methods/gpgv.cc

   1 #include <config.h>
   2
   3 #include <apt-pkg/configuration.h>
   4 #include <apt-pkg/error.h>
   5 #include <apt-pkg/gpgv.h>
   6 #include <apt-pkg/strutl.h>
   7 #include <apt-pkg/fileutl.h>
   8 #include "aptmethod.h"
   9
  10 #include <ctype.h>
  11 #include <errno.h>
  12 #include <stddef.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <sys/wait.h>
  17 #include <unistd.h>
  18
  19 #include <array>
  20 #include <algorithm>
  21 #include <sstream>
  22 #include <iterator>
  23 #include <iostream>
  24 #include <string>
  25 #include <vector>
  26
  27 #include <apti18n.h>
  28
  29 using std::string;
  30 using std::vector;
  31
  32 #define GNUPGPREFIX "[GNUPG:]"
  33 #define GNUPGBADSIG "[GNUPG:] BADSIG"
  34 #define GNUPGERRSIG "[GNUPG:] ERRSIG"
  35 #define GNUPGNOPUBKEY "[GNUPG:] NO_PUBKEY"
  36 #define GNUPGVALIDSIG "[GNUPG:] VALIDSIG"
  37 #define GNUPGGOODSIG "[GNUPG:] GOODSIG"
  38 #define GNUPGEXPKEYSIG "[GNUPG:] EXPKEYSIG"
  39 #define GNUPGEXPSIG "[GNUPG:] EXPSIG"
  40 #define GNUPGREVKEYSIG "[GNUPG:] REVKEYSIG"
  41 #define GNUPGNODATA "[GNUPG:] NODATA"
  42 #define APTKEYWARNING "[APTKEY:] WARNING"
  43
  44 struct Digest {
  45    enum class State {
  46       Untrusted,
  47       Weak,
  48       Trusted,
  49    } state;
  50    char name[32];
  51
  52    State getState() const {
  53       std::string optionUntrusted;
  54       std::string optionWeak;
  55       strprintf(optionUntrusted, "APT::Hashes::%s::Untrusted", name);
  56       strprintf(optionWeak, "APT::Hashes::%s::Weak", name);
  57       if (_config->FindB(optionUntrusted, state == State::Untrusted) == true)
  58          return State::Untrusted;
  59       if (_config->FindB(optionWeak, state == State::Weak) == true)
  60          return State::Weak;
  61
  62       return state;
  63    }
  64 };
  65
  66 static constexpr Digest Digests[] = {
  67    {Digest::State::Untrusted, "Invalid digest"},
  68    {Digest::State::Untrusted, "MD5"},
  69    {Digest::State::Weak, "SHA1"},
  70    {Digest::State::Weak, "RIPE-MD/160"},
  71    {Digest::State::Trusted, "Reserved digest"},
  72    {Digest::State::Trusted, "Reserved digest"},
  73    {Digest::State::Trusted, "Reserved digest"},
  74    {Digest::State::Trusted, "Reserved digest"},
  75    {Digest::State::Trusted, "SHA256"},
  76    {Digest::State::Trusted, "SHA384"},
  77    {Digest::State::Trusted, "SHA512"},
  78    {Digest::State::Trusted, "SHA224"},
  79 };
  80
  81 static Digest FindDigest(std::string const & Digest)
  82 {
  83    int id = atoi(Digest.c_str());
  84    if (id >= 0 && static_cast<unsigned>(id) < _count(Digests)) {
  85       return Digests[id];
  86    } else {
  87       return Digests[0];
  88    }
  89 }
  90
  91 struct Signer {
  92    std::string key;
  93    std::string note;
  94 };
  95 static bool IsTheSameKey(std::string const &validsig, std::string const &goodsig) {
  96    // VALIDSIG reports a keyid (40 = 24 + 16), GOODSIG is a longid (16) only
  97    return validsig.compare(24, 16, goodsig, strlen("GOODSIG "), 16) == 0;
  98 }
  99
 100 class GPGVMethod : public aptMethod
 101 {
 102    private:
 103    string VerifyGetSigners(const char *file, const char *outfile,
 104                                 std::string const &key,
 105                                 vector<string> &GoodSigners,
 106                                 vector<string> &BadSigners,
 107                                 vector<string> &WorthlessSigners,
 108                                 vector<Signer> &SoonWorthlessSigners,
 109                                 vector<string> &NoPubKeySigners);
 110    protected:
 111    virtual bool URIAcquire(std::string const &Message, FetchItem *Itm) APT_OVERRIDE;
 112    public:
 113    GPGVMethod() : aptMethod("gpgv","1.0",SingleInstance | SendConfig) {};
 114 };
 115 static void PushEntryWithKeyID(std::vector<std::string> &Signers, char * const buffer, bool const Debug)
 116 {
 117    char * const msg = buffer + sizeof(GNUPGPREFIX);
 118    char *p = msg;
 119    // skip the message
 120    while (*p && !isspace(*p))
 121       ++p;
 122    // skip the seperator whitespace
 123    ++p;
 124    // skip the hexdigit fingerprint
 125    while (*p && isxdigit(*p))
 126       ++p;
 127    // cut the rest from the message
 128    *p = '\0';
 129    if (Debug == true)
 130       std::clog << "Got " << msg << " !" << std::endl;
 131    Signers.push_back(msg);
 132 }
 133 static void PushEntryWithUID(std::vector<std::string> &Signers, char * const buffer, bool const Debug)
 134 {
 135    std::string msg = buffer + sizeof(GNUPGPREFIX);
 136    auto const nuke = msg.find_last_not_of("\n\t\r");
 137    if (nuke != std::string::npos)
 138       msg.erase(nuke + 1);
 139    if (Debug == true)
 140       std::clog << "Got " << msg << " !" << std::endl;
 141    Signers.push_back(msg);
 142 }
 143 string GPGVMethod::VerifyGetSigners(const char *file, const char *outfile,
 144                                          std::string const &key,
 145                                          vector<string> &GoodSigners,
 146                                          vector<string> &BadSigners,
 147                                          vector<string> &WorthlessSigners,
 148                                          vector<Signer> &SoonWorthlessSigners,
 149                                          vector<string> &NoPubKeySigners)
 150 {
 151    bool const Debug = DebugEnabled();
 152
 153    if (Debug == true)
 154       std::clog << "inside VerifyGetSigners" << std::endl;
 155
 156    int fd[2];
 157    bool const keyIsID = (key.empty() == false && key[0] != '/');
 158
 159    if (pipe(fd) < 0)
 160       return "Couldn't create pipe";
 161
 162    pid_t pid = fork();
 163    if (pid < 0)
 164       return string("Couldn't spawn new process") + strerror(errno);
 165    else if (pid == 0)
 166       ExecGPGV(outfile, file, 3, fd, (keyIsID ? "" : key));
 167    close(fd[1]);
 168
 169    FILE *pipein = fdopen(fd[0], "r");
 170
 171    // Loop over the output of apt-key (which really is gnupg), and check the signatures.
 172    std::vector<std::string> ValidSigners;
 173    std::vector<std::string> ErrSigners;
 174    size_t buffersize = 0;
 175    char *buffer = NULL;
 176    bool gotNODATA = false;
 177    while (1)
 178    {
 179       if (getline(&buffer, &buffersize, pipein) == -1)
 180          break;
 181       if (Debug == true)
 182          std::clog << "Read: " << buffer << std::endl;
 183
 184       // Push the data into three separate vectors, which
 185       // we later concatenate.  They're kept separate so
 186       // if we improve the apt method communication stuff later
 187       // it will be better.
 188       if (strncmp(buffer, GNUPGBADSIG, sizeof(GNUPGBADSIG)-1) == 0)
 189          PushEntryWithUID(BadSigners, buffer, Debug);
 190       else if (strncmp(buffer, GNUPGERRSIG, sizeof(GNUPGERRSIG)-1) == 0)
 191          PushEntryWithKeyID(ErrSigners, buffer, Debug);
 192       else if (strncmp(buffer, GNUPGNOPUBKEY, sizeof(GNUPGNOPUBKEY)-1) == 0)
 193       {
 194          PushEntryWithKeyID(NoPubKeySigners, buffer, Debug);
 195          ErrSigners.erase(std::remove_if(ErrSigners.begin(), ErrSigners.end(), [&](std::string const &errsig) {
 196                   return errsig.compare(strlen("ERRSIG "), 16, buffer, sizeof(GNUPGNOPUBKEY), 16) == 0;  }), ErrSigners.end());
 197       }
 198       else if (strncmp(buffer, GNUPGNODATA, sizeof(GNUPGNODATA)-1) == 0)
 199          gotNODATA = true;
 200       else if (strncmp(buffer, GNUPGEXPKEYSIG, sizeof(GNUPGEXPKEYSIG)-1) == 0)
 201          PushEntryWithUID(WorthlessSigners, buffer, Debug);
 202       else if (strncmp(buffer, GNUPGEXPSIG, sizeof(GNUPGEXPSIG)-1) == 0)
 203          PushEntryWithUID(WorthlessSigners, buffer, Debug);
 204       else if (strncmp(buffer, GNUPGREVKEYSIG, sizeof(GNUPGREVKEYSIG)-1) == 0)
 205          PushEntryWithUID(WorthlessSigners, buffer, Debug);
 206       else if (strncmp(buffer, GNUPGGOODSIG, sizeof(GNUPGGOODSIG)-1) == 0)
 207          PushEntryWithKeyID(GoodSigners, buffer, Debug);
 208       else if (strncmp(buffer, GNUPGVALIDSIG, sizeof(GNUPGVALIDSIG)-1) == 0)
 209       {
 210          std::istringstream iss(buffer + sizeof(GNUPGVALIDSIG));
 211          vector<string> tokens{std::istream_iterator<string>{iss},
 212                                std::istream_iterator<string>{}};
 213          auto const sig = tokens[0];
 214          // Reject weak digest algorithms
 215          Digest digest = FindDigest(tokens[7]);
 216          switch (digest.getState()) {
 217          case Digest::State::Weak:
 218             // Treat them like an expired key: For that a message about expiry
 219             // is emitted, a VALIDSIG, but no GOODSIG.
 220             SoonWorthlessSigners.push_back({sig, digest.name});
 221             if (Debug == true)
 222                std::clog << "Got weak VALIDSIG, key ID: " << sig << std::endl;
 223             break;
 224          case Digest::State::Untrusted:
 225             // Treat them like an expired key: For that a message about expiry
 226             // is emitted, a VALIDSIG, but no GOODSIG.
 227             WorthlessSigners.push_back(sig);
 228             GoodSigners.erase(std::remove_if(GoodSigners.begin(), GoodSigners.end(), [&](std::string const &goodsig) {
 229                      return IsTheSameKey(sig, goodsig); }), GoodSigners.end());
 230             if (Debug == true)
 231                std::clog << "Got untrusted VALIDSIG, key ID: " << sig << std::endl;
 232             break;
 233
 234          case Digest::State::Trusted:
 235             if (Debug == true)
 236                std::clog << "Got trusted VALIDSIG, key ID: " << sig << std::endl;
 237             break;
 238          }
 239
 240          ValidSigners.push_back(sig);
 241       }
 242       else if (strncmp(buffer, APTKEYWARNING, sizeof(APTKEYWARNING)-1) == 0)
 243          Warning("%s", buffer + sizeof(APTKEYWARNING));
 244    }
 245    fclose(pipein);
 246    free(buffer);
 247    std::move(ErrSigners.begin(), ErrSigners.end(), std::back_inserter(WorthlessSigners));
 248
 249    // apt-key has a --keyid parameter, but this requires gpg, so we call it without it
 250    // and instead check after the fact which keyids where used for verification
 251    if (keyIsID == true)
 252    {
 253       if (Debug == true)
 254          std::clog << "GoodSigs needs to be limited to keyid " << key << std::endl;
 255       bool foundGood = false;
 256       for (auto const &k: VectorizeString(key, ','))
 257       {
 258          if (std::find(ValidSigners.begin(), ValidSigners.end(), k) == ValidSigners.end())
 259             continue;
 260          // we look for GOODSIG here as well as an expired sig is a valid sig as well (but not a good one)
 261          std::string const goodlongkeyid = "GOODSIG " + k.substr(24, 16);
 262          foundGood = std::find(GoodSigners.begin(), GoodSigners.end(), goodlongkeyid) != GoodSigners.end();
 263          if (Debug == true)
 264             std::clog << "Key " << k << " is valid sig, is " << goodlongkeyid << " also a good one? " << (foundGood ? "yes" : "no") << std::endl;
 265          if (foundGood == false)
 266             continue;
 267          std::copy(GoodSigners.begin(), GoodSigners.end(), std::back_insert_iterator<std::vector<std::string> >(NoPubKeySigners));
 268          GoodSigners.clear();
 269          GoodSigners.push_back(goodlongkeyid);
 270          NoPubKeySigners.erase(std::remove(NoPubKeySigners.begin(), NoPubKeySigners.end(), goodlongkeyid), NoPubKeySigners.end());
 271          break;
 272       }
 273       if (foundGood == false)
 274       {
 275          std::copy(GoodSigners.begin(), GoodSigners.end(), std::back_insert_iterator<std::vector<std::string> >(NoPubKeySigners));
 276          GoodSigners.clear();
 277       }
 278    }
 279
 280    int status;
 281    waitpid(pid, &status, 0);
 282    if (Debug == true)
 283    {
 284       ioprintf(std::clog, "gpgv exited with status %i\n", WEXITSTATUS(status));
 285    }
 286
 287    if (Debug)
 288    {
 289       std::cerr << "Summary:" << std::endl << "  Good: ";
 290       std::copy(GoodSigners.begin(), GoodSigners.end(), std::ostream_iterator<std::string>(std::cerr, ", "));
 291       std::cerr << std::endl << "  Bad: ";
 292       std::copy(BadSigners.begin(), BadSigners.end(), std::ostream_iterator<std::string>(std::cerr, ", "));
 293       std::cerr << std::endl << "  Worthless: ";
 294       std::copy(WorthlessSigners.begin(), WorthlessSigners.end(), std::ostream_iterator<std::string>(std::cerr, ", "));
 295       std::cerr << std::endl << "  SoonWorthless: ";
 296       std::for_each(SoonWorthlessSigners.begin(), SoonWorthlessSigners.end(), [](Signer const &sig) { std::cerr << sig.key << ", "; });
 297       std::cerr << std::endl << "  NoPubKey: ";
 298       std::copy(NoPubKeySigners.begin(), NoPubKeySigners.end(), std::ostream_iterator<std::string>(std::cerr, ", "));
 299       std::cerr << std::endl << "  NODATA: " << (gotNODATA ? "yes" : "no") << std::endl;
 300    }
 301
 302    if (WEXITSTATUS(status) == 112)
 303    {
 304       // acquire system checks for "NODATA" to generate GPG errors (the others are only warnings)
 305       std::string errmsg;
 306       //TRANSLATORS: %s is a single techy word like 'NODATA'
 307       strprintf(errmsg, _("Clearsigned file isn't valid, got '%s' (does the network require authentication?)"), "NODATA");
 308       return errmsg;
 309    }
 310    else if (gotNODATA)
 311    {
 312       // acquire system checks for "NODATA" to generate GPG errors (the others are only warnings)
 313       std::string errmsg;
 314       //TRANSLATORS: %s is a single techy word like 'NODATA'
 315       strprintf(errmsg, _("Signed file isn't valid, got '%s' (does the network require authentication?)"), "NODATA");
 316       return errmsg;
 317    }
 318    else if (WEXITSTATUS(status) == 0)
 319    {
 320       if (keyIsID)
 321       {
 322          // gpgv will report success, but we want to enforce a certain keyring
 323          // so if we haven't found the key the valid we found is in fact invalid
 324          if (GoodSigners.empty())
 325             return _("At least one invalid signature was encountered.");
 326       }
 327       else
 328       {
 329          if (GoodSigners.empty())
 330             return _("Internal error: Good signature, but could not determine key fingerprint?!");
 331       }
 332       return "";
 333    }
 334    else if (WEXITSTATUS(status) == 1)
 335       return _("At least one invalid signature was encountered.");
 336    else if (WEXITSTATUS(status) == 111)
 337       return _("Could not execute 'apt-key' to verify signature (is gnupg installed?)");
 338    else
 339       return _("Unknown error executing apt-key");
 340 }
 341
 342 bool GPGVMethod::URIAcquire(std::string const &Message, FetchItem *Itm)
 343 {
 344    URI const Get = Itm->Uri;
 345    string const Path = Get.Host + Get.Path; // To account for relative paths
 346    std::string const key = LookupTag(Message, "Signed-By");
 347    vector<string> GoodSigners;
 348    vector<string> BadSigners;
 349    // a worthless signature is a expired or revoked one
 350    vector<string> WorthlessSigners;
 351    vector<Signer> SoonWorthlessSigners;
 352    vector<string> NoPubKeySigners;
 353
 354    FetchResult Res;
 355    Res.Filename = Itm->DestFile;
 356    URIStart(Res);
 357
 358    // Run apt-key on file, extract contents and get the key ID of the signer
 359    string msg = VerifyGetSigners(Path.c_str(), Itm->DestFile.c_str(), key,
 360                                  GoodSigners, BadSigners, WorthlessSigners,
 361                                  SoonWorthlessSigners, NoPubKeySigners);
 362
 363    // Check if all good signers are soon worthless and warn in that case
 364    if (std::all_of(GoodSigners.begin(), GoodSigners.end(), [&](std::string const &good) {
 365             return std::any_of(SoonWorthlessSigners.begin(), SoonWorthlessSigners.end(), [&](Signer const &weak) {
 366                   return IsTheSameKey(weak.key, good);
 367                   });
 368             }))
 369    {
 370       for (auto const & Signer : SoonWorthlessSigners)
 371          // TRANSLATORS: The second %s is the reason and is untranslated for repository owners.
 372          Warning(_("Signature by key %s uses weak digest algorithm (%s)"), Signer.key.c_str(), Signer.note.c_str());
 373    }
 374
 375    if (GoodSigners.empty() || !BadSigners.empty() || !NoPubKeySigners.empty())
 376    {
 377       string errmsg;
 378       // In this case, something bad probably happened, so we just go
 379       // with what the other method gave us for an error message.
 380       if (BadSigners.empty() && WorthlessSigners.empty() && NoPubKeySigners.empty())
 381          errmsg = msg;
 382       else
 383       {
 384          if (!BadSigners.empty())
 385          {
 386             errmsg += _("The following signatures were invalid:\n");
 387             for (vector<string>::iterator I = BadSigners.begin();
 388                  I != BadSigners.end(); ++I)
 389                errmsg += (*I + "\n");
 390          }
 391          if (!WorthlessSigners.empty())
 392          {
 393             errmsg += _("The following signatures were invalid:\n");
 394             for (vector<string>::iterator I = WorthlessSigners.begin();
 395                  I != WorthlessSigners.end(); ++I)
 396                errmsg += (*I + "\n");
 397          }
 398          if (!NoPubKeySigners.empty())
 399          {
 400              errmsg += _("The following signatures couldn't be verified because the public key is not available:\n");
 401             for (vector<string>::iterator I = NoPubKeySigners.begin();
 402                  I != NoPubKeySigners.end(); ++I)
 403                errmsg += (*I + "\n");
 404          }
 405       }
 406       // this is only fatal if we have no good sigs or if we have at
 407       // least one bad signature. good signatures and NoPubKey signatures
 408       // happen easily when a file is signed with multiple signatures
 409       if(GoodSigners.empty() or !BadSigners.empty())
 410          return _error->Error("%s", errmsg.c_str());
 411    }
 412
 413    // Just pass the raw output up, because passing it as a real data
 414    // structure is too difficult with the method stuff.  We keep it
 415    // as three separate vectors for future extensibility.
 416    Res.GPGVOutput = GoodSigners;
 417    std::move(BadSigners.begin(), BadSigners.end(), std::back_inserter(Res.GPGVOutput));
 418    std::move(NoPubKeySigners.begin(), NoPubKeySigners.end(), std::back_inserter(Res.GPGVOutput));
 419    URIDone(Res);
 420
 421    if (DebugEnabled())
 422       std::clog << "apt-key succeeded\n";
 423
 424    return true;
 425 }
 426
 427
 428 int main()
 429 {
 430    return GPGVMethod().Run();
 431 }