diff options
Diffstat (limited to 'sm/certchain.c')
| -rw-r--r-- | sm/certchain.c | 793 |
1 files changed, 793 insertions, 0 deletions
diff --git a/sm/certchain.c b/sm/certchain.c new file mode 100644 index 000000000..6323c725e --- /dev/null +++ b/sm/certchain.c @@ -0,0 +1,793 @@ +/* certchain.c - certificate chain validation + * Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc. + * + * This file is part of GnuPG. + * + * GnuPG 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. + * + * GnuPG 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, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <time.h> +#include <assert.h> + +#include "gpgsm.h" +#include <gcrypt.h> +#include <ksba.h> + +#include "keydb.h" +#include "i18n.h" + +static int +unknown_criticals (KsbaCert cert) +{ + static const char *known[] = { + "2.5.29.15", /* keyUsage */ + "2.5.29.19", /* basic Constraints */ + "2.5.29.32", /* certificatePolicies */ + NULL + }; + int rc = 0, i, idx, crit; + const char *oid; + KsbaError err; + + for (idx=0; !(err=ksba_cert_get_extension (cert, idx, + &oid, &crit, NULL, NULL));idx++) + { + if (!crit) + continue; + for (i=0; known[i] && strcmp (known[i],oid); i++) + ; + if (!known[i]) + { + log_error (_("critical certificate extension %s is not supported\n"), + oid); + rc = gpg_error (GPG_ERR_UNSUPPORTED_CERT); + } + } + if (err && err != -1) + rc = map_ksba_err (err); + + return rc; +} + +static int +allowed_ca (KsbaCert cert, int *chainlen) +{ + KsbaError err; + int flag; + + err = ksba_cert_is_ca (cert, &flag, chainlen); + if (err) + return map_ksba_err (err); + if (!flag) + { + log_error (_("issuer certificate is not marked as a CA\n")); + return gpg_error (GPG_ERR_BAD_CA_CERT); + } + return 0; +} + + +static int +check_cert_policy (KsbaCert cert) +{ + KsbaError err; + char *policies; + FILE *fp; + int any_critical; + + err = ksba_cert_get_cert_policies (cert, &policies); + if (err == KSBA_No_Data) + return 0; /* no policy given */ + if (err) + return map_ksba_err (err); + + /* STRING is a line delimited list of certifiate policies as stored + in the certificate. The line itself is colon delimited where the + first field is the OID of the policy and the second field either + N or C for normal or critical extension */ + + if (opt.verbose > 1) + log_info ("certificate's policy list: %s\n", policies); + + /* The check is very minimal but won't give false positives */ + any_critical = !!strstr (policies, ":C"); + + if (!opt.policy_file) + { + xfree (policies); + if (any_critical) + { + log_error ("critical marked policy without configured policies\n"); + return gpg_error (GPG_ERR_NO_POLICY_MATCH); + } + return 0; + } + + fp = fopen (opt.policy_file, "r"); + if (!fp) + { + log_error ("failed to open `%s': %s\n", + opt.policy_file, strerror (errno)); + xfree (policies); + return gpg_error (GPG_ERR_NO_POLICY_MATCH); + } + + for (;;) + { + int c; + char *p, line[256]; + char *haystack, *allowed; + + /* read line */ + do + { + if (!fgets (line, DIM(line)-1, fp) ) + { + gpg_error_t tmperr; + + xfree (policies); + if (feof (fp)) + { + fclose (fp); + /* with no critical policies this is only a warning */ + if (!any_critical) + { + log_info (_("note: certificate policy not allowed\n")); + return 0; + } + log_error (_("certificate policy not allowed\n")); + return gpg_error (GPG_ERR_NO_POLICY_MATCH); + } + tmperr = gpg_error (gpg_err_code_from_errno (errno)); + fclose (fp); + return tmperr; + } + + if (!*line || line[strlen(line)-1] != '\n') + { + /* eat until end of line */ + while ( (c=getc (fp)) != EOF && c != '\n') + ; + fclose (fp); + xfree (policies); + return gpg_error (*line? GPG_ERR_LINE_TOO_LONG + : GPG_ERR_INCOMPLETE_LINE); + } + + /* Allow for empty lines and spaces */ + for (p=line; spacep (p); p++) + ; + } + while (!*p || *p == '\n' || *p == '#'); + + /* parse line */ + for (allowed=line; spacep (allowed); allowed++) + ; + p = strpbrk (allowed, " :\n"); + if (!*p || p == allowed) + { + fclose (fp); + xfree (policies); + return gpg_error (GPG_ERR_CONFIGURATION); + } + *p = 0; /* strip the rest of the line */ + /* See whether we find ALLOWED (which is an OID) in POLICIES */ + for (haystack=policies; (p=strstr (haystack, allowed)); haystack = p+1) + { + if ( !(p == policies || p[-1] == '\n') ) + continue; /* does not match the begin of a line */ + if (p[strlen (allowed)] != ':') + continue; /* the length does not match */ + /* Yep - it does match so return okay */ + fclose (fp); + xfree (policies); + return 0; + } + } +} + + +static void +find_up_store_certs_cb (void *cb_value, KsbaCert cert) +{ + if (keydb_store_cert (cert, 1, NULL)) + log_error ("error storing issuer certificate as ephemeral\n"); + ++*(int*)cb_value; +} + + +static int +find_up (KEYDB_HANDLE kh, KsbaCert cert, const char *issuer) +{ + KsbaName authid; + KsbaSexp authidno; + int rc = -1; + + if (!ksba_cert_get_auth_key_id (cert, NULL, &authid, &authidno)) + { + const char *s = ksba_name_enum (authid, 0); + if (s && *authidno) + { + rc = keydb_search_issuer_sn (kh, s, authidno); + if (rc) + keydb_search_reset (kh); + if (rc == -1) + { /* And try the ephemeral DB. */ + int old = keydb_set_ephemeral (kh, 1); + if (!old) + { + rc = keydb_search_issuer_sn (kh, s, authidno); + if (rc) + keydb_search_reset (kh); + } + keydb_set_ephemeral (kh, old); + } + } + /* print a note so that the user does not feel too helpless when + an issuer certificate was found and gpgsm prints BAD + signature becuase it is not the correct one. */ + if (rc == -1) + { + log_info ("issuer certificate (#"); + gpgsm_dump_serial (authidno); + log_printf ("/"); + gpgsm_dump_string (s); + log_printf (") not found\n"); + } + else if (rc) + log_error ("failed to find authorityKeyIdentifier: rc=%d\n", rc); + ksba_name_release (authid); + xfree (authidno); + /* Fixme: don't know how to do dirmngr lookup with serial+issuer. */ + } + + if (rc) /* not found via authorithyKeyIdentifier, try regular issuer name */ + rc = keydb_search_subject (kh, issuer); + if (rc == -1) + { + /* Not found, lets see whether we have one in the ephemeral key DB. */ + int old = keydb_set_ephemeral (kh, 1); + if (!old) + { + keydb_search_reset (kh); + rc = keydb_search_subject (kh, issuer); + } + keydb_set_ephemeral (kh, old); + } + + if (rc == -1 && opt.auto_issuer_key_retrieve) + { + STRLIST names = NULL; + int count = 0; + char *pattern; + const char *s; + + if (opt.verbose) + log_info (_("looking up issuer at external location\n")); + /* dirmngr is confused about unknown attributes so has a quick + and ugly hack we locate the CN and use this and the + following. Fixme: we should have far better parsing in the + dirmngr. */ + s = strstr (issuer, "CN="); + if (!s || s == issuer || s[-1] != ',') + s = issuer; + + pattern = xtrymalloc (strlen (s)+2); + if (!pattern) + return OUT_OF_CORE (errno); + strcpy (stpcpy (pattern, "/"), s); + add_to_strlist (&names, pattern); + xfree (pattern); + rc = gpgsm_dirmngr_lookup (NULL, names, find_up_store_certs_cb, &count); + free_strlist (names); + if (opt.verbose) + log_info (_("number of issuers matching: %d\n"), count); + if (rc) + { + log_error ("external key lookup failed: %s\n", gpg_strerror (rc)); + rc = -1; + } + else if (!count) + rc = -1; + else + { + int old; + /* The issuers are currently stored in the ephemeral key + DB, so we temporary switch to ephemeral mode. */ + old = keydb_set_ephemeral (kh, 1); + keydb_search_reset (kh); + rc = keydb_search_subject (kh, issuer); + keydb_set_ephemeral (kh, old); + } + } + return rc; +} + + +/* Return the next certificate up in the chain starting at START. + Returns -1 when there are no more certificates. */ +int +gpgsm_walk_cert_chain (KsbaCert start, KsbaCert *r_next) +{ + int rc = 0; + char *issuer = NULL; + char *subject = NULL; + KEYDB_HANDLE kh = keydb_new (0); + + *r_next = NULL; + if (!kh) + { + log_error (_("failed to allocated keyDB handle\n")); + rc = gpg_error (GPG_ERR_GENERAL); + goto leave; + } + + issuer = ksba_cert_get_issuer (start, 0); + subject = ksba_cert_get_subject (start, 0); + if (!issuer) + { + log_error ("no issuer found in certificate\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + if (!subject) + { + log_error ("no subject found in certificate\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + + if (!strcmp (issuer, subject)) + { + rc = -1; /* we are at the root */ + goto leave; + } + + rc = find_up (kh, start, issuer); + if (rc) + { + /* it is quite common not to have a certificate, so better don't + print an error here */ + if (rc != -1 && opt.verbose > 1) + log_error ("failed to find issuer's certificate: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_MISSING_CERT); + goto leave; + } + + rc = keydb_get_cert (kh, r_next); + if (rc) + { + log_error ("failed to get cert: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_GENERAL); + } + + leave: + xfree (issuer); + xfree (subject); + keydb_release (kh); + return rc; +} + + +/* Check whether the CERT is a root certificate. Returns True if this + is the case. */ +int +gpgsm_is_root_cert (KsbaCert cert) +{ + char *issuer; + char *subject; + int yes; + + issuer = ksba_cert_get_issuer (cert, 0); + subject = ksba_cert_get_subject (cert, 0); + yes = (issuer && subject && !strcmp (issuer, subject)); + xfree (issuer); + xfree (subject); + return yes; +} + + +/* Validate a chain and optionally return the nearest expiration time + in R_EXPTIME */ +int +gpgsm_validate_chain (CTRL ctrl, KsbaCert cert, time_t *r_exptime) +{ + int rc = 0, depth = 0, maxdepth; + char *issuer = NULL; + char *subject = NULL; + KEYDB_HANDLE kh = keydb_new (0); + KsbaCert subject_cert = NULL, issuer_cert = NULL; + time_t current_time = gnupg_get_time (); + time_t exptime = 0; + int any_expired = 0; + int any_revoked = 0; + int any_no_crl = 0; + int any_crl_too_old = 0; + int any_no_policy_match = 0; + + if (r_exptime) + *r_exptime = 0; + + if (opt.no_chain_validation) + { + log_info ("WARNING: bypassing certificate chain validation\n"); + return 0; + } + + if (!kh) + { + log_error (_("failed to allocated keyDB handle\n")); + rc = gpg_error (GPG_ERR_GENERAL); + goto leave; + } + + if (DBG_X509) + gpgsm_dump_cert ("subject", cert); + + subject_cert = cert; + maxdepth = 50; + + for (;;) + { + xfree (issuer); + xfree (subject); + issuer = ksba_cert_get_issuer (subject_cert, 0); + subject = ksba_cert_get_subject (subject_cert, 0); + + if (!issuer) + { + log_error ("no issuer found in certificate\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + + { + time_t not_before, not_after; + + not_before = ksba_cert_get_validity (subject_cert, 0); + not_after = ksba_cert_get_validity (subject_cert, 1); + if (not_before == (time_t)(-1) || not_after == (time_t)(-1)) + { + log_error ("certificate with invalid validity\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + + if (not_after) + { + if (!exptime) + exptime = not_after; + else if (not_after < exptime) + exptime = not_after; + } + + if (not_before && current_time < not_before) + { + log_error ("certificate too young; valid from "); + gpgsm_dump_time (not_before); + log_printf ("\n"); + rc = gpg_error (GPG_ERR_CERT_TOO_YOUNG); + goto leave; + } + if (not_after && current_time > not_after) + { + log_error ("certificate has expired at "); + gpgsm_dump_time (not_after); + log_printf ("\n"); + any_expired = 1; + } + } + + rc = unknown_criticals (subject_cert); + if (rc) + goto leave; + + if (!opt.no_policy_check) + { + rc = check_cert_policy (subject_cert); + if (gpg_err_code (rc) == GPG_ERR_NO_POLICY_MATCH) + { + any_no_policy_match = 1; + rc = 1; + } + else if (rc) + goto leave; + } + + if (!opt.no_crl_check) + { + rc = gpgsm_dirmngr_isvalid (subject_cert); + if (rc) + { + switch (rc) + { + case GPG_ERR_CERT_REVOKED: + log_error (_("the certificate has been revoked\n")); + any_revoked = 1; + break; + case GPG_ERR_NO_CRL_KNOWN: + log_error (_("no CRL found for certificate\n")); + any_no_crl = 1; + break; + case GPG_ERR_CRL_TOO_OLD: + log_error (_("the available CRL is too old\n")); + log_info (_("please make sure that the " + "\"dirmngr\" is properly installed\n")); + any_crl_too_old = 1; + break; + default: + log_error (_("checking the CRL failed: %s\n"), + gpg_strerror (rc)); + goto leave; + } + rc = 0; + } + } + + if (subject && !strcmp (issuer, subject)) + { + if (gpgsm_check_cert_sig (subject_cert, subject_cert) ) + { + log_error ("selfsigned certificate has a BAD signatures\n"); + rc = gpg_error (depth? GPG_ERR_BAD_CERT_CHAIN + : GPG_ERR_BAD_CERT); + goto leave; + } + rc = allowed_ca (subject_cert, NULL); + if (rc) + goto leave; + + rc = gpgsm_agent_istrusted (subject_cert); + if (!rc) + ; + else if (gpg_err_code (rc) == GPG_ERR_NOT_TRUSTED) + { + int rc2; + + char *fpr = gpgsm_get_fingerprint_string (subject_cert, + GCRY_MD_SHA1); + log_info (_("root certificate is not marked trusted\n")); + log_info (_("fingerprint=%s\n"), fpr? fpr : "?"); + xfree (fpr); + rc2 = gpgsm_agent_marktrusted (subject_cert); + if (!rc2) + { + log_info (_("root certificate has now" + " been marked as trusted\n")); + rc = 0; + } + else + { + gpgsm_dump_cert ("issuer", subject_cert); + log_info ("after checking the fingerprint, you may want " + "to enter it manually into " + "\"~/.gnupg-test/trustlist.txt\"\n"); + } + } + else + { + log_error (_("checking the trust list failed: %s\n"), + gpg_strerror (rc)); + } + + break; /* okay, a self-signed certicate is an end-point */ + } + + depth++; + if (depth > maxdepth) + { + log_error (_("certificate chain too long\n")); + rc = gpg_error (GPG_ERR_BAD_CERT_CHAIN); + goto leave; + } + + /* find the next cert up the tree */ + keydb_search_reset (kh); + rc = find_up (kh, subject_cert, issuer); + if (rc) + { + if (rc == -1) + { + log_info ("issuer certificate (#/"); + gpgsm_dump_string (issuer); + log_printf (") not found\n"); + } + else + log_error ("failed to find issuer's certificate: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_MISSING_CERT); + goto leave; + } + + ksba_cert_release (issuer_cert); issuer_cert = NULL; + rc = keydb_get_cert (kh, &issuer_cert); + if (rc) + { + log_error ("failed to get cert: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_GENERAL); + goto leave; + } + + if (DBG_X509) + { + log_debug ("got issuer's certificate:\n"); + gpgsm_dump_cert ("issuer", issuer_cert); + } + + if (gpgsm_check_cert_sig (issuer_cert, subject_cert) ) + { + log_error ("certificate has a BAD signatures\n"); + rc = gpg_error (GPG_ERR_BAD_CERT_CHAIN); + goto leave; + } + + { + int chainlen; + rc = allowed_ca (issuer_cert, &chainlen); + if (rc) + goto leave; + if (chainlen >= 0 && (depth - 1) > chainlen) + { + log_error (_("certificate chain longer than allowed by CA (%d)\n"), + chainlen); + rc = gpg_error (GPG_ERR_BAD_CERT_CHAIN); + goto leave; + } + } + + rc = gpgsm_cert_use_cert_p (issuer_cert); + if (rc) + { + char numbuf[50]; + sprintf (numbuf, "%d", rc); + gpgsm_status2 (ctrl, STATUS_ERROR, "certcert.issuer.keyusage", + numbuf, NULL); + rc = 0; + } + + if (opt.verbose) + log_info ("certificate is good\n"); + + keydb_search_reset (kh); + subject_cert = issuer_cert; + issuer_cert = NULL; + } + + if (opt.no_policy_check) + log_info ("policies not checked due to --disable-policy-checks option\n"); + if (opt.no_crl_check) + log_info ("CRLs not checked due to --disable-crl-checks option\n"); + + if (!rc) + { /* If we encountered an error somewhere during the checks, set + the error code to the most critical one */ + if (any_revoked) + rc = gpg_error (GPG_ERR_CERT_REVOKED); + else if (any_no_crl) + rc = gpg_error (GPG_ERR_NO_CRL_KNOWN); + else if (any_crl_too_old) + rc = gpg_error (GPG_ERR_CRL_TOO_OLD); + else if (any_no_policy_match) + rc = gpg_error (GPG_ERR_NO_POLICY_MATCH); + else if (any_expired) + rc = gpg_error (GPG_ERR_CERT_EXPIRED); + } + + leave: + if (r_exptime) + *r_exptime = exptime; + xfree (issuer); + keydb_release (kh); + ksba_cert_release (issuer_cert); + if (subject_cert != cert) + ksba_cert_release (subject_cert); + return rc; +} + + +/* Check that the given certificate is valid but DO NOT check any + constraints. We assume that the issuers certificate is already in + the DB and that this one is valid; which it should be because it + has been checked using this function. */ +int +gpgsm_basic_cert_check (KsbaCert cert) +{ + int rc = 0; + char *issuer = NULL; + char *subject = NULL; + KEYDB_HANDLE kh = keydb_new (0); + KsbaCert issuer_cert = NULL; + + if (opt.no_chain_validation) + { + log_info ("WARNING: bypassing basic certificate checks\n"); + return 0; + } + + if (!kh) + { + log_error (_("failed to allocated keyDB handle\n")); + rc = gpg_error (GPG_ERR_GENERAL); + goto leave; + } + + issuer = ksba_cert_get_issuer (cert, 0); + subject = ksba_cert_get_subject (cert, 0); + if (!issuer) + { + log_error ("no issuer found in certificate\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + + if (subject && !strcmp (issuer, subject)) + { + if (gpgsm_check_cert_sig (cert, cert) ) + { + log_error ("selfsigned certificate has a BAD signatures\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + } + else + { + /* find the next cert up the tree */ + keydb_search_reset (kh); + rc = find_up (kh, cert, issuer); + if (rc) + { + if (rc == -1) + { + log_info ("issuer certificate (#/"); + gpgsm_dump_string (issuer); + log_printf (") not found\n"); + } + else + log_error ("failed to find issuer's certificate: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_MISSING_CERT); + goto leave; + } + + ksba_cert_release (issuer_cert); issuer_cert = NULL; + rc = keydb_get_cert (kh, &issuer_cert); + if (rc) + { + log_error ("failed to get cert: rc=%d\n", rc); + rc = gpg_error (GPG_ERR_GENERAL); + goto leave; + } + + if (gpgsm_check_cert_sig (issuer_cert, cert) ) + { + log_error ("certificate has a BAD signatures\n"); + rc = gpg_error (GPG_ERR_BAD_CERT); + goto leave; + } + if (opt.verbose) + log_info ("certificate is good\n"); + } + + leave: + xfree (issuer); + keydb_release (kh); + ksba_cert_release (issuer_cert); + return rc; +} + |