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RestAPIHelper.php
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1 <?PHP
2 #
3 # FILE: RestAPIHelper
4 #
5 # Part of the Collection Workflow Integration System (CWIS)
6 # Copyright 2017 Edward Almasy and Internet Scout Research Group
7 # http://scout.wisc.edu/cwis/
8 #
9
19 class RestAPIHelper
20 {
31 public function __construct($APIUrl, $APIPassword,
32 $CheckForDuplicateFn, $RegisterMessageFn)
33 {
34 $this->APIUrl = $APIUrl;
35 $this->APIPassword = $APIPassword;
36 $this->CheckForDuplicateFn = $CheckForDuplicateFn;
37 $this->RegisterMessageFn = $RegisterMessageFn;
38 }
39
46 public function DoRestCommand($Params)
47 {
48 # build an encrypted message
49 $PostData = $this->EncodeEncryptedMessage($Params);
50
51 # set up curl to do the post
52 $Context = curl_init();
53
54 # enable cookie handling
55 curl_setopt($Context, CURLOPT_COOKIEFILE, '');
56
57 # use our configured endpoint
58 curl_setopt($Context, CURLOPT_URL, $this->APIUrl);
59
60 # get results back as a string
61 curl_setopt($Context, CURLOPT_RETURNTRANSFER, TRUE);
62
63 # send data in a POST
64 curl_setopt($Context, CURLOPT_POST, TRUE);
65
66 # load the POST data
67 curl_setopt($Context, CURLOPT_POSTFIELDS, http_build_query($PostData));
68
69 # fetch the data
70 $Data = curl_exec($Context);
71
72 # attempt to parse the reply into an encrypted envelope
73 $Result = json_decode($Data, TRUE);
74 if ($Result === NULL)
75 {
76 return array(
77 "Status" => "Error",
78 "Message" => "Could not parse PostData.",
79 "Data" => $Data,
80 );
81 }
82
83 # attempt to decode the encrypted envelope
84 $Result = $this->DecodeEncryptedMessage($Result);
85
86 # if we decoded the envelope, return the message contents
87 if ($Result["Status"] == "OK")
88 {
89 $Result = $Result["Data"];
90 }
91
92 return $Result;
93 }
94
100 public function EncodeEncryptedMessage($Data)
101 {
102 # create an envelope for our message, put the provided data inside
103 $Env = array();
104 $Env["Version"] = "3";
105 $Env["Timestamp"] = time();
106 $Env["Cookie"] = base64_encode(mcrypt_create_iv(16, MCRYPT_DEV_URANDOM));
107 $Env["Data"] = $Data;
108
109 # generate full key from provided password
110 $FullKey = hash("sha512", $this->APIPassword, TRUE);
111
112 # split into encryption and MAC keys
113 $EncKey = mb_substr($FullKey, 0, 32, '8bit');
114 $MacKey = mb_substr($FullKey, 32, 32, '8bit');
115
116 # generate a random IV (initialization vector), required by
117 # AES (and for most ciphers) to provide some randomness in the
118 # data and prevent identical messages from having identical
119 # encrypted content
120
121 # the mcrypt extension is deprecated, but unfortunately
122 # mcrypt_create_iv() is the only function available in both PHP
123 # 5.x and PHP 7.x that reliably provides randomness.
124 # see slides # 24-28 in "Using Encryption in PHP" at
125 # http://otscripts.com/wp-content/uploads/2016/10/UsingEncryption-v02.pdf
126
127 $IV = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);
128
129 # encrypt and base64 our payload
130 $Payload = base64_encode(openssl_encrypt(
131 json_encode($Env), "aes-256-cbc", $EncKey, OPENSSL_RAW_DATA, $IV));
132
133 # base64 encode our IV
134 $IV = base64_encode($IV);
135
136 # construct data we will POST
137 $PostData = array(
138 "IV" => $IV,
139 "Payload" => $Payload,
140 "MAC" => base64_encode(hash_hmac("sha256", $IV.":".$Payload, $MacKey, TRUE)),
141 );
142
143 return $PostData;
144 }
145
155 public function DecodeEncryptedMessage($PostData)
156 {
157 # verify that the provided POST data has the correct elements
158 if (!isset($PostData["MAC"]) || !isset($PostData["Payload"]) ||
159 !isset($PostData["IV"]))
160 {
161 return array(
162 "Status" => "Error",
163 "Message" => "PostData lacks required elements.");
164 }
165
166 # generate full key from provided password
167 $FullKey = hash("sha512", $this->APIPassword, TRUE);
168
169 # split into encryption and MAC keys
170 $EncKey = mb_substr($FullKey, 0, 32, '8bit');
171 $MacKey = mb_substr($FullKey, 32, 32, '8bit');
172
173 # compute MAC
174 $MAC = hash_hmac(
175 "sha256", $PostData["IV"].":".$PostData["Payload"], $MacKey, TRUE);
176
177 # check MAC, bail if it was not valid
178 if (!hash_equals($MAC, base64_decode($PostData["MAC"])))
179 {
180 return array(
181 "Status" => "Error",
182 "Message" => "HMAC validation failure -- message is corrupted.");
183 }
184
185 # strip base64 encoding from payload and IV
186 $Payload = base64_decode($PostData["Payload"]);
187 $IV = base64_decode($PostData["IV"]);
188
189 # decrypt the payload to get the envelope
190 $Env = openssl_decrypt(
191 $Payload, "aes-256-cbc", $EncKey, OPENSSL_RAW_DATA, $IV);
192
193 # attempt to unserialize the envelope, bailing on failure
194 $Env = json_decode($Env, TRUE);
195 if ($Env === NULL)
196 {
197 return array(
198 "Status" => "Error",
199 "Message" => "Could not decode message envelope.");
200 }
201
202 # check that the envelope contains all the required headers
203 if (!isset($Env["Version"]) || !isset($Env["Timestamp"]) ||
204 !isset($Env["Cookie"]) || !isset($Env["Data"]) )
205 {
206 return array(
207 "Status" => "Error",
208 "Message" => "Payload did not include all required parameters.");
209 }
210
211 # check that this is an envelope in a version we understand
212 if ($Env["Version"] != "3")
213 {
214 return array(
215 "Status" => "Error",
216 "Message" => "Message was not version 3.");
217 }
218
219 # check that this envelope isn't too old
220 if (time() - $Env["Timestamp"] > 300)
221 {
222 return array(
223 "Status" => "Error",
224 "Message" => "Message is more than 5 minutes old.");
225 }
226
227 # check if this is a duplicate message
228 if (call_user_func($this->CheckForDuplicateFn,
229 $Env["Timestamp"], $Env["Cookie"]))
230 {
231 return array(
232 "Status" => "Error",
233 "Message" => "This is a duplicate message");
234 }
235
236 call_user_func($this->RegisterMessageFn,
237 $Env["Timestamp"], $Env["Cookie"]);
238
239 return array(
240 "Status" => "OK",
241 "Data" => $Env["Data"]);
242 }
243 }
RestAPIHelper\EncodeEncryptedMessage
EncodeEncryptedMessage($Data)
Construct an encrypted message packet from provided data.
Definition: RestAPIHelper.php:100
RestAPIHelper\DoRestCommand
DoRestCommand($Params)
Run a REST API command against a remote site.
Definition: RestAPIHelper.php:46
RestAPIHelper\__construct
__construct($APIUrl, $APIPassword, $CheckForDuplicateFn, $RegisterMessageFn)
Constructor.
Definition: RestAPIHelper.php:31
PHP
PHP
Definition: RSSClient--Test.php:12
RestAPIHelper\DecodeEncryptedMessage
DecodeEncryptedMessage($PostData)
Decrypt an encrypted message packet.
Definition: RestAPIHelper.php:155
RestAPIHelper
This class provides a general-purpose library for encrypted REST calls and responses.
Definition: RestAPIHelper.php:19