From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA7E2C433E0 for ; Thu, 30 Jul 2020 20:57:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C397820809 for ; Thu, 30 Jul 2020 20:57:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730505AbgG3U55 (ORCPT ); Thu, 30 Jul 2020 16:57:57 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35216 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728171AbgG3U55 (ORCPT ); Thu, 30 Jul 2020 16:57:57 -0400 Received: from static-50-53-58-29.bvtn.or.frontiernet.net ([50.53.58.29] helo=[192.168.192.153]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1k1FcZ-00015Y-NM; Thu, 30 Jul 2020 20:57:47 +0000 Subject: Re: [PATCH v19 22/23] LSM: Add /proc attr entry for full LSM context To: Casey Schaufler , casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Cc: linux-audit@redhat.com, keescook@chromium.org, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com, sds@tycho.nsa.gov, linux-api@vger.kernel.org References: <20200724203226.16374-1-casey@schaufler-ca.com> <20200724203226.16374-23-casey@schaufler-ca.com> <705fb82d-ad7a-2874-59ed-ba6bc7ae3722@schaufler-ca.com> From: John Johansen Autocrypt: addr=john.johansen@canonical.com; prefer-encrypt=mutual; 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X-Mailing-List: selinux@vger.kernel.org On 7/30/20 1:44 PM, Casey Schaufler wrote: > On 7/30/2020 3:03 AM, John Johansen wrote: >> On 7/24/20 1:32 PM, Casey Schaufler wrote: >>> Add an entry /proc/.../attr/context which displays the full >>> process security "context" in compound format: >>> lsm1\0value\0lsm2\0value\0... >>> This entry is not writable. >>> >>> A security module may decide that its policy does not allow >>> this information to be displayed. In this case none of the >>> information will be displayed. >>> >>> Reviewed-by: Kees Cook >>> Signed-off-by: Casey Schaufler >>> Cc: linux-api@vger.kernel.org >>> --- >>> Documentation/security/lsm.rst | 28 +++++++++++ >>> fs/proc/base.c | 1 + >>> include/linux/lsm_hooks.h | 6 +++ >>> security/apparmor/include/procattr.h | 2 +- >>> security/apparmor/lsm.c | 8 +++- >>> security/apparmor/procattr.c | 22 +++++---- >>> security/security.c | 70 ++++++++++++++++++++++++++++ >>> security/selinux/hooks.c | 2 +- >>> security/smack/smack_lsm.c | 2 +- >>> 9 files changed, 126 insertions(+), 15 deletions(-) > > > >>> >>> /** >>> diff --git a/security/security.c b/security/security.c >>> index d35e578fa45b..bce6be720401 100644 >>> --- a/security/security.c >>> +++ b/security/security.c >>> @@ -754,6 +754,48 @@ static void __init lsm_early_task(struct task_struct *task) >>> panic("%s: Early task alloc failed.\n", __func__); >>> } >>> >>> +/** >>> + * append_ctx - append a lsm/context pair to a compound context >>> + * @ctx: the existing compound context >>> + * @ctxlen: size of the old context, including terminating nul byte >>> + * @lsm: new lsm name, nul terminated >>> + * @new: new context, possibly nul terminated >>> + * @newlen: maximum size of @new >>> + * >>> + * replace @ctx with a new compound context, appending @newlsm and @new >>> + * to @ctx. On exit the new data replaces the old, which is freed. >>> + * @ctxlen is set to the new size, which includes a trailing nul byte. >>> + * >>> + * Returns 0 on success, -ENOMEM if no memory is available. >>> + */ >>> +static int append_ctx(char **ctx, int *ctxlen, const char *lsm, char *new, >>> + int newlen) >>> +{ >>> + char *final; >>> + size_t llen; >>> + >>> + llen = strlen(lsm) + 1; >>> + /* >>> + * A security module may or may not provide a trailing nul on >>> + * when returning a security context. There is no definition >>> + * of which it should be, and there are modules that do it >>> + * each way. >>> + */ >>> + newlen = strnlen(new, newlen) + 1; >>> + >>> + final = kzalloc(*ctxlen + llen + newlen, GFP_KERNEL); >>> + if (final == NULL) >>> + return -ENOMEM; >>> + if (*ctxlen) >>> + memcpy(final, *ctx, *ctxlen); >>> + memcpy(final + *ctxlen, lsm, llen); >>> + memcpy(final + *ctxlen + llen, new, newlen); >> if @new doesn't have a newline appended at its end this will read 1 byte >> passed the end of the @new buffer. Nor will the result have a trailing >> \0 as expected unless we get lucky. > > @new will never have a newline at the end. The trailing nul comes > from the allocation being done with kzalloc(). This function has to > be considered in the context of its caller. > ugh, sorry not trailing newline, I meant trailing \0. The problem isn't the kzalloc, the target has the space. It is the source @new. It is dangerous to assume that the @new buffer has a null byte after its declared length. Which is potentially what we are doing if @new doesn't have an embedded null byte. In that case strlen(new, newlen) will then return newlen and we add 1 to it. which means in the memcpy we are copying an extra byte beyond what was declared to exist in @new. >> >> >>> + kfree(*ctx); >>> + *ctx = final; >>> + *ctxlen = *ctxlen + llen + newlen; >>> + return 0; >>> +} >>> + >>> /* >>> * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and >>> * can be accessed with: >>> @@ -2124,6 +2166,10 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name, >>> char **value) >>> { >>> struct security_hook_list *hp; >>> + char *final = NULL; >>> + char *cp; >>> + int rc = 0; >>> + int finallen = 0; >> these are only used by context so they could be moved under its if, this >> is really just a style comment and I'll leave it up to you > > Old coding habits die hard. Unless there's value to gain, I'll leave it > as is. > >> >>> int display = lsm_task_display(current); >>> int slot = 0; >>> >>> @@ -2151,6 +2197,30 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name, >>> return -ENOMEM; >>> } >>> >>> + if (!strcmp(name, "context")) { >>> + hlist_for_each_entry(hp, &security_hook_heads.getprocattr, >>> + list) { >>> + rc = hp->hook.getprocattr(p, "context", &cp); >>> + if (rc == -EINVAL) >>> + continue; >>> + if (rc < 0) { >>> + kfree(final); >>> + return rc; >>> + } >>> + rc = append_ctx(&final, &finallen, hp->lsmid->lsm, >>> + cp, rc); >>> + kfree(cp); >>> + if (rc < 0) { >>> + kfree(final); >>> + return rc; >>> + } >>> + } >>> + if (final == NULL) >>> + return -EINVAL; >>> + *value = final; >>> + return finallen; >>> + } >>> + >>> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) { >>> if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm)) >>> continue; >>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c >>> index c13c207c5da1..43d5c09b9a9e 100644 >>> --- a/security/selinux/hooks.c >>> +++ b/security/selinux/hooks.c >>> @@ -6288,7 +6288,7 @@ static int selinux_getprocattr(struct task_struct *p, >>> goto bad; >>> } >>> >>> - if (!strcmp(name, "current")) >>> + if (!strcmp(name, "current") || !strcmp(name, "context")) >>> sid = __tsec->sid; >>> else if (!strcmp(name, "prev")) >>> sid = __tsec->osid; >>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c >>> index 6f0cdb40addc..d7bb6442f192 100644 >>> --- a/security/smack/smack_lsm.c >>> +++ b/security/smack/smack_lsm.c >>> @@ -3463,7 +3463,7 @@ static int smack_getprocattr(struct task_struct *p, char *name, char **value) >>> char *cp; >>> int slen; >>> >>> - if (strcmp(name, "current") != 0) >>> + if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0) >>> return -EINVAL; >>> >>> cp = kstrdup(skp->smk_known, GFP_KERNEL); >>> From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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us-mta-323-r0y8V4uRObO7QgKeLFHuYg-1; Thu, 30 Jul 2020 16:57:59 -0400 X-MC-Unique: r0y8V4uRObO7QgKeLFHuYg-1 Received: from static-50-53-58-29.bvtn.or.frontiernet.net ([50.53.58.29] helo=[192.168.192.153]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1k1FcZ-00015Y-NM; Thu, 30 Jul 2020 20:57:47 +0000 Subject: Re: [PATCH v19 22/23] LSM: Add /proc attr entry for full LSM context To: Casey Schaufler , casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org References: <20200724203226.16374-1-casey@schaufler-ca.com> <20200724203226.16374-23-casey@schaufler-ca.com> <705fb82d-ad7a-2874-59ed-ba6bc7ae3722@schaufler-ca.com> From: John Johansen Autocrypt: addr=john.johansen@canonical.com; prefer-encrypt=mutual; keydata= LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCgptUUlOQkU1bXJQb0JFQURB azE5UHNnVmdCS2tJbW1SMmlzUFE2bzdLSmhUVEtqSmR3VmJrV1NuTm4rbzZVcDVrCm5LUDFm 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Rm5td05PMHBzaVVzbmh2SEZ3UE8vdkFibDNSc1I1KzBSbytodnMyY0VtUXV2OXIvYkRsQ2Zw enAydDMKY0srcmh4VXFpc094OERaZnoxQm5rYW9DUkZidnZ2ays3TC9mb21QbnRHUGtxSmNp WUU4VEdIa1p3MWhPa3UrNApPb00yR0I1bkVEbGorMlRGL2pMUStFaXBYOVBrUEpZdnhmUmxD NmRLOFBLS2ZYOUtkZm1BSWNnSGZuVjFqU24rCjh5SDJkakJQdEtpcVcwSjY5YUlzeXg3aVYv MDNwYVBDakpoN1hxOXZBenlkTjVVL1VBPT0KPTZQL2IKLS0tLS1FTkQgUEdQIFBVQkxJQyBL RVkgQkxPQ0stLS0tLQo= Organization: Canonical Message-ID: <97330b2d-5447-cfef-b6d0-444249e671b7@canonical.com> Date: Thu, 30 Jul 2020 13:57:44 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <705fb82d-ad7a-2874-59ed-ba6bc7ae3722@schaufler-ca.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-loop: linux-audit@redhat.com X-Mailman-Approved-At: Thu, 30 Jul 2020 17:41:23 -0400 Cc: linux-api@vger.kernel.org, linux-audit@redhat.com, sds@tycho.nsa.gov X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On 7/30/20 1:44 PM, Casey Schaufler wrote: > On 7/30/2020 3:03 AM, John Johansen wrote: >> On 7/24/20 1:32 PM, Casey Schaufler wrote: >>> Add an entry /proc/.../attr/context which displays the full >>> process security "context" in compound format: >>> lsm1\0value\0lsm2\0value\0... >>> This entry is not writable. >>> >>> A security module may decide that its policy does not allow >>> this information to be displayed. In this case none of the >>> information will be displayed. >>> >>> Reviewed-by: Kees Cook >>> Signed-off-by: Casey Schaufler >>> Cc: linux-api@vger.kernel.org >>> --- >>> Documentation/security/lsm.rst | 28 +++++++++++ >>> fs/proc/base.c | 1 + >>> include/linux/lsm_hooks.h | 6 +++ >>> security/apparmor/include/procattr.h | 2 +- >>> security/apparmor/lsm.c | 8 +++- >>> security/apparmor/procattr.c | 22 +++++---- >>> security/security.c | 70 ++++++++++++++++++++++++++++ >>> security/selinux/hooks.c | 2 +- >>> security/smack/smack_lsm.c | 2 +- >>> 9 files changed, 126 insertions(+), 15 deletions(-) > > > >>> >>> /** >>> diff --git a/security/security.c b/security/security.c >>> index d35e578fa45b..bce6be720401 100644 >>> --- a/security/security.c >>> +++ b/security/security.c >>> @@ -754,6 +754,48 @@ static void __init lsm_early_task(struct task_struct *task) >>> panic("%s: Early task alloc failed.\n", __func__); >>> } >>> >>> +/** >>> + * append_ctx - append a lsm/context pair to a compound context >>> + * @ctx: the existing compound context >>> + * @ctxlen: size of the old context, including terminating nul byte >>> + * @lsm: new lsm name, nul terminated >>> + * @new: new context, possibly nul terminated >>> + * @newlen: maximum size of @new >>> + * >>> + * replace @ctx with a new compound context, appending @newlsm and @new >>> + * to @ctx. On exit the new data replaces the old, which is freed. >>> + * @ctxlen is set to the new size, which includes a trailing nul byte. >>> + * >>> + * Returns 0 on success, -ENOMEM if no memory is available. >>> + */ >>> +static int append_ctx(char **ctx, int *ctxlen, const char *lsm, char *new, >>> + int newlen) >>> +{ >>> + char *final; >>> + size_t llen; >>> + >>> + llen = strlen(lsm) + 1; >>> + /* >>> + * A security module may or may not provide a trailing nul on >>> + * when returning a security context. There is no definition >>> + * of which it should be, and there are modules that do it >>> + * each way. >>> + */ >>> + newlen = strnlen(new, newlen) + 1; >>> + >>> + final = kzalloc(*ctxlen + llen + newlen, GFP_KERNEL); >>> + if (final == NULL) >>> + return -ENOMEM; >>> + if (*ctxlen) >>> + memcpy(final, *ctx, *ctxlen); >>> + memcpy(final + *ctxlen, lsm, llen); >>> + memcpy(final + *ctxlen + llen, new, newlen); >> if @new doesn't have a newline appended at its end this will read 1 byte >> passed the end of the @new buffer. Nor will the result have a trailing >> \0 as expected unless we get lucky. > > @new will never have a newline at the end. The trailing nul comes > from the allocation being done with kzalloc(). This function has to > be considered in the context of its caller. > ugh, sorry not trailing newline, I meant trailing \0. The problem isn't the kzalloc, the target has the space. It is the source @new. It is dangerous to assume that the @new buffer has a null byte after its declared length. Which is potentially what we are doing if @new doesn't have an embedded null byte. In that case strlen(new, newlen) will then return newlen and we add 1 to it. which means in the memcpy we are copying an extra byte beyond what was declared to exist in @new. >> >> >>> + kfree(*ctx); >>> + *ctx = final; >>> + *ctxlen = *ctxlen + llen + newlen; >>> + return 0; >>> +} >>> + >>> /* >>> * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and >>> * can be accessed with: >>> @@ -2124,6 +2166,10 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name, >>> char **value) >>> { >>> struct security_hook_list *hp; >>> + char *final = NULL; >>> + char *cp; >>> + int rc = 0; >>> + int finallen = 0; >> these are only used by context so they could be moved under its if, this >> is really just a style comment and I'll leave it up to you > > Old coding habits die hard. Unless there's value to gain, I'll leave it > as is. > >> >>> int display = lsm_task_display(current); >>> int slot = 0; >>> >>> @@ -2151,6 +2197,30 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name, >>> return -ENOMEM; >>> } >>> >>> + if (!strcmp(name, "context")) { >>> + hlist_for_each_entry(hp, &security_hook_heads.getprocattr, >>> + list) { >>> + rc = hp->hook.getprocattr(p, "context", &cp); >>> + if (rc == -EINVAL) >>> + continue; >>> + if (rc < 0) { >>> + kfree(final); >>> + return rc; >>> + } >>> + rc = append_ctx(&final, &finallen, hp->lsmid->lsm, >>> + cp, rc); >>> + kfree(cp); >>> + if (rc < 0) { >>> + kfree(final); >>> + return rc; >>> + } >>> + } >>> + if (final == NULL) >>> + return -EINVAL; >>> + *value = final; >>> + return finallen; >>> + } >>> + >>> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) { >>> if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm)) >>> continue; >>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c >>> index c13c207c5da1..43d5c09b9a9e 100644 >>> --- a/security/selinux/hooks.c >>> +++ b/security/selinux/hooks.c >>> @@ -6288,7 +6288,7 @@ static int selinux_getprocattr(struct task_struct *p, >>> goto bad; >>> } >>> >>> - if (!strcmp(name, "current")) >>> + if (!strcmp(name, "current") || !strcmp(name, "context")) >>> sid = __tsec->sid; >>> else if (!strcmp(name, "prev")) >>> sid = __tsec->osid; >>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c >>> index 6f0cdb40addc..d7bb6442f192 100644 >>> --- a/security/smack/smack_lsm.c >>> +++ b/security/smack/smack_lsm.c >>> @@ -3463,7 +3463,7 @@ static int smack_getprocattr(struct task_struct *p, char *name, char **value) >>> char *cp; >>> int slen; >>> >>> - if (strcmp(name, "current") != 0) >>> + if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0) >>> return -EINVAL; >>> >>> cp = kstrdup(skp->smk_known, GFP_KERNEL); >>> -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit