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Message-ID: <026c9596-9ebe-d148-fc5f-442a7e16f48b@linux.ibm.com>
Date: Fri, 29 Apr 2022 11:09:05 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, linux-integrity@...r.kernel.org
Cc: Eric Biggers <ebiggers@...nel.org>, linux-fscrypt@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/7] ima: define a new template field named 'd-ngv2'
and templates
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@...ux.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... ?
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