github.com/dtroyer-salad/og2/v2@v2.0.0-20240412154159-c47231610877/registry/remote/warning.go (about)

     1  /*
     2  Copyright The ORAS Authors.
     3  Licensed under the Apache License, Version 2.0 (the "License");
     4  you may not use this file except in compliance with the License.
     5  You may obtain a copy of the License at
     6  
     7  http://www.apache.org/licenses/LICENSE-2.0
     8  
     9  Unless required by applicable law or agreed to in writing, software
    10  distributed under the License is distributed on an "AS IS" BASIS,
    11  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  See the License for the specific language governing permissions and
    13  limitations under the License.
    14  */
    15  
    16  package remote
    17  
    18  import (
    19  	"errors"
    20  	"fmt"
    21  	"strconv"
    22  	"strings"
    23  )
    24  
    25  const (
    26  	// headerWarning is the "Warning" header.
    27  	// Reference: https://www.rfc-editor.org/rfc/rfc7234#section-5.5
    28  	headerWarning = "Warning"
    29  
    30  	// warnCode299 is the 299 warn-code.
    31  	// Reference: https://www.rfc-editor.org/rfc/rfc7234#section-5.5
    32  	warnCode299 = 299
    33  
    34  	// warnAgentUnknown represents an unknown warn-agent.
    35  	// Reference: https://www.rfc-editor.org/rfc/rfc7234#section-5.5
    36  	warnAgentUnknown = "-"
    37  )
    38  
    39  // errUnexpectedWarningFormat is returned by parseWarningHeader when
    40  // an unexpected warning format is encountered.
    41  var errUnexpectedWarningFormat = errors.New("unexpected warning format")
    42  
    43  // WarningValue represents the value of the Warning header.
    44  //
    45  // References:
    46  //   - https://github.com/opencontainers/distribution-spec/blob/v1.1.0/spec.md#warnings
    47  //   - https://www.rfc-editor.org/rfc/rfc7234#section-5.5
    48  type WarningValue struct {
    49  	// Code is the warn-code.
    50  	Code int
    51  	// Agent is the warn-agent.
    52  	Agent string
    53  	// Text is the warn-text.
    54  	Text string
    55  }
    56  
    57  // Warning contains the value of the warning header and may contain
    58  // other information related to the warning.
    59  //
    60  // References:
    61  //   - https://github.com/opencontainers/distribution-spec/blob/v1.1.0/spec.md#warnings
    62  //   - https://www.rfc-editor.org/rfc/rfc7234#section-5.5
    63  type Warning struct {
    64  	// WarningValue is the value of the warning header.
    65  	WarningValue
    66  }
    67  
    68  // parseWarningHeader parses the warning header into WarningValue.
    69  func parseWarningHeader(header string) (WarningValue, error) {
    70  	if len(header) < 9 || !strings.HasPrefix(header, `299 - "`) || !strings.HasSuffix(header, `"`) {
    71  		// minimum header value: `299 - "x"`
    72  		return WarningValue{}, fmt.Errorf("%s: %w", header, errUnexpectedWarningFormat)
    73  	}
    74  
    75  	// validate text only as code and agent are fixed
    76  	quotedText := header[6:] // behind `299 - `, quoted by "
    77  	text, err := strconv.Unquote(quotedText)
    78  	if err != nil {
    79  		return WarningValue{}, fmt.Errorf("%s: unexpected text: %w: %v", header, errUnexpectedWarningFormat, err)
    80  	}
    81  
    82  	return WarningValue{
    83  		Code:  warnCode299,
    84  		Agent: warnAgentUnknown,
    85  		Text:  text,
    86  	}, nil
    87  }
    88  
    89  // handleWarningHeaders parses the warning headers and handles the parsed
    90  // warnings using handleWarning.
    91  func handleWarningHeaders(headers []string, handleWarning func(Warning)) {
    92  	for _, h := range headers {
    93  		if value, err := parseWarningHeader(h); err == nil {
    94  			// ignore warnings in unexpected formats
    95  			handleWarning(Warning{
    96  				WarningValue: value,
    97  			})
    98  		}
    99  	}
   100  }