On Thu, 28 Sep 2023 19:32:32 +0200 Lukas Wunner <lukas@xxxxxxxxx> wrote: > The upcoming in-kernel SPDM library (Security Protocol and Data Model, > https://www.dmtf.org/dsp/DSP0274) needs to retrieve the length from > ASN.1 DER-encoded X.509 certificates. > > Such code already exists in x509_load_certificate_list(), so move it > into a new helper for reuse by SPDM. > > No functional change intended. > > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Good find :) I vaguely remember carrying a hack for this so good to do something more general + save on the duplication. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > --- > crypto/asymmetric_keys/x509_loader.c | 38 +++++++++++++++++++--------- > include/keys/asymmetric-type.h | 2 ++ > 2 files changed, 28 insertions(+), 12 deletions(-) > > diff --git a/crypto/asymmetric_keys/x509_loader.c b/crypto/asymmetric_keys/x509_loader.c > index a41741326998..121460a0de46 100644 > --- a/crypto/asymmetric_keys/x509_loader.c > +++ b/crypto/asymmetric_keys/x509_loader.c > @@ -4,28 +4,42 @@ > #include <linux/key.h> > #include <keys/asymmetric-type.h> > > +int x509_get_certificate_length(const u8 *p, unsigned long buflen) > +{ > + int plen; > + > + /* Each cert begins with an ASN.1 SEQUENCE tag and must be more > + * than 256 bytes in size. > + */ > + if (buflen < 4) > + return -EINVAL; > + > + if (p[0] != 0x30 && > + p[1] != 0x82) > + return -EINVAL; > + > + plen = (p[2] << 8) | p[3]; > + plen += 4; > + if (plen > buflen) > + return -EINVAL; > + > + return plen; > +} > +EXPORT_SYMBOL_GPL(x509_get_certificate_length); > + > int x509_load_certificate_list(const u8 cert_list[], > const unsigned long list_size, > const struct key *keyring) > { > key_ref_t key; > const u8 *p, *end; > - size_t plen; > + int plen; > > p = cert_list; > end = p + list_size; > while (p < end) { > - /* Each cert begins with an ASN.1 SEQUENCE tag and must be more > - * than 256 bytes in size. > - */ > - if (end - p < 4) > - goto dodgy_cert; > - if (p[0] != 0x30 && > - p[1] != 0x82) > - goto dodgy_cert; > - plen = (p[2] << 8) | p[3]; > - plen += 4; > - if (plen > end - p) > + plen = x509_get_certificate_length(p, end - p); > + if (plen < 0) > goto dodgy_cert; > > key = key_create_or_update(make_key_ref(keyring, 1), > diff --git a/include/keys/asymmetric-type.h b/include/keys/asymmetric-type.h > index 69a13e1e5b2e..6705cfde25b9 100644 > --- a/include/keys/asymmetric-type.h > +++ b/include/keys/asymmetric-type.h > @@ -84,6 +84,8 @@ extern struct key *find_asymmetric_key(struct key *keyring, > const struct asymmetric_key_id *id_2, > bool partial); > > +int x509_get_certificate_length(const u8 *p, unsigned long buflen); > + > int x509_load_certificate_list(const u8 cert_list[], const unsigned long list_size, > const struct key *keyring); >
