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package trailerparser
import (
"bytes"
"gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb"
)
const (
// The maximum number of trailers that we'll parse.
maxTrailers = 64
// The maximum size (in bytes) of trailer keys
//
// The limit should be sufficient enough to support multi-byte trailer keys
// (or just long trailer keys).
maxKeySize = 128
// The maximum size (in bytes) of trailer values.
//
// This limit should be sufficient enough to support URLs, long Email
// addresses, etc.
maxValueSize = 512
)
// Parse parses Git trailers into a list of CommitTrailer objects.
//
// The expected input is a single line containing trailers in the following
// format:
//
// KEY:VALUE\0KEY:VALUE
//
// Where \0 is a NULL byte. The input should not end in a NULL byte.
//
// Trailers must be separated with a null byte, as their values can include any
// other separator character. NULL bytes however are not allowed in commit
// messages, and thus can't occur in trailers.
//
// The key-value separator must be a colon, as this is the separator the Git CLI
// uses when obtaining the trailers of a commit message.
//
// Trailer keys and values are limited to a certain number of bytes. If these
// limits are reached, parsing stops and all trailers parsed until that point
// are returned. This ensures we don't continue to consume a potentially very
// large input.
//
// The limits this parser imposes on the sizes/amounts are loosely based on
// trailers found in GitLab's own repository. Here are just a few examples:
//
// Change-Id: I009c716ce2475b9efa3fd07aee9215fca7a1c150
// Changelog: https://github.com/nahi/httpclient/blob/b51d7a8bb78f71726b08fbda5abfb900d627569f/CHANGELOG.md#changes-in-282
// Co-Authored-By: Alex Kalderimis <akalderimis@gitlab.com>
// fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/44458
// Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
// See: https://gitlab.com/gitlab-org/gitlab-ee/blob/ff9ad690650c23665439499d23f3ed22103b55bb/spec/spec_helper.rb#L50
func Parse(input []byte) []*gitalypb.CommitTrailer {
// The choice of a nil slice instead of an empty one is deliberate: gRPC
// turns empty slices into nil.
//
// If we were to use an empty array, then compare that with a commit
// retrieved using e.g. the Ruby server, we'd be comparing different types:
// the Ruby server would produce a nil for an empty list of trailers, while
// Gitaly would produce an empty slice. Using a nil slice here ensures these
// type differences don't occur.
var trailers []*gitalypb.CommitTrailer
startPos := 0
max := len(input)
for startPos < max && len(trailers) < maxTrailers {
endPos := bytes.IndexByte(input[startPos:], byte('\000'))
// endPos starts as an index relative to the start position, so we need
// to convert this to an absolute index before we use it for slicing.
if endPos >= 0 {
endPos = startPos + endPos
} else {
endPos = max
}
sepPos := bytes.IndexByte(input[startPos:endPos], byte(':'))
if sepPos > 0 {
key := input[startPos : startPos+sepPos]
value := bytes.TrimSpace(input[startPos+sepPos+1 : endPos])
if len(key) > maxKeySize || len(value) > maxValueSize {
break
}
trailers = append(trailers, &gitalypb.CommitTrailer{
Key: key,
Value: value,
})
}
startPos = endPos + 1
}
return trailers
}
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