timestamp.go

Documentation: github.com/sigstore/timestamp-authority/pkg/api

     1  // Copyright 2022 The Sigstore Authors.
     2  //
     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  package api
    16  
    17  import (
    18  	"bytes"
    19  	"crypto"
    20  	"encoding/asn1"
    21  	"encoding/base64"
    22  	"encoding/json"
    23  	"fmt"
    24  	"io"
    25  	"math/big"
    26  	"net/http"
    27  	"strconv"
    28  	"strings"
    29  	"time"
    30  
    31  	"github.com/digitorus/timestamp"
    32  	"github.com/go-openapi/runtime/middleware"
    33  	"github.com/pkg/errors"
    34  	ts "github.com/sigstore/timestamp-authority/pkg/generated/restapi/operations/timestamp"
    35  	"github.com/sigstore/timestamp-authority/pkg/verification"
    36  )
    37  
    38  type JSONRequest struct {
    39  	ArtifactHash  string   `json:"artifactHash"`
    40  	Certificates  bool     `json:"certificates"`
    41  	HashAlgorithm string   `json:"hashAlgorithm"`
    42  	Nonce         *big.Int `json:"nonce"`
    43  	TSAPolicyOID  string   `json:"tsaPolicyOID"`
    44  }
    45  
    46  func getHashAlg(alg string) (crypto.Hash, string, error) {
    47  	lowercaseAlg := strings.ToLower(alg)
    48  	switch lowercaseAlg {
    49  	case "sha256":
    50  		return crypto.SHA256, "", nil
    51  	case "sha384":
    52  		return crypto.SHA384, "", nil
    53  	case "sha512":
    54  		return crypto.SHA512, "", nil
    55  	case "sha1":
    56  		return 0, WeakHashAlgorithmTimestampRequest, verification.ErrWeakHashAlg
    57  	default:
    58  		return 0, failedToGenerateTimestampResponse, fmt.Errorf("unsupported hash algorithm: %s", alg)
    59  	}
    60  }
    61  
    62  // ParseJSONRequest parses a JSON request into a timestamp.Request struct
    63  func ParseJSONRequest(reqBytes []byte) (*timestamp.Request, string, error) {
    64  	// unmarshal the request bytes into a JSONRequest struct
    65  	var req JSONRequest
    66  	if err := json.Unmarshal(reqBytes, &req); err != nil {
    67  		return nil, failedToGenerateTimestampResponse, fmt.Errorf("failed to parse JSON into request: %v", err)
    68  	}
    69  
    70  	// after unmarshalling, parse the JSONRequest.Artifact into a Reader and parse the remaining
    71  	// fields into a a timestamp.RequestOptions struct
    72  	hashAlgo, errMsg, err := getHashAlg(req.HashAlgorithm)
    73  	if err != nil {
    74  		return nil, errMsg, fmt.Errorf("failed to parse hash algorithm: %v", err)
    75  	}
    76  
    77  	var oidInts []int
    78  	if req.TSAPolicyOID == "" {
    79  		oidInts = nil
    80  	} else {
    81  		for _, v := range strings.Split(req.TSAPolicyOID, ".") {
    82  			i, _ := strconv.Atoi(v)
    83  			oidInts = append(oidInts, i)
    84  		}
    85  	}
    86  
    87  	// decode the base64 encoded artifact hash
    88  	decoded, err := base64.StdEncoding.DecodeString(req.ArtifactHash)
    89  	if err != nil {
    90  		return nil, failedToGenerateTimestampResponse, fmt.Errorf("failed to decode base64 encoded artifact hash: %v", err)
    91  	}
    92  
    93  	// create a timestamp request from the request's JSON body
    94  	tsReq := timestamp.Request{
    95  		HashAlgorithm: hashAlgo,
    96  		HashedMessage: decoded,
    97  		Certificates:  req.Certificates,
    98  		Nonce:         req.Nonce,
    99  		TSAPolicyOID:  oidInts,
   100  	}
   101  
   102  	return &tsReq, "", nil
   103  }
   104  
   105  func parseDERRequest(reqBytes []byte) (*timestamp.Request, string, error) {
   106  	parsed, err := timestamp.ParseRequest(reqBytes)
   107  	if err != nil {
   108  		return nil, failedToGenerateTimestampResponse, err
   109  	}
   110  
   111  	// verify that the request's hash algorithm is supported
   112  	if err := verification.VerifyRequest(parsed); err != nil {
   113  		return nil, WeakHashAlgorithmTimestampRequest, err
   114  	}
   115  
   116  	return parsed, "", nil
   117  }
   118  
   119  func getContentType(r *http.Request) (string, error) {
   120  	contentTypeHeader := r.Header.Get("Content-Type")
   121  	splitHeader := strings.Split(contentTypeHeader, "application/")
   122  	if len(splitHeader) != 2 {
   123  		return "", errors.New("expected header value to be split into two pieces")
   124  	}
   125  	return splitHeader[1], nil
   126  }
   127  
   128  func requestBodyToTimestampReq(reqBytes []byte, contentType string) (*timestamp.Request, string, error) {
   129  	switch contentType {
   130  	case "json":
   131  		return ParseJSONRequest(reqBytes)
   132  	case "timestamp-query":
   133  		return parseDERRequest(reqBytes)
   134  	default:
   135  		return nil, failedToGenerateTimestampResponse, fmt.Errorf("unsupported content type")
   136  	}
   137  }
   138  
   139  func TimestampResponseHandler(params ts.GetTimestampResponseParams) middleware.Responder {
   140  	requestBytes, err := io.ReadAll(params.Request)
   141  	if err != nil {
   142  		return handleTimestampAPIError(params, http.StatusBadRequest, err, failedToGenerateTimestampResponse)
   143  	}
   144  
   145  	contentType, err := getContentType(params.HTTPRequest)
   146  	if err != nil {
   147  		return handleTimestampAPIError(params, http.StatusUnsupportedMediaType, err, failedToGenerateTimestampResponse)
   148  	}
   149  
   150  	req, errMsg, err := requestBodyToTimestampReq(requestBytes, contentType)
   151  	if err != nil {
   152  		return handleTimestampAPIError(params, http.StatusBadRequest, err, errMsg)
   153  	}
   154  
   155  	policyID := req.TSAPolicyOID
   156  	if policyID.String() == "" {
   157  		policyID = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 57264, 2}
   158  	}
   159  
   160  	duration, _ := time.ParseDuration("1s")
   161  
   162  	tsStruct := timestamp.Timestamp{
   163  		HashAlgorithm: req.HashAlgorithm,
   164  		HashedMessage: req.HashedMessage,
   165  		Time:          time.Now(),
   166  		Nonce:         req.Nonce,
   167  		Policy:        policyID,
   168  		Ordering:      false,
   169  		Accuracy:      duration,
   170  		// Not qualified for the european directive
   171  		Qualified:         false,
   172  		AddTSACertificate: req.Certificates,
   173  		ExtraExtensions:   req.Extensions,
   174  	}
   175  
   176  	resp, err := tsStruct.CreateResponseWithOpts(api.certChain[0], api.tsaSigner, api.tsaSignerHash)
   177  	if err != nil {
   178  		return handleTimestampAPIError(params, http.StatusInternalServerError, err, failedToGenerateTimestampResponse)
   179  	}
   180  
   181  	return ts.NewGetTimestampResponseCreated().WithPayload(io.NopCloser(bytes.NewReader(resp)))
   182  }
   183  
   184  func GetTimestampCertChainHandler(_ ts.GetTimestampCertChainParams) middleware.Responder {
   185  	return ts.NewGetTimestampCertChainOK().WithPayload(api.certChainPem)
   186  }
   187
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