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Message-ID: <20241115133619.114393-22-cgoettsche@seltendoof.de>
Date: Fri, 15 Nov 2024 14:35:41 +0100
From: Christian Göttsche <cgoettsche@...tendoof.de>
To: selinux@...r.kernel.org
Cc: Christian Göttsche <cgzones@...glemail.com>,
Paul Moore <paul@...l-moore.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH 22/22] selinux: restrict policy strings
From: Christian Göttsche <cgzones@...glemail.com>
Validate the characters and the lengths of strings parsed from binary
policies.
* Disallow control characters
* Limit characters of identifiers to alphanumeric, underscore, dash,
and dot
* Limit identifiers in length to 128, expect types to 1024 and
categories to 32, characters (excluding NUL-terminator)
Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
security/selinux/ss/conditional.c | 2 +-
security/selinux/ss/policydb.c | 60 ++++++++++++++++++++-----------
security/selinux/ss/policydb.h | 5 ++-
3 files changed, 44 insertions(+), 23 deletions(-)
diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index d37b4bdf6ba9..346102417cbf 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -280,7 +280,7 @@ int cond_read_bool(struct policydb *p, struct symtab *s, struct policy_file *fp)
len = le32_to_cpu(buf[2]);
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto err;
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 917b468c5144..d98dfa6c3f30 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -1221,8 +1221,9 @@ static int context_read_and_validate(struct context *c, struct policydb *p,
* binary representation file.
*/
-int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len)
+int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len, int kind, u32 max_len)
{
+ u32 i;
int rc;
char *str;
@@ -1232,19 +1233,35 @@ int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len)
if (oom_check(sizeof(char), len, fp))
return -EINVAL;
+ if (max_len != 0 && len > max_len)
+ return -EINVAL;
+
str = kmalloc(len + 1, flags | __GFP_NOWARN);
if (!str)
return -ENOMEM;
rc = next_entry(str, fp, len);
- if (rc) {
- kfree(str);
- return rc;
+ if (rc)
+ goto bad_str;
+
+ rc = -EINVAL;
+ for (i = 0; i < len; i++) {
+ if (iscntrl(str[i]))
+ goto bad_str;
+
+ if (kind == STR_IDENTIFIER &&
+ !(isalnum(str[i]) || str[i] == '_' || str[i] == '-' || str[i] == '.'))
+ goto bad_str;
+
}
str[len] = '\0';
*strp = str;
return 0;
+
+bad_str:
+ kfree(str);
+ return rc;
}
static int perm_read(struct policydb *p, struct symtab *s, struct policy_file *fp)
@@ -1269,7 +1286,7 @@ static int perm_read(struct policydb *p, struct symtab *s, struct policy_file *f
if (perdatum->value < 1 || perdatum->value > 32)
goto bad;
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1315,7 +1332,7 @@ static int common_read(struct policydb *p, struct symtab *s, struct policy_file
goto bad;
comdatum->permissions.nprim = le32_to_cpu(buf[2]);
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1552,12 +1569,12 @@ static int class_read(struct policydb *p, struct symtab *s, struct policy_file *
ncons = le32_to_cpu(buf[5]);
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
if (len2) {
- rc = str_read(&cladatum->comkey, GFP_KERNEL, fp, len2);
+ rc = str_read(&cladatum->comkey, GFP_KERNEL, fp, len2, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1691,7 +1708,7 @@ static int role_read(struct policydb *p, struct symtab *s, struct policy_file *f
if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
role->bounds = le32_to_cpu(buf[2]);
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1758,7 +1775,7 @@ static int type_read(struct policydb *p, struct symtab *s, struct policy_file *f
typdatum->primary = le32_to_cpu(buf[2]);
}
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 1024);
if (rc)
goto bad;
@@ -1822,7 +1839,7 @@ static int user_read(struct policydb *p, struct symtab *s, struct policy_file *f
if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
usrdatum->bounds = le32_to_cpu(buf[2]);
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1871,7 +1888,7 @@ static int sens_read(struct policydb *p, struct symtab *s, struct policy_file *f
goto bad;
levdatum->isalias = val;
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto bad;
@@ -1914,7 +1931,7 @@ static int cat_read(struct policydb *p, struct symtab *s, struct policy_file *fp
goto bad;
catdatum->isalias = val;
- rc = str_read(&key, GFP_KERNEL, fp, len);
+ rc = str_read(&key, GFP_KERNEL, fp, len, STR_IDENTIFIER, 32);
if (rc)
goto bad;
@@ -2220,7 +2237,7 @@ static int filename_trans_read_helper_compat(struct policydb *p, struct policy_f
len = le32_to_cpu(buf[0]);
/* path component string */
- rc = str_read(&name, GFP_KERNEL, fp, len);
+ rc = str_read(&name, GFP_KERNEL, fp, len, STR_UNCONSTRAINT, 0);
if (rc)
return rc;
@@ -2319,7 +2336,7 @@ static int filename_trans_read_helper(struct policydb *p, struct policy_file *fp
len = le32_to_cpu(buf[0]);
/* path component string */
- rc = str_read(&name, GFP_KERNEL, fp, len);
+ rc = str_read(&name, GFP_KERNEL, fp, len, STR_UNCONSTRAINT, 0);
if (rc)
return rc;
@@ -2473,7 +2490,7 @@ static int genfs_read(struct policydb *p, struct policy_file *fp)
if (!newgenfs)
goto out;
- rc = str_read(&newgenfs->fstype, GFP_KERNEL, fp, len);
+ rc = str_read(&newgenfs->fstype, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto out;
@@ -2512,7 +2529,7 @@ static int genfs_read(struct policydb *p, struct policy_file *fp)
if (!newc)
goto out;
- rc = str_read(&newc->u.name, GFP_KERNEL, fp, len);
+ rc = str_read(&newc->u.name, GFP_KERNEL, fp, len, STR_UNCONSTRAINT, 0);
if (rc)
goto out;
@@ -2615,7 +2632,7 @@ static int ocontext_read(struct policydb *p,
goto out;
len = le32_to_cpu(buf[0]);
- rc = str_read(&c->u.name, GFP_KERNEL, fp, len);
+ rc = str_read(&c->u.name, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto out;
@@ -2683,7 +2700,7 @@ static int ocontext_read(struct policydb *p,
goto out;
len = le32_to_cpu(buf[1]);
- rc = str_read(&c->u.name, GFP_KERNEL, fp, len);
+ rc = str_read(&c->u.name, GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto out;
@@ -2749,7 +2766,7 @@ static int ocontext_read(struct policydb *p,
len = le32_to_cpu(buf[0]);
rc = str_read(&c->u.ibendport.dev_name,
- GFP_KERNEL, fp, len);
+ GFP_KERNEL, fp, len, STR_IDENTIFIER, 128);
if (rc)
goto out;
@@ -2817,7 +2834,8 @@ int policydb_read(struct policydb *p, struct policy_file *fp)
goto bad;
}
- rc = str_read(&policydb_str, GFP_KERNEL, fp, len);
+ rc = str_read(&policydb_str, GFP_KERNEL, fp, len,
+ STR_UNCONSTRAINT, strlen(POLICYDB_STRING));
if (rc) {
if (rc == -ENOMEM) {
pr_err("SELinux: unable to allocate memory for policydb string of length %d\n",
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 73a0b793354e..fb05174b1b16 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -403,7 +403,10 @@ static inline const char *sym_name(const struct policydb *p, unsigned int sym_nu
return p->sym_val_to_name[sym_num][element_nr];
}
-extern int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len);
+#define STR_UNCONSTRAINT 0
+#define STR_IDENTIFIER 1
+extern int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len,
+ int kind, u32 max_len);
extern u16 string_to_security_class(struct policydb *p, const char *name);
extern u32 string_to_av_perm(struct policydb *p, u16 tclass, const char *name);
--
2.45.2
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