[PATCH v4 1/7] lib: crypto: add public_key_verify_signature()

Heinrich Schuchardt
2020-07-19T08:20:58Z

On 7/17/20 9:16 AM, AKASHI Takahiro wrote:
> This function will be called from x509_check_for_self_signed() and
> pkcs7_verify_one(), which will be imported from linux in a later patch.
>
> While it does exist in linux code and has a similar functionality of
> rsa_verify(), it calls further linux-specific interfaces inside.
> That could lead to more files being imported from linux.
>
> So simply re-implement it here instead of re-using the code.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> include/crypto/public_key.h | 2 +-
> lib/crypto/public_key.c | 70 ++++++++++++++++++++++++++++++++++++-
> 2 files changed, 70 insertions(+), 2 deletions(-)
>
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 436a1ee1ee64..3ba90fcc3483 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -82,9 +82,9 @@ extern int decrypt_blob(struct kernel_pkey_params *, const void *, void *);
> extern int create_signature(struct kernel_pkey_params *, const void *, void *);
> extern int verify_signature(const struct key *,
> const struct public_key_signature *);
> +#endif /* __UBOOT__ */
>
> int public_key_verify_signature(const struct public_key *pkey,
> const struct public_key_signature *sig);
> -#endif /* !__UBOOT__ */
>
> #endif /* _LINUX_PUBLIC_KEY_H */
> diff --git a/lib/crypto/public_key.c b/lib/crypto/public_key.c
> index e12ebbb3d0c5..71a0e0356beb 100644
> --- a/lib/crypto/public_key.c
> +++ b/lib/crypto/public_key.c
> @@ -25,7 +25,10 @@
> #include <keys/asymmetric-subtype.h>
> #endif
> #include <crypto/public_key.h>
> -#ifndef __UBOOT__
> +#ifdef __UBOOT__
> +#include <image.h>
> +#include <u-boot/rsa.h>
> +#else
> #include <crypto/akcipher.h>
> #endif

Shouldn't we describe in the header of the file that the code is taken
(at least partially) from Linux' crypto/asymmetric_keys/public_key.c?

Please, also state the Linux version number.

>
> @@ -80,6 +83,71 @@ void public_key_signature_free(struct public_key_signature *sig)
> }
> EXPORT_SYMBOL_GPL(public_key_signature_free);
>
> +/**
> + * public_key_verify_signature - Verify a signature using a public key.
> + *
> + * @pkey: Public key
> + * @sig: Signature
> + *
> + * Verify a signature, @sig, using a RSA public key, @pkey.
> + *
> + * Return: 0 - verified, non-zero error code - otherwise
> + */
> +int public_key_verify_signature(const struct public_key *pkey,
> + const struct public_key_signature *sig)
> +{
> + struct image_sign_info info;
> + struct image_region region;
> + int ret;
> +
> + pr_devel("==>%s()\n", __func__);
> +
> + if (!pkey || !sig)
> + return -EINVAL;
> +
> + if (pkey->key_is_private)
> + return -EINVAL;
> +
> + memset(&info, '\0', sizeof(info));
> + info.padding = image_get_padding_algo("pkcs-1.5");
> + /*
> + * Note: image_get_[checksum|crypto]_algo takes a string
> + * argument like "<checksum>,<crypto>"
> + * TODO: support other hash algorithms
> + */
> + if (strcmp(sig->pkey_algo, "rsa") || (sig->s_size * 8) != 2048) {
> + pr_warn("Encryption is not RSA2048: %s%d\n",
> + sig->pkey_algo, sig->s_size * 8);
> + return -ENOPKG;
> + }
> + if (!strcmp(sig->hash_algo, "sha1")) {
> + info.checksum = image_get_checksum_algo("sha1,rsa2048");
> + info.name = "sha1,rsa2048";
> + } else if (!strcmp(sig->hash_algo, "sha256")) {
> + info.checksum = image_get_checksum_algo("sha256,rsa2048");
> + info.name = "sha256,rsa2048";
> + } else {
> + pr_warn("unknown msg digest algo: %s\n", sig->hash_algo);
> + return -ENOPKG;
> + }
> + info.crypto = image_get_crypto_algo(info.name);
> + if (unlikely(IS_ERR(info.checksum) || IS_ERR(info.crypto)))
> + return -ENOPKG;

scripts/checkpatch.pl complains:

WARNING: nested (un)?likely() calls, IS_ERR already uses unlikely()
internally
#104: FILE: lib/crypto/public_key.c:134:
+ if (unlikely(IS_ERR(info.checksum) || IS_ERR(info.crypto)))

I cannot find this unlikely in the Linux v5.8-rc4
crypto/asymmetric_keys/public_key.c file. From where did you copy this code?

Best regards

Heinrich

> +
> + info.key = pkey->key;
> + info.keylen = pkey->keylen;
> +
> + region.data = sig->digest;
> + region.size = sig->digest_size;
> +
> + if (rsa_verify_with_pkey(&info, sig->digest, sig->s, sig->s_size))
> + ret = -EKEYREJECTED;
> + else
> + ret = 0;
> +
> + pr_devel("<==%s() = %d\n", __func__, ret);
> + return ret;
> +}
> #else
> /*
> * Destroy a public key algorithm key.
>