Re: [PATCH] ecc: enforce strict length with l_ecc_point_from_data

Re: [PATCH] ecc: enforce strict length with l_ecc_point_from_data

[James Prestwood]

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On Fri, 2022-01-21 at 10:51 -0600, Denis Kenzior wrote:
> Hi James,
> 
> On 1/21/22 10:45, James Prestwood wrote:
> > This add some extra convenience to users of l_ecc_point_from_data
> > allowing the exact length to be verified in addition to creating
> > the point.
> > ---
> >   ell/ecc.c | 10 +++++-----
> >   1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> 
> This seems to break test-sae?

Yes patch coming. Every other use passed the exact bytes except SAE.

> 
> Regards,
> -Denis
> 

Re: [PATCH] ecc: enforce strict length with l_ecc_point_from_data

[Denis Kenzior]

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Hi James,

On 1/21/22 10:45, James Prestwood wrote:
> This add some extra convenience to users of l_ecc_point_from_data
> allowing the exact length to be verified in addition to creating
> the point.
> ---
>   ell/ecc.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 

This seems to break test-sae?

Regards,
-Denis

[PATCH] ecc: enforce strict length with l_ecc_point_from_data

[James Prestwood]

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This add some extra convenience to users of l_ecc_point_from_data
allowing the exact length to be verified in addition to creating
the point.
---
 ell/ecc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/ell/ecc.c b/ell/ecc.c
index a16b1c0..f1adcc4 100644
--- a/ell/ecc.c
+++ b/ell/ecc.c
@@ -538,8 +538,11 @@ LIB_EXPORT struct l_ecc_point *l_ecc_point_from_data(
 	if (!data)
 		return NULL;
 
-	/* In all cases there should be an X coordinate in data */
-	if (len < bytes)
+	/* Verify the data length matches a full point or X coordinate */
+	if (type == L_ECC_POINT_TYPE_FULL) {
+		if (len != bytes * 2)
+			return NULL;
+	} else if (len != bytes)
 		return NULL;
 
 	p = l_ecc_point_new(curve);
@@ -570,9 +573,6 @@ LIB_EXPORT struct l_ecc_point *l_ecc_point_from_data(
 
 		break;
 	case L_ECC_POINT_TYPE_FULL:
-		if (len < bytes * 2)
-			goto failed;
-
 		_ecc_be2native(p->y, (void *) data + bytes, curve->ndigits);
 
 		if (!ecc_valid_point(p))
-- 
2.31.1