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![Junio C Hamano](/assets/img/avatar_default.png)
When gpg-interface API unified support for signature verification codepaths for signed tags and signed commits in mid 2015 at around v2.6.0-rc0~114, we accidentally loosened the GPG signature verification. Before that change, signed commits were verified by looking for "G"ood signature from GPG, while ignoring the exit status of "gpg --verify" process, while signed tags were verified by simply passing the exit status of "gpg --verify" through. The unified code we currently have ignores the exit status of "gpg --verify" and returns successful verification when the signature matches an unexpired key regardless of the trust placed on the key (i.e. in addition to "G"ood ones, we accept "U"ntrusted ones). Make these commands signal failure with their exit status when underlying "gpg --verify" (or the custom command specified by "gpg.program" configuration variable) does so. This essentially changes their behaviour in a backward incompatible way to reject signatures that have been made with untrusted keys even if they correctly verify, as that is how "gpg --verify" behaves. Note that the code still overrides a zero exit status obtained from "gpg" (or gpg.program) if the output does not say the signature is good or computes correctly but made with untrusted keys, to catch a poorly written wrapper around "gpg" the user may give us. We could exclude "U"ntrusted support from this fallback code, but that would be making two backward incompatible changes in a single commit, so let's avoid that for now. A follow-up change could do so if desired. Helped-by: Vojtech Myslivec <vojtech.myslivec@nic.cz> Helped-by: brian m. carlson <sandals@crustytoothpaste.net> Helped-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
242 lines
5.8 KiB
C
242 lines
5.8 KiB
C
#include "cache.h"
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#include "config.h"
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#include "run-command.h"
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#include "strbuf.h"
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#include "gpg-interface.h"
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#include "sigchain.h"
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#include "tempfile.h"
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static char *configured_signing_key;
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static const char *gpg_program = "gpg";
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#define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
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#define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
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void signature_check_clear(struct signature_check *sigc)
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{
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FREE_AND_NULL(sigc->payload);
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FREE_AND_NULL(sigc->gpg_output);
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FREE_AND_NULL(sigc->gpg_status);
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FREE_AND_NULL(sigc->signer);
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FREE_AND_NULL(sigc->key);
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}
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static struct {
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char result;
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const char *check;
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} sigcheck_gpg_status[] = {
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{ 'G', "\n[GNUPG:] GOODSIG " },
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{ 'B', "\n[GNUPG:] BADSIG " },
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{ 'U', "\n[GNUPG:] TRUST_NEVER" },
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{ 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
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{ 'E', "\n[GNUPG:] ERRSIG "},
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{ 'X', "\n[GNUPG:] EXPSIG "},
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{ 'Y', "\n[GNUPG:] EXPKEYSIG "},
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{ 'R', "\n[GNUPG:] REVKEYSIG "},
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};
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void parse_gpg_output(struct signature_check *sigc)
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{
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const char *buf = sigc->gpg_status;
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int i;
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/* Iterate over all search strings */
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for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
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const char *found, *next;
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if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
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found = strstr(buf, sigcheck_gpg_status[i].check);
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if (!found)
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continue;
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found += strlen(sigcheck_gpg_status[i].check);
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}
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sigc->result = sigcheck_gpg_status[i].result;
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/* The trust messages are not followed by key/signer information */
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if (sigc->result != 'U') {
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sigc->key = xmemdupz(found, 16);
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/* The ERRSIG message is not followed by signer information */
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if (sigc-> result != 'E') {
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found += 17;
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next = strchrnul(found, '\n');
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sigc->signer = xmemdupz(found, next - found);
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}
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}
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}
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}
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int check_signature(const char *payload, size_t plen, const char *signature,
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size_t slen, struct signature_check *sigc)
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{
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struct strbuf gpg_output = STRBUF_INIT;
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struct strbuf gpg_status = STRBUF_INIT;
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int status;
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sigc->result = 'N';
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status = verify_signed_buffer(payload, plen, signature, slen,
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&gpg_output, &gpg_status);
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if (status && !gpg_output.len)
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goto out;
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sigc->payload = xmemdupz(payload, plen);
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sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
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sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
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parse_gpg_output(sigc);
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status |= sigc->result != 'G' && sigc->result != 'U';
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out:
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strbuf_release(&gpg_status);
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strbuf_release(&gpg_output);
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return !!status;
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}
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void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
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{
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const char *output = flags & GPG_VERIFY_RAW ?
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sigc->gpg_status : sigc->gpg_output;
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if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
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fputs(sigc->payload, stdout);
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if (output)
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fputs(output, stderr);
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}
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static int is_gpg_start(const char *line)
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{
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return starts_with(line, PGP_SIGNATURE) ||
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starts_with(line, PGP_MESSAGE);
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}
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size_t parse_signature(const char *buf, size_t size)
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{
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size_t len = 0;
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size_t match = size;
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while (len < size) {
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const char *eol;
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if (is_gpg_start(buf + len))
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match = len;
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eol = memchr(buf + len, '\n', size - len);
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len += eol ? eol - (buf + len) + 1 : size - len;
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}
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return match;
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}
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void set_signing_key(const char *key)
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{
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free(configured_signing_key);
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configured_signing_key = xstrdup(key);
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}
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int git_gpg_config(const char *var, const char *value, void *cb)
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{
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if (!strcmp(var, "user.signingkey")) {
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if (!value)
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return config_error_nonbool(var);
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set_signing_key(value);
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return 0;
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}
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if (!strcmp(var, "gpg.program")) {
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if (!value)
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return config_error_nonbool(var);
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gpg_program = xstrdup(value);
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return 0;
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}
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return 0;
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}
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const char *get_signing_key(void)
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{
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if (configured_signing_key)
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return configured_signing_key;
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return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
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}
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int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
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{
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struct child_process gpg = CHILD_PROCESS_INIT;
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int ret;
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size_t i, j, bottom;
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struct strbuf gpg_status = STRBUF_INIT;
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argv_array_pushl(&gpg.args,
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gpg_program,
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"--status-fd=2",
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"-bsau", signing_key,
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NULL);
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bottom = signature->len;
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/*
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* When the username signingkey is bad, program could be terminated
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* because gpg exits without reading and then write gets SIGPIPE.
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*/
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sigchain_push(SIGPIPE, SIG_IGN);
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ret = pipe_command(&gpg, buffer->buf, buffer->len,
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signature, 1024, &gpg_status, 0);
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sigchain_pop(SIGPIPE);
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ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
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strbuf_release(&gpg_status);
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if (ret)
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return error(_("gpg failed to sign the data"));
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/* Strip CR from the line endings, in case we are on Windows. */
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for (i = j = bottom; i < signature->len; i++)
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if (signature->buf[i] != '\r') {
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if (i != j)
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signature->buf[j] = signature->buf[i];
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j++;
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}
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strbuf_setlen(signature, j);
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return 0;
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}
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int verify_signed_buffer(const char *payload, size_t payload_size,
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const char *signature, size_t signature_size,
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struct strbuf *gpg_output, struct strbuf *gpg_status)
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{
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struct child_process gpg = CHILD_PROCESS_INIT;
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struct tempfile *temp;
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int ret;
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struct strbuf buf = STRBUF_INIT;
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temp = mks_tempfile_t(".git_vtag_tmpXXXXXX");
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if (!temp)
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return error_errno(_("could not create temporary file"));
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if (write_in_full(temp->fd, signature, signature_size) < 0 ||
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close_tempfile_gently(temp) < 0) {
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error_errno(_("failed writing detached signature to '%s'"),
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temp->filename.buf);
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delete_tempfile(&temp);
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return -1;
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}
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argv_array_pushl(&gpg.args,
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gpg_program,
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"--status-fd=1",
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"--keyid-format=long",
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"--verify", temp->filename.buf, "-",
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NULL);
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if (!gpg_status)
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gpg_status = &buf;
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sigchain_push(SIGPIPE, SIG_IGN);
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ret = pipe_command(&gpg, payload, payload_size,
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gpg_status, 0, gpg_output, 0);
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sigchain_pop(SIGPIPE);
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delete_tempfile(&temp);
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ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
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strbuf_release(&buf); /* no matter it was used or not */
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return ret;
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}
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