http-walker: fix buffer underflow processing remote alternates
[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         { 'E', "\n[GNUPG:] ERRSIG "},
37         { 'X', "\n[GNUPG:] EXPSIG "},
38         { 'Y', "\n[GNUPG:] EXPKEYSIG "},
39         { 'R', "\n[GNUPG:] REVKEYSIG "},
40 };
41
42 void parse_gpg_output(struct signature_check *sigc)
43 {
44         const char *buf = sigc->gpg_status;
45         int i;
46
47         /* Iterate over all search strings */
48         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
49                 const char *found, *next;
50
51                 if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
52                         found = strstr(buf, sigcheck_gpg_status[i].check);
53                         if (!found)
54                                 continue;
55                         found += strlen(sigcheck_gpg_status[i].check);
56                 }
57                 sigc->result = sigcheck_gpg_status[i].result;
58                 /* The trust messages are not followed by key/signer information */
59                 if (sigc->result != 'U') {
60                         sigc->key = xmemdupz(found, 16);
61                         /* The ERRSIG message is not followed by signer information */
62                         if (sigc-> result != 'E') {
63                                 found += 17;
64                                 next = strchrnul(found, '\n');
65                                 sigc->signer = xmemdupz(found, next - found);
66                         }
67                 }
68         }
69 }
70
71 int check_signature(const char *payload, size_t plen, const char *signature,
72         size_t slen, struct signature_check *sigc)
73 {
74         struct strbuf gpg_output = STRBUF_INIT;
75         struct strbuf gpg_status = STRBUF_INIT;
76         int status;
77
78         sigc->result = 'N';
79
80         status = verify_signed_buffer(payload, plen, signature, slen,
81                                       &gpg_output, &gpg_status);
82         if (status && !gpg_output.len)
83                 goto out;
84         sigc->payload = xmemdupz(payload, plen);
85         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
86         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
87         parse_gpg_output(sigc);
88
89  out:
90         strbuf_release(&gpg_status);
91         strbuf_release(&gpg_output);
92
93         return sigc->result != 'G' && sigc->result != 'U';
94 }
95
96 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
97 {
98         const char *output = flags & GPG_VERIFY_RAW ?
99                 sigc->gpg_status : sigc->gpg_output;
100
101         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
102                 fputs(sigc->payload, stdout);
103
104         if (output)
105                 fputs(output, stderr);
106 }
107
108 /*
109  * Look at GPG signed content (e.g. a signed tag object), whose
110  * payload is followed by a detached signature on it.  Return the
111  * offset where the embedded detached signature begins, or the end of
112  * the data when there is no such signature.
113  */
114 size_t parse_signature(const char *buf, unsigned long size)
115 {
116         char *eol;
117         size_t len = 0;
118         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
119                         !starts_with(buf + len, PGP_MESSAGE)) {
120                 eol = memchr(buf + len, '\n', size - len);
121                 len += eol ? eol - (buf + len) + 1 : size - len;
122         }
123         return len;
124 }
125
126 void set_signing_key(const char *key)
127 {
128         free(configured_signing_key);
129         configured_signing_key = xstrdup(key);
130 }
131
132 int git_gpg_config(const char *var, const char *value, void *cb)
133 {
134         if (!strcmp(var, "user.signingkey")) {
135                 set_signing_key(value);
136         }
137         if (!strcmp(var, "gpg.program")) {
138                 if (!value)
139                         return config_error_nonbool(var);
140                 gpg_program = xstrdup(value);
141         }
142         return 0;
143 }
144
145 const char *get_signing_key(void)
146 {
147         if (configured_signing_key)
148                 return configured_signing_key;
149         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
150 }
151
152 /*
153  * Create a detached signature for the contents of "buffer" and append
154  * it after "signature"; "buffer" and "signature" can be the same
155  * strbuf instance, which would cause the detached signature appended
156  * at the end.
157  */
158 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
159 {
160         struct child_process gpg = CHILD_PROCESS_INIT;
161         int ret;
162         size_t i, j, bottom;
163         struct strbuf gpg_status = STRBUF_INIT;
164
165         argv_array_pushl(&gpg.args,
166                          gpg_program,
167                          "--status-fd=2",
168                          "-bsau", signing_key,
169                          NULL);
170
171         bottom = signature->len;
172
173         /*
174          * When the username signingkey is bad, program could be terminated
175          * because gpg exits without reading and then write gets SIGPIPE.
176          */
177         sigchain_push(SIGPIPE, SIG_IGN);
178         ret = pipe_command(&gpg, buffer->buf, buffer->len,
179                            signature, 1024, &gpg_status, 0);
180         sigchain_pop(SIGPIPE);
181
182         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
183         strbuf_release(&gpg_status);
184         if (ret)
185                 return error(_("gpg failed to sign the data"));
186
187         /* Strip CR from the line endings, in case we are on Windows. */
188         for (i = j = bottom; i < signature->len; i++)
189                 if (signature->buf[i] != '\r') {
190                         if (i != j)
191                                 signature->buf[j] = signature->buf[i];
192                         j++;
193                 }
194         strbuf_setlen(signature, j);
195
196         return 0;
197 }
198
199 /*
200  * Run "gpg" to see if the payload matches the detached signature.
201  * gpg_output, when set, receives the diagnostic output from GPG.
202  * gpg_status, when set, receives the status output from GPG.
203  */
204 int verify_signed_buffer(const char *payload, size_t payload_size,
205                          const char *signature, size_t signature_size,
206                          struct strbuf *gpg_output, struct strbuf *gpg_status)
207 {
208         struct child_process gpg = CHILD_PROCESS_INIT;
209         static struct tempfile temp;
210         int fd, ret;
211         struct strbuf buf = STRBUF_INIT;
212
213         fd = mks_tempfile_t(&temp, ".git_vtag_tmpXXXXXX");
214         if (fd < 0)
215                 return error_errno(_("could not create temporary file"));
216         if (write_in_full(fd, signature, signature_size) < 0) {
217                 error_errno(_("failed writing detached signature to '%s'"),
218                             temp.filename.buf);
219                 delete_tempfile(&temp);
220                 return -1;
221         }
222         close(fd);
223
224         argv_array_pushl(&gpg.args,
225                          gpg_program,
226                          "--status-fd=1",
227                          "--keyid-format=long",
228                          "--verify", temp.filename.buf, "-",
229                          NULL);
230
231         if (!gpg_status)
232                 gpg_status = &buf;
233
234         sigchain_push(SIGPIPE, SIG_IGN);
235         ret = pipe_command(&gpg, payload, payload_size,
236                            gpg_status, 0, gpg_output, 0);
237         sigchain_pop(SIGPIPE);
238
239         delete_tempfile(&temp);
240
241         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
242         strbuf_release(&buf); /* no matter it was used or not */
243
244         return ret;
245 }