#include "cache.h"
#include "run-command.h"
#include "strbuf.h"
#include "gpg-interface.h"
#include "sigchain.h"
#include "tempfile.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_AND_NULL(sigc->payload);
        FREE_AND_NULL(sigc->gpg_output);
        FREE_AND_NULL(sigc->gpg_status);
        FREE_AND_NULL(sigc->signer);
        FREE_AND_NULL(sigc->key);
}

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" },
        { 'E', "\n[GNUPG:] ERRSIG "},
        { 'X', "\n[GNUPG:] EXPSIG "},
        { 'Y', "\n[GNUPG:] EXPKEYSIG "},
        { 'R', "\n[GNUPG:] REVKEYSIG "},
};

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);
                        /* The ERRSIG message is not followed by signer information */
                        if (sigc-> result != 'E') {
                                found += 17;
                                next = strchrnul(found, '\n');
                                sigc->signer = xmemdupz(found, next - found);
                        }
                }
        }
}

int 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);

        return sigc->result != 'G' && sigc->result != 'U';
}

void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
{
        const char *output = flags & GPG_VERIFY_RAW ?
                sigc->gpg_status : sigc->gpg_output;

        if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
                fputs(sigc->payload, stdout);

        if (output)
                fputs(output, stderr);
}

/*
 * 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;
        int ret;
        size_t i, j, bottom;
        struct strbuf gpg_status = STRBUF_INIT;

        argv_array_pushl(&gpg.args,
                         gpg_program,
                         "--status-fd=2",
                         "-bsau", signing_key,
                         NULL);

        bottom = signature->len;

        /*
         * 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);
        ret = pipe_command(&gpg, buffer->buf, buffer->len,
                           signature, 1024, &gpg_status, 0);
        sigchain_pop(SIGPIPE);

        ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
        strbuf_release(&gpg_status);
        if (ret)
                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;
        static struct tempfile temp;
        int fd, ret;
        struct strbuf buf = STRBUF_INIT;

        fd = mks_tempfile_t(&temp, ".git_vtag_tmpXXXXXX");
        if (fd < 0)
                return error_errno(_("could not create temporary file"));
        if (write_in_full(fd, signature, signature_size) < 0) {
                error_errno(_("failed writing detached signature to '%s'"),
                            temp.filename.buf);
                delete_tempfile(&temp);
                return -1;
        }
        close(fd);

        argv_array_pushl(&gpg.args,
                         gpg_program,
                         "--status-fd=1",
                         "--keyid-format=long",
                         "--verify", temp.filename.buf, "-",
                         NULL);

        if (!gpg_status)
                gpg_status = &buf;

        sigchain_push(SIGPIPE, SIG_IGN);
        ret = pipe_command(&gpg, payload, payload_size,
                           gpg_status, 0, gpg_output, 0);
        sigchain_pop(SIGPIPE);

        delete_tempfile(&temp);

        ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
        strbuf_release(&buf); /* no matter it was used or not */

        return ret;
}