1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
#include <mod/jwt.hxx>
#include <libbutl/base64.hxx>
#include <libbutl/openssl.hxx>
#include <libbutl/json/serializer.hxx>
using namespace std;
using namespace butl;
// Note that only GitHub's requirements are implemented, not the entire JWT
// spec. The following elements are currently supported:
//
// - The RS256 message authentication code algorithm (RSA with SHA256)
// - The `typ` and `alg` header fields
// - The `iat`, `exp`, and `iss` claims
//
// A JWT consists of a message and its signature.
//
// The message consists of a base64url-encoded JSON header and payload (set of
// claims). The signature is calculated over the message and then also
// base64url-encoded.
//
// base64url is base64 with a slightly different alphabet and optional padding
// to make it URL and filesystem safe. See base64.hxx for details.
//
// Header:
//
// {
// "typ": "JWT",
// "alg": "RS256"
// }
//
// Payload:
//
// {
// "iat": 1234567,
// "exp": 1234577,
// "iss": "MyName"
// }
//
// Where:
// iat := Issued At (NumericDate: seconds since 1970-01-01T00:00:00Z UTC)
// exp := Expiration Time (NumericDate)
// iss := Issuer
//
// Signature:
//
// RSA_SHA256(PKEY, base64url($header) + '.' + base64url($payload))
//
// JWT:
//
// base64url($header) + '.' + base64url($payload) + '.' + base64url($signature)
//
string brep::
generate_jwt (const options::openssl_options& o,
const path& pk,
const string& iss,
const chrono::seconds& vp,
const chrono::seconds& bd)
{
// Create the header.
//
string h; // Header (base64url-encoded).
{
vector<char> b;
json::buffer_serializer s (b, 0 /* indentation */);
s.begin_object ();
s.member ("typ", "JWT");
s.member ("alg", "RS256"); // RSA with SHA256.
s.end_object ();
h = base64url_encode (b);
}
// Create the payload.
//
string p; // Payload (base64url-encoded).
{
using namespace std::chrono;
// "Issued at" time.
//
seconds iat (duration_cast<seconds> (
system_clock::now ().time_since_epoch () - bd));
// Expiration time.
//
seconds exp (iat + vp);
vector<char> b;
json::buffer_serializer s (b, 0 /* indentation */);
s.begin_object ();
s.member ("iss", iss);
s.member ("iat", iat.count ());
s.member ("exp", exp.count ());
s.end_object ();
p = base64url_encode (b);
}
// Create the signature.
//
string s; // Signature (base64url-encoded).
try
{
// Sign the concatenated header and payload using openssl.
//
// openssl dgst -sha256 -sign <pkey> file...
//
// Note that RSA is indicated by the contents of the private key.
//
// Note that here we assume both output and diagnostics will fit into pipe
// buffers and don't poll both with fdselect().
//
fdpipe errp (fdopen_pipe ()); // stderr pipe.
openssl os (path ("-"), // Read message from openssl::out.
path ("-"), // Write output to openssl::in.
process::pipe (errp.in.get (), move (errp.out)),
process_env (o.openssl (), o.openssl_envvar ()),
"dgst", o.openssl_option (), "-sha256", "-sign", pk);
ifdstream err (move (errp.in));
vector<char> bs; // Binary signature (openssl output).
try
{
// In case of exception, skip and close input after output.
//
// Note: re-open in/out so that they get automatically closed on
// exception.
//
ifdstream in (os.in.release (), fdstream_mode::skip);
ofdstream out (os.out.release ());
// Write the concatenated header and payload to openssl's input.
//
out << h << '.' << p;
out.close ();
// Read the binary signature from openssl's output.
//
bs = in.read_binary ();
in.close ();
}
catch (const io_error& e)
{
// If the process exits with non-zero status, assume the IO error is due
// to that and fall through.
//
if (os.wait ())
{
throw_generic_error (
e.code ().value (),
(string ("unable to read/write openssl stdout/stdin: ") +
e.what ()).c_str ());
}
}
if (!os.wait ())
{
string et (err.read_text ());
throw_generic_error (EINVAL,
("non-zero openssl exit status: " + et).c_str ());
}
err.close ();
s = base64url_encode (bs);
}
catch (const process_error& e)
{
throw_generic_error (
e.code ().value (),
(string ("unable to execute openssl: ") + e.what ()).c_str ());
}
catch (const io_error& e)
{
// Unable to read diagnostics from stderr.
//
throw_generic_error (
e.code ().value (),
(string ("unable to read openssl stderr : ") + e.what ()).c_str ());
}
return h + '.' + p + '.' + s; // Return the token.
}
|
