519255 - Add the PK11_ExportDERPrivateKeyInfo function

Status: RESOLVED FIXED

(NSS :: Libraries, enhancement, P2)

Description

[Wan-Teh Chang]

Attachment: Proposed patch

This bug report is FYI only.  You don't need to review
the patch or comment on it.

The attached patch implements a function for exporting
a private key in the PrivateKeyInfo format.  I submitted
the patch in the hope that it could be useful to someone.

Comment 1

[Nelson Bolyard (seldom reads bugmail)]

May I infer from this that someone at Google believes that exporting 
private keys in the clear is in the security interests of its users?

Comment 2

[Wan-Teh Chang]

This was an intellectual exercise for me.  I saw an
unimplemented function PK11_ExportPrivateKeyInfo in
our API.  I was curious as to how much work it would
take to implement it, so I spent a couple hours of a
Friday night to implement it.  The patch works and
has no memory leaks under valgrind.

Comment 3

[Wan-Teh Chang]

Attachment: Proposed patch v2

The previous patch has a bug: the "version" local variable in
PK11_ExportPrivKeyInfo should be static.

In this patch, I fixed that bug and some coding style issues,
and updated the patch to the current NSS trunk.

Comment 4

[Wan-Teh Chang]

Attachment: Proposed patch v2.1

Removed a space at the end of a line.

Comment 5

[Wan-Teh Chang]

Comment on attachment 8393865 [details] [diff] [review]
Proposed patch v2.1

Review of attachment 8393865 [details] [diff] [review]:
-----------------------------------------------------------------

::: lib/pk11wrap/pk11pk12.c
@@ +542,5 @@
> +{
> +    /* PrivateKeyInfo version (always zero) */
> +    static const unsigned char pkiVersion = 0;
> +    /* RSAPrivateKey version (always zero) */
> +    static const unsigned char rsaVersion = 0;

Note that rsaVersion doesn't need to be static. Only
pkiVersion needs to be static because the returned |pki|
points to it.

Comment 6

[Wan-Teh Chang]

Attachment: Proposed patch v3

This patch was reviewed at https://codereview.chromium.org/205343004.

Richard: do you need this function?

The current NSS policy is to only export EncryptedPrivateKeyInfo.
If you need to export unencrypted PrivateKeyInfo for WebCrypto, I'll
check in this patch.

Comment 7

[Wan-Teh Chang]

Attachment: Document that PK11_ReadAttribute doesn't modify the 'type' field of the SECItem

I checked in the comment patch separately:
https://hg.mozilla.org/projects/nss/rev/8fea8214ffbf

Comment 8

[Wan-Teh Chang]

Attachment: Proposed patch v3 (PK11_ReadAttribute comment change excluded)

Comment 9

[Richard Barnes [:rbarnes]]

Yes, there is a need for exporting unencrypted PrivateKeyInfo for WebCrypto.  

I would note that this doesn't really change the capabilities that NSS exposes, since you could do basically the same thing outside of NSS.  But just being able to call PK11_ExportDERPrivateKeyInfo would be easier.

Comment 10

[Wan-Teh Chang]

Comment on attachment 8398718 [details] [diff] [review]
Proposed patch v3 (PK11_ReadAttribute comment change excluded)

Patch checked in: https://hg.mozilla.org/projects/nss/rev/a751a5146718