signing.c

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/*
 *  signing.c
 *
 *  Copyright (c) 2008-2011 Pacman Development Team <pacman-dev@archlinux.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#if HAVE_LIBGPGME
#include <locale.h> /* setlocale() */
#include <gpgme.h>
#include "base64.h"
#endif

/* libalpm */
#include "signing.h"
#include "package.h"
#include "util.h"
#include "log.h"
#include "alpm.h"
#include "handle.h"

#if HAVE_LIBGPGME
#define CHECK_ERR(void) do { \
        if(gpg_err_code(err) != GPG_ERR_NO_ERROR) { goto error; } \
    } while(0)

/**
 * Return a statically allocated validity string based on the GPGME validity
 * code. This is mainly for debug purposes and is not translated.
 * @param validity a validity code returned by GPGME
 * @return a string such as "marginal"
 */
static const char *string_validity(gpgme_validity_t validity)
{
    switch(validity) {
        case GPGME_VALIDITY_UNKNOWN:
            return "unknown";
        case GPGME_VALIDITY_UNDEFINED:
            return "undefined";
        case GPGME_VALIDITY_NEVER:
            return "never";
        case GPGME_VALIDITY_MARGINAL:
            return "marginal";
        case GPGME_VALIDITY_FULL:
            return "full";
        case GPGME_VALIDITY_ULTIMATE:
            return "ultimate";
    }
    return "???";
}

static void sigsum_test_bit(gpgme_sigsum_t sigsum, alpm_list_t **summary,
        gpgme_sigsum_t bit, const char *value)
{
    if(sigsum & bit) {
        *summary = alpm_list_add(*summary, (void *)value);
    }
}

/**
 * Calculate a set of strings to represent the given GPGME signature summary
 * value. This is a bitmask so you may get any number of strings back.
 * @param sigsum a GPGME signature summary bitmask
 * @return the list of signature summary strings
 */
static alpm_list_t *list_sigsum(gpgme_sigsum_t sigsum)
{
    alpm_list_t *summary = NULL;
    /* The docs say this can be a bitmask...not sure I believe it, but we'll code
     * for it anyway and show all possible flags in the returned string. */

    /* The signature is fully valid.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_VALID, "valid");
    /* The signature is good.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_GREEN, "green");
    /* The signature is bad.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_RED, "red");
    /* One key has been revoked.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_KEY_REVOKED, "key revoked");
    /* One key has expired.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_KEY_EXPIRED, "key expired");
    /* The signature has expired.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_SIG_EXPIRED, "sig expired");
    /* Can't verify: key missing.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_KEY_MISSING, "key missing");
    /* CRL not available.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_CRL_MISSING, "crl missing");
    /* Available CRL is too old.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_CRL_TOO_OLD, "crl too old");
    /* A policy was not met.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_BAD_POLICY, "bad policy");
    /* A system error occured.  */
    sigsum_test_bit(sigsum, &summary, GPGME_SIGSUM_SYS_ERROR, "sys error");
    /* Fallback case */
    if(!sigsum) {
        summary = alpm_list_add(summary, (void *)"(empty)");
    }
    return summary;
}

/**
 * Initialize the GPGME library.
 * This can be safely called multiple times; however it is not thread-safe.
 * @param handle the context handle
 * @return 0 on success, -1 on error
 */
static int init_gpgme(alpm_handle_t *handle)
{
    static int init = 0;
    const char *version, *sigdir;
    gpgme_error_t err;
    gpgme_engine_info_t enginfo;

    if(init) {
        /* we already successfully initialized the library */
        return 0;
    }

    sigdir = handle->gpgdir;

    if(_alpm_access(handle, sigdir, "pubring.gpg", R_OK)
            || _alpm_access(handle, sigdir, "trustdb.gpg", R_OK)) {
        handle->pm_errno = ALPM_ERR_NOT_A_FILE;
        _alpm_log(handle, ALPM_LOG_DEBUG, "Signature verification will fail!\n");
        _alpm_log(handle, ALPM_LOG_WARNING,
                _("Public keyring not found; have you run '%s'?\n"),
                "pacman-key --init");
    }

    /* calling gpgme_check_version() returns the current version and runs
     * some internal library setup code */
    version = gpgme_check_version(NULL);
    _alpm_log(handle, ALPM_LOG_DEBUG, "GPGME version: %s\n", version);
    gpgme_set_locale(NULL, LC_CTYPE, setlocale(LC_CTYPE, NULL));
#ifdef LC_MESSAGES
    gpgme_set_locale(NULL, LC_MESSAGES, setlocale(LC_MESSAGES, NULL));
#endif
    /* NOTE:
     * The GPGME library installs a SIGPIPE signal handler automatically if
     * the default signal hander is in use. The only time we set a handler
     * for SIGPIPE is in dload.c, and we reset it when we are done. Given that
     * we do this, we can let GPGME do its automagic. However, if we install
     * a library-wide SIGPIPE handler, we will have to be careful.
     */

    /* check for OpenPGP support (should be a no-brainer, but be safe) */
    err = gpgme_engine_check_version(GPGME_PROTOCOL_OpenPGP);
    CHECK_ERR();

    /* set and check engine information */
    err = gpgme_set_engine_info(GPGME_PROTOCOL_OpenPGP, NULL, sigdir);
    CHECK_ERR();
    err = gpgme_get_engine_info(&enginfo);
    CHECK_ERR();
    _alpm_log(handle, ALPM_LOG_DEBUG, "GPGME engine info: file=%s, home=%s\n",
            enginfo->file_name, enginfo->home_dir);

    init = 1;
    return 0;

error:
    _alpm_log(handle, ALPM_LOG_ERROR, _("GPGME error: %s\n"), gpgme_strerror(err));
    RET_ERR(handle, ALPM_ERR_GPGME, -1);
}

/**
 * Determine if we have a key is known in our local keyring.
 * @param handle the context handle
 * @param fpr the fingerprint key ID to look up
 * @return 1 if key is known, 0 if key is unknown, -1 on error
 */
static int key_in_keychain(alpm_handle_t *handle, const char *fpr)
{
    gpgme_error_t err;
    gpgme_ctx_t ctx;
    gpgme_key_t key;
    int ret = -1;

    memset(&ctx, 0, sizeof(ctx));
    err = gpgme_new(&ctx);
    CHECK_ERR();

    _alpm_log(handle, ALPM_LOG_DEBUG, "looking up key %s locally\n", fpr);

    err = gpgme_get_key(ctx, fpr, &key, 0);
    if(gpg_err_code(err) == GPG_ERR_EOF) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "key lookup failed, unknown key\n");
        ret = 0;
    } else if(gpg_err_code(err) == GPG_ERR_NO_ERROR) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "key lookup success, key exists\n");
        ret = 1;
    } else {
        _alpm_log(handle, ALPM_LOG_DEBUG, "gpg error: %s\n", gpgme_strerror(err));
    }

error:
    gpgme_key_unref(key);
    gpgme_release(ctx);
    return ret;
}

/**
 * Search for a GPG key in a remote location.
 * This requires GPGME to call the gpg binary and have a keyserver previously
 * defined in a gpg.conf configuration file.
 * @param handle the context handle
 * @param fpr the fingerprint key ID to look up
 * @param pgpkey storage location for the given key if found
 * @return 1 on success, 0 on key not found, -1 on error
 */
static int key_search(alpm_handle_t *handle, const char *fpr,
        alpm_pgpkey_t *pgpkey)
{
    gpgme_error_t err;
    gpgme_ctx_t ctx;
    gpgme_keylist_mode_t mode;
    gpgme_key_t key;
    int ret = -1;

    memset(&ctx, 0, sizeof(ctx));
    err = gpgme_new(&ctx);
    CHECK_ERR();

    mode = gpgme_get_keylist_mode(ctx);
    /* using LOCAL and EXTERN together doesn't work for GPG 1.X. Ugh. */
    mode &= ~GPGME_KEYLIST_MODE_LOCAL;
    mode |= GPGME_KEYLIST_MODE_EXTERN;
    err = gpgme_set_keylist_mode(ctx, mode);
    CHECK_ERR();

    _alpm_log(handle, ALPM_LOG_DEBUG, "looking up key %s remotely\n", fpr);

    err = gpgme_get_key(ctx, fpr, &key, 0);
    if(gpg_err_code(err) == GPG_ERR_EOF) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "key lookup failed, unknown key\n");
        /* Try an alternate lookup using the 8 character fingerprint value, since
         * busted-ass keyservers can't support lookups using subkeys with the full
         * value as of now. This is why 2012 is not the year of PGP encryption. */
        if(strlen(fpr) > 8) {
            const char *short_fpr = fpr + strlen(fpr) - 8;
            _alpm_log(handle, ALPM_LOG_DEBUG,
                    "looking up key %s remotely\n", short_fpr);
            err = gpgme_get_key(ctx, short_fpr, &key, 0);
            if(gpg_err_code(err) == GPG_ERR_EOF) {
                _alpm_log(handle, ALPM_LOG_DEBUG, "key lookup failed, unknown key\n");
                ret = 0;
            }
        } else {
            ret = 0;
        }
    }

    if(gpg_err_code(err) != GPG_ERR_NO_ERROR) {
        goto error;
    }

    /* should only get here if key actually exists */
    pgpkey->data = key;
    if(key->subkeys->fpr) {
        pgpkey->fingerprint = key->subkeys->fpr;
    } else if(key->subkeys->keyid) {
        pgpkey->fingerprint = key->subkeys->keyid;
    }
    pgpkey->uid = key->uids->uid;
    pgpkey->name = key->uids->name;
    pgpkey->email = key->uids->email;
    pgpkey->created = key->subkeys->timestamp;
    pgpkey->expires = key->subkeys->expires;
    pgpkey->length = key->subkeys->length;
    pgpkey->revoked = key->subkeys->revoked;

    switch (key->subkeys->pubkey_algo) {
        case GPGME_PK_RSA:
        case GPGME_PK_RSA_E:
        case GPGME_PK_RSA_S:
            pgpkey->pubkey_algo = 'R';
            break;

        case GPGME_PK_DSA:
            pgpkey->pubkey_algo = 'D';
            break;

        case GPGME_PK_ELG_E:
        case GPGME_PK_ELG:
        case GPGME_PK_ECDSA:
        case GPGME_PK_ECDH:
            pgpkey->pubkey_algo = 'E';
            break;
    }

    ret = 1;

error:
    if(ret != 1) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "gpg error: %s\n", gpgme_strerror(err));
    }
    gpgme_release(ctx);
    return ret;
}

/**
 * Import a key into the local keyring.
 * @param handle the context handle
 * @param key the key to import, likely retrieved from #key_search
 * @return 0 on success, -1 on error
 */
static int key_import(alpm_handle_t *handle, alpm_pgpkey_t *key)
{
    gpgme_error_t err;
    gpgme_ctx_t ctx;
    gpgme_key_t keys[2];
    gpgme_import_result_t result;
    int ret = -1;

    if(_alpm_access(handle, handle->gpgdir, "pubring.gpg", W_OK)) {
        /* no chance of import succeeding if pubring isn't writable */
        _alpm_log(handle, ALPM_LOG_ERROR, _("keyring is not writable\n"));
        return -1;
    }

    memset(&ctx, 0, sizeof(ctx));
    err = gpgme_new(&ctx);
    CHECK_ERR();

    _alpm_log(handle, ALPM_LOG_DEBUG, "importing key\n");

    keys[0] = key->data;
    keys[1] = NULL;
    err = gpgme_op_import_keys(ctx, keys);
    CHECK_ERR();
    result = gpgme_op_import_result(ctx);
    CHECK_ERR();
    /* we know we tried to import exactly one key, so check for this */
    if(result->considered != 1 || !result->imports) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "could not import key, 0 results\n");
        ret = -1;
    } else if(result->imports->result != GPG_ERR_NO_ERROR) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "gpg error: %s\n", gpgme_strerror(err));
        ret = -1;
    } else {
        ret = 0;
    }

error:
    gpgme_release(ctx);
    return ret;
}

/**
 * Decode a loaded signature in base64 form.
 * @param base64_data the signature to attempt to decode
 * @param data the decoded data; must be freed by the caller
 * @param data_len the length of the returned data
 * @return 0 on success, -1 on failure to properly decode
 */
static int decode_signature(const char *base64_data,
        unsigned char **data, size_t *data_len) {
    size_t len = strlen(base64_data);
    unsigned char *usline = (unsigned char *)base64_data;
    /* reasonable allocation of expected length is 3/4 of encoded length */
    size_t destlen = len * 3 / 4;
    MALLOC(*data, destlen, goto error);
    if(base64_decode(*data, &destlen, usline, len)) {
        free(*data);
        goto error;
    }
    *data_len = destlen;
    return 0;

error:
    *data = NULL;
    *data_len = 0;
    return -1;
}

/**
 * Check the PGP signature for the given file path.
 * If base64_sig is provided, it will be used as the signature data after
 * decoding. If base64_sig is NULL, expect a signature file next to path
 * (e.g. "%s.sig").
 *
 * The return value will be 0 if nothing abnormal happened during the signature
 * check, and -1 if an error occurred while checking signatures or if a
 * signature could not be found; pm_errno will be set. Note that "abnormal"
 * does not include a failed signature; the value in siglist should be checked
 * to determine if the signature(s) are good.
 * @param handle the context handle
 * @param path the full path to a file
 * @param base64_sig optional PGP signature data in base64 encoding
 * @param siglist a pointer to storage for signature results
 * @return 0 in normal cases, -1 if the something failed in the check process
 */
int _alpm_gpgme_checksig(alpm_handle_t *handle, const char *path,
        const char *base64_sig, alpm_siglist_t *siglist)
{
    int ret = -1, sigcount;
    gpgme_error_t err = 0;
    gpgme_ctx_t ctx;
    gpgme_data_t filedata, sigdata;
    gpgme_verify_result_t verify_result;
    gpgme_signature_t gpgsig;
    char *sigpath = NULL;
    unsigned char *decoded_sigdata = NULL;
    FILE *file = NULL, *sigfile = NULL;

    if(!path || _alpm_access(handle, NULL, path, R_OK) != 0) {
        RET_ERR(handle, ALPM_ERR_NOT_A_FILE, -1);
    }

    if(!siglist) {
        RET_ERR(handle, ALPM_ERR_WRONG_ARGS, -1);
    }
    siglist->count = 0;

    if(!base64_sig) {
        sigpath = _alpm_sigpath(handle, path);
        /* this will just help debugging */
        _alpm_access(handle, NULL, sigpath, R_OK);
    }

    /* does the file we are verifying exist? */
    file = fopen(path, "rb");
    if(file == NULL) {
        handle->pm_errno = ALPM_ERR_NOT_A_FILE;
        goto error;
    }

    /* does the sig file exist (if we didn't get the data directly)? */
    if(!base64_sig) {
        sigfile = fopen(sigpath, "rb");
        if(sigfile == NULL) {
            _alpm_log(handle, ALPM_LOG_DEBUG, "sig path %s could not be opened\n",
                    sigpath);
            handle->pm_errno = ALPM_ERR_SIG_MISSING;
            goto error;
        }
    }

    if(init_gpgme(handle)) {
        /* pm_errno was set in gpgme_init() */
        goto error;
    }

    _alpm_log(handle, ALPM_LOG_DEBUG, "checking signature for %s\n", path);

    memset(&ctx, 0, sizeof(ctx));
    memset(&sigdata, 0, sizeof(sigdata));
    memset(&filedata, 0, sizeof(filedata));

    err = gpgme_new(&ctx);
    CHECK_ERR();

    /* create our necessary data objects to verify the signature */
    err = gpgme_data_new_from_stream(&filedata, file);
    CHECK_ERR();

    /* next create data object for the signature */
    if(base64_sig) {
        /* memory-based, we loaded it from a sync DB */
        size_t data_len;
        int decode_ret = decode_signature(base64_sig,
                &decoded_sigdata, &data_len);
        if(decode_ret) {
            handle->pm_errno = ALPM_ERR_SIG_INVALID;
            goto gpg_error;
        }
        err = gpgme_data_new_from_mem(&sigdata,
                (char *)decoded_sigdata, data_len, 0);
    } else {
        /* file-based, it is on disk */
        err = gpgme_data_new_from_stream(&sigdata, sigfile);
    }
    CHECK_ERR();

    /* here's where the magic happens */
    err = gpgme_op_verify(ctx, sigdata, filedata, NULL);
    CHECK_ERR();
    verify_result = gpgme_op_verify_result(ctx);
    CHECK_ERR();
    if(!verify_result || !verify_result->signatures) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "no signatures returned\n");
        handle->pm_errno = ALPM_ERR_SIG_MISSING;
        goto gpg_error;
    }
    for(gpgsig = verify_result->signatures, sigcount = 0;
            gpgsig; gpgsig = gpgsig->next, sigcount++);
    _alpm_log(handle, ALPM_LOG_DEBUG, "%d signatures returned\n", sigcount);

    CALLOC(siglist->results, sigcount, sizeof(alpm_sigresult_t),
            handle->pm_errno = ALPM_ERR_MEMORY; goto gpg_error);
    siglist->count = sigcount;

    for(gpgsig = verify_result->signatures, sigcount = 0; gpgsig;
            gpgsig = gpgsig->next, sigcount++) {
        alpm_list_t *summary_list, *summary;
        alpm_sigstatus_t status;
        alpm_sigvalidity_t validity;
        gpgme_key_t key;
        alpm_sigresult_t *result;

        _alpm_log(handle, ALPM_LOG_DEBUG, "fingerprint: %s\n", gpgsig->fpr);
        summary_list = list_sigsum(gpgsig->summary);
        for(summary = summary_list; summary; summary = summary->next) {
            _alpm_log(handle, ALPM_LOG_DEBUG, "summary: %s\n", (const char *)summary->data);
        }
        alpm_list_free(summary_list);
        _alpm_log(handle, ALPM_LOG_DEBUG, "status: %s\n", gpgme_strerror(gpgsig->status));
        _alpm_log(handle, ALPM_LOG_DEBUG, "timestamp: %lu\n", gpgsig->timestamp);
        _alpm_log(handle, ALPM_LOG_DEBUG, "exp_timestamp: %lu\n", gpgsig->exp_timestamp);
        _alpm_log(handle, ALPM_LOG_DEBUG, "validity: %s; reason: %s\n",
                string_validity(gpgsig->validity),
                gpgme_strerror(gpgsig->validity_reason));

        result = siglist->results + sigcount;
        err = gpgme_get_key(ctx, gpgsig->fpr, &key, 0);
        if(gpg_err_code(err) == GPG_ERR_EOF) {
            _alpm_log(handle, ALPM_LOG_DEBUG, "key lookup failed, unknown key\n");
            err = GPG_ERR_NO_ERROR;
            /* we dupe the fpr in this case since we have no key to point at */
            STRDUP(result->key.fingerprint, gpgsig->fpr,
                    handle->pm_errno = ALPM_ERR_MEMORY; goto gpg_error);
        } else {
            CHECK_ERR();
            if(key->uids) {
                result->key.data = key;
                result->key.fingerprint = key->subkeys->fpr;
                result->key.uid = key->uids->uid;
                result->key.name = key->uids->name;
                result->key.email = key->uids->email;
                result->key.created = key->subkeys->timestamp;
                result->key.expires = key->subkeys->expires;
                _alpm_log(handle, ALPM_LOG_DEBUG,
                        "key: %s, %s, owner_trust %s, disabled %d\n",
                        key->subkeys->fpr, key->uids->uid,
                        string_validity(key->owner_trust), key->disabled);
            }
        }

        switch(gpg_err_code(gpgsig->status)) {
            /* good cases */
            case GPG_ERR_NO_ERROR:
                status = ALPM_SIGSTATUS_VALID;
                break;
            case GPG_ERR_KEY_EXPIRED:
                status = ALPM_SIGSTATUS_KEY_EXPIRED;
                break;
            /* bad cases */
            case GPG_ERR_SIG_EXPIRED:
                status = ALPM_SIGSTATUS_SIG_EXPIRED;
                break;
            case GPG_ERR_NO_PUBKEY:
                status = ALPM_SIGSTATUS_KEY_UNKNOWN;
                break;
            case GPG_ERR_BAD_SIGNATURE:
            default:
                status = ALPM_SIGSTATUS_INVALID;
                break;
        }
        /* special case: key disabled is not returned in above status code */
        if(result->key.data && key->disabled) {
            status = ALPM_SIGSTATUS_KEY_DISABLED;
        }

        switch(gpgsig->validity) {
            case GPGME_VALIDITY_ULTIMATE:
            case GPGME_VALIDITY_FULL:
                validity = ALPM_SIGVALIDITY_FULL;
                break;
            case GPGME_VALIDITY_MARGINAL:
                validity = ALPM_SIGVALIDITY_MARGINAL;
                break;
            case GPGME_VALIDITY_NEVER:
                validity = ALPM_SIGVALIDITY_NEVER;
                break;
            case GPGME_VALIDITY_UNKNOWN:
            case GPGME_VALIDITY_UNDEFINED:
            default:
                validity = ALPM_SIGVALIDITY_UNKNOWN;
                break;
        }

        result->status = status;
        result->validity = validity;
    }

    ret = 0;

gpg_error:
    gpgme_data_release(sigdata);
    gpgme_data_release(filedata);
    gpgme_release(ctx);

error:
    if(sigfile) {
        fclose(sigfile);
    }
    if(file) {
        fclose(file);
    }
    FREE(sigpath);
    FREE(decoded_sigdata);
    if(gpg_err_code(err) != GPG_ERR_NO_ERROR) {
        _alpm_log(handle, ALPM_LOG_ERROR, _("GPGME error: %s\n"), gpgme_strerror(err));
        RET_ERR(handle, ALPM_ERR_GPGME, -1);
    }
    return ret;
}

#else  /* HAVE_LIBGPGME */
static int key_in_keychain(alpm_handle_t UNUSED *handle, const char UNUSED *fpr)
{
    return -1;
}
int _alpm_gpgme_checksig(alpm_handle_t UNUSED *handle, const char UNUSED *path,
        const char UNUSED *base64_sig, alpm_siglist_t UNUSED *siglist)
{
    return -1;
}
#endif /* HAVE_LIBGPGME */

/**
 * Form a signature path given a file path.
 * Caller must free the result.
 * @param handle the context handle
 * @param path the full path to a file
 * @return the path with '.sig' appended, NULL on errors
 */
char *_alpm_sigpath(alpm_handle_t *handle, const char *path)
{
    char *sigpath;
    size_t len;

    if(!path) {
        return NULL;
    }
    len = strlen(path) + 5;
    CALLOC(sigpath, len, sizeof(char), RET_ERR(handle, ALPM_ERR_MEMORY, NULL));
    sprintf(sigpath, "%s.sig", path);
    return sigpath;
}

/**
 * Helper for checking the PGP signature for the given file path.
 * This wraps #_alpm_gpgme_checksig in a slightly friendlier manner to simplify
 * handling of optional signatures and marginal/unknown trust levels and
 * handling the correct error code return values.
 * @param handle the context handle
 * @param path the full path to a file
 * @param base64_sig optional PGP signature data in base64 encoding
 * @param optional whether signatures are optional (e.g., missing OK)
 * @param marginal whether signatures with marginal trust are acceptable
 * @param unknown whether signatures with unknown trust are acceptable
 * @param sigdata a pointer to storage for signature results
 * @return 0 on success, -1 on error (consult pm_errno or sigdata)
 */
int _alpm_check_pgp_helper(alpm_handle_t *handle, const char *path,
        const char *base64_sig, int optional, int marginal, int unknown,
        alpm_siglist_t **sigdata)
{
    alpm_siglist_t *siglist;
    int ret;

    CALLOC(siglist, 1, sizeof(alpm_siglist_t),
            RET_ERR(handle, ALPM_ERR_MEMORY, -1));

    ret = _alpm_gpgme_checksig(handle, path, base64_sig, siglist);
    if(ret && handle->pm_errno == ALPM_ERR_SIG_MISSING) {
        if(optional) {
            _alpm_log(handle, ALPM_LOG_DEBUG, "missing optional signature\n");
            handle->pm_errno = 0;
            ret = 0;
        } else {
            _alpm_log(handle, ALPM_LOG_DEBUG, "missing required signature\n");
            /* ret will already be -1 */
        }
    } else if(ret) {
        _alpm_log(handle, ALPM_LOG_DEBUG, "signature check failed\n");
        /* ret will already be -1 */
    } else {
        size_t num;
        for(num = 0; !ret && num < siglist->count; num++) {
            switch(siglist->results[num].status) {
                case ALPM_SIGSTATUS_VALID:
                case ALPM_SIGSTATUS_KEY_EXPIRED:
                    _alpm_log(handle, ALPM_LOG_DEBUG, "signature is valid\n");
                    switch(siglist->results[num].validity) {
                        case ALPM_SIGVALIDITY_FULL:
                            _alpm_log(handle, ALPM_LOG_DEBUG, "signature is fully trusted\n");
                            break;
                        case ALPM_SIGVALIDITY_MARGINAL:
                            _alpm_log(handle, ALPM_LOG_DEBUG, "signature is marginal trust\n");
                            if(!marginal) {
                                ret = -1;
                            }
                            break;
                        case ALPM_SIGVALIDITY_UNKNOWN:
                            _alpm_log(handle, ALPM_LOG_DEBUG, "signature is unknown trust\n");
                            if(!unknown) {
                                ret = -1;
                            }
                            break;
                        case ALPM_SIGVALIDITY_NEVER:
                            _alpm_log(handle, ALPM_LOG_DEBUG, "signature should never be trusted\n");
                            ret = -1;
                            break;
                    }
                    break;
                case ALPM_SIGSTATUS_SIG_EXPIRED:
                case ALPM_SIGSTATUS_KEY_UNKNOWN:
                case ALPM_SIGSTATUS_KEY_DISABLED:
                case ALPM_SIGSTATUS_INVALID:
                    _alpm_log(handle, ALPM_LOG_DEBUG, "signature is not valid\n");
                    ret = -1;
                    break;
            }
        }
    }

    if(sigdata) {
        *sigdata = siglist;
    } else {
        alpm_siglist_cleanup(siglist);
        free(siglist);
    }

    return ret;
}

/**
 * Examine a signature result list and take any appropriate or necessary
 * actions. This may include asking the user to import a key or simply printing
 * helpful failure messages so the user can take action out of band.
 * @param handle the context handle
 * @param identifier a friendly name for the signed resource; usually a
 * database or package name
 * @param siglist a pointer to storage for signature results
 * @param optional whether signatures are optional (e.g., missing OK)
 * @param marginal whether signatures with marginal trust are acceptable
 * @param unknown whether signatures with unknown trust are acceptable
 * @return 0 if all signatures are OK, -1 on errors, 1 if we should retry the
 * validation process
 */
int _alpm_process_siglist(alpm_handle_t *handle, const char *identifier,
        alpm_siglist_t *siglist, int optional, int marginal, int unknown)
{
    size_t i;
    int retry = 0;

    if(!optional && siglist->count == 0) {
        _alpm_log(handle, ALPM_LOG_ERROR,
                _("%s: missing required signature\n"), identifier);
    }

    for(i = 0; i < siglist->count; i++) {
        alpm_sigresult_t *result = siglist->results + i;
        const char *name = result->key.uid ? result->key.uid : result->key.fingerprint;
        switch(result->status) {
            case ALPM_SIGSTATUS_VALID:
            case ALPM_SIGSTATUS_KEY_EXPIRED:
                switch(result->validity) {
                    case ALPM_SIGVALIDITY_FULL:
                        break;
                    case ALPM_SIGVALIDITY_MARGINAL:
                        if(!marginal) {
                            _alpm_log(handle, ALPM_LOG_ERROR,
                                    _("%s: signature from \"%s\" is marginal trust\n"),
                                    identifier, name);
                            /* QUESTION(handle, ALPM_QUESTION_EDIT_KEY_TRUST, &result->key, NULL, NULL, &answer); */
                        }
                        break;
                    case ALPM_SIGVALIDITY_UNKNOWN:
                        if(!unknown) {
                            _alpm_log(handle, ALPM_LOG_ERROR,
                                    _("%s: signature from \"%s\" is unknown trust\n"),
                                    identifier, name);
                            /* QUESTION(handle, ALPM_QUESTION_EDIT_KEY_TRUST, &result->key, NULL, NULL, &answer); */
                        }
                        break;
                    case ALPM_SIGVALIDITY_NEVER:
                        _alpm_log(handle, ALPM_LOG_ERROR,
                                _("%s: signature from \"%s\" should never be trusted\n"),
                                identifier, name);
                        break;
                }
                break;
            case ALPM_SIGSTATUS_KEY_UNKNOWN:
                /* ensure this key is still actually unknown; we may have imported it
                 * on an earlier call to this function. */
                if(key_in_keychain(handle, result->key.fingerprint) == 1) {
                    break;
                }
                _alpm_log(handle, ALPM_LOG_ERROR,
                        _("%s: key \"%s\" is unknown\n"), identifier, name);
#ifdef HAVE_LIBGPGME
                {
                    int answer;
                    alpm_pgpkey_t fetch_key;
                    memset(&fetch_key, 0, sizeof(fetch_key));

                    if(key_search(handle, result->key.fingerprint, &fetch_key) == 1) {
                        _alpm_log(handle, ALPM_LOG_DEBUG,
                                "unknown key, found %s on keyserver\n", fetch_key.uid);
                        if(!_alpm_access(handle, handle->gpgdir, "pubring.gpg", W_OK)) {
                            QUESTION(handle, ALPM_QUESTION_IMPORT_KEY,
                                    &fetch_key, NULL, NULL, &answer);
                            if(answer) {
                                if(key_import(handle, &fetch_key) == 0) {
                                    retry = 1;
                                } else {
                                    _alpm_log(handle, ALPM_LOG_ERROR,
                                            _("key \"%s\" could not be imported\n"), fetch_key.uid);
                                }
                            }
                        } else {
                            /* keyring directory was not writable, so we don't even try */
                            _alpm_log(handle, ALPM_LOG_WARNING,
                                    _("key %s, \"%s\" found on keyserver, keyring is not writable\n"),
                                    fetch_key.fingerprint, fetch_key.uid);
                        }
                    } else {
                        _alpm_log(handle, ALPM_LOG_ERROR,
                                _("key \"%s\" could not be looked up remotely\n"), name);
                    }
                    gpgme_key_unref(fetch_key.data);
                }
#endif
                break;
            case ALPM_SIGSTATUS_KEY_DISABLED:
                _alpm_log(handle, ALPM_LOG_ERROR,
                        _("%s: key \"%s\" is disabled\n"), identifier, name);
                break;
            case ALPM_SIGSTATUS_SIG_EXPIRED:
                _alpm_log(handle, ALPM_LOG_ERROR,
                        _("%s: signature from \"%s\" is expired\n"), identifier, name);
                break;
            case ALPM_SIGSTATUS_INVALID:
                _alpm_log(handle, ALPM_LOG_ERROR,
                        _("%s: signature from \"%s\" is invalid\n"),
                        identifier, name);
                break;
        }
    }

    return retry;
}

/**
 * Check the PGP signature for the given package file.
 * @param pkg the package to check
 * @param siglist a pointer to storage for signature results
 * @return a int value : 0 (valid), 1 (invalid), -1 (an error occurred)
 */
int SYMEXPORT alpm_pkg_check_pgp_signature(alpm_pkg_t *pkg,
        alpm_siglist_t *siglist)
{
    ASSERT(pkg != NULL, return -1);
    ASSERT(siglist != NULL, RET_ERR(pkg->handle, ALPM_ERR_WRONG_ARGS, -1));
    pkg->handle->pm_errno = 0;

    return _alpm_gpgme_checksig(pkg->handle, pkg->filename,
            pkg->base64_sig, siglist);
}

/**
 * Check the PGP signature for the given database.
 * @param db the database to check
 * @param siglist a pointer to storage for signature results
 * @return a int value : 0 (valid), 1 (invalid), -1 (an error occurred)
 */
int SYMEXPORT alpm_db_check_pgp_signature(alpm_db_t *db,
        alpm_siglist_t *siglist)
{
    ASSERT(db != NULL, return -1);
    ASSERT(siglist != NULL, RET_ERR(db->handle, ALPM_ERR_WRONG_ARGS, -1));
    db->handle->pm_errno = 0;

    return _alpm_gpgme_checksig(db->handle, _alpm_db_path(db), NULL, siglist);
}

/**
 * Clean up and free a signature result list.
 * Note that this does not free the siglist object itself in case that
 * was allocated on the stack; this is the responsibility of the caller.
 * @param siglist a pointer to storage for signature results
 * @return 0 on success, -1 on error
 */
int SYMEXPORT alpm_siglist_cleanup(alpm_siglist_t *siglist)
{
    ASSERT(siglist != NULL, return -1);
    size_t num;
    for(num = 0; num < siglist->count; num++) {
        alpm_sigresult_t *result = siglist->results + num;
        if(result->key.data) {
#if HAVE_LIBGPGME
            gpgme_key_unref(result->key.data);
#endif
        } else {
            free(result->key.fingerprint);
        }
    }
    if(siglist->count) {
        free(siglist->results);
    }
    siglist->results = NULL;
    siglist->count = 0;
    return 0;
}

/* vim: set ts=2 sw=2 noet: */