| Message ID | 874llhoz89.fsf@morokweng.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Quoting Thiago Jung Bauermann (bauerman@linux.vnet.ibm.com): > > Mimi Zohar <zohar@linux.vnet.ibm.com> writes: > > On Wed, 2018-03-14 at 21:03 -0300, Thiago Jung Bauermann wrote: > >> Hello Serge, > >> > >> Thanks for quickly reviewing these patches! > >> > >> Serge E. Hallyn <serge@hallyn.com> writes: > >> > >> > Quoting Thiago Jung Bauermann (bauerman@linux.vnet.ibm.com): > >> >> From: Mimi Zohar <zohar@linux.vnet.ibm.com> > >> >> @@ -241,16 +241,20 @@ int ima_appraise_measurement(enum ima_hooks func, > >> >> } > >> >> > >> >> status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); > >> >> - if ((status != INTEGRITY_PASS) && > >> >> - (status != INTEGRITY_PASS_IMMUTABLE) && > >> >> - (status != INTEGRITY_UNKNOWN)) { > >> >> - if ((status == INTEGRITY_NOLABEL) > >> >> - || (status == INTEGRITY_NOXATTRS)) > >> >> - cause = "missing-HMAC"; > >> >> - else if (status == INTEGRITY_FAIL) > >> >> - cause = "invalid-HMAC"; > >> >> + switch (status) { > >> >> + case INTEGRITY_PASS: > >> >> + case INTEGRITY_PASS_IMMUTABLE: > >> >> + case INTEGRITY_UNKNOWN: > >> > > >> > Wouldn't it be more future-proof to replace this with a 'default', or > >> > to at least add a "default: BUG()" to catch new status values? > >> > >> I agree. I like the "default: BUG()" option. > > > > Agreed. I would put it at the end after INTEGRITY_FAIL. > > Ok, what about the version below? Since the status is returned by evm, it seems like an actual BUG() is appropriate, but ok. Acked-by: Serge Hallyn <serge@hallyn.com> > > >> > >> >> + break; > >> >> + case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ > >> >> + case INTEGRITY_NOLABEL: /* No security.evm xattr. */ > >> >> + cause = "missing-HMAC"; > >> >> + goto out; > >> >> + case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ > >> >> + cause = "invalid-HMAC"; > >> >> goto out; > >> >> } > >> >> + > >> >> switch (xattr_value->type) { > >> >> case IMA_XATTR_DIGEST_NG: > >> >> /* first byte contains algorithm id */ > >> >> @@ -316,17 +320,20 @@ int ima_appraise_measurement(enum ima_hooks func, > >> >> integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > >> >> op, cause, rc, 0); > >> >> } else if (status != INTEGRITY_PASS) { > >> >> + /* Fix mode, but don't replace file signatures. */ > >> >> if ((ima_appraise & IMA_APPRAISE_FIX) && > >> >> (!xattr_value || > >> >> xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { > >> >> if (!ima_fix_xattr(dentry, iint)) > >> >> status = INTEGRITY_PASS; > >> >> - } else if ((inode->i_size == 0) && > >> >> - (iint->flags & IMA_NEW_FILE) && > >> >> - (xattr_value && > >> >> - xattr_value->type == EVM_IMA_XATTR_DIGSIG)) { > >> >> + } > >> >> + > >> >> + /* Permit new files with file signatures, but without data. */ > >> >> + if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && > >> > > >> > This may be correct, but it's not identical to what you're replacing. > >> > Since in either case you're setting status to INTEGRITY_PASS the final > >> > result is the same, but with a few extra possible steps. Not sure > >> > whether that matters. > >> > >> Good point. I'll have to defer this one to Mimi though. > > > > The end result is the same, but add some needed comments. Yes, the same, but with a few extra possible steps, impacting performance, so I just wanted to call that out. -serge
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 0c5f94b7b9c3..8bd7a0733e51 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -215,7 +215,7 @@ int ima_appraise_measurement(enum ima_hooks func, int xattr_len, int opened) { static const char op[] = "appraise_data"; - char *cause = "unknown"; + const char *cause = "unknown"; struct dentry *dentry = file_dentry(file); struct inode *inode = d_backing_inode(dentry); enum integrity_status status = INTEGRITY_UNKNOWN; @@ -241,16 +241,22 @@ int ima_appraise_measurement(enum ima_hooks func, } status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); - if ((status != INTEGRITY_PASS) && - (status != INTEGRITY_PASS_IMMUTABLE) && - (status != INTEGRITY_UNKNOWN)) { - if ((status == INTEGRITY_NOLABEL) - || (status == INTEGRITY_NOXATTRS)) - cause = "missing-HMAC"; - else if (status == INTEGRITY_FAIL) - cause = "invalid-HMAC"; + switch (status) { + case INTEGRITY_PASS: + case INTEGRITY_PASS_IMMUTABLE: + case INTEGRITY_UNKNOWN: + break; + case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ + case INTEGRITY_NOLABEL: /* No security.evm xattr. */ + cause = "missing-HMAC"; + goto out; + case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ + cause = "invalid-HMAC"; goto out; + default: + WARN_ONCE(true, "Unexpected integrity status %d\n", status); } + switch (xattr_value->type) { case IMA_XATTR_DIGEST_NG: /* first byte contains algorithm id */ @@ -316,17 +322,20 @@ int ima_appraise_measurement(enum ima_hooks func, integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, op, cause, rc, 0); } else if (status != INTEGRITY_PASS) { + /* Fix mode, but don't replace file signatures. */ if ((ima_appraise & IMA_APPRAISE_FIX) && (!xattr_value || xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { if (!ima_fix_xattr(dentry, iint)) status = INTEGRITY_PASS; - } else if ((inode->i_size == 0) && - (iint->flags & IMA_NEW_FILE) && - (xattr_value && - xattr_value->type == EVM_IMA_XATTR_DIGSIG)) { + } + + /* Permit new files with file signatures, but without data. */ + if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && + xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { status = INTEGRITY_PASS; } + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, op, cause, rc, 0); } else {