diff options
Diffstat (limited to 'security/integrity/evm')
| -rw-r--r-- | security/integrity/evm/evm.h | 9 | ||||
| -rw-r--r-- | security/integrity/evm/evm_crypto.c | 75 | ||||
| -rw-r--r-- | security/integrity/evm/evm_main.c | 67 | ||||
| -rw-r--r-- | security/integrity/evm/evm_secfs.c | 20 |
4 files changed, 139 insertions, 32 deletions
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index 241aca315b0c..04825393facb 100644 --- a/security/integrity/evm/evm.h +++ b/security/integrity/evm/evm.h @@ -23,9 +23,12 @@ #define EVM_INIT_HMAC 0x0001 #define EVM_INIT_X509 0x0002 -#define EVM_SETUP 0x80000000 /* userland has signaled key load */ +#define EVM_ALLOW_METADATA_WRITES 0x0004 +#define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */ -#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP) +#define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509) +#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \ + EVM_ALLOW_METADATA_WRITES) extern int evm_initialized; extern char *evm_hmac; @@ -51,7 +54,7 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name, size_t req_xattr_value_len, char *digest); int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, const char *req_xattr_value, - size_t req_xattr_value_len, char *digest); + size_t req_xattr_value_len, char type, char *digest); int evm_init_hmac(struct inode *inode, const struct xattr *xattr, char *hmac_val); int evm_init_secfs(void); diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index bcd64baf8788..691f3e09154c 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -138,7 +138,7 @@ out: * protection.) */ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode, - char *digest) + char type, char *digest) { struct h_misc { unsigned long ino; @@ -149,8 +149,13 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode, } hmac_misc; memset(&hmac_misc, 0, sizeof(hmac_misc)); - hmac_misc.ino = inode->i_ino; - hmac_misc.generation = inode->i_generation; + /* Don't include the inode or generation number in portable + * signatures + */ + if (type != EVM_XATTR_PORTABLE_DIGSIG) { + hmac_misc.ino = inode->i_ino; + hmac_misc.generation = inode->i_generation; + } /* The hmac uid and gid must be encoded in the initial user * namespace (not the filesystems user namespace) as encoding * them in the filesystems user namespace allows an attack @@ -163,7 +168,8 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode, hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid); hmac_misc.mode = inode->i_mode; crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc)); - if (evm_hmac_attrs & EVM_ATTR_FSUUID) + if ((evm_hmac_attrs & EVM_ATTR_FSUUID) && + type != EVM_XATTR_PORTABLE_DIGSIG) crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0], sizeof(inode->i_sb->s_uuid)); crypto_shash_final(desc, digest); @@ -189,6 +195,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry, char *xattr_value = NULL; int error; int size; + bool ima_present = false; if (!(inode->i_opflags & IOP_XATTR)) return -EOPNOTSUPP; @@ -199,11 +206,18 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry, error = -ENODATA; for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) { + bool is_ima = false; + + if (strcmp(*xattrname, XATTR_NAME_IMA) == 0) + is_ima = true; + if ((req_xattr_name && req_xattr_value) && !strcmp(*xattrname, req_xattr_name)) { error = 0; crypto_shash_update(desc, (const u8 *)req_xattr_value, req_xattr_value_len); + if (is_ima) + ima_present = true; continue; } size = vfs_getxattr_alloc(dentry, *xattrname, @@ -218,9 +232,14 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry, error = 0; xattr_size = size; crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size); + if (is_ima) + ima_present = true; } - hmac_add_misc(desc, inode, digest); + hmac_add_misc(desc, inode, type, digest); + /* Portable EVM signatures must include an IMA hash */ + if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present) + return -EPERM; out: kfree(xattr_value); kfree(desc); @@ -232,17 +251,45 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name, char *digest) { return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value, - req_xattr_value_len, EVM_XATTR_HMAC, digest); + req_xattr_value_len, EVM_XATTR_HMAC, digest); } int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, const char *req_xattr_value, size_t req_xattr_value_len, - char *digest) + char type, char *digest) { return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value, - req_xattr_value_len, IMA_XATTR_DIGEST, digest); + req_xattr_value_len, type, digest); +} + +static int evm_is_immutable(struct dentry *dentry, struct inode *inode) +{ + const struct evm_ima_xattr_data *xattr_data = NULL; + struct integrity_iint_cache *iint; + int rc = 0; + + iint = integrity_iint_find(inode); + if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG)) + return 1; + + /* Do this the hard way */ + rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0, + GFP_NOFS); + if (rc <= 0) { + if (rc == -ENODATA) + return 0; + return rc; + } + if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) + rc = 1; + else + rc = 0; + + kfree(xattr_data); + return rc; } + /* * Calculate the hmac and update security.evm xattr * @@ -255,6 +302,16 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name, struct evm_ima_xattr_data xattr_data; int rc = 0; + /* + * Don't permit any transformation of the EVM xattr if the signature + * is of an immutable type + */ + rc = evm_is_immutable(dentry, inode); + if (rc < 0) + return rc; + if (rc) + return -EPERM; + rc = evm_calc_hmac(dentry, xattr_name, xattr_value, xattr_value_len, xattr_data.digest); if (rc == 0) { @@ -280,7 +337,7 @@ int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr, } crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len); - hmac_add_misc(desc, inode, hmac_val); + hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val); kfree(desc); return 0; } diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 9826c02e2db8..a8d502827270 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -31,7 +31,7 @@ int evm_initialized; static char *integrity_status_msg[] = { - "pass", "fail", "no_label", "no_xattrs", "unknown" + "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown" }; char *evm_hmac = "hmac(sha1)"; char *evm_hash = "sha1"; @@ -76,6 +76,11 @@ static void __init evm_init_config(void) pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs); } +static bool evm_key_loaded(void) +{ + return (bool)(evm_initialized & EVM_KEY_MASK); +} + static int evm_find_protected_xattrs(struct dentry *dentry) { struct inode *inode = d_backing_inode(dentry); @@ -123,7 +128,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, enum integrity_status evm_status = INTEGRITY_PASS; int rc, xattr_len; - if (iint && iint->evm_status == INTEGRITY_PASS) + if (iint && (iint->evm_status == INTEGRITY_PASS || + iint->evm_status == INTEGRITY_PASS_IMMUTABLE)) return iint->evm_status; /* if status is not PASS, try to check again - against -ENOMEM */ @@ -164,22 +170,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, rc = -EINVAL; break; case EVM_IMA_XATTR_DIGSIG: + case EVM_XATTR_PORTABLE_DIGSIG: rc = evm_calc_hash(dentry, xattr_name, xattr_value, - xattr_value_len, calc.digest); + xattr_value_len, xattr_data->type, + calc.digest); if (rc) break; rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, (const char *)xattr_data, xattr_len, calc.digest, sizeof(calc.digest)); if (!rc) { - /* Replace RSA with HMAC if not mounted readonly and - * not immutable - */ - if (!IS_RDONLY(d_backing_inode(dentry)) && - !IS_IMMUTABLE(d_backing_inode(dentry))) + if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) { + if (iint) + iint->flags |= EVM_IMMUTABLE_DIGSIG; + evm_status = INTEGRITY_PASS_IMMUTABLE; + } else if (!IS_RDONLY(d_backing_inode(dentry)) && + !IS_IMMUTABLE(d_backing_inode(dentry))) { evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); + } } break; default: @@ -241,7 +251,7 @@ enum integrity_status evm_verifyxattr(struct dentry *dentry, void *xattr_value, size_t xattr_value_len, struct integrity_iint_cache *iint) { - if (!evm_initialized || !evm_protected_xattr(xattr_name)) + if (!evm_key_loaded() || !evm_protected_xattr(xattr_name)) return INTEGRITY_UNKNOWN; if (!iint) { @@ -265,7 +275,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) { struct inode *inode = d_backing_inode(dentry); - if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode) + if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode) return 0; return evm_verify_hmac(dentry, NULL, NULL, 0, NULL); } @@ -280,7 +290,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) * affect security.evm. An interesting side affect of writing posix xattr * acls is their modifying of the i_mode, which is included in security.evm. * For posix xattr acls only, permit security.evm, even if it currently - * doesn't exist, to be updated. + * doesn't exist, to be updated unless the EVM signature is immutable. */ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len) @@ -299,6 +309,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, return 0; goto out; } + evm_status = evm_verify_current_integrity(dentry); if (evm_status == INTEGRITY_NOXATTRS) { struct integrity_iint_cache *iint; @@ -345,10 +356,17 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, { const struct evm_ima_xattr_data *xattr_data = xattr_value; + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { if (!xattr_value_len) return -EINVAL; - if (xattr_data->type != EVM_IMA_XATTR_DIGSIG) + if (xattr_data->type != EVM_IMA_XATTR_DIGSIG && + xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG) return -EPERM; } return evm_protect_xattr(dentry, xattr_name, xattr_value, @@ -365,6 +383,12 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, */ int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name) { + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + return evm_protect_xattr(dentry, xattr_name, NULL, 0); } @@ -393,8 +417,8 @@ static void evm_reset_status(struct inode *inode) void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len) { - if (!evm_initialized || (!evm_protected_xattr(xattr_name) - && !posix_xattr_acl(xattr_name))) + if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name) + && !posix_xattr_acl(xattr_name))) return; evm_reset_status(dentry->d_inode); @@ -414,7 +438,7 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, */ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) { - if (!evm_initialized || !evm_protected_xattr(xattr_name)) + if (!evm_key_loaded() || !evm_protected_xattr(xattr_name)) return; evm_reset_status(dentry->d_inode); @@ -425,12 +449,21 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) /** * evm_inode_setattr - prevent updating an invalid EVM extended attribute * @dentry: pointer to the affected dentry + * + * Permit update of file attributes when files have a valid EVM signature, + * except in the case of them having an immutable portable signature. */ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) { unsigned int ia_valid = attr->ia_valid; enum integrity_status evm_status; + /* Policy permits modification of the protected attrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))) return 0; evm_status = evm_verify_current_integrity(dentry); @@ -456,7 +489,7 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) */ void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) { - if (!evm_initialized) + if (!evm_key_loaded()) return; if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) @@ -473,7 +506,7 @@ int evm_inode_init_security(struct inode *inode, struct evm_ima_xattr_data *xattr_data; int rc; - if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name)) + if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name)) return 0; xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c index 319cf16d6603..feba03bbedae 100644 --- a/security/integrity/evm/evm_secfs.c +++ b/security/integrity/evm/evm_secfs.c @@ -40,7 +40,7 @@ static ssize_t evm_read_key(struct file *filp, char __user *buf, if (*ppos != 0) return 0; - sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP)); + sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE)); rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); return rc; @@ -63,7 +63,7 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf, { int i, ret; - if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP)) + if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE)) return -EPERM; ret = kstrtoint_from_user(buf, count, 0, &i); @@ -75,16 +75,30 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf, if (!i || (i & ~EVM_INIT_MASK) != 0) return -EINVAL; + /* Don't allow a request to freshly enable metadata writes if + * keys are loaded. + */ + if ((i & EVM_ALLOW_METADATA_WRITES) && + ((evm_initialized & EVM_KEY_MASK) != 0) && + !(evm_initialized & EVM_ALLOW_METADATA_WRITES)) + return -EPERM; + if (i & EVM_INIT_HMAC) { ret = evm_init_key(); if (ret != 0) return ret; /* Forbid further writes after the symmetric key is loaded */ - i |= EVM_SETUP; + i |= EVM_SETUP_COMPLETE; } evm_initialized |= i; + /* Don't allow protected metadata modification if a symmetric key + * is loaded + */ + if (evm_initialized & EVM_INIT_HMAC) + evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES); + return count; } |