path: root/lib/libalpm/signing.c

/*
 *  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 "config.h"

#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)

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);
  }
}

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  /* One key has been revoked.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;
}

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");
  }

  /* 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);
}

/**
 * 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)) {
    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 #result 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
 * @result
 * @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_sigresult_t *result)
{
  int ret = -1, sigcount;
  gpgme_error_t err;
  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(!result) {
    RET_ERR(handle, ALPM_ERR_WRONG_ARGS, -1);
  }
  result->count = 0;

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

  if(init_gpgme(handle)) {
    /* pm_errno was set in gpgme_init() */
    return -1;
  }

  _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 */
  file = fopen(path, "rb");
  if(file == NULL) {
    handle->pm_errno = ALPM_ERR_NOT_A_FILE;
    goto error;
  }
  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 error;
    }
    err = gpgme_data_new_from_mem(&sigdata,
        (char *)decoded_sigdata, data_len, 0);
  } else {
    /* file-based, it is on disk */
    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;
    }
    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 error;
  }
  for(gpgsig = verify_result->signatures, sigcount = 0;
      gpgsig; gpgsig = gpgsig->next, sigcount++);
  _alpm_log(handle, ALPM_LOG_DEBUG, "%d signatures returned\n", sigcount);

  result->status = calloc(sigcount, sizeof(alpm_sigstatus_t));
  result->validity = calloc(sigcount, sizeof(alpm_sigvalidity_t));
  result->uid = calloc(sigcount, sizeof(char*));
  if(!result->status || !result->validity || !result->uid) {
    handle->pm_errno = ALPM_ERR_MEMORY;
    goto error;
  }
  result->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_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));

    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;
      STRDUP(result->uid[sigcount], gpgsig->fpr,
          handle->pm_errno = ALPM_ERR_MEMORY; goto error);
    } else {
      CHECK_ERR();
      if(key->uids) {
        const char *uid = key->uids->uid;
        STRDUP(result->uid[sigcount], uid,
            handle->pm_errno = ALPM_ERR_MEMORY; goto error);
        _alpm_log(handle, ALPM_LOG_DEBUG, "key user: %s\n", uid);
      }
      gpgme_key_unref(key);
    }

    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;
    }

    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[sigcount] = status;
    result->validity[sigcount] = validity;
  }

  ret = 0;

error:
  gpgme_data_release(sigdata);
  gpgme_data_release(filedata);
  gpgme_release(ctx);
  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
int _alpm_gpgme_checksig(alpm_handle_t UNUSED *handle, const char UNUSED *path,
    const char UNUSED *base64_sig, alpm_sigresult_t UNUSED *result)
{
  return -1;
}
#endif

/**
 * 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;
}

int _alpm_check_pgp_helper(alpm_handle_t *handle, const char *path,
    const char *base64_sig, int optional, int marginal, int unknown)
{
  alpm_sigresult_t result;
  int ret;

  memset(&result, 0, sizeof(result));

  _alpm_log(handle, ALPM_LOG_DEBUG, "checking signatures for %s\n", path);
  ret = _alpm_gpgme_checksig(handle, path, base64_sig, &result);
  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 {
    int num;
    for(num = 0; !ret && num < result.count; num++) {
      switch(result.status[num]) {
        case ALPM_SIGSTATUS_VALID:
        case ALPM_SIGSTATUS_KEY_EXPIRED:
          _alpm_log(handle, ALPM_LOG_DEBUG, "signature is valid\n");
          switch(result.validity[num]) {
            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_INVALID:
          _alpm_log(handle, ALPM_LOG_DEBUG, "signature is not valid\n");
          ret = -1;
          break;
      }
    }
  }

  alpm_sigresult_cleanup(&result);
  return ret;
}

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

  return _alpm_gpgme_checksig(pkg->handle, alpm_pkg_get_filename(pkg),
      pkg->base64_sig, result);
}

/**
 * Check the PGP signature for the given database.
 * @param db the database to check
 * @return a int value : 0 (valid), 1 (invalid), -1 (an error occurred)
 */
int SYMEXPORT alpm_db_check_pgp_signature(alpm_db_t *db,
    alpm_sigresult_t *result)
{
  ASSERT(db != NULL, return -1);
  ASSERT(result != 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, result);
}

int SYMEXPORT alpm_sigresult_cleanup(alpm_sigresult_t *result)
{
  ASSERT(result != NULL, return -1);
  /* Because it is likely result is on the stack, uid and status may have bogus
   * values in the struct. Only look at them if count is greater than 0. */
  if(result->count > 0) {
    free(result->status);
    free(result->validity);
    if(result->uid) {
      int i;
      for(i = 0; i < result->count; i++) {
        free(result->uid[i]);
      }
      free(result->uid);
    }
  }
  return 0;
}

/* vim: set ts=2 sw=2 noet: */