methods/gpgv.cc

   1 #include <config.h>
   2
   3 #include <apt-pkg/acquire-method.h>
   4 #include <apt-pkg/configuration.h>
   5 #include <apt-pkg/error.h>
   6 #include <apt-pkg/gpgv.h>
   7 #include <apt-pkg/strutl.h>
   8 #include <apt-pkg/fileutl.h>
   9 #include "aptmethod.h"
  10
  11 #include <ctype.h>
  12 #include <errno.h>
  13 #include <stddef.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <sys/wait.h>
  18 #include <unistd.h>
  19
  20 #include <array>
  21 #include <algorithm>
  22 #include <sstream>
  23 #include <iterator>
  24 #include <iostream>
  25 #include <string>
  26 #include <vector>
  27
  28 #include <apti18n.h>
  29
  30 using std::string;
  31 using std::vector;
  32
  33 #define GNUPGPREFIX "[GNUPG:]"
  34 #define GNUPGBADSIG "[GNUPG:] BADSIG"
  35 #define GNUPGNOPUBKEY "[GNUPG:] NO_PUBKEY"
  36 #define GNUPGVALIDSIG "[GNUPG:] VALIDSIG"
  37 #define GNUPGGOODSIG "[GNUPG:] GOODSIG"
  38 #define GNUPGKEYEXPIRED "[GNUPG:] KEYEXPIRED"
  39 #define GNUPGREVKEYSIG "[GNUPG:] REVKEYSIG"
  40 #define GNUPGNODATA "[GNUPG:] NODATA"
  41
  42 static const std::array<string, 1> WeakDigests {
  43    "1", // MD5
  44 // "2", // SHA1
  45 // "3", // RIPEMD-160
  46 };
  47
  48 class GPGVMethod : public aptMethod
  49 {
  50    private:
  51    string VerifyGetSigners(const char *file, const char *outfile,
  52                                 std::string const &key,
  53                                 vector<string> &GoodSigners,
  54                                 vector<string> &BadSigners,
  55                                 vector<string> &WorthlessSigners,
  56                                 vector<string> &NoPubKeySigners);
  57
  58    protected:
  59    virtual bool URIAcquire(std::string const &Message, FetchItem *Itm) APT_OVERRIDE;
  60    public:
  61
  62    GPGVMethod() : aptMethod("gpgv","1.0",SingleInstance | SendConfig) {};
  63 };
  64
  65 string GPGVMethod::VerifyGetSigners(const char *file, const char *outfile,
  66                                          std::string const &key,
  67                                          vector<string> &GoodSigners,
  68                                          vector<string> &BadSigners,
  69                                          vector<string> &WorthlessSigners,
  70                                          vector<string> &NoPubKeySigners)
  71 {
  72    bool const Debug = _config->FindB("Debug::Acquire::gpgv", false);
  73
  74    if (Debug == true)
  75       std::clog << "inside VerifyGetSigners" << std::endl;
  76
  77    int fd[2];
  78    bool const keyIsID = (key.empty() == false && key[0] != '/');
  79
  80    if (pipe(fd) < 0)
  81       return "Couldn't create pipe";
  82
  83    pid_t pid = fork();
  84    if (pid < 0)
  85       return string("Couldn't spawn new process") + strerror(errno);
  86    else if (pid == 0)
  87       ExecGPGV(outfile, file, 3, fd, (keyIsID ? "" : key));
  88    close(fd[1]);
  89
  90    FILE *pipein = fdopen(fd[0], "r");
  91
  92    // Loop over the output of apt-key (which really is gnupg), and check the signatures.
  93    std::vector<std::string> ValidSigners;
  94    size_t buffersize = 0;
  95    char *buffer = NULL;
  96    while (1)
  97    {
  98       if (getline(&buffer, &buffersize, pipein) == -1)
  99          break;
 100       if (Debug == true)
 101          std::clog << "Read: " << buffer << std::endl;
 102
 103       // Push the data into three separate vectors, which
 104       // we later concatenate.  They're kept separate so
 105       // if we improve the apt method communication stuff later
 106       // it will be better.
 107       if (strncmp(buffer, GNUPGBADSIG, sizeof(GNUPGBADSIG)-1) == 0)
 108       {
 109          if (Debug == true)
 110             std::clog << "Got BADSIG! " << std::endl;
 111          BadSigners.push_back(string(buffer+sizeof(GNUPGPREFIX)));
 112       }
 113       else if (strncmp(buffer, GNUPGNOPUBKEY, sizeof(GNUPGNOPUBKEY)-1) == 0)
 114       {
 115          if (Debug == true)
 116             std::clog << "Got NO_PUBKEY " << std::endl;
 117          NoPubKeySigners.push_back(string(buffer+sizeof(GNUPGPREFIX)));
 118       }
 119       else if (strncmp(buffer, GNUPGNODATA, sizeof(GNUPGBADSIG)-1) == 0)
 120       {
 121          if (Debug == true)
 122             std::clog << "Got NODATA! " << std::endl;
 123          BadSigners.push_back(string(buffer+sizeof(GNUPGPREFIX)));
 124       }
 125       else if (strncmp(buffer, GNUPGKEYEXPIRED, sizeof(GNUPGKEYEXPIRED)-1) == 0)
 126       {
 127          if (Debug == true)
 128             std::clog << "Got KEYEXPIRED! " << std::endl;
 129          WorthlessSigners.push_back(string(buffer+sizeof(GNUPGPREFIX)));
 130       }
 131       else if (strncmp(buffer, GNUPGREVKEYSIG, sizeof(GNUPGREVKEYSIG)-1) == 0)
 132       {
 133          if (Debug == true)
 134             std::clog << "Got REVKEYSIG! " << std::endl;
 135          WorthlessSigners.push_back(string(buffer+sizeof(GNUPGPREFIX)));
 136       }
 137       else if (strncmp(buffer, GNUPGGOODSIG, sizeof(GNUPGGOODSIG)-1) == 0)
 138       {
 139          char *sig = buffer + sizeof(GNUPGPREFIX);
 140          char *p = sig + sizeof("GOODSIG");
 141          while (*p && isxdigit(*p))
 142             p++;
 143          *p = 0;
 144          if (Debug == true)
 145             std::clog << "Got GOODSIG, key ID:" << sig << std::endl;
 146          GoodSigners.push_back(string(sig));
 147       }
 148       else if (strncmp(buffer, GNUPGVALIDSIG, sizeof(GNUPGVALIDSIG)-1) == 0)
 149       {
 150          char *sig = buffer + sizeof(GNUPGVALIDSIG);
 151          std::istringstream iss((string(sig)));
 152          vector<string> tokens{std::istream_iterator<string>{iss},
 153                                std::istream_iterator<string>{}};
 154          char *p = sig;
 155          while (*p && isxdigit(*p))
 156             p++;
 157          *p = 0;
 158          if (Debug == true)
 159             std::clog << "Got VALIDSIG, key ID: " << sig << std::endl;
 160          // Reject weak digest algorithms
 161          if (std::find(WeakDigests.begin(), WeakDigests.end(), tokens[7]) != WeakDigests.end())
 162          {
 163             // Treat them like an expired key: For that a message about expiry
 164             // is emitted, a VALIDSIG, but no GOODSIG.
 165             WorthlessSigners.push_back("WEAKDIGEST " + string(sig));
 166             GoodSigners.erase(std::remove(GoodSigners.begin(), GoodSigners.end(), string(sig)));
 167          }
 168
 169          ValidSigners.push_back(string(sig));
 170       }
 171    }
 172    fclose(pipein);
 173    free(buffer);
 174
 175    // apt-key has a --keyid parameter, but this requires gpg, so we call it without it
 176    // and instead check after the fact which keyids where used for verification
 177    if (keyIsID == true)
 178    {
 179       if (Debug == true)
 180          std::clog << "GoodSigs needs to be limited to keyid " << key << std::endl;
 181       std::vector<std::string>::iterator const foundItr = std::find(ValidSigners.begin(), ValidSigners.end(), key);
 182       bool const found = (foundItr != ValidSigners.end());
 183       std::copy(GoodSigners.begin(), GoodSigners.end(), std::back_insert_iterator<std::vector<std::string> >(NoPubKeySigners));
 184       if (found)
 185       {
 186          // we look for GOODSIG here as well as an expired sig is a valid sig as well (but not a good one)
 187          std::string const goodlongkeyid = "GOODSIG " + key.substr(24, 16);
 188          bool const foundGood = std::find(GoodSigners.begin(), GoodSigners.end(), goodlongkeyid) != GoodSigners.end();
 189          if (Debug == true)
 190             std::clog << "Key " << key << " is valid sig, is " << goodlongkeyid << " also a good one? " << (foundGood ? "yes" : "no") << std::endl;
 191          GoodSigners.clear();
 192          if (foundGood)
 193          {
 194             GoodSigners.push_back(goodlongkeyid);
 195             NoPubKeySigners.erase(std::remove(NoPubKeySigners.begin(), NoPubKeySigners.end(), goodlongkeyid), NoPubKeySigners.end());
 196          }
 197       }
 198       else
 199          GoodSigners.clear();
 200    }
 201
 202    int status;
 203    waitpid(pid, &status, 0);
 204    if (Debug == true)
 205    {
 206       ioprintf(std::clog, "gpgv exited with status %i\n", WEXITSTATUS(status));
 207    }
 208
 209    if (WEXITSTATUS(status) == 0)
 210    {
 211       if (keyIsID)
 212       {
 213          // gpgv will report success, but we want to enforce a certain keyring
 214          // so if we haven't found the key the valid we found is in fact invalid
 215          if (GoodSigners.empty())
 216             return _("At least one invalid signature was encountered.");
 217       }
 218       else
 219       {
 220          if (GoodSigners.empty())
 221             return _("Internal error: Good signature, but could not determine key fingerprint?!");
 222       }
 223       return "";
 224    }
 225    else if (WEXITSTATUS(status) == 1)
 226       return _("At least one invalid signature was encountered.");
 227    else if (WEXITSTATUS(status) == 111)
 228       return _("Could not execute 'apt-key' to verify signature (is gnupg installed?)");
 229    else if (WEXITSTATUS(status) == 112)
 230    {
 231       // acquire system checks for "NODATA" to generate GPG errors (the others are only warnings)
 232       std::string errmsg;
 233       //TRANSLATORS: %s is a single techy word like 'NODATA'
 234       strprintf(errmsg, _("Clearsigned file isn't valid, got '%s' (does the network require authentication?)"), "NODATA");
 235       return errmsg;
 236    }
 237    else
 238       return _("Unknown error executing apt-key");
 239 }
 240
 241 bool GPGVMethod::URIAcquire(std::string const &Message, FetchItem *Itm)
 242 {
 243    URI const Get = Itm->Uri;
 244    string const Path = Get.Host + Get.Path; // To account for relative paths
 245    std::string const key = LookupTag(Message, "Signed-By");
 246    vector<string> GoodSigners;
 247    vector<string> BadSigners;
 248    // a worthless signature is a expired or revoked one
 249    vector<string> WorthlessSigners;
 250    vector<string> NoPubKeySigners;
 251
 252    FetchResult Res;
 253    Res.Filename = Itm->DestFile;
 254    URIStart(Res);
 255
 256    // Run apt-key on file, extract contents and get the key ID of the signer
 257    string msg = VerifyGetSigners(Path.c_str(), Itm->DestFile.c_str(), key,
 258                                  GoodSigners, BadSigners, WorthlessSigners,
 259                                  NoPubKeySigners);
 260    if (GoodSigners.empty() || !BadSigners.empty() || !NoPubKeySigners.empty())
 261    {
 262       string errmsg;
 263       // In this case, something bad probably happened, so we just go
 264       // with what the other method gave us for an error message.
 265       if (BadSigners.empty() && WorthlessSigners.empty() && NoPubKeySigners.empty())
 266          errmsg = msg;
 267       else
 268       {
 269          if (!BadSigners.empty())
 270          {
 271             errmsg += _("The following signatures were invalid:\n");
 272             for (vector<string>::iterator I = BadSigners.begin();
 273                  I != BadSigners.end(); ++I)
 274                errmsg += (*I + "\n");
 275          }
 276          if (!WorthlessSigners.empty())
 277          {
 278             errmsg += _("The following signatures were invalid:\n");
 279             for (vector<string>::iterator I = WorthlessSigners.begin();
 280                  I != WorthlessSigners.end(); ++I)
 281                errmsg += (*I + "\n");
 282          }
 283          if (!NoPubKeySigners.empty())
 284          {
 285              errmsg += _("The following signatures couldn't be verified because the public key is not available:\n");
 286             for (vector<string>::iterator I = NoPubKeySigners.begin();
 287                  I != NoPubKeySigners.end(); ++I)
 288                errmsg += (*I + "\n");
 289          }
 290       }
 291       // this is only fatal if we have no good sigs or if we have at
 292       // least one bad signature. good signatures and NoPubKey signatures
 293       // happen easily when a file is signed with multiple signatures
 294       if(GoodSigners.empty() or !BadSigners.empty())
 295          return _error->Error("%s", errmsg.c_str());
 296    }
 297
 298    // Just pass the raw output up, because passing it as a real data
 299    // structure is too difficult with the method stuff.  We keep it
 300    // as three separate vectors for future extensibility.
 301    Res.GPGVOutput = GoodSigners;
 302    Res.GPGVOutput.insert(Res.GPGVOutput.end(),BadSigners.begin(),BadSigners.end());
 303    Res.GPGVOutput.insert(Res.GPGVOutput.end(),NoPubKeySigners.begin(),NoPubKeySigners.end());
 304    URIDone(Res);
 305
 306    if (_config->FindB("Debug::Acquire::gpgv", false))
 307    {
 308       std::clog << "apt-key succeeded\n";
 309    }
 310
 311    return true;
 312 }
 313
 314
 315 int main()
 316 {
 317    setlocale(LC_ALL, "");
 318
 319    GPGVMethod Mth;
 320
 321    return Mth.Run();
 322 }