basis that the OCSP signer certificate (if existent) must
be signed directly by the issuer certificate.
Using an empty root certificate list is not required to achieve this
goal, since x509_validate() already accepts an explicit issuer
certificate parameter. The explicit empty root certificate list
merely prevents the signer certificate from being evaluated as a
potential trusted root certificate.
Remove the dummy OCSP root certificate list and use the default root
certificate list when calling x509_validate().
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>
Various implementation quirks in OCSP servers make it impractical to
use anything other than SHA1 to construct the issuerNameHash and
issuerKeyHash identifiers in the request certID. For example: both
the OpenCA OCSP responder used by ipxe.org and the Boulder OCSP
responder used by LetsEncrypt will fail if SHA256 is used in the
request certID.
As of commit 6ffe28a ("[ocsp] Accept response certID with missing
hashAlgorithm parameters") we rely on asn1_digest_algorithm() to parse
the algorithm identifier in the response certID. This will fail if
SHA1 is disabled via config/crypto.h.
Fix by using a direct ASN.1 object comparison on the OID within the
algorithm identifier.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
There are many ways in which the object for a cryptographic algorithm
may be included, even if not explicitly enabled in config/crypto.h.
For example: the MD5 algorithm is required by TLSv1.1 or earlier, by
iSCSI CHAP authentication, by HTTP digest authentication, and by NTLM
authentication.
In the current implementation, inclusion of an algorithm for any
reason will result in the algorithm's ASN.1 object identifier being
included in the "asn1_algorithms" table, which consequently allows the
algorithm to be used for any ASN1-identified purpose. For example: if
the MD5 algorithm is included in order to support HTTP digest
authentication, then iPXE would accept a (validly signed) TLS
certificate using an MD5 digest.
Split the ASN.1 object identifiers into separate files that are
required only if explicitly enabled in config/crypto.h. This allows
an algorithm to be omitted from the "asn1_algorithms" table even if
the algorithm implementation is dragged in for some other purpose.
The end result is that only the algorithms that are explicitly enabled
in config/crypto.h can be used for ASN1-identified purposes such as
signature verification.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Ensure that the configured RSA digestInfo prefixes are included in any
build that includes rsa.o (rather than relying on x509.o or tls.o also
being present in the final binary).
This allows the RSA self-tests to be run in isolation.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
One of the design goals of ASN.1 DER is to provide a canonical
serialization of a data structure, thereby allowing for equality of
values to be tested by simply comparing the serialized bytes.
Some OCSP servers will modify the request certID to omit the optional
(and null) "parameters" portion of the hashAlgorithm. This is
arguably legal but breaks the ability to perform a straightforward
bitwise comparison on the entire certID field between request and
response.
Fix by comparing the OID-identified hashAlgorithm separately from the
remaining certID fields.
Originally-fixed-by: Thilo Fromm <Thilo@kinvolk.io>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently perform various min-entropy calculations using build-time
floating-point arithmetic. No floating-point code ends up in the
final binary, since the results are eventually converted to integers
and asserted to be compile-time constants.
Though this mechanism is undoubtedly cute, it inhibits us from using
"-mno-sse" to prevent the use of SSE registers by the compiler.
Fix by using fixed-point arithmetic instead.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow certificates to be marked as having been added explicitly at run
time. Such certificates will not be discarded via the certificate
store cache discarder.
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>
