linux-kernel - Re: [RESEND] crypto: public_key: fix overflow during implicit conversion

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Message-ID: <f7bc5822c2376aa833e1299a66cb267b098512b2.camel@kernel.org>
Date:   Thu, 19 Aug 2021 15:54:03 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     zhenwei pi <pizhenwei@...edance.com>
Cc:     dhowells@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND] crypto: public_key: fix overflow during implicit
 conversion

On Thu, 2021-08-19 at 20:37 +0800, zhenwei pi wrote:
> Hit kernel warning like this, it can be reproduced by verifying 256
> bytes datafile by keyctl command, run script:
> RAWDATA=rawdata
> SIGDATA=sigdata
> 
> modprobe pkcs8_key_parser
> 
> rm -rf *.der *.pem *.pfx
> rm -rf $RAWDATA
> dd if=/dev/random of=$RAWDATA bs=256 count=1
> 
> openssl req -nodes -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem \
>   -subj "/C=CN/ST=GD/L=SZ/O=vihoo/OU=dev/CN=xx.com/emailAddress=yy@...com"
> 
> KEY_ID=`openssl pkcs8 -in key.pem -topk8 -nocrypt -outform DER | keyctl \
>   padd asymmetric 123 @s`
> 
> keyctl pkey_sign $KEY_ID 0 $RAWDATA enc=pkcs1 hash=sha1 > $SIGDATA
> keyctl pkey_verify $KEY_ID 0 $RAWDATA $SIGDATA enc=pkcs1 hash=sha1
> 
> Then the kernel reports:
>  WARNING: CPU: 5 PID: 344556 at crypto/rsa-pkcs1pad.c:540
>    pkcs1pad_verify+0x160/0x190
>  ...
>  Call Trace:
>   public_key_verify_signature+0x282/0x380
>   ? software_key_query+0x12d/0x180
>   ? keyctl_pkey_params_get+0xd6/0x130
>   asymmetric_key_verify_signature+0x66/0x80
>   keyctl_pkey_verify+0xa5/0x100
>   do_syscall_64+0x35/0xb0
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> The reason of this issue, in function 'asymmetric_key_verify_signature':
> '.digest_size(u8) = params->in_len(u32)' leads overflow of an u8 value,
> so use u32 instead of u8 for digest_size field. And reorder struct
> public_key_signature, it saves 8 bytes on a 64-bit machine.
> 
> Thanks to Jarkko Sakkinen for suggestions.

I appreciate this but since it is not relevant for the commit message,
I have to rip it off :-)

Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

/Jarkko

> Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> ---
>  include/crypto/public_key.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 47accec68cb0..f603325c0c30 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -38,9 +38,9 @@ extern void public_key_free(struct public_key *key);
>  struct public_key_signature {
>  	struct asymmetric_key_id *auth_ids[2];
>  	u8 *s;			/* Signature */
> -	u32 s_size;		/* Number of bytes in signature */
>  	u8 *digest;
> -	u8 digest_size;		/* Number of bytes in digest */
> +	u32 s_size;		/* Number of bytes in signature */
> +	u32 digest_size;	/* Number of bytes in digest */
>  	const char *pkey_algo;
>  	const char *hash_algo;
>  	const char *encoding;