fix: Privilege escalation in IAM import API (#20756)

This API had missing permissions checking, allowing a user to change
their policy mapping by:

1. Craft iam-info.zip file: Update own user permission in
user_mappings.json
2. Upload it via `mc admin cluster iam import nobody iam-info.zip`

Here `nobody` can be a user with pretty much any kind of permission (but
not anonymous) and this ends up working.

Some more detailed steps - start from a fresh setup:

```
./minio server /tmp/d{1...4} &
mc alias set myminio http://localhost:9000 minioadmin minioadmin
mc admin user add myminio nobody nobody123
mc admin policy attach myminio readwrite nobody nobody123
mc alias set nobody http://localhost:9000 nobody nobody123

mc admin cluster iam export myminio
mkdir /tmp/x && mv myminio-iam-info.zip /tmp/x
cd /tmp/x
unzip myminio-iam-info.zip
echo '{"nobody":{"version":1,"policy":"consoleAdmin","updatedAt":"2024-08-13T19:47:10.1Z"}}' > \
      iam-assets/user_mappings.json
zip -r myminio-iam-info-updated.zip iam-assets/

mc admin cluster iam import nobody ./myminio-iam-info-updated.zip
mc admin service restart nobody
```
This commit is contained in:
Aditya Manthramurthy 2024-12-11 18:09:40 -08:00 committed by GitHub
parent 9cdd204ae4
commit f246c9053f
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@ -2032,6 +2032,7 @@ func (a adminAPIHandlers) ExportIAM(w http.ResponseWriter, r *http.Request) {
// Get current object layer instance.
objectAPI, _ := validateAdminReq(ctx, w, r, policy.ExportIAMAction)
if objectAPI == nil {
writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrServerNotInitialized), r.URL)
return
}
// Initialize a zip writer which will provide a zipped content
@ -2254,17 +2255,13 @@ func (a adminAPIHandlers) ImportIAMV2(w http.ResponseWriter, r *http.Request) {
func (a adminAPIHandlers) importIAM(w http.ResponseWriter, r *http.Request, apiVer string) {
ctx := r.Context()
// Get current object layer instance.
objectAPI := newObjectLayerFn()
// Validate signature, permissions and get current object layer instance.
objectAPI, _ := validateAdminReq(ctx, w, r, policy.ImportIAMAction)
if objectAPI == nil || globalNotificationSys == nil {
writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrServerNotInitialized), r.URL)
return
}
cred, owner, s3Err := validateAdminSignature(ctx, r, "")
if s3Err != ErrNone {
writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(s3Err), r.URL)
return
}
data, err := io.ReadAll(r.Body)
if err != nil {
writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInvalidRequest), r.URL)
@ -2354,38 +2351,12 @@ func (a adminAPIHandlers) importIAM(w http.ResponseWriter, r *http.Request, apiV
return
}
if (cred.IsTemp() || cred.IsServiceAccount()) && cred.ParentUser == accessKey {
// Incoming access key matches parent user then we should
// reject password change requests.
writeErrorResponseJSON(ctx, w, importErrorWithAPIErr(ctx, ErrAddUserInvalidArgument, err, allUsersFile, accessKey), r.URL)
return
}
// Check if accessKey has beginning and end space characters, this only applies to new users.
if !exists && hasSpaceBE(accessKey) {
writeErrorResponseJSON(ctx, w, importErrorWithAPIErr(ctx, ErrAdminResourceInvalidArgument, err, allUsersFile, accessKey), r.URL)
return
}
checkDenyOnly := false
if accessKey == cred.AccessKey {
// Check that there is no explicit deny - otherwise it's allowed
// to change one's own password.
checkDenyOnly = true
}
if !globalIAMSys.IsAllowed(policy.Args{
AccountName: cred.AccessKey,
Groups: cred.Groups,
Action: policy.CreateUserAdminAction,
ConditionValues: getConditionValues(r, "", cred),
IsOwner: owner,
Claims: cred.Claims,
DenyOnly: checkDenyOnly,
}) {
writeErrorResponseJSON(ctx, w, importErrorWithAPIErr(ctx, ErrAccessDenied, err, allUsersFile, accessKey), r.URL)
return
}
if _, err = globalIAMSys.CreateUser(ctx, accessKey, ureq); err != nil {
failed.Users = append(failed.Users, madmin.IAMErrEntity{Name: accessKey, Error: err})
} else {
@ -2485,17 +2456,6 @@ func (a adminAPIHandlers) importIAM(w http.ResponseWriter, r *http.Request, apiV
writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrAdminResourceInvalidArgument), r.URL)
return
}
if !globalIAMSys.IsAllowed(policy.Args{
AccountName: cred.AccessKey,
Groups: cred.Groups,
Action: policy.CreateServiceAccountAdminAction,
ConditionValues: getConditionValues(r, "", cred),
IsOwner: owner,
Claims: cred.Claims,
}) {
writeErrorResponseJSON(ctx, w, importErrorWithAPIErr(ctx, ErrAccessDenied, err, allSvcAcctsFile, user), r.URL)
return
}
updateReq := true
_, _, err = globalIAMSys.GetServiceAccount(ctx, svcAcctReq.AccessKey)
if err != nil {