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(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  /* One key has been revoked.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 = alpm_option_get_gpgdir(handle);
  if(!sigdir) {
    RET_ERR(handle, PM_ERR_SIG_MISSINGDIR, 1);
  }

  /* calling gpgme_check_version() returns the current version and runs
   * some internal library setup code */
  version = gpgme_check_version(NULL);
  _alpm_log(handle, PM_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, PM_LOG_DEBUG, "GPGME engine info: file=%s, home=%s\n",
      enginfo->file_name, enginfo->home_dir);

  init = 1;
  return 0;

error:
  _alpm_log(handle, PM_LOG_ERROR, _("GPGME error: %s\n"), gpgme_strerror(err));
  RET_ERR(handle, PM_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, int *data_len) {
  unsigned char *usline;
  int len;

  len = strlen(base64_data);
  usline = (unsigned char *)base64_data;
  int ret, destlen = 0;
  /* get the necessary size for the buffer by passing 0 */
  ret = base64_decode(NULL, &destlen, usline, len);
  if(ret != 0 && ret != POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL) {
    goto error;
  }
  /* alloc our memory and repeat the call to decode */
  MALLOC(*data, (size_t)destlen, goto error);
  ret = base64_decode(*data, &destlen, usline, len);
  if(ret != 0) {
    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 all checked signatures are
 * valid, 1 if there was some sort of problem (but not necessarily rejection),
 * and -1 if an error occurred while checking signatures. If 1 is returned,
 * pm_errno should be checked to see why the signatures did not pass muster.
 * @param handle the context handle
 * @param path the full path to a file
 * @param base64_sig optional PGP signature data in base64 encoding
 * @return a int value : 0 (valid), 1 (invalid), -1 (an error occurred)
 */
int _alpm_gpgme_checksig(alpm_handle_t *handle, const char *path,
    const char *base64_sig)
{
  int ret = 0;
  gpgme_error_t err;
  gpgme_ctx_t ctx;
  gpgme_data_t filedata, sigdata;
  gpgme_verify_result_t result;
  gpgme_signature_t gpgsig;
  char *sigpath = NULL;
  unsigned char *decoded_sigdata = NULL;
  FILE *file = NULL, *sigfile = NULL;

  if(!path || access(path, R_OK) != 0) {
    RET_ERR(handle, PM_ERR_NOT_A_FILE, -1);
  }

  if(!base64_sig) {
    size_t len = strlen(path) + 5;
    CALLOC(sigpath, len, sizeof(char), RET_ERR(handle, PM_ERR_MEMORY, -1));
    snprintf(sigpath, len, "%s.sig", path);

    if(!access(sigpath, R_OK) == 0) {
      FREE(sigpath);
      RET_ERR(handle, PM_ERR_SIG_UNKNOWN, -1);
    }
  }

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

  _alpm_log(handle, PM_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 = PM_ERR_NOT_A_FILE;
    ret = -1;
    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 */
    int data_len;
    int decode_ret = decode_signature(base64_sig,
        &decoded_sigdata, &data_len);
    if(decode_ret) {
      ret = -1;
      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) {
      handle->pm_errno = PM_ERR_NOT_A_FILE;
      ret = -1;
      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();
  result = gpgme_op_verify_result(ctx);
  gpgsig = result->signatures;
  if(!gpgsig) {
    _alpm_log(handle, PM_LOG_DEBUG, "no signatures returned\n");
    ret = -1;
    goto error;
  }

  while(gpgsig) {
    alpm_list_t *summary_list, *summary;

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

    /* Note: this is structured so any bad signature will set the return code
     * to a bad one, but good ones just leave the default value in place; e.g.
     * worst case wins out. */
    if(gpgsig->summary & GPGME_SIGSUM_VALID) {
      /* definite good signature */
      _alpm_log(handle, PM_LOG_DEBUG, "result: valid signature\n");
    } else if(gpgsig->summary & GPGME_SIGSUM_GREEN) {
      /* good signature */
      _alpm_log(handle, PM_LOG_DEBUG, "result: green signature\n");
    } else if(gpgsig->summary & GPGME_SIGSUM_RED) {
      /* definite bad signature, error */
      _alpm_log(handle, PM_LOG_DEBUG, "result: red signature\n");
      handle->pm_errno = PM_ERR_SIG_INVALID;
      ret = 1;
    } else if(gpgsig->summary & GPGME_SIGSUM_KEY_MISSING) {
      _alpm_log(handle, PM_LOG_DEBUG, "result: signature from unknown key\n");
      handle->pm_errno = PM_ERR_SIG_UNKNOWN;
      ret = 1;
    } else {
      /* we'll capture everything else here */
      _alpm_log(handle, PM_LOG_DEBUG, "result: invalid signature\n");
      handle->pm_errno = PM_ERR_SIG_INVALID;
      ret = 1;
    }

    gpgsig = gpgsig->next;
  }

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(err != GPG_ERR_NO_ERROR) {
    _alpm_log(handle, PM_LOG_ERROR, _("GPGME error: %s\n"), gpgme_strerror(err));
    RET_ERR(handle, PM_ERR_GPGME, -1);
  }
  return ret;
}
#else
int _alpm_gpgme_checksig(alpm_handle_t *handle, const char *path,
    const char *base64_sig)
{
  return -1;
}
#endif

/**
 * 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)
{
  ASSERT(pkg != NULL, return -1);
  pkg->handle->pm_errno = 0;

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

/**
 * 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)
{
  ASSERT(db != NULL, return -1);
  db->handle->pm_errno = 0;

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

/* vim: set ts=2 sw=2 noet: */