| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Snap.Util.FileUploads
Description
This module contains primitives and helper functions for handling
requests with Content-type: multipart/form-data, i.e. HTML forms and file
uploads.
Typically most users will want to use handleFileUploads, which writes
uploaded files to a temporary directory before sending them on to a handler
specified by the user.
Users who wish to handle their file uploads differently can use the
lower-level interface called handleMultipart. That function takes
uploaded files and streams them to a consumer of the user's choosing.
Using these functions requires making "policy" decisions which Snap can't
really make for users, such as "what's the largest PDF file a user is
allowed to upload?" and "should we read form inputs into the parameters
mapping?". Policy is specified on a "global" basis (using
UploadPolicy), and on a per-file basis (using PartUploadPolicy, which
allows you to reject or limit the size of certain uploaded
Content-types).
Example usage:
{-# LANGUAGE OverloadedStrings #-}
module Main where
import qualified Data.ByteString.Char8 as B8
import Data.Functor ((<$>))
import Snap.Core (Snap, route, writeBS)
import Snap.Http.Server (quickHttpServe)
import Snap.Util.FileUploads
import System.Posix (FileOffset, fileSize, getFileStatus)
uploadForm :: Snap ()
uploadForm = writeBS "<form enctype=\"multipart/form-data\" action=\"/do-upload\" method=\"POST\">\
\<input name=\"file\" type=\"file\" />\
\<input type=\"submit\" value=\"Send File\" />\
\</form>"
getFileSize :: FilePath -> IO FileOffset
getFileSize path = fileSize <$> getFileStatus path
-- Upload handler that prints out the uploaded file's size.
doUpload :: Snap ()
doUpload = do
l <- handleFileUploads "/tmp" defaultUploadPolicy
(const $ allowWithMaximumSize (getMaximumFormInputSize defaultUploadPolicy))
(\pinfo mbfname -> do fsize <- either (const $ return 0) getFileSize mbfname
return (partFileName pinfo, fsize))
writeBS . B8.pack . show $ l
site :: Snap ()
site = route
[ ("/upload", uploadForm)
, ("/do-upload", doUpload)]
main :: IO ()
main = quickHttpServe site
- handleFileUploads :: MonadSnap m => FilePath -> UploadPolicy -> (PartInfo -> PartUploadPolicy) -> (PartInfo -> Either PolicyViolationException FilePath -> IO a) -> m [a]
- handleMultipart :: MonadSnap m => UploadPolicy -> PartProcessor a -> m [a]
- type PartProcessor a = PartInfo -> InputStream ByteString -> IO a
- data PartInfo
- data PartDisposition
- partFieldName :: PartInfo -> ByteString
- partFileName :: PartInfo -> Maybe ByteString
- partContentType :: PartInfo -> ByteString
- partHeaders :: PartInfo -> Headers
- partDisposition :: PartInfo -> PartDisposition
- data UploadPolicy
- defaultUploadPolicy :: UploadPolicy
- doProcessFormInputs :: UploadPolicy -> Bool
- setProcessFormInputs :: Bool -> UploadPolicy -> UploadPolicy
- getMaximumFormInputSize :: UploadPolicy -> Int64
- setMaximumFormInputSize :: Int64 -> UploadPolicy -> UploadPolicy
- getMaximumNumberOfFormInputs :: UploadPolicy -> Int
- setMaximumNumberOfFormInputs :: Int -> UploadPolicy -> UploadPolicy
- getMinimumUploadRate :: UploadPolicy -> Double
- setMinimumUploadRate :: Double -> UploadPolicy -> UploadPolicy
- getMinimumUploadSeconds :: UploadPolicy -> Int
- setMinimumUploadSeconds :: Int -> UploadPolicy -> UploadPolicy
- getUploadTimeout :: UploadPolicy -> Int
- setUploadTimeout :: Int -> UploadPolicy -> UploadPolicy
- data PartUploadPolicy
- disallow :: PartUploadPolicy
- allowWithMaximumSize :: Int64 -> PartUploadPolicy
- data FileUploadException
- fileUploadExceptionReason :: FileUploadException -> Text
- data BadPartException
- badPartExceptionReason :: BadPartException -> Text
- data PolicyViolationException
- policyViolationExceptionReason :: PolicyViolationException -> Text
Functions
Arguments
| :: MonadSnap m | |
| => FilePath | temporary directory |
| -> UploadPolicy | general upload policy |
| -> (PartInfo -> PartUploadPolicy) | per-part upload policy |
| -> (PartInfo -> Either PolicyViolationException FilePath -> IO a) | user handler (see function description) |
| -> m [a] |
Reads uploaded files into a temporary directory and calls a user handler to process them.
Note: THE REQUEST MUST BE CORRECTLY ENCODED. If the request's
Content-type is not "multipart/formdata", this function skips
processing using pass.
Given a temporary directory, global and file-specific upload policies, and a
user handler, this function consumes a request body uploaded with
Content-type: multipart/form-data. Each file is read into the temporary
directory, and is then passed to the user handler. After the user handler
runs (but before the Response body is streamed to the client), the files
are deleted from disk; so if you want to retain or use the uploaded files in
the generated response, you need to move or otherwise process them.
The argument passed to the user handler is a tuple:
(PartInfo, Either PolicyViolationException FilePath)
The first half of this tuple is a PartInfo, which contains the
information the client browser sent about the given upload part (like
filename, content-type, etc). The second half of this tuple is an Either
stipulating that either:
- the file was rejected on a policy basis because of the provided
PartUploadPolicyhandler - the file was accepted and exists at the given path.
Exceptions
If the client's upload rate passes below the configured minimum (see
setMinimumUploadRate and setMinimumUploadSeconds), this function
terminates the connection. This setting is there to protect the server
against slowloris-style denial of service attacks.
If the given UploadPolicy stipulates that you wish form inputs to be
placed in the rqParams parameter map (using setProcessFormInputs), and
a form input exceeds the maximum allowable size, this function will throw a
PolicyViolationException.
If an uploaded part contains MIME headers longer than a fixed internal
threshold (currently 32KB), this function will throw a BadPartException.
Arguments
| :: MonadSnap m | |
| => UploadPolicy | global upload policy |
| -> PartProcessor a | part processor |
| -> m [a] |
Given an upload policy and a function to consume uploaded "parts",
consume a request body uploaded with Content-type: multipart/form-data.
Note: THE REQUEST MUST BE CORRECTLY ENCODED. If the request's
Content-type is not "multipart/formdata", this function skips
processing using pass.
Most users will opt for the higher-level handleFileUploads, which writes
to temporary files, rather than handleMultipart. This function should be
chosen, however, if you need to stream uploaded files directly to your own
processing function: e.g. to a database or a remote service via RPC.
If the client's upload rate passes below the configured minimum (see
setMinimumUploadRate and setMinimumUploadSeconds), this function
terminates the connection. This setting is there to protect the server
against slowloris-style denial of service attacks.
Exceptions
If the given UploadPolicy stipulates that you wish form inputs to be
placed in the rqParams parameter map (using setProcessFormInputs), and
a form input exceeds the maximum allowable size, this function will throw a
PolicyViolationException.
If an uploaded part contains MIME headers longer than a fixed internal
threshold (currently 32KB), this function will throw a BadPartException.
type PartProcessor a = PartInfo -> InputStream ByteString -> IO a Source #
A type alias for a function that will process one of the parts of a
multipart/form-data HTTP request body.
Uploaded parts
PartInfo contains information about a "part" in a request uploaded
with Content-type: multipart/form-data.
data PartDisposition Source #
Represents the disposition type specified via the Content-Disposition
header field. See RFC 1806.
Constructors
| DispositionAttachment |
|
| DispositionFile |
|
| DispositionFormData |
|
| DispositionOther ByteString | Any other value. |
Instances
partFieldName :: PartInfo -> ByteString Source #
Field name associated with this part (i.e., the name specified with
<input name="partFieldName" ...).
partFileName :: PartInfo -> Maybe ByteString Source #
Name of the uploaded file.
partContentType :: PartInfo -> ByteString Source #
Content type of this part.
partHeaders :: PartInfo -> Headers Source #
Remaining headers associated with this part.
partDisposition :: PartInfo -> PartDisposition Source #
Disposition type of this part. See PartDisposition.
Policy
General upload policy
data UploadPolicy Source #
UploadPolicy controls overall policy decisions relating to
multipart/form-data uploads, specifically:
- whether to treat parts without filenames as form input (reading them into
the
rqParamsmap) - because form input is read into memory, the maximum size of a form input read in this manner, and the maximum number of form inputs
- the minimum upload rate a client must maintain before we kill the connection; if very low-bitrate uploads were allowed then a Snap server would be vulnerable to a trivial denial-of-service using a "slowloris"-type attack
- the minimum number of seconds which must elapse before we start killing uploads for having too low an upload rate.
- the amount of time we should wait before timing out the connection whenever we receive input from the client.
defaultUploadPolicy :: UploadPolicy Source #
A reasonable set of defaults for upload policy. The default policy is:
maximum form input size- 128kB
maximum number of form inputs- 10
minimum upload rate- 1kB/s
seconds before rate limiting kicks in- 10
inactivity timeout- 20 seconds
doProcessFormInputs :: UploadPolicy -> Bool Source #
Does this upload policy stipulate that we want to treat parts without filenames as form input?
setProcessFormInputs :: Bool -> UploadPolicy -> UploadPolicy Source #
Set the upload policy for treating parts without filenames as form input.
getMaximumFormInputSize :: UploadPolicy -> Int64 Source #
Get the maximum size of a form input which will be read into our
rqParams map.
setMaximumFormInputSize :: Int64 -> UploadPolicy -> UploadPolicy Source #
Set the maximum size of a form input which will be read into our
rqParams map.
getMaximumNumberOfFormInputs :: UploadPolicy -> Int Source #
Get the maximum size of a form input which will be read into our
rqParams map.
setMaximumNumberOfFormInputs :: Int -> UploadPolicy -> UploadPolicy Source #
Set the maximum size of a form input which will be read into our
rqParams map.
getMinimumUploadRate :: UploadPolicy -> Double Source #
Get the minimum rate (in bytes/second) a client must maintain before we kill the connection.
setMinimumUploadRate :: Double -> UploadPolicy -> UploadPolicy Source #
Set the minimum rate (in bytes/second) a client must maintain before we kill the connection.
getMinimumUploadSeconds :: UploadPolicy -> Int Source #
Get the amount of time which must elapse before we begin enforcing the upload rate minimum
setMinimumUploadSeconds :: Int -> UploadPolicy -> UploadPolicy Source #
Set the amount of time which must elapse before we begin enforcing the upload rate minimum
getUploadTimeout :: UploadPolicy -> Int Source #
Get the "upload timeout". Whenever input is received from the client, the connection timeout is set this many seconds in the future.
setUploadTimeout :: Int -> UploadPolicy -> UploadPolicy Source #
Set the upload timeout.
Per-file upload policy
data PartUploadPolicy Source #
Upload policy can be set on an "general" basis (using UploadPolicy),
but handlers can also make policy decisions on individual files/parts
uploaded. For each part uploaded, handlers can decide:
- whether to allow the file upload at all
- the maximum size of uploaded files, if allowed
disallow :: PartUploadPolicy Source #
Disallows the file to be uploaded.
allowWithMaximumSize :: Int64 -> PartUploadPolicy Source #
Allows the file to be uploaded, with maximum size n.
Exceptions
data FileUploadException Source #
All of the exceptions defined in this package inherit from
FileUploadException, so if you write
foo `catch` \(e :: FileUploadException) -> ...
you can catch a BadPartException, a PolicyViolationException, etc.
Instances
fileUploadExceptionReason :: FileUploadException -> Text Source #
Human-readable error message corresponding to the FileUploadException.
data BadPartException Source #
Thrown when a part is invalid in some way (e.g. the headers are too large).
Instances
badPartExceptionReason :: BadPartException -> Text Source #
Human-readable error message corresponding to the BadPartException.
data PolicyViolationException Source #
Thrown when an UploadPolicy or PartUploadPolicy is violated.
policyViolationExceptionReason :: PolicyViolationException -> Text Source #
Human-readable error message corresponding to the
PolicyViolationException.