gpg-interface: allow use of a custom GPG binary
[git/git.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
7 static char *configured_signing_key;
8 static const char *gpg_program = "gpg";
9
10 void set_signing_key(const char *key)
11 {
12 free(configured_signing_key);
13 configured_signing_key = xstrdup(key);
14 }
15
16 int git_gpg_config(const char *var, const char *value, void *cb)
17 {
18 if (!strcmp(var, "user.signingkey")) {
19 set_signing_key(value);
20 }
21 if (!strcmp(var, "gpg.program")) {
22 if (!value)
23 return config_error_nonbool(var);
24 gpg_program = xstrdup(value);
25 }
26 return 0;
27 }
28
29 const char *get_signing_key(void)
30 {
31 if (configured_signing_key)
32 return configured_signing_key;
33 return git_committer_info(IDENT_ERROR_ON_NO_NAME|IDENT_NO_DATE);
34 }
35
36 /*
37 * Create a detached signature for the contents of "buffer" and append
38 * it after "signature"; "buffer" and "signature" can be the same
39 * strbuf instance, which would cause the detached signature appended
40 * at the end.
41 */
42 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
43 {
44 struct child_process gpg;
45 const char *args[4];
46 ssize_t len;
47 size_t i, j, bottom;
48
49 memset(&gpg, 0, sizeof(gpg));
50 gpg.argv = args;
51 gpg.in = -1;
52 gpg.out = -1;
53 args[0] = gpg_program;
54 args[1] = "-bsau";
55 args[2] = signing_key;
56 args[3] = NULL;
57
58 if (start_command(&gpg))
59 return error(_("could not run gpg."));
60
61 /*
62 * When the username signingkey is bad, program could be terminated
63 * because gpg exits without reading and then write gets SIGPIPE.
64 */
65 sigchain_push(SIGPIPE, SIG_IGN);
66
67 if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
68 close(gpg.in);
69 close(gpg.out);
70 finish_command(&gpg);
71 return error(_("gpg did not accept the data"));
72 }
73 close(gpg.in);
74
75 bottom = signature->len;
76 len = strbuf_read(signature, gpg.out, 1024);
77 close(gpg.out);
78
79 sigchain_pop(SIGPIPE);
80
81 if (finish_command(&gpg) || !len || len < 0)
82 return error(_("gpg failed to sign the data"));
83
84 /* Strip CR from the line endings, in case we are on Windows. */
85 for (i = j = bottom; i < signature->len; i++)
86 if (signature->buf[i] != '\r') {
87 if (i != j)
88 signature->buf[j] = signature->buf[i];
89 j++;
90 }
91 strbuf_setlen(signature, j);
92
93 return 0;
94 }
95
96 /*
97 * Run "gpg" to see if the payload matches the detached signature.
98 * gpg_output_to tells where the output from "gpg" should go:
99 * < 0: /dev/null
100 * = 0: standard error of the calling process
101 * > 0: the specified file descriptor
102 */
103 int verify_signed_buffer(const char *payload, size_t payload_size,
104 const char *signature, size_t signature_size,
105 struct strbuf *gpg_output)
106 {
107 struct child_process gpg;
108 const char *args_gpg[] = {NULL, "--verify", "FILE", "-", NULL};
109 char path[PATH_MAX];
110 int fd, ret;
111
112 args_gpg[0] = gpg_program;
113 fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
114 if (fd < 0)
115 return error("could not create temporary file '%s': %s",
116 path, strerror(errno));
117 if (write_in_full(fd, signature, signature_size) < 0)
118 return error("failed writing detached signature to '%s': %s",
119 path, strerror(errno));
120 close(fd);
121
122 memset(&gpg, 0, sizeof(gpg));
123 gpg.argv = args_gpg;
124 gpg.in = -1;
125 if (gpg_output)
126 gpg.err = -1;
127 args_gpg[2] = path;
128 if (start_command(&gpg)) {
129 unlink(path);
130 return error("could not run gpg.");
131 }
132
133 write_in_full(gpg.in, payload, payload_size);
134 close(gpg.in);
135
136 if (gpg_output)
137 strbuf_read(gpg_output, gpg.err, 0);
138 ret = finish_command(&gpg);
139
140 unlink_or_warn(path);
141
142 return ret;
143 }