summaryrefslogtreecommitdiff
path: root/gpg-interface.c
blob: 77a4da627e227eb191ce99812f53cc7f90479f1f (plain)
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
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
#include "cache.h"
#include "run-command.h"
#include "strbuf.h"
#include "gpg-interface.h"
#include "sigchain.h"
 
static char *configured_signing_key;
static const char *gpg_program = "gpg";
 
#define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
#define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
 
void signature_check_clear(struct signature_check *sigc)
{
	free(sigc->payload);
	free(sigc->gpg_output);
	free(sigc->gpg_status);
	free(sigc->signer);
	free(sigc->key);
	sigc->payload = NULL;
	sigc->gpg_output = NULL;
	sigc->gpg_status = NULL;
	sigc->signer = NULL;
	sigc->key = NULL;
}
 
static struct {
	char result;
	const char *check;
} sigcheck_gpg_status[] = {
	{ 'G', "\n[GNUPG:] GOODSIG " },
	{ 'B', "\n[GNUPG:] BADSIG " },
	{ 'U', "\n[GNUPG:] TRUST_NEVER" },
	{ 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
};
 
void parse_gpg_output(struct signature_check *sigc)
{
	const char *buf = sigc->gpg_status;
	int i;
 
	/* Iterate over all search strings */
	for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
		const char *found, *next;
 
		if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
			found = strstr(buf, sigcheck_gpg_status[i].check);
			if (!found)
				continue;
			found += strlen(sigcheck_gpg_status[i].check);
		}
		sigc->result = sigcheck_gpg_status[i].result;
		/* The trust messages are not followed by key/signer information */
		if (sigc->result != 'U') {
			sigc->key = xmemdupz(found, 16);
			found += 17;
			next = strchrnul(found, '\n');
			sigc->signer = xmemdupz(found, next - found);
		}
	}
}
 
int check_signature(const char *payload, size_t plen, const char *signature,
	size_t slen, struct signature_check *sigc)
{
	struct strbuf gpg_output = STRBUF_INIT;
	struct strbuf gpg_status = STRBUF_INIT;
	int status;
 
	sigc->result = 'N';
 
	status = verify_signed_buffer(payload, plen, signature, slen,
				      &gpg_output, &gpg_status);
	if (status && !gpg_output.len)
		goto out;
	sigc->payload = xmemdupz(payload, plen);
	sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
	sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
	parse_gpg_output(sigc);
 
 out:
	strbuf_release(&gpg_status);
	strbuf_release(&gpg_output);
 
	return sigc->result != 'G' && sigc->result != 'U';
}
 
/*
 * Look at GPG signed content (e.g. a signed tag object), whose
 * payload is followed by a detached signature on it.  Return the
 * offset where the embedded detached signature begins, or the end of
 * the data when there is no such signature.
 */
size_t parse_signature(const char *buf, unsigned long size)
{
	char *eol;
	size_t len = 0;
	while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
			!starts_with(buf + len, PGP_MESSAGE)) {
		eol = memchr(buf + len, '\n', size - len);
		len += eol ? eol - (buf + len) + 1 : size - len;
	}
	return len;
}
 
void set_signing_key(const char *key)
{
	free(configured_signing_key);
	configured_signing_key = xstrdup(key);
}
 
int git_gpg_config(const char *var, const char *value, void *cb)
{
	if (!strcmp(var, "user.signingkey")) {
		set_signing_key(value);
	}
	if (!strcmp(var, "gpg.program")) {
		if (!value)
			return config_error_nonbool(var);
		gpg_program = xstrdup(value);
	}
	return 0;
}
 
const char *get_signing_key(void)
{
	if (configured_signing_key)
		return configured_signing_key;
	return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
}
 
/*
 * Create a detached signature for the contents of "buffer" and append
 * it after "signature"; "buffer" and "signature" can be the same
 * strbuf instance, which would cause the detached signature appended
 * at the end.
 */
int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
{
	struct child_process gpg = CHILD_PROCESS_INIT;
	const char *args[4];
	ssize_t len;
	size_t i, j, bottom;
 
	gpg.argv = args;
	gpg.in = -1;
	gpg.out = -1;
	args[0] = gpg_program;
	args[1] = "-bsau";
	args[2] = signing_key;
	args[3] = NULL;
 
	if (start_command(&gpg))
		return error(_("could not run gpg."));
 
	/*
	 * When the username signingkey is bad, program could be terminated
	 * because gpg exits without reading and then write gets SIGPIPE.
	 */
	sigchain_push(SIGPIPE, SIG_IGN);
 
	if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
		close(gpg.in);
		close(gpg.out);
		finish_command(&gpg);
		return error(_("gpg did not accept the data"));
	}
	close(gpg.in);
 
	bottom = signature->len;
	len = strbuf_read(signature, gpg.out, 1024);
	close(gpg.out);
 
	sigchain_pop(SIGPIPE);
 
	if (finish_command(&gpg) || !len || len < 0)
		return error(_("gpg failed to sign the data"));
 
	/* Strip CR from the line endings, in case we are on Windows. */
	for (i = j = bottom; i < signature->len; i++)
		if (signature->buf[i] != '\r') {
			if (i != j)
				signature->buf[j] = signature->buf[i];
			j++;
		}
	strbuf_setlen(signature, j);
 
	return 0;
}
 
/*
 * Run "gpg" to see if the payload matches the detached signature.
 * gpg_output, when set, receives the diagnostic output from GPG.
 * gpg_status, when set, receives the status output from GPG.
 */
int verify_signed_buffer(const char *payload, size_t payload_size,
			 const char *signature, size_t signature_size,
			 struct strbuf *gpg_output, struct strbuf *gpg_status)
{
	struct child_process gpg = CHILD_PROCESS_INIT;
	const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
	char path[PATH_MAX];
	int fd, ret;
	struct strbuf buf = STRBUF_INIT;
	struct strbuf *pbuf = &buf;
 
	args_gpg[0] = gpg_program;
	fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
	if (fd < 0)
		return error(_("could not create temporary file '%s': %s"),
			     path, strerror(errno));
	if (write_in_full(fd, signature, signature_size) < 0)
		return error(_("failed writing detached signature to '%s': %s"),
			     path, strerror(errno));
	close(fd);
 
	gpg.argv = args_gpg;
	gpg.in = -1;
	gpg.out = -1;
	if (gpg_output)
		gpg.err = -1;
	args_gpg[3] = path;
	if (start_command(&gpg)) {
		unlink(path);
		return error(_("could not run gpg."));
	}
 
	write_in_full(gpg.in, payload, payload_size);
	close(gpg.in);
 
	if (gpg_output) {
		strbuf_read(gpg_output, gpg.err, 0);
		close(gpg.err);
	}
	if (gpg_status)
		pbuf = gpg_status;
	strbuf_read(pbuf, gpg.out, 0);
	close(gpg.out);
 
	ret = finish_command(&gpg);
 
	unlink_or_warn(path);
 
	ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
	strbuf_release(&buf); /* no matter it was used or not */
 
	return ret;
}