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Message-ID: <026c9596-9ebe-d148-fc5f-442a7e16f48b@linux.ibm.com>
Date:   Fri, 29 Apr 2022 11:09:05 -0400
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Subject: Re: [PATCH v8 4/7] ima: define a new template field named 'd-ngv2'
 and templates
Content-Language: en-US
To:     Mimi Zohar <zohar@linux.ibm.com>, linux-integrity@vger.kernel.org
Cc:     Eric Biggers <ebiggers@kernel.org>, linux-fscrypt@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220429112601.1421947-1-zohar@linux.ibm.com>
 <20220429112601.1421947-5-zohar@linux.ibm.com>
From:   Stefan Berger <stefanb@linux.ibm.com>
In-Reply-To: <20220429112601.1421947-5-zohar@linux.ibm.com>
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On 4/29/22 07:25, Mimi Zohar wrote:
> In preparation to differentiate between unsigned regular IMA file
> hashes and fs-verity's file digests in the IMA measurement list,
> define a new template field named 'd-ngv2'.
> 
> Also define two new templates named 'ima-ngv2' and 'ima-sigv2', which
> include the new 'd-ngv2' field.
> 
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
>   .../admin-guide/kernel-parameters.txt         |  3 +-
>   Documentation/security/IMA-templates.rst      |  4 +
>   security/integrity/ima/ima_template.c         |  4 +
>   security/integrity/ima/ima_template_lib.c     | 79 ++++++++++++++++---
>   security/integrity/ima/ima_template_lib.h     |  4 +
>   5 files changed, 82 insertions(+), 12 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 3f1cc5e317ed..5e866be89f5d 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1903,7 +1903,8 @@
>   
>   	ima_template=	[IMA]
>   			Select one of defined IMA measurements template formats.
> -			Formats: { "ima" | "ima-ng" | "ima-sig" }
> +			Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
> +				   "ima-sigv2" }
>   			Default: "ima-ng"
>   
>   	ima_template_fmt=
> diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
> index cab97f49971d..eafc4e34f890 100644
> --- a/Documentation/security/IMA-templates.rst
> +++ b/Documentation/security/IMA-templates.rst
> @@ -67,6 +67,8 @@ descriptors by adding their identifier to the format string
>    - 'n': the name of the event (i.e. the file name), with size up to 255 bytes;
>    - 'd-ng': the digest of the event, calculated with an arbitrary hash
>      algorithm (field format: <hash algo>:digest);
> + - 'd-ngv2': same as d-ng, but prefixed with the "ima" digest type
> +   (field format: <digest type>:<hash algo>:digest);
>    - 'd-modsig': the digest of the event without the appended modsig;
>    - 'n-ng': the name of the event, without size limitations;
>    - 'sig': the file signature, or the EVM portable signature if the file
> @@ -87,7 +89,9 @@ Below, there is the list of defined template descriptors:
>   
>    - "ima": its format is ``d|n``;
>    - "ima-ng" (default): its format is ``d-ng|n-ng``;
> + - "ima-ngv2": its format is ``d-ngv2|n-ng``;
>    - "ima-sig": its format is ``d-ng|n-ng|sig``;
> + - "ima-sigv2": its format is ``d-ngv2|n-ng|sig``;
>    - "ima-buf": its format is ``d-ng|n-ng|buf``;
>    - "ima-modsig": its format is ``d-ng|n-ng|sig|d-modsig|modsig``;
>    - "evm-sig": its format is ``d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode``;
> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> index db1ad6d7a57f..c25079faa208 100644
> --- a/security/integrity/ima/ima_template.c
> +++ b/security/integrity/ima/ima_template.c
> @@ -20,6 +20,8 @@ static struct ima_template_desc builtin_templates[] = {
>   	{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
>   	{.name = "ima-ng", .fmt = "d-ng|n-ng"},
>   	{.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
> +	{.name = "ima-ngv2", .fmt = "d-ngv2|n-ng"},
> +	{.name = "ima-sigv2", .fmt = "d-ngv2|n-ng|sig"},
>   	{.name = "ima-buf", .fmt = "d-ng|n-ng|buf"},
>   	{.name = "ima-modsig", .fmt = "d-ng|n-ng|sig|d-modsig|modsig"},
>   	{.name = "evm-sig",
> @@ -38,6 +40,8 @@ static const struct ima_template_field supported_fields[] = {
>   	 .field_show = ima_show_template_string},
>   	{.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
>   	 .field_show = ima_show_template_digest_ng},
> +	{.field_id = "d-ngv2", .field_init = ima_eventdigest_ngv2_init,
> +	 .field_show = ima_show_template_digest_ngv2},
>   	{.field_id = "n-ng", .field_init = ima_eventname_ng_init,
>   	 .field_show = ima_show_template_string},
>   	{.field_id = "sig", .field_init = ima_eventsig_init,
> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
> index 4b6706f864d4..ff82e699149c 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -24,11 +24,22 @@ static bool ima_template_hash_algo_allowed(u8 algo)
>   enum data_formats {
>   	DATA_FMT_DIGEST = 0,
>   	DATA_FMT_DIGEST_WITH_ALGO,
> +	DATA_FMT_DIGEST_WITH_TYPE_AND_ALGO,
>   	DATA_FMT_STRING,
>   	DATA_FMT_HEX,
>   	DATA_FMT_UINT
>   };
>   
> +enum digest_type {
> +	DIGEST_TYPE_IMA,
> +	DIGEST_TYPE__LAST
> +};
> +
> +#define DIGEST_TYPE_NAME_LEN_MAX 4	/* including NULL */

You probably mean 'NUL' ('\0') here: 
https://man7.org/linux/man-pages/man7/ascii.7.html

> +static const char * const digest_type_name[DIGEST_TYPE__LAST] = {
> +	[DIGEST_TYPE_IMA] = "ima"
> +};
> +
>   static int ima_write_template_field_data(const void *data, const u32 datalen,
>   					 enum data_formats datafmt,
>   					 struct ima_field_data *field_data)
> @@ -72,8 +83,9 @@ static void ima_show_template_data_ascii(struct seq_file *m,
>   	u32 buflen = field_data->len;
>   
>   	switch (datafmt) {
> +	case DATA_FMT_DIGEST_WITH_TYPE_AND_ALGO:
>   	case DATA_FMT_DIGEST_WITH_ALGO:
> -		buf_ptr = strnchr(field_data->data, buflen, ':');
> +		buf_ptr = strrchr(field_data->data, ':');
>   		if (buf_ptr != field_data->data)
>   			seq_printf(m, "%s", field_data->data);
>   
> @@ -178,6 +190,14 @@ void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
>   				     field_data);
>   }
>   
> +void ima_show_template_digest_ngv2(struct seq_file *m, enum ima_show_type show,
> +				   struct ima_field_data *field_data)
> +{
> +	ima_show_template_field_data(m, show,
> +				     DATA_FMT_DIGEST_WITH_TYPE_AND_ALGO,
> +				     field_data);
> +}
> +
>   void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
>   			      struct ima_field_data *field_data)
>   {
> @@ -265,28 +285,38 @@ int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
>   }
>   
>   static int ima_eventdigest_init_common(const u8 *digest, u32 digestsize,
> -				       u8 hash_algo,
> +				       u8 digest_type, u8 hash_algo,
>   				       struct ima_field_data *field_data)
>   {
>   	/*
>   	 * digest formats:
>   	 *  - DATA_FMT_DIGEST: digest
>   	 *  - DATA_FMT_DIGEST_WITH_ALGO: <hash algo> + ':' + '\0' + digest,
> +	 *  - DATA_FMT_DIGEST_WITH_TYPE_AND_ALGO:
> +	 *	<digest type> + ':' + <hash algo> + ':' + '\0' + digest,
>   	 *
>   	 *    where 'DATA_FMT_DIGEST' is the original digest format ('d')
>   	 *      with a hash size limitation of 20 bytes,
> +	 *    where <digest type> is "ima",
>   	 *    where <hash algo> is the hash_algo_name[] string.
>   	 */
> -	u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
> +	u8 buffer[DIGEST_TYPE_NAME_LEN_MAX + CRYPTO_MAX_ALG_NAME + 2 +
> +		IMA_MAX_DIGEST_SIZE] = { 0 };
>   	enum data_formats fmt = DATA_FMT_DIGEST;
>   	u32 offset = 0;
>   
> -	if (hash_algo < HASH_ALGO__LAST) {
> +	if (digest_type < DIGEST_TYPE__LAST && hash_algo < HASH_ALGO__LAST) {
> +		fmt = DATA_FMT_DIGEST_WITH_TYPE_AND_ALGO;
> +		offset += 1 + sprintf(buffer, "%*s:%*s:",
> +				      (int)strlen(digest_type_name[digest_type]),
> +				      digest_type_name[digest_type],
> +				      (int)strlen(hash_algo_name[hash_algo]),
> +				      hash_algo_name[hash_algo]);

'%*s' seems to be for right-alignment but only makes sense if the length 
indicator is different than then following string. sprintf(buffer, 
"|%*s|",5,"test") prints | test|. Otherwise it seems to behave like 
plain '%s' in this case... ?