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Message-ID: <438e2a17-a16f-4d3d-b115-7ebf625f64fb@linux.ibm.com>
Date: Mon, 2 Dec 2024 16:25:39 -0500
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, linux-integrity@...r.kernel.org
Cc: Mickaël Salaün <mic@...ikod.net>,
roberto.sassu@...wei.com, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ima: instantiate the bprm_creds_for_exec() hook
On 11/27/24 4:02 PM, Mimi Zohar wrote:
> Like direct file execution (e.g. ./script.sh), indirect file execution
> (e.g. sh script.sh) needs to be measured and appraised. Instantiate
> the new security_bprm_creds_for_exec() hook to measure and verify the
> indirect file's integrity. Unlike direct file execution, indirect file
> execution integrity is optionally enforced by the interpreter.
>
> Update the audit messages to differentiate between kernel and userspace
> enforced integrity.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
> ---
> security/integrity/ima/ima_appraise.c | 84 ++++++++++++++++++++-------
> security/integrity/ima/ima_main.c | 22 +++++++
> 2 files changed, 86 insertions(+), 20 deletions(-)
>
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 656c709b974f..b5f8e49cde9d 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -8,6 +8,7 @@
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/file.h>
> +#include <linux/binfmts.h>
> #include <linux/fs.h>
> #include <linux/xattr.h>
> #include <linux/magic.h>
> @@ -16,6 +17,7 @@
> #include <linux/fsverity.h>
> #include <keys/system_keyring.h>
> #include <uapi/linux/fsverity.h>
> +#include <linux/securebits.h>
>
> #include "ima.h"
>
> @@ -276,7 +278,8 @@ static int calc_file_id_hash(enum evm_ima_xattr_type type,
> */
> static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> struct evm_ima_xattr_data *xattr_value, int xattr_len,
> - enum integrity_status *status, const char **cause)
> + enum integrity_status *status, const char **cause,
> + bool is_check)
> {
> struct ima_max_digest_data hash;
> struct signature_v2_hdr *sig;
> @@ -292,9 +295,11 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> if (*status != INTEGRITY_PASS_IMMUTABLE) {
> if (iint->flags & IMA_DIGSIG_REQUIRED) {
> if (iint->flags & IMA_VERITY_REQUIRED)
> - *cause = "verity-signature-required";
> + *cause = !is_check ? "verity-signature-required" :
> + "verity-signature-required(userspace)";
> else
> - *cause = "IMA-signature-required";
> + *cause = !is_check ? "IMA-signature-required" :
> + "IMA-signature-required(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -314,7 +319,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> else
> rc = -EINVAL;
> if (rc) {
> - *cause = "invalid-hash";
> + *cause = !is_check ? "invalid-hash" :
> + "invalid-hash(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -325,14 +331,16 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
>
> mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
> if ((iint->flags & mask) == mask) {
> - *cause = "verity-signature-required";
> + *cause = !is_check ? "verity-signature-required" :
> + "verity-signature-required(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
>
> sig = (typeof(sig))xattr_value;
> if (sig->version >= 3) {
> - *cause = "invalid-signature-version";
> + *cause = !is_check ? "invalid-signature-version" :
> + "invalid-signature-version(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -353,7 +361,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> iint->ima_hash->digest,
> iint->ima_hash->length);
> if (rc) {
> - *cause = "invalid-signature";
> + *cause = !is_check ? "invalid-signature" :
> + "invalid-signature(userspace)";
> *status = INTEGRITY_FAIL;
> } else {
> *status = INTEGRITY_PASS;
> @@ -364,7 +373,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
>
> if (iint->flags & IMA_DIGSIG_REQUIRED) {
> if (!(iint->flags & IMA_VERITY_REQUIRED)) {
> - *cause = "IMA-signature-required";
> + *cause = !is_check ? "IMA-signature-required" :
> + "IMA-signature-required(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -372,7 +382,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
>
> sig = (typeof(sig))xattr_value;
> if (sig->version != 3) {
> - *cause = "invalid-signature-version";
> + *cause = !is_check ? "invalid-signature-version" :
> + "invalid-signature-version(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -382,7 +393,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> container_of(&hash.hdr,
> struct ima_digest_data, hdr));
> if (rc) {
> - *cause = "sigv3-hashing-error";
> + *cause = !is_check ? "sigv3-hashing-error" :
> + "sigv3-hashing-error(userspace)";
> *status = INTEGRITY_FAIL;
> break;
> }
> @@ -392,7 +404,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> xattr_len, hash.digest,
> hash.hdr.length);
> if (rc) {
> - *cause = "invalid-verity-signature";
> + *cause = !is_check ? "invalid-verity-signature" :
> + "invalid-verify-signature(userspace)";
> *status = INTEGRITY_FAIL;
> } else {
> *status = INTEGRITY_PASS;
> @@ -401,7 +414,8 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> break;
> default:
> *status = INTEGRITY_UNKNOWN;
> - *cause = "unknown-ima-data";
> + *cause = !is_check ? "unknown-ima-data" :
> + "unknown-ima-data(userspace)";
> break;
> }
>
> @@ -469,6 +483,18 @@ int ima_check_blacklist(struct ima_iint_cache *iint,
> return rc;
> }
>
> +static int is_bprm_creds_for_exec(enum ima_hooks func, struct file *file)
is_check is bool, so this should probably also return bool
> +{
> + struct linux_binprm *bprm = NULL;
> +
> + if (func == BPRM_CHECK) {
> + bprm = container_of(&file, struct linux_binprm, file);
> + if (bprm->is_check)
> + return 1;
> + }
> + return 0;
> +}
> +
> /*
> * ima_appraise_measurement - appraise file measurement
> *
> @@ -489,11 +515,24 @@ int ima_appraise_measurement(enum ima_hooks func, struct ima_iint_cache *iint,
> enum integrity_status status = INTEGRITY_UNKNOWN;
> int rc = xattr_len;
> bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
> + bool is_check = false;
no need to initialize it
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