1 files changed, 293 insertions, 0 deletions
diff --git a/src/gpg2ssh/gpg2ssh.c b/src/gpg2ssh/gpg2ssh.c
new file mode 100644
index 0000000..c99f03f
--- /dev/null
+++ b/src/gpg2ssh/gpg2ssh.c
@@ -0,0 +1,293 @@
+#include "gnutls-helpers.h"
+
+#include <gnutls/openpgp.h>
+#include <gnutls/x509.h>
+
+/* for waitpid() */
+#include <sys/types.h>
+#include <sys/wait.h>
+
+/* 
+   Author: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
+   Date: Tue, 08 Apr 2008
+   License: GPL v3 or later
+
+   monkeysphere public key translator: execute this with an GPG
+   certificate (public key(s) + userid(s)) on stdin.  It currently
+   only works with RSA keys.
+
+   It will spit out a version of the first key capable of being used
+   for authentication on stdout.  The output format should be suitable
+   for appending a known_hosts file.
+
+   Requirements: I've only built this so far with GnuTLS v2.3.4 --
+   version 2.2.0 does not contain the appropriate pieces.
+
+ */
+
+int main(int argc, char* argv[]) {
+  gnutls_datum_t data;
+  int ret;
+  gnutls_openpgp_crt_t openpgp_crt;
+  gnutls_openpgp_keyid_t keyid;
+  printable_keyid p_keyid;
+  unsigned int keyidx;
+  unsigned int usage, bits;
+  gnutls_pk_algorithm_t algo;
+
+  gnutls_datum_t m, e, p, q, g, y;
+  gnutls_datum_t algolabel;
+
+  char output_data[10240];
+  char userid[10240];
+  size_t uidsz = sizeof(userid);
+
+  const gnutls_datum_t* all[5];
+  int pipefd;
+  pid_t child_pid;
+  char* const args[] = {"/usr/bin/base64", "--wrap=0", NULL};
+  const char* algoname;
+  int mpicount;
+  int pipestatus;
+
+  init_gnutls();
+  
+  init_datum(&data);
+
+  init_datum(&m);
+  init_datum(&e);
+  init_datum(&p);
+  init_datum(&q);
+  init_datum(&g);
+  init_datum(&y);
+
+  init_datum(&algolabel);
+
+  init_keyid(keyid);
+
+  /* slurp in the private key from stdin */
+  if (ret = set_datum_fd(&data, 0), ret) {
+    err("didn't read file descriptor 0\n");
+    return 1;
+  }
+
+
+  if (ret = gnutls_openpgp_crt_init(&openpgp_crt), ret) {
+    err("Failed to initialize OpenPGP certificate (error: %d)\n", ret);
+    return 1;
+  }
+
+  /* format could be either: GNUTLS_OPENPGP_FMT_RAW,
+     GNUTLS_OPENPGP_FMT_BASE64; if MONKEYSPHERE_RAW is set, use RAW,
+     otherwise, use BASE64: */
+
+  /* FIXME: we should be auto-detecting the input format, and
+     translating it as needed. */
+
+  if (getenv("MONKEYSPHERE_RAW")) {
+    err("assuming RAW formatted certificate\n");
+    if (ret = gnutls_openpgp_crt_import(openpgp_crt, &data, GNUTLS_OPENPGP_FMT_RAW), ret) {
+      err("failed to import the OpenPGP certificate in RAW format (error: %d)\n", ret);
+      return ret;
+    }
+  } else {
+    err("assuming BASE64 formatted certificate\n");
+    if (ret = gnutls_openpgp_crt_import (openpgp_crt, &data, GNUTLS_OPENPGP_FMT_BASE64), ret) {
+      err("failed to import the OpenPGP certificate in BASE64 format (error: %d)\n", ret);
+      return ret;
+    }
+  }
+
+  if (gnutls_openpgp_crt_get_revoked_status(openpgp_crt)) {
+    err("the primary key was revoked!\n");
+    return 1;
+  }
+
+  /* FIXME: We're currently looking at the primary key or maybe the
+     first authentication-capable subkey.  
+
+     Instead, we should be iterating through the primary key and all
+     subkeys: for each one with the authentication usage flag set of a
+     algorithm we can handle, we should output matching UserIDs and
+     the SSH version of the key. */
+     
+
+  if (ret = gnutls_openpgp_crt_get_key_usage(openpgp_crt, &usage), ret) {
+    err("failed to get the usage flags for the primary key (error: %d)\n", ret);
+    return ret;
+  }
+  if (usage & GNUTLS_KEY_KEY_AGREEMENT &&
+      usage & GNUTLS_KEY_KEY_ENCIPHERMENT) {
+    err("the primary key can be used for authentication and communication encryption!\n");
+
+    algo = gnutls_openpgp_crt_get_pk_algorithm(openpgp_crt, &bits);
+    if (algo < 0) {
+      err("failed to get the algorithm of the OpenPGP public key (error: %d)\n", algo);
+      return algo;
+    } else if (algo == GNUTLS_PK_RSA) {
+      
+      err("OpenPGP RSA certificate, with %d bits\n", bits);
+      ret = gnutls_openpgp_crt_get_pk_rsa_raw(openpgp_crt, &m, &e);
+      if (GNUTLS_E_SUCCESS != ret) {
+	err ("failed to export RSA key parameters (error: %d)\n", ret);
+	return 1;
+      }
+    } else if (algo == GNUTLS_PK_DSA) {
+      err("OpenPGP DSA Key, with %d bits\n", bits);
+      ret = gnutls_openpgp_crt_get_pk_dsa_raw(openpgp_crt, &p, &q, &g, &y);
+      if (GNUTLS_E_SUCCESS != ret) {
+	err ("failed to export DSA key parameters (error: %d)\n", ret);
+	return 1;
+      }
+    } else {
+      err("OpenPGP Key was not RSA or DSA -- can't deal! (actual algorithm was: %d)\n", algo);
+      return 1;
+    }
+    
+  } else {
+    err("primary key is not good for authentication and communication encryption.  Trying subkeys...\n");
+    
+    if (ret = gnutls_openpgp_crt_get_auth_subkey(openpgp_crt, keyid, 0), ret) {
+      err("failed to find a subkey capable of authentication and communication encryption (error: %d)\n", ret);
+      return ret;
+    }
+    make_keyid_printable(p_keyid, keyid);
+    err("found authentication subkey %.16s\n", p_keyid);
+
+    ret = gnutls_openpgp_crt_get_subkey_idx(openpgp_crt, keyid);
+    if (ret < 0) {
+      err("could not get the index of subkey %.16s (error: %d)\n", ret);
+      return ret;
+    }
+    keyidx = ret;
+
+    if (gnutls_openpgp_crt_get_subkey_revoked_status(openpgp_crt, keyidx)) {
+      err("The authentication subkey was revoked!\n");
+      return 1;
+    }
+
+    if (ret = gnutls_openpgp_crt_get_subkey_usage(openpgp_crt, keyidx, &usage), ret) {
+      err("could not figure out usage of subkey %.16s (error: %d)\n", p_keyid, ret);
+      return ret;
+    }
+    if ((usage & GNUTLS_KEY_KEY_AGREEMENT) == 0 &&
+	usage & GNUTLS_KEY_KEY_ENCIPHERMENT) {
+      err("could not find a subkey with authentication and communication encryption.\n");
+      return 1;
+    }
+
+    /* switch, based on the algorithm in question, to extract the MPI
+       components: */
+
+    algo = gnutls_openpgp_crt_get_subkey_pk_algorithm(openpgp_crt, keyidx, &bits);
+    if (algo < 0) {
+      err("failed to get the algorithm of the authentication subkey (error: %d)\n", algo);
+      return algo;
+    } else if (algo == GNUTLS_PK_RSA) {
+      
+      err("OpenPGP RSA subkey, with %d bits\n", bits);
+      ret = gnutls_openpgp_crt_get_subkey_pk_rsa_raw(openpgp_crt, keyidx, &m, &e);
+      if (GNUTLS_E_SUCCESS != ret) {
+	err ("failed to export RSA subkey parameters (error: %d)\n", ret);
+	return 1;
+      }
+    } else if (algo == GNUTLS_PK_DSA) {
+      err("OpenPGP DSA subkey, with %d bits\n", bits);
+      ret = gnutls_openpgp_crt_get_subkey_pk_dsa_raw(openpgp_crt, keyidx, &p, &q, &g, &y);
+      if (GNUTLS_E_SUCCESS != ret) {
+	err ("failed to export DSA subkey parameters (error: %d)\n", ret);
+	return 1;
+      }
+    } else {
+      err("OpenPGP subkey was not RSA or DSA -- can't deal! (actual algorithm was: %d)\n", algo);
+      return 1;
+    }
+  } 
+
+  /* make sure userid is NULL-terminated */
+  userid[sizeof(userid) - 1] = 0;
+  uidsz--;
+
+  /* FIXME: we're just choosing the first UserID from the certificate:
+     instead, we should be selecting every User ID that is adequately
+     signed and matches the spec, and aggregating them with commas for
+     known_hosts output */
+
+  if (ret = gnutls_openpgp_crt_get_name(openpgp_crt, 0, userid, &uidsz), ret) {
+    err("Failed to fetch the first UserID (error: %d)\n", ret);
+    return ret;
+  }
+
+  if (ret = validate_ssh_host_userid(userid), ret) {
+    err("bad userid: not a valid ssh host.\n");
+    return ret;
+  }
+
+  /* remove ssh:// from the beginning of userid */
+  memmove(userid, userid + strlen("ssh://"), 1 + strlen(userid) - strlen("ssh://"));
+  
+
+  /* now we have algo, and the various MPI data are set.  Can we
+     export them cleanly? */
+
+  /* for the moment, we'll just dump the info raw, and pipe it
+     externally through coreutils' /usr/bin/base64 */
+
+  if (algo == GNUTLS_PK_RSA) {
+    algoname = "ssh-rsa";
+    mpicount = 3;
+
+    all[0] = &algolabel;
+    all[1] = &e;
+    all[2] = &m;
+  } else if (algo == GNUTLS_PK_DSA) {
+    algoname = "ssh-dss";
+    mpicount = 5;
+
+    all[0] = &algolabel;
+    all[1] = &p;
+    all[2] = &q;
+    all[3] = &g;
+    all[4] = &y;
+  } else {
+    err("no idea what this algorithm is: %d\n", algo);
+    return 1;
+  }
+
+  if (ret = datum_from_string(&algolabel, algoname), ret) {
+    err("couldn't label string (error: %d)\n", ret);
+    return ret;
+  }
+
+  snprintf(output_data, sizeof(output_data), "%s %s ", userid, algoname);
+
+  pipefd = create_writing_pipe(&child_pid, args[0], args);
+  if (pipefd < 0) {
+    err("failed to create a writing pipe (returned %d)\n", pipefd);
+    return pipefd;
+  }
+    
+  write(1, output_data, strlen(output_data));
+
+  if (0 != write_data_fd_with_length(pipefd, all, mpicount)) {
+    err("was not able to write out RSA key data\n");
+    return 1;
+  }
+  close(pipefd);
+  if (child_pid != waitpid(child_pid, &pipestatus, 0)) {
+    err("could not wait for child process to return for some reason.\n");
+    return 1;
+  }
+  if (pipestatus != 0) {
+    err("base64 pipe died with return code %d\n", pipestatus);
+    return pipestatus;
+  }
+
+  write(1, "\n", 1);
+
+
+
+  gnutls_openpgp_crt_deinit(openpgp_crt);
+  gnutls_global_deinit();
+  return 0;
+}