On Tue May 28, 2024 at 1:18 AM EEST, Jarkko Sakkinen wrote: > On Tue May 28, 2024 at 12:58 AM EEST, Jarkko Sakkinen wrote: > > On Tue May 28, 2024 at 12:05 AM EEST, Jarkko Sakkinen wrote: > > > On Mon May 27, 2024 at 11:28 PM EEST, Jarkko Sakkinen wrote: > > > > Public key blob is not just x and y concatenated. It follows RFC5480 > > > > section 2.2. Address this by re-documenting the function with the > > > > correct description of the format. > > > > > > > > Link: https://datatracker.ietf.org/doc/html/rfc5480 > > > > Fixes: 4e6602916bc6 ("crypto: ecdsa - Add support for ECDSA signature verification") > > > > Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> > > > > --- > > > > It is a bug fix that does not really need a stable backport. Still > > > > categorizes as a bug because by following the existing documentation > > > > you end up with an error code. > > > > crypto/ecdsa.c | 5 ++--- > > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c > > > > index 258fffbf623d..55114146ff84 100644 > > > > --- a/crypto/ecdsa.c > > > > +++ b/crypto/ecdsa.c > > > > @@ -215,9 +215,8 @@ static int ecdsa_ecc_ctx_reset(struct ecc_ctx *ctx) > > > > } > > > > > > > > /* > > > > - * Set the public key given the raw uncompressed key data from an X509 > > > > - * certificate. The key data contain the concatenated X and Y coordinates of > > > > - * the public key. > > > > + * Set the public ECC key as defined by RFC5480 section 2.2 "Subject Public > > > > + * Key". Only the uncompressed format is supported. > > > > */ > > > > static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen) > > > > { > > > > > > Based on this, is this now along the lines of correct format": > > > > > > *ptr++ = 0x04; /* uncompressed */ > > > ptr = asn1_encode_octet_string(&ptr[0], &in[sizeof(in)], &x[0], x_size); > > > ptr = asn1_encode_octet_string(&ptr[0], &in[sizeof(in)], &x[x_size + 2], x_size); > > > in_len = ptr - in; > > > ret = crypto_akcipher_set_pub_key(tfm, in, in_len); > > > > > > I fixed up the above as it should be only single octect string to this: > > > > ptr = &in[0]; > > *ptr++ = 0x04; /* uncompressed */ > > ptr = asn1_encode_octet_string(&ptr[0], &in[sizeof(in)], > > &data[0], 2 * x_size); > > in_len = ptr - in; > > pr_info("in_len=%u\n", in_len); > > ret = crypto_akcipher_set_pub_key(tfm, in, in_len); > > crypto_free_akcipher(tfm); > > > > It fails in: > > > > ndigits = DIV_ROUND_UP(digitlen, sizeof(u64)); > > if (ndigits != ctx->curve->g.ndigits) > > return -EINVAL; > > > > I checked that in_len=67. > > > > The tfm is deleted at instant because the above code is part of *_query. > > TPM2 ECDSA asymmetric key that way that signature verification will work > > when it is needed. The key type signs with TPM and verifies with the > > software cipher. > > 3rd trial, i.e. no octect encoding at all but with the undocumented > (in the current mainline) prefix byte: > > ptr = &data[0]; > *ptr++ = 0x04; /* uncompressed */ > memcpy(&ptr[0], &x[0], x_size); > memcpy(&ptr[x_size], &x[x_size + 2], x_size); > ret = crypto_akcipher_set_pub_key(tfm, data, 3 * x_size + 1); > crypto_free_akcipher(tfm); > > I added also kprobe: > > echo 'r:ecdsa ecdsa_set_pub_key $retval' >> /sys/kernel/tracing/kprobe_events > echo 1 > /sys/kernel/tracing/events/kprobes/enable > cat /sys/kernel/tracing/dynamic_events > > Results: > > ecdsa: (ecdsa_set_pub_key+0xc1/0xe0 <- ecc_is_pubkey_valid_full) arg1=0xffffffea > > So I guess this is on a right track reverse engineering the format used > in this API at least :-) AFAIK TPM2 x and y are big-endian but I have no idea what ecc_digits_from_bytes() expects because it has no documentation. I guess it expect little-endian format, is this correct? BR, Jarkko
