Re: [PATCH] capabilities: Ambient capability set V2
From: "Serge E. Hallyn" <serge@hallyn.com>
Date: 2015-03-05 17:13:30
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On Thu, Mar 05, 2015 at 09:26:24AM -0600, Christoph Lameter wrote:
On Sun, 1 Mar 2015, Serge E. Hallyn wrote:quoted
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+++ linux/security/commoncap.c 2015-02-26 16:10:02.347913397 -0600@@ -347,15 +347,17 @@ static inline int bprm_caps_from_vfs_cap *has_cap = true; CAP_FOR_EACH_U32(i) { + __u32 ambient = current_cred()->cap_ambient.cap[i]; __u32 permitted = caps->permitted.cap[i]; __u32 inheritable = caps->inheritable.cap[i]; /* - * pP' = (X & fP) | (pI & fI) + * pP' = (X & fP) | (pI & (fI | pA)) */ new->cap_permitted.cap[i] = (new->cap_bset.cap[i] & permitted) | - (new->cap_inheritable.cap[i] & inheritable); + (new->cap_inheritable.cap[i] & + (inheritable | ambient));So I'd say drop this change ^Then the ambient caps get ignored for a executables that have capabilities seton the file?
Yes. Those are assumed to already know what they're doing.
I think we need to keep this one.
Why? Do you foresee cases where a file that has fP set needs capabilities that aren't in its fP? It seems more likely that they'll risk misbehaving due to an unexpected set of caps. If you have a good use case I'm not entirely opposed, but it just seems unneeded and a potentially bad idea.
quoted hunk ↗ jump to hunk
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@@ -453,8 +455,18 @@ static int get_file_caps(struct linux_bi if (rc == -EINVAL) printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", __func__, rc, bprm->filename); - else if (rc == -ENODATA) + else if (rc == -ENODATA) { rc = 0; + if (!cap_isclear(current_cred()->cap_ambient)) { + /* + * The ambient caps are permitted for + * files that have no caps + */ + bprm->cred->cap_permitted = + current_cred()->cap_ambient;and here set vcaps inheritable to current_cred()->ambient.We do not call bprm_caps_from_vfs_cap() for files that have no caps so this would have no effect. But we could set cap_inheritable here? Fixup patch: Subject: ambient_caps: Set inheritable bits too We were not setting the inheritable bits as they ought to be set. Signed-off-by: Christoph Lameter <redacted> Index: linux/security/commoncap.c ===================================================================--- linux.orig/security/commoncap.c 2015-03-05 09:22:32.123047869 -0600 +++ linux/security/commoncap.c 2015-03-05 09:22:32.119048001 -0600@@ -461,6 +461,8 @@ static int get_file_caps(struct linux_bi */ bprm->cred->cap_permitted = current_cred()->cap_ambient; + bprm->cred->cap_inheritable = + current_cred()->cap_ambient; *effective = true; } }