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