diff options
Diffstat (limited to 'crypto/openssh/auth2-pubkey.c')
| -rw-r--r-- | crypto/openssh/auth2-pubkey.c | 465 |
1 files changed, 465 insertions, 0 deletions
diff --git a/crypto/openssh/auth2-pubkey.c b/crypto/openssh/auth2-pubkey.c new file mode 100644 index 0000000..137887e --- /dev/null +++ b/crypto/openssh/auth2-pubkey.c @@ -0,0 +1,465 @@ +/* $OpenBSD: auth2-pubkey.c,v 1.29 2011/05/23 03:30:07 djm Exp $ */ +/* + * Copyright (c) 2000 Markus Friedl. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <sys/types.h> +#include <sys/stat.h> + +#include <fcntl.h> +#include <pwd.h> +#include <stdio.h> +#include <stdarg.h> +#include <string.h> +#include <time.h> +#include <unistd.h> + +#include "xmalloc.h" +#include "ssh.h" +#include "ssh2.h" +#include "packet.h" +#include "buffer.h" +#include "log.h" +#include "servconf.h" +#include "compat.h" +#include "key.h" +#include "hostfile.h" +#include "auth.h" +#include "pathnames.h" +#include "uidswap.h" +#include "auth-options.h" +#include "canohost.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "misc.h" +#include "authfile.h" +#include "match.h" + +/* import */ +extern ServerOptions options; +extern u_char *session_id2; +extern u_int session_id2_len; + +static int +userauth_pubkey(Authctxt *authctxt) +{ + Buffer b; + Key *key = NULL; + char *pkalg; + u_char *pkblob, *sig; + u_int alen, blen, slen; + int have_sig, pktype; + int authenticated = 0; + + if (!authctxt->valid) { + debug2("userauth_pubkey: disabled because of invalid user"); + return 0; + } + have_sig = packet_get_char(); + if (datafellows & SSH_BUG_PKAUTH) { + debug2("userauth_pubkey: SSH_BUG_PKAUTH"); + /* no explicit pkalg given */ + pkblob = packet_get_string(&blen); + buffer_init(&b); + buffer_append(&b, pkblob, blen); + /* so we have to extract the pkalg from the pkblob */ + pkalg = buffer_get_string(&b, &alen); + buffer_free(&b); + } else { + pkalg = packet_get_string(&alen); + pkblob = packet_get_string(&blen); + } + pktype = key_type_from_name(pkalg); + if (pktype == KEY_UNSPEC) { + /* this is perfectly legal */ + logit("userauth_pubkey: unsupported public key algorithm: %s", + pkalg); + goto done; + } + key = key_from_blob(pkblob, blen); + if (key == NULL) { + error("userauth_pubkey: cannot decode key: %s", pkalg); + goto done; + } + if (key->type != pktype) { + error("userauth_pubkey: type mismatch for decoded key " + "(received %d, expected %d)", key->type, pktype); + goto done; + } + if (have_sig) { + sig = packet_get_string(&slen); + packet_check_eom(); + buffer_init(&b); + if (datafellows & SSH_OLD_SESSIONID) { + buffer_append(&b, session_id2, session_id2_len); + } else { + buffer_put_string(&b, session_id2, session_id2_len); + } + /* reconstruct packet */ + buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); + buffer_put_cstring(&b, authctxt->user); + buffer_put_cstring(&b, + datafellows & SSH_BUG_PKSERVICE ? + "ssh-userauth" : + authctxt->service); + if (datafellows & SSH_BUG_PKAUTH) { + buffer_put_char(&b, have_sig); + } else { + buffer_put_cstring(&b, "publickey"); + buffer_put_char(&b, have_sig); + buffer_put_cstring(&b, pkalg); + } + buffer_put_string(&b, pkblob, blen); +#ifdef DEBUG_PK + buffer_dump(&b); +#endif + /* test for correct signature */ + authenticated = 0; + if (PRIVSEP(user_key_allowed(authctxt->pw, key)) && + PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), + buffer_len(&b))) == 1) + authenticated = 1; + buffer_free(&b); + xfree(sig); + } else { + debug("test whether pkalg/pkblob are acceptable"); + packet_check_eom(); + + /* XXX fake reply and always send PK_OK ? */ + /* + * XXX this allows testing whether a user is allowed + * to login: if you happen to have a valid pubkey this + * message is sent. the message is NEVER sent at all + * if a user is not allowed to login. is this an + * issue? -markus + */ + if (PRIVSEP(user_key_allowed(authctxt->pw, key))) { + packet_start(SSH2_MSG_USERAUTH_PK_OK); + packet_put_string(pkalg, alen); + packet_put_string(pkblob, blen); + packet_send(); + packet_write_wait(); + authctxt->postponed = 1; + } + } + if (authenticated != 1) + auth_clear_options(); +done: + debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg); + if (key != NULL) + key_free(key); + xfree(pkalg); + xfree(pkblob); + return authenticated; +} + +static int +match_principals_option(const char *principal_list, struct KeyCert *cert) +{ + char *result; + u_int i; + + /* XXX percent_expand() sequences for authorized_principals? */ + + for (i = 0; i < cert->nprincipals; i++) { + if ((result = match_list(cert->principals[i], + principal_list, NULL)) != NULL) { + debug3("matched principal from key options \"%.100s\"", + result); + xfree(result); + return 1; + } + } + return 0; +} + +static int +match_principals_file(char *file, struct passwd *pw, struct KeyCert *cert) +{ + FILE *f; + char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts; + u_long linenum = 0; + u_int i; + + temporarily_use_uid(pw); + debug("trying authorized principals file %s", file); + if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { + restore_uid(); + return 0; + } + while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { + /* Skip leading whitespace. */ + for (cp = line; *cp == ' ' || *cp == '\t'; cp++) + ; + /* Skip blank and comment lines. */ + if ((ep = strchr(cp, '#')) != NULL) + *ep = '\0'; + if (!*cp || *cp == '\n') + continue; + /* Trim trailing whitespace. */ + ep = cp + strlen(cp) - 1; + while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) + *ep-- = '\0'; + /* + * If the line has internal whitespace then assume it has + * key options. + */ + line_opts = NULL; + if ((ep = strrchr(cp, ' ')) != NULL || + (ep = strrchr(cp, '\t')) != NULL) { + for (; *ep == ' ' || *ep == '\t'; ep++) + ; + line_opts = cp; + cp = ep; + } + for (i = 0; i < cert->nprincipals; i++) { + if (strcmp(cp, cert->principals[i]) == 0) { + debug3("matched principal from file \"%.100s\"", + cert->principals[i]); + if (auth_parse_options(pw, line_opts, + file, linenum) != 1) + continue; + fclose(f); + restore_uid(); + return 1; + } + } + } + fclose(f); + restore_uid(); + return 0; +} + +/* return 1 if user allows given key */ +static int +user_key_allowed2(struct passwd *pw, Key *key, char *file) +{ + char line[SSH_MAX_PUBKEY_BYTES]; + const char *reason; + int found_key = 0; + FILE *f; + u_long linenum = 0; + Key *found; + char *fp; + + /* Temporarily use the user's uid. */ + temporarily_use_uid(pw); + + debug("trying public key file %s", file); + f = auth_openkeyfile(file, pw, options.strict_modes); + + if (!f) { + restore_uid(); + return 0; + } + + found_key = 0; + found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type); + + while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { + char *cp, *key_options = NULL; + + auth_clear_options(); + + /* Skip leading whitespace, empty and comment lines. */ + for (cp = line; *cp == ' ' || *cp == '\t'; cp++) + ; + if (!*cp || *cp == '\n' || *cp == '#') + continue; + + if (key_read(found, &cp) != 1) { + /* no key? check if there are options for this key */ + int quoted = 0; + debug2("user_key_allowed: check options: '%s'", cp); + key_options = cp; + for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { + if (*cp == '\\' && cp[1] == '"') + cp++; /* Skip both */ + else if (*cp == '"') + quoted = !quoted; + } + /* Skip remaining whitespace. */ + for (; *cp == ' ' || *cp == '\t'; cp++) + ; + if (key_read(found, &cp) != 1) { + debug2("user_key_allowed: advance: '%s'", cp); + /* still no key? advance to next line*/ + continue; + } + } + if (key_is_cert(key)) { + if (!key_equal(found, key->cert->signature_key)) + continue; + if (auth_parse_options(pw, key_options, file, + linenum) != 1) + continue; + if (!key_is_cert_authority) + continue; + fp = key_fingerprint(found, SSH_FP_MD5, + SSH_FP_HEX); + debug("matching CA found: file %s, line %lu, %s %s", + file, linenum, key_type(found), fp); + /* + * If the user has specified a list of principals as + * a key option, then prefer that list to matching + * their username in the certificate principals list. + */ + if (authorized_principals != NULL && + !match_principals_option(authorized_principals, + key->cert)) { + reason = "Certificate does not contain an " + "authorized principal"; + fail_reason: + xfree(fp); + error("%s", reason); + auth_debug_add("%s", reason); + continue; + } + if (key_cert_check_authority(key, 0, 0, + authorized_principals == NULL ? pw->pw_name : NULL, + &reason) != 0) + goto fail_reason; + if (auth_cert_options(key, pw) != 0) { + xfree(fp); + continue; + } + verbose("Accepted certificate ID \"%s\" " + "signed by %s CA %s via %s", key->cert->key_id, + key_type(found), fp, file); + xfree(fp); + found_key = 1; + break; + } else if (key_equal(found, key)) { + if (auth_parse_options(pw, key_options, file, + linenum) != 1) + continue; + if (key_is_cert_authority) + continue; + found_key = 1; + debug("matching key found: file %s, line %lu", + file, linenum); + fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); + verbose("Found matching %s key: %s", + key_type(found), fp); + xfree(fp); + break; + } + } + restore_uid(); + fclose(f); + key_free(found); + if (!found_key) + debug2("key not found"); + return found_key; +} + +/* Authenticate a certificate key against TrustedUserCAKeys */ +static int +user_cert_trusted_ca(struct passwd *pw, Key *key) +{ + char *ca_fp, *principals_file = NULL; + const char *reason; + int ret = 0; + + if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL) + return 0; + + ca_fp = key_fingerprint(key->cert->signature_key, + SSH_FP_MD5, SSH_FP_HEX); + + if (key_in_file(key->cert->signature_key, + options.trusted_user_ca_keys, 1) != 1) { + debug2("%s: CA %s %s is not listed in %s", __func__, + key_type(key->cert->signature_key), ca_fp, + options.trusted_user_ca_keys); + goto out; + } + /* + * If AuthorizedPrincipals is in use, then compare the certificate + * principals against the names in that file rather than matching + * against the username. + */ + if ((principals_file = authorized_principals_file(pw)) != NULL) { + if (!match_principals_file(principals_file, pw, key->cert)) { + reason = "Certificate does not contain an " + "authorized principal"; + fail_reason: + error("%s", reason); + auth_debug_add("%s", reason); + goto out; + } + } + if (key_cert_check_authority(key, 0, 1, + principals_file == NULL ? pw->pw_name : NULL, &reason) != 0) + goto fail_reason; + if (auth_cert_options(key, pw) != 0) + goto out; + + verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s", + key->cert->key_id, key_type(key->cert->signature_key), ca_fp, + options.trusted_user_ca_keys); + ret = 1; + + out: + if (principals_file != NULL) + xfree(principals_file); + if (ca_fp != NULL) + xfree(ca_fp); + return ret; +} + +/* check whether given key is in .ssh/authorized_keys* */ +int +user_key_allowed(struct passwd *pw, Key *key) +{ + u_int success, i; + char *file; + + if (auth_key_is_revoked(key)) + return 0; + if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key)) + return 0; + + success = user_cert_trusted_ca(pw, key); + if (success) + return success; + + for (i = 0; !success && i < options.num_authkeys_files; i++) { + file = expand_authorized_keys( + options.authorized_keys_files[i], pw); + success = user_key_allowed2(pw, key, file); + xfree(file); + } + + return success; +} + +Authmethod method_pubkey = { + "publickey", + userauth_pubkey, + &options.pubkey_authentication +}; |
