files_read_raw_ref: prevent infinite retry loops in general
[git] / gpg-interface.c
1 #include "cache.h"
2 #include "run-command.h"
3 #include "strbuf.h"
4 #include "gpg-interface.h"
5 #include "sigchain.h"
6 #include "tempfile.h"
7
8 static char *configured_signing_key;
9 static const char *gpg_program = "gpg";
10
11 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
12 #define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
13
14 void signature_check_clear(struct signature_check *sigc)
15 {
16         free(sigc->payload);
17         free(sigc->gpg_output);
18         free(sigc->gpg_status);
19         free(sigc->signer);
20         free(sigc->key);
21         sigc->payload = NULL;
22         sigc->gpg_output = NULL;
23         sigc->gpg_status = NULL;
24         sigc->signer = NULL;
25         sigc->key = NULL;
26 }
27
28 static struct {
29         char result;
30         const char *check;
31 } sigcheck_gpg_status[] = {
32         { 'G', "\n[GNUPG:] GOODSIG " },
33         { 'B', "\n[GNUPG:] BADSIG " },
34         { 'U', "\n[GNUPG:] TRUST_NEVER" },
35         { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
36 };
37
38 void parse_gpg_output(struct signature_check *sigc)
39 {
40         const char *buf = sigc->gpg_status;
41         int i;
42
43         /* Iterate over all search strings */
44         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
45                 const char *found, *next;
46
47                 if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
48                         found = strstr(buf, sigcheck_gpg_status[i].check);
49                         if (!found)
50                                 continue;
51                         found += strlen(sigcheck_gpg_status[i].check);
52                 }
53                 sigc->result = sigcheck_gpg_status[i].result;
54                 /* The trust messages are not followed by key/signer information */
55                 if (sigc->result != 'U') {
56                         sigc->key = xmemdupz(found, 16);
57                         found += 17;
58                         next = strchrnul(found, '\n');
59                         sigc->signer = xmemdupz(found, next - found);
60                 }
61         }
62 }
63
64 int check_signature(const char *payload, size_t plen, const char *signature,
65         size_t slen, struct signature_check *sigc)
66 {
67         struct strbuf gpg_output = STRBUF_INIT;
68         struct strbuf gpg_status = STRBUF_INIT;
69         int status;
70
71         sigc->result = 'N';
72
73         status = verify_signed_buffer(payload, plen, signature, slen,
74                                       &gpg_output, &gpg_status);
75         if (status && !gpg_output.len)
76                 goto out;
77         sigc->payload = xmemdupz(payload, plen);
78         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
79         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
80         parse_gpg_output(sigc);
81
82  out:
83         strbuf_release(&gpg_status);
84         strbuf_release(&gpg_output);
85
86         return sigc->result != 'G' && sigc->result != 'U';
87 }
88
89 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
90 {
91         const char *output = flags & GPG_VERIFY_RAW ?
92                 sigc->gpg_status : sigc->gpg_output;
93
94         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
95                 fputs(sigc->payload, stdout);
96
97         if (output)
98                 fputs(output, stderr);
99 }
100
101 /*
102  * Look at GPG signed content (e.g. a signed tag object), whose
103  * payload is followed by a detached signature on it.  Return the
104  * offset where the embedded detached signature begins, or the end of
105  * the data when there is no such signature.
106  */
107 size_t parse_signature(const char *buf, unsigned long size)
108 {
109         char *eol;
110         size_t len = 0;
111         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
112                         !starts_with(buf + len, PGP_MESSAGE)) {
113                 eol = memchr(buf + len, '\n', size - len);
114                 len += eol ? eol - (buf + len) + 1 : size - len;
115         }
116         return len;
117 }
118
119 void set_signing_key(const char *key)
120 {
121         free(configured_signing_key);
122         configured_signing_key = xstrdup(key);
123 }
124
125 int git_gpg_config(const char *var, const char *value, void *cb)
126 {
127         if (!strcmp(var, "user.signingkey")) {
128                 set_signing_key(value);
129         }
130         if (!strcmp(var, "gpg.program")) {
131                 if (!value)
132                         return config_error_nonbool(var);
133                 gpg_program = xstrdup(value);
134         }
135         return 0;
136 }
137
138 const char *get_signing_key(void)
139 {
140         if (configured_signing_key)
141                 return configured_signing_key;
142         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
143 }
144
145 /*
146  * Create a detached signature for the contents of "buffer" and append
147  * it after "signature"; "buffer" and "signature" can be the same
148  * strbuf instance, which would cause the detached signature appended
149  * at the end.
150  */
151 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
152 {
153         struct child_process gpg = CHILD_PROCESS_INIT;
154         int ret;
155         size_t i, j, bottom;
156         struct strbuf gpg_status = STRBUF_INIT;
157
158         argv_array_pushl(&gpg.args,
159                          gpg_program,
160                          "--status-fd=2",
161                          "-bsau", signing_key,
162                          NULL);
163
164         bottom = signature->len;
165
166         /*
167          * When the username signingkey is bad, program could be terminated
168          * because gpg exits without reading and then write gets SIGPIPE.
169          */
170         sigchain_push(SIGPIPE, SIG_IGN);
171         ret = pipe_command(&gpg, buffer->buf, buffer->len,
172                            signature, 1024, &gpg_status, 0);
173         sigchain_pop(SIGPIPE);
174
175         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
176         strbuf_release(&gpg_status);
177         if (ret)
178                 return error(_("gpg failed to sign the data"));
179
180         /* Strip CR from the line endings, in case we are on Windows. */
181         for (i = j = bottom; i < signature->len; i++)
182                 if (signature->buf[i] != '\r') {
183                         if (i != j)
184                                 signature->buf[j] = signature->buf[i];
185                         j++;
186                 }
187         strbuf_setlen(signature, j);
188
189         return 0;
190 }
191
192 /*
193  * Run "gpg" to see if the payload matches the detached signature.
194  * gpg_output, when set, receives the diagnostic output from GPG.
195  * gpg_status, when set, receives the status output from GPG.
196  */
197 int verify_signed_buffer(const char *payload, size_t payload_size,
198                          const char *signature, size_t signature_size,
199                          struct strbuf *gpg_output, struct strbuf *gpg_status)
200 {
201         struct child_process gpg = CHILD_PROCESS_INIT;
202         static struct tempfile temp;
203         int fd, ret;
204         struct strbuf buf = STRBUF_INIT;
205
206         fd = mks_tempfile_t(&temp, ".git_vtag_tmpXXXXXX");
207         if (fd < 0)
208                 return error_errno(_("could not create temporary file"));
209         if (write_in_full(fd, signature, signature_size) < 0) {
210                 error_errno(_("failed writing detached signature to '%s'"),
211                             temp.filename.buf);
212                 delete_tempfile(&temp);
213                 return -1;
214         }
215         close(fd);
216
217         argv_array_pushl(&gpg.args,
218                          gpg_program,
219                          "--status-fd=1",
220                          "--keyid-format=long",
221                          "--verify", temp.filename.buf, "-",
222                          NULL);
223
224         if (!gpg_status)
225                 gpg_status = &buf;
226
227         sigchain_push(SIGPIPE, SIG_IGN);
228         ret = pipe_command(&gpg, payload, payload_size,
229                            gpg_status, 0, gpg_output, 0);
230         sigchain_pop(SIGPIPE);
231
232         delete_tempfile(&temp);
233
234         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
235         strbuf_release(&buf); /* no matter it was used or not */
236
237         return ret;
238 }