#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);
                }
        }
}

void 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);
}

/*
 * 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;
}