| Message ID | 20220418145945.38797-29-casey@schaufler-ca.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v35,01/29] integrity: disassociate ima_filter_rule from security_audit_rule | expand |
On 4/18/22 07:59, 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 <keescook@chromium.org> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: John Johansen <john.johansen@canonical.com> > Cc: linux-api@vger.kernel.org > Cc: linux-doc@vger.kernel.org > --- > Documentation/security/lsm.rst | 14 +++++ > 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 | 79 ++++++++++++++++++++++++++++ > security/selinux/hooks.c | 2 +- > security/smack/smack_lsm.c | 2 +- > 9 files changed, 121 insertions(+), 15 deletions(-) > > diff --git a/Documentation/security/lsm.rst b/Documentation/security/lsm.rst > index b77b4a540391..070225ae6ceb 100644 > --- a/Documentation/security/lsm.rst > +++ b/Documentation/security/lsm.rst > @@ -143,3 +143,17 @@ separated list of the active security modules. > The file ``/proc/pid/attr/interface_lsm`` contains the name of the security > module for which the ``/proc/pid/attr/current`` interface will > apply. This interface can be written to. > + > +The infrastructure does provide an interface for the special > +case where multiple security modules provide a process context. > +This is provided in compound context format. > + > +- `lsm\0value\0lsm\0value\0` > + > +The `lsm` and `value` fields are NUL-terminated bytestrings. > +Each field may contain whitespace or non-printable characters. > +The NUL bytes are included in the size of a compound context. > +The context ``Bell\0Secret\0Biba\0Loose\0`` has a size of 23. > + > +The file ``/proc/pid/attr/context`` provides the security > +context of the identified process. > diff --git a/fs/proc/base.c b/fs/proc/base.c > index f2d15348bdff..f8aed4404e7e 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -2828,6 +2828,7 @@ static const struct pid_entry attr_dir_stuff[] = { > ATTR(NULL, "keycreate", 0666), > ATTR(NULL, "sockcreate", 0666), > ATTR(NULL, "interface_lsm", 0666), > + ATTR(NULL, "context", 0444), > #ifdef CONFIG_SECURITY_SMACK > DIR("smack", 0555, > proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops), > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index fd63ae215104..425538ebc606 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -1401,6 +1401,12 @@ > * @pages contains the number of pages. > * Return 0 if permission is granted. > * > + * @getprocattr: > + * Provide the named process attribute for display in special files in > + * the /proc/.../attr directory. Attribute naming and the data displayed > + * is at the discretion of the security modules. The exception is the > + * "context" attribute, which will contain the security context of the > + * task as a nul terminated text string without trailing whitespace. > * @ismaclabel: > * Check if the extended attribute specified by @name > * represents a MAC label. Returns 1 if name is a MAC > diff --git a/security/apparmor/include/procattr.h b/security/apparmor/include/procattr.h > index 31689437e0e1..03dbfdb2f2c0 100644 > --- a/security/apparmor/include/procattr.h > +++ b/security/apparmor/include/procattr.h > @@ -11,7 +11,7 @@ > #ifndef __AA_PROCATTR_H > #define __AA_PROCATTR_H > > -int aa_getprocattr(struct aa_label *label, char **string); > +int aa_getprocattr(struct aa_label *label, char **string, bool newline); > int aa_setprocattr_changehat(char *args, size_t size, int flags); > > #endif /* __AA_PROCATTR_H */ > diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c > index 29181bc8c693..1ee58c1491ab 100644 > --- a/security/apparmor/lsm.c > +++ b/security/apparmor/lsm.c > @@ -602,6 +602,7 @@ static int apparmor_getprocattr(struct task_struct *task, char *name, > const struct cred *cred = get_task_cred(task); > struct aa_task_ctx *ctx = task_ctx(current); > struct aa_label *label = NULL; > + bool newline = true; > > if (strcmp(name, "current") == 0) > label = aa_get_newest_label(cred_label(cred)); > @@ -609,11 +610,14 @@ static int apparmor_getprocattr(struct task_struct *task, char *name, > label = aa_get_newest_label(ctx->previous); > else if (strcmp(name, "exec") == 0 && ctx->onexec) > label = aa_get_newest_label(ctx->onexec); > - else > + else if (strcmp(name, "context") == 0) { > + label = aa_get_newest_label(cred_label(cred)); > + newline = false; > + } else > error = -EINVAL; > > if (label) > - error = aa_getprocattr(label, value); > + error = aa_getprocattr(label, value, newline); > > aa_put_label(label); > put_cred(cred); > diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c > index fde332e0ea7d..172550f67fc0 100644 > --- a/security/apparmor/procattr.c > +++ b/security/apparmor/procattr.c > @@ -20,6 +20,7 @@ > * aa_getprocattr - Return the profile information for @profile > * @profile: the profile to print profile info about (NOT NULL) > * @string: Returns - string containing the profile info (NOT NULL) > + * @newline: Should a newline be added to @string. > * > * Requires: profile != NULL > * > @@ -28,20 +29,21 @@ > * > * Returns: size of string placed in @string else error code on failure > */ > -int aa_getprocattr(struct aa_label *label, char **string) > +int aa_getprocattr(struct aa_label *label, char **string, bool newline) > { > struct aa_ns *ns = labels_ns(label); > struct aa_ns *current_ns = aa_get_current_ns(); > + int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED; > int len; > > if (!aa_ns_visible(current_ns, ns, true)) { > aa_put_ns(current_ns); > return -EACCES; > } > + if (newline) > + flags |= FLAG_SHOW_MODE; > > - len = aa_label_snxprint(NULL, 0, current_ns, label, > - FLAG_SHOW_MODE | FLAG_VIEW_SUBNS | > - FLAG_HIDDEN_UNCONFINED); > + len = aa_label_snxprint(NULL, 0, current_ns, label, flags); > AA_BUG(len < 0); > > *string = kmalloc(len + 2, GFP_KERNEL); > @@ -50,19 +52,19 @@ int aa_getprocattr(struct aa_label *label, char **string) > return -ENOMEM; > } > > - len = aa_label_snxprint(*string, len + 2, current_ns, label, > - FLAG_SHOW_MODE | FLAG_VIEW_SUBNS | > - FLAG_HIDDEN_UNCONFINED); > + len = aa_label_snxprint(*string, len + 2, current_ns, label, flags); > if (len < 0) { > aa_put_ns(current_ns); > return len; > } > > - (*string)[len] = '\n'; > - (*string)[len + 1] = 0; > + if (newline) { > + (*string)[len] = '\n'; > + (*string)[++len] = 0; > + } > > aa_put_ns(current_ns); > - return len + 1; > + return len; > } > > /** > diff --git a/security/security.c b/security/security.c > index be6682768760..4c6d4171ded6 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -802,6 +802,57 @@ static int lsm_superblock_alloc(struct super_block *sb) > return 0; > } > > +/** > + * 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; > + size_t nlen; > + size_t flen; > + > + 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. > + */ > + nlen = strnlen(new, newlen); > + > + flen = *ctxlen + llen + nlen + 1; > + final = kzalloc(flen, GFP_KERNEL); > + > + if (final == NULL) > + return -ENOMEM; > + > + if (*ctxlen) > + memcpy(final, *ctx, *ctxlen); > + > + memcpy(final + *ctxlen, lsm, llen); > + memcpy(final + *ctxlen + llen, new, nlen); > + > + kfree(*ctx); > + > + *ctx = final; > + *ctxlen = flen; > + > + return 0; > +} > + > /* > * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and > * can be accessed with: > @@ -2223,6 +2274,10 @@ 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; > int ilsm = lsm_task_ilsm(current); > int slot = 0; > > @@ -2250,6 +2305,30 @@ 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 653dd2e236f1..cd977493f734 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -6346,7 +6346,7 @@ 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 2190c03ae3d0..9e442c4495bf 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -3485,7 +3485,7 @@ 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);
diff --git a/Documentation/security/lsm.rst b/Documentation/security/lsm.rst index b77b4a540391..070225ae6ceb 100644 --- a/Documentation/security/lsm.rst +++ b/Documentation/security/lsm.rst @@ -143,3 +143,17 @@ separated list of the active security modules. The file ``/proc/pid/attr/interface_lsm`` contains the name of the security module for which the ``/proc/pid/attr/current`` interface will apply. This interface can be written to. + +The infrastructure does provide an interface for the special +case where multiple security modules provide a process context. +This is provided in compound context format. + +- `lsm\0value\0lsm\0value\0` + +The `lsm` and `value` fields are NUL-terminated bytestrings. +Each field may contain whitespace or non-printable characters. +The NUL bytes are included in the size of a compound context. +The context ``Bell\0Secret\0Biba\0Loose\0`` has a size of 23. + +The file ``/proc/pid/attr/context`` provides the security +context of the identified process. diff --git a/fs/proc/base.c b/fs/proc/base.c index f2d15348bdff..f8aed4404e7e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2828,6 +2828,7 @@ static const struct pid_entry attr_dir_stuff[] = { ATTR(NULL, "keycreate", 0666), ATTR(NULL, "sockcreate", 0666), ATTR(NULL, "interface_lsm", 0666), + ATTR(NULL, "context", 0444), #ifdef CONFIG_SECURITY_SMACK DIR("smack", 0555, proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops), diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index fd63ae215104..425538ebc606 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1401,6 +1401,12 @@ * @pages contains the number of pages. * Return 0 if permission is granted. * + * @getprocattr: + * Provide the named process attribute for display in special files in + * the /proc/.../attr directory. Attribute naming and the data displayed + * is at the discretion of the security modules. The exception is the + * "context" attribute, which will contain the security context of the + * task as a nul terminated text string without trailing whitespace. * @ismaclabel: * Check if the extended attribute specified by @name * represents a MAC label. Returns 1 if name is a MAC diff --git a/security/apparmor/include/procattr.h b/security/apparmor/include/procattr.h index 31689437e0e1..03dbfdb2f2c0 100644 --- a/security/apparmor/include/procattr.h +++ b/security/apparmor/include/procattr.h @@ -11,7 +11,7 @@ #ifndef __AA_PROCATTR_H #define __AA_PROCATTR_H -int aa_getprocattr(struct aa_label *label, char **string); +int aa_getprocattr(struct aa_label *label, char **string, bool newline); int aa_setprocattr_changehat(char *args, size_t size, int flags); #endif /* __AA_PROCATTR_H */ diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c index 29181bc8c693..1ee58c1491ab 100644 --- a/security/apparmor/lsm.c +++ b/security/apparmor/lsm.c @@ -602,6 +602,7 @@ static int apparmor_getprocattr(struct task_struct *task, char *name, const struct cred *cred = get_task_cred(task); struct aa_task_ctx *ctx = task_ctx(current); struct aa_label *label = NULL; + bool newline = true; if (strcmp(name, "current") == 0) label = aa_get_newest_label(cred_label(cred)); @@ -609,11 +610,14 @@ static int apparmor_getprocattr(struct task_struct *task, char *name, label = aa_get_newest_label(ctx->previous); else if (strcmp(name, "exec") == 0 && ctx->onexec) label = aa_get_newest_label(ctx->onexec); - else + else if (strcmp(name, "context") == 0) { + label = aa_get_newest_label(cred_label(cred)); + newline = false; + } else error = -EINVAL; if (label) - error = aa_getprocattr(label, value); + error = aa_getprocattr(label, value, newline); aa_put_label(label); put_cred(cred); diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c index fde332e0ea7d..172550f67fc0 100644 --- a/security/apparmor/procattr.c +++ b/security/apparmor/procattr.c @@ -20,6 +20,7 @@ * aa_getprocattr - Return the profile information for @profile * @profile: the profile to print profile info about (NOT NULL) * @string: Returns - string containing the profile info (NOT NULL) + * @newline: Should a newline be added to @string. * * Requires: profile != NULL * @@ -28,20 +29,21 @@ * * Returns: size of string placed in @string else error code on failure */ -int aa_getprocattr(struct aa_label *label, char **string) +int aa_getprocattr(struct aa_label *label, char **string, bool newline) { struct aa_ns *ns = labels_ns(label); struct aa_ns *current_ns = aa_get_current_ns(); + int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED; int len; if (!aa_ns_visible(current_ns, ns, true)) { aa_put_ns(current_ns); return -EACCES; } + if (newline) + flags |= FLAG_SHOW_MODE; - len = aa_label_snxprint(NULL, 0, current_ns, label, - FLAG_SHOW_MODE | FLAG_VIEW_SUBNS | - FLAG_HIDDEN_UNCONFINED); + len = aa_label_snxprint(NULL, 0, current_ns, label, flags); AA_BUG(len < 0); *string = kmalloc(len + 2, GFP_KERNEL); @@ -50,19 +52,19 @@ int aa_getprocattr(struct aa_label *label, char **string) return -ENOMEM; } - len = aa_label_snxprint(*string, len + 2, current_ns, label, - FLAG_SHOW_MODE | FLAG_VIEW_SUBNS | - FLAG_HIDDEN_UNCONFINED); + len = aa_label_snxprint(*string, len + 2, current_ns, label, flags); if (len < 0) { aa_put_ns(current_ns); return len; } - (*string)[len] = '\n'; - (*string)[len + 1] = 0; + if (newline) { + (*string)[len] = '\n'; + (*string)[++len] = 0; + } aa_put_ns(current_ns); - return len + 1; + return len; } /** diff --git a/security/security.c b/security/security.c index be6682768760..4c6d4171ded6 100644 --- a/security/security.c +++ b/security/security.c @@ -802,6 +802,57 @@ static int lsm_superblock_alloc(struct super_block *sb) return 0; } +/** + * 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; + size_t nlen; + size_t flen; + + 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. + */ + nlen = strnlen(new, newlen); + + flen = *ctxlen + llen + nlen + 1; + final = kzalloc(flen, GFP_KERNEL); + + if (final == NULL) + return -ENOMEM; + + if (*ctxlen) + memcpy(final, *ctx, *ctxlen); + + memcpy(final + *ctxlen, lsm, llen); + memcpy(final + *ctxlen + llen, new, nlen); + + kfree(*ctx); + + *ctx = final; + *ctxlen = flen; + + return 0; +} + /* * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and * can be accessed with: @@ -2223,6 +2274,10 @@ 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; int ilsm = lsm_task_ilsm(current); int slot = 0; @@ -2250,6 +2305,30 @@ 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 653dd2e236f1..cd977493f734 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6346,7 +6346,7 @@ 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 2190c03ae3d0..9e442c4495bf 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -3485,7 +3485,7 @@ 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);
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 <keescook@chromium.org> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> Cc: linux-api@vger.kernel.org Cc: linux-doc@vger.kernel.org --- Documentation/security/lsm.rst | 14 +++++ 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 | 79 ++++++++++++++++++++++++++++ security/selinux/hooks.c | 2 +- security/smack/smack_lsm.c | 2 +- 9 files changed, 121 insertions(+), 15 deletions(-)