ecdsa_set_pub_key

ecdsa_set_pub_key

[Jarkko Sakkinen]

Hi,

The documentation of ecdsa_set_pub_key() is the following:

/*
 * 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.
 */

If you interpret this literally it would mean 64 bytes buffer for p256
with two 32 byte blobs for x and y.

With such buffer the function fails with -EINVAL, which is obvious from
the code that does checks on the contents.

Instead of responding to this, can you please fix the documentation bug?

There was also badly documented stuff in akcipher that has been
unreacted so far so putting also that one here:

https://lore.kernel.org/keyrings/D1HCVOZ1IN7S.1SUZ75QRE8QUZ@kernel.org/

BR, Jarkko

Re: ecdsa_set_pub_key

[Jarkko Sakkinen]

On Mon May 27, 2024 at 8:25 PM EEST, Jarkko Sakkinen wrote:
> Hi,
>
> The documentation of ecdsa_set_pub_key() is the following:
>
> /*
>  * 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.
>  */
>
> If you interpret this literally it would mean 64 bytes buffer for p256
> with two 32 byte blobs for x and y.
>
> With such buffer the function fails with -EINVAL, which is obvious from
> the code that does checks on the contents.
>
> Instead of responding to this, can you please fix the documentation bug?
>
> There was also badly documented stuff in akcipher that has been
> unreacted so far so putting also that one here:
>
> https://lore.kernel.org/keyrings/D1HCVOZ1IN7S.1SUZ75QRE8QUZ@kernel.org/
>
> BR, Jarkko

The best reference I could quickly find is Wikipedia:

"The older uncompressed keys are 65 bytes, consisting of constant prefix
(0x04), followed by two 256-bit integers called x and y (2 * 32 bytes).
The prefix of a compressed key allows for the y value to be derived from
the x value."

The documentation says absolutely nothing about the prefix byte, and
neither Wikipedia nor kernel documentation has a reference to this
"older format".

BR, Jarkko