Subject: Re: [PATCH v6 02/12] PKCS#7: Introduce pkcs7_get_message_sig() and verify_pkcs7_message_sig()

From: Mimi Zohar <[email-masked]>
Date: Thu, 22 Mar 2018 17:49:38 -0400

Hi Thiago,

On Fri, 2018-03-16 at 17:38 -0300, Thiago Jung Bauermann wrote:
> IMA will need to know the key that signed a given PKCS#7 message, so add
> pkcs7_get_message_sig().
> 
> It will also need to verify an already parsed PKCS#7 message. For this
> purpose, add verify_pkcs7_message_sig() which takes a struct pkcs7_message
> for verification instead of the raw bytes that verify_pkcs7_signature()
> takes.

The title "PKCS#7: refactor verify_pkcs7_signature()" might be more
appropriate.  The patch description would then explain why it needs to
be refactored.  In this case, verify_pkcs7_signature() verifies the
signature using keys on the builtin and secondary keyrings.  IMA-
appraisal needs to verify the signature using keys on its keyring.

The patch itself looks good!

Reviewed-by: Mimi Zohar <[email-masked]>

> Signed-off-by: Thiago Jung Bauermann <[email-masked]>
> Cc: David Howells <[email-masked]>
> Cc: David Woodhouse <[email-masked]>
> Cc: Herbert Xu <[email-masked]>
> Cc: "David S. Miller" <[email-masked]>
> ---
>  certs/system_keyring.c                | 61 ++++++++++++++++++++++++++---------
>  crypto/asymmetric_keys/pkcs7_parser.c | 16 +++++++++
>  include/crypto/pkcs7.h                |  2 ++
>  include/linux/verification.h          | 10 ++++++
>  4 files changed, 73 insertions(+), 16 deletions(-)
> 
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 6251d1b27f0c..7ddc8b7a3062 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -190,33 +190,27 @@ late_initcall(load_system_certificate_list);
>  #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
> 
>  /**
> - * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
> + * verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
>   * @data: The data to be verified (NULL if expecting internal data).
>   * @len: Size of @data.
> - * @raw_pkcs7: The PKCS#7 message that is the signature.
> - * @pkcs7_len: The size of @raw_pkcs7.
> + * @pkcs7: The PKCS#7 message that is the signature.
>   * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
>   *					(void *)1UL for all trusted keys).
>   * @usage: The use to which the key is being put.
>   * @view_content: Callback to gain access to content.
>   * @ctx: Context for callback.
>   */
> -int verify_pkcs7_signature(const void *data, size_t len,
> -			   const void *raw_pkcs7, size_t pkcs7_len,
> -			   struct key *trusted_keys,
> -			   enum key_being_used_for usage,
> -			   int (*view_content)(void *ctx,
> -					       const void *data, size_t len,
> -					       size_t asn1hdrlen),
> -			   void *ctx)
> +int verify_pkcs7_message_sig(const void *data, size_t len,
> +			     struct pkcs7_message *pkcs7,
> +			     struct key *trusted_keys,
> +			     enum key_being_used_for usage,
> +			     int (*view_content)(void *ctx,
> +						 const void *data, size_t len,
> +						 size_t asn1hdrlen),
> +			     void *ctx)
>  {
> -	struct pkcs7_message *pkcs7;
>  	int ret;
> 
> -	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
> -	if (IS_ERR(pkcs7))
> -		return PTR_ERR(pkcs7);
> -
>  	/* The data should be detached - so we need to supply it. */
>  	if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
>  		pr_err("PKCS#7 signature with non-detached data\n");
> @@ -258,6 +252,41 @@ int verify_pkcs7_signature(const void *data, size_t len,
>  	}
> 
>  error:
> +	pr_devel("<==%s() = %d\n", __func__, ret);
> +	return ret;
> +}
> +
> +/**
> + * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
> + * @data: The data to be verified (NULL if expecting internal data).
> + * @len: Size of @data.
> + * @raw_pkcs7: The PKCS#7 message that is the signature.
> + * @pkcs7_len: The size of @raw_pkcs7.
> + * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
> + *					(void *)1UL for all trusted keys).
> + * @usage: The use to which the key is being put.
> + * @view_content: Callback to gain access to content.
> + * @ctx: Context for callback.
> + */
> +int verify_pkcs7_signature(const void *data, size_t len,
> +			   const void *raw_pkcs7, size_t pkcs7_len,
> +			   struct key *trusted_keys,
> +			   enum key_being_used_for usage,
> +			   int (*view_content)(void *ctx,
> +					       const void *data, size_t len,
> +					       size_t asn1hdrlen),
> +			   void *ctx)
> +{
> +	struct pkcs7_message *pkcs7;
> +	int ret;
> +
> +	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
> +	if (IS_ERR(pkcs7))
> +		return PTR_ERR(pkcs7);
> +
> +	ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
> +				       view_content, ctx);
> +
>  	pkcs7_free_message(pkcs7);
>  	pr_devel("<==%s() = %d\n", __func__, ret);
>  	return ret;
> diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
> index a6dcaa659aa8..456b803972b5 100644
> --- a/crypto/asymmetric_keys/pkcs7_parser.c
> +++ b/crypto/asymmetric_keys/pkcs7_parser.c
> @@ -683,3 +683,19 @@ int pkcs7_note_signed_info(void *context, size_t hdrlen,
>  		return -ENOMEM;
>  	return 0;
>  }
> +
> +/**
> + * pkcs7_get_message_sig - get signature in @pkcs7
> + */
> +const struct public_key_signature *pkcs7_get_message_sig(
> +					const struct pkcs7_message *pkcs7)
> +{
> +	/*
> +	 * This function doesn't support messages with more than one signature,
> +	 * so don't return anything in that case.
> +	 */
> +	if (pkcs7->signed_infos == NULL || pkcs7->signed_infos->next != NULL)
> +		return NULL;
> +
> +	return pkcs7->signed_infos->sig;
> +}
> diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
> index 583f199400a3..6f51d0cb6d12 100644
> --- a/include/crypto/pkcs7.h
> +++ b/include/crypto/pkcs7.h
> @@ -28,6 +28,8 @@ extern void pkcs7_free_message(struct pkcs7_message *pkcs7);
>  extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
>  				  const void **_data, size_t *_datalen,
>  				  size_t *_headerlen);
> +extern const struct public_key_signature *pkcs7_get_message_sig(
> +					const struct pkcs7_message *pkcs7);
> 
>  /*
>   * pkcs7_trust.c
> diff --git a/include/linux/verification.h b/include/linux/verification.h
> index a10549a6c7cd..f04dac2728ec 100644
> --- a/include/linux/verification.h
> +++ b/include/linux/verification.h
> @@ -29,6 +29,7 @@ extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR];
>  #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
> 
>  struct key;
> +struct pkcs7_message;
> 
>  extern int verify_pkcs7_signature(const void *data, size_t len,
>  				  const void *raw_pkcs7, size_t pkcs7_len,
> @@ -38,6 +39,15 @@ extern int verify_pkcs7_signature(const void *data, size_t len,
>  						      const void *data, size_t len,
>  						      size_t asn1hdrlen),
>  				  void *ctx);
> +extern int verify_pkcs7_message_sig(const void *data, size_t len,
> +				    struct pkcs7_message *pkcs7,
> +				    struct key *trusted_keys,
> +				    enum key_being_used_for usage,
> +				    int (*view_content)(void *ctx,
> +							const void *data,
> +							size_t len,
> +							size_t asn1hdrlen),
> +				    void *ctx);
> 
>  #ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
>  extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
>