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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftNIO open source project
//
// Copyright (c) 2022 Apple Inc. and the SwiftNIO project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
extension String {
/// Validates a given header field value against the definition in RFC 9110.
///
/// The spec in [RFC 9110](https://httpwg.org/specs/rfc9110.html#fields.values) defines the valid
/// characters as the following:
///
/// ```
/// field-value = *field-content
/// field-content = field-vchar
/// [ 1*( SP / HTAB / field-vchar ) field-vchar ]
/// field-vchar = VCHAR / obs-text
/// obs-text = %x80-FF
/// ```
///
/// Additionally, it makes the following note:
///
/// "Field values containing CR, LF, or NUL characters are invalid and dangerous, due to the
/// varying ways that implementations might parse and interpret those characters; a recipient
/// of CR, LF, or NUL within a field value MUST either reject the message or replace each of
/// those characters with SP before further processing or forwarding of that message. Field
/// values containing other CTL characters are also invalid; however, recipients MAY retain
/// such characters for the sake of robustness when they appear within a safe context (e.g.,
/// an application-specific quoted string that will not be processed by any downstream HTTP
/// parser)."
///
/// As we cannot guarantee the context is safe, this code will reject all ASCII control characters
/// directly _except_ for HTAB, which is explicitly allowed.
fileprivate var isValidHeaderFieldValue: Bool {
let fastResult = self.utf8.withContiguousStorageIfAvailable { ptr in
ptr.allSatisfy { $0.isValidHeaderFieldValueByte }
}
if let fastResult = fastResult {
return fastResult
} else {
return self.utf8._isValidHeaderFieldValue_slowPath
}
}
/// Validates a given header field name against the definition in RFC 9110.
///
/// The spec in [RFC 9110](https://httpwg.org/specs/rfc9110.html#fields.values) defines the valid
/// characters as the following:
///
/// ```
/// field-name = token
///
/// token = 1*tchar
///
/// tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/// / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/// / DIGIT / ALPHA
/// ; any VCHAR, except delimiters
/// ```
///
/// We implement this check directly.
fileprivate var isValidHeaderFieldName: Bool {
let fastResult = self.utf8.withContiguousStorageIfAvailable { ptr in
ptr.allSatisfy { $0.isValidHeaderFieldNameByte }
}
if let fastResult = fastResult {
return fastResult
} else {
return self.utf8._isValidHeaderFieldName_slowPath
}
}
}
extension String.UTF8View {
/// The equivalent of `String.isValidHeaderFieldName`, but a slow-path when a
/// contiguous UTF8 storage is not available.
///
/// This is deliberately `@inline(never)`, as slow paths should be forcibly outlined
/// to encourage inlining the fast-path.
@inline(never)
fileprivate var _isValidHeaderFieldName_slowPath: Bool {
self.allSatisfy { $0.isValidHeaderFieldNameByte }
}
/// The equivalent of `String.isValidHeaderFieldValue`, but a slow-path when a
/// contiguous UTF8 storage is not available.
///
/// This is deliberately `@inline(never)`, as slow paths should be forcibly outlined
/// to encourage inlining the fast-path.
@inline(never)
fileprivate var _isValidHeaderFieldValue_slowPath: Bool {
self.allSatisfy { $0.isValidHeaderFieldValueByte }
}
}
extension UInt8 {
/// Validates a byte of a given header field name against the definition in RFC 9110.
///
/// The spec in [RFC 9110](https://httpwg.org/specs/rfc9110.html#fields.values) defines the valid
/// characters as the following:
///
/// ```
/// field-name = token
///
/// token = 1*tchar
///
/// tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/// / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/// / DIGIT / ALPHA
/// ; any VCHAR, except delimiters
/// ```
///
/// We implement this check directly.
///
/// We use inline always here to force the check to be inlined, which it isn't always, leading to less optimal code.
@inline(__always)
fileprivate var isValidHeaderFieldNameByte: Bool {
switch self {
case UInt8(ascii: "0")...UInt8(ascii: "9"), // DIGIT
UInt8(ascii: "a")...UInt8(ascii: "z"),
UInt8(ascii: "A")...UInt8(ascii: "Z"), // ALPHA
UInt8(ascii: "!"), UInt8(ascii: "#"),
UInt8(ascii: "$"), UInt8(ascii: "%"),
UInt8(ascii: "&"), UInt8(ascii: "'"),
UInt8(ascii: "*"), UInt8(ascii: "+"),
UInt8(ascii: "-"), UInt8(ascii: "."),
UInt8(ascii: "^"), UInt8(ascii: "_"),
UInt8(ascii: "`"), UInt8(ascii: "|"),
UInt8(ascii: "~"):
return true
default:
return false
}
}
/// Validates a byte of a given header field value against the definition in RFC 9110.
///
/// The spec in [RFC 9110](https://httpwg.org/specs/rfc9110.html#fields.values) defines the valid
/// characters as the following:
///
/// ```
/// field-value = *field-content
/// field-content = field-vchar
/// [ 1*( SP / HTAB / field-vchar ) field-vchar ]
/// field-vchar = VCHAR / obs-text
/// obs-text = %x80-FF
/// ```
///
/// Additionally, it makes the following note:
///
/// "Field values containing CR, LF, or NUL characters are invalid and dangerous, due to the
/// varying ways that implementations might parse and interpret those characters; a recipient
/// of CR, LF, or NUL within a field value MUST either reject the message or replace each of
/// those characters with SP before further processing or forwarding of that message. Field
/// values containing other CTL characters are also invalid; however, recipients MAY retain
/// such characters for the sake of robustness when they appear within a safe context (e.g.,
/// an application-specific quoted string that will not be processed by any downstream HTTP
/// parser)."
///
/// As we cannot guarantee the context is safe, this code will reject all ASCII control characters
/// directly _except_ for HTAB, which is explicitly allowed.
///
/// We use inline always here to force the check to be inlined, which it isn't always, leading to less optimal code.
@inline(__always)
fileprivate var isValidHeaderFieldValueByte: Bool {
switch self {
case UInt8(ascii: "\t"):
// HTAB, explicitly allowed.
return true
case 0...0x1f, 0x7F:
// ASCII control character, forbidden.
return false
default:
// Printable or non-ASCII, allowed.
return true
}
}
}
extension HTTPHeaders {
/// Whether these HTTPHeaders are valid to send on the wire.
var areValidToSend: Bool {
for (name, value) in self.headers {
if !name.isValidHeaderFieldName {
return false
}
if !value.isValidHeaderFieldValue {
return false
}
}
return true
}
}
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