=================================================================== RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/ssh/auth2.c,v retrieving revision 1.89.2.5 retrieving revision 1.90 diff -u -r1.89.2.5 -r1.90 --- src/usr.bin/ssh/auth2.c 2003/04/03 22:35:16 1.89.2.5 +++ src/usr.bin/ssh/auth2.c 2002/05/12 23:53:45 1.90 @@ -23,17 +23,33 @@ */ #include "includes.h" -RCSID("$OpenBSD: auth2.c,v 1.89.2.5 2003/04/03 22:35:16 miod Exp $"); +RCSID("$OpenBSD: auth2.c,v 1.90 2002/05/12 23:53:45 djm Exp $"); +#include + #include "ssh2.h" #include "xmalloc.h" +#include "rsa.h" +#include "sshpty.h" #include "packet.h" +#include "buffer.h" #include "log.h" #include "servconf.h" #include "compat.h" +#include "channels.h" +#include "bufaux.h" #include "auth.h" +#include "session.h" #include "dispatch.h" +#include "key.h" +#include "cipher.h" +#include "kex.h" #include "pathnames.h" +#include "uidswap.h" +#include "auth-options.h" +#include "hostfile.h" +#include "canohost.h" +#include "match.h" #include "monitor_wrap.h" /* import */ @@ -42,22 +58,13 @@ extern int session_id2_len; Authctxt *x_authctxt = NULL; +static int one = 1; -/* methods */ - -extern Authmethod method_none; -extern Authmethod method_pubkey; -extern Authmethod method_passwd; -extern Authmethod method_kbdint; -extern Authmethod method_hostbased; - -Authmethod *authmethods[] = { - &method_none, - &method_pubkey, - &method_passwd, - &method_kbdint, - &method_hostbased, - NULL +typedef struct Authmethod Authmethod; +struct Authmethod { + char *name; + int (*userauth)(Authctxt *authctxt); + int *enabled; }; /* protocol */ @@ -71,6 +78,33 @@ int user_key_allowed(struct passwd *, Key *); int hostbased_key_allowed(struct passwd *, const char *, char *, Key *); +/* auth */ +static void userauth_banner(void); +static int userauth_none(Authctxt *); +static int userauth_passwd(Authctxt *); +static int userauth_pubkey(Authctxt *); +static int userauth_hostbased(Authctxt *); +static int userauth_kbdint(Authctxt *); + +Authmethod authmethods[] = { + {"none", + userauth_none, + &one}, + {"publickey", + userauth_pubkey, + &options.pubkey_authentication}, + {"password", + userauth_passwd, + &options.password_authentication}, + {"keyboard-interactive", + userauth_kbdint, + &options.kbd_interactive_authentication}, + {"hostbased", + userauth_hostbased, + &options.hostbased_authentication}, + {NULL, NULL, NULL} +}; + /* * loop until authctxt->success == TRUE */ @@ -98,7 +132,7 @@ { Authctxt *authctxt = ctxt; u_int len; - int acceptit = 0; + int accept = 0; char *service = packet_get_string(&len); packet_check_eom(); @@ -107,14 +141,14 @@ if (strcmp(service, "ssh-userauth") == 0) { if (!authctxt->success) { - acceptit = 1; + accept = 1; /* now we can handle user-auth requests */ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); } } /* XXX all other service requests are denied */ - if (acceptit) { + if (accept) { packet_start(SSH2_MSG_SERVICE_ACCEPT); packet_put_cstring(service); packet_send(); @@ -227,6 +261,304 @@ } } +char * +auth2_read_banner(void) +{ + struct stat st; + char *banner = NULL; + off_t len, n; + int fd; + + if ((fd = open(options.banner, O_RDONLY)) == -1) + return (NULL); + if (fstat(fd, &st) == -1) { + close(fd); + return (NULL); + } + len = st.st_size; + banner = xmalloc(len + 1); + n = atomicio(read, fd, banner, len); + close(fd); + + if (n != len) { + free(banner); + return (NULL); + } + banner[n] = '\0'; + + return (banner); +} + +static void +userauth_banner(void) +{ + char *banner = NULL; + + if (options.banner == NULL || (datafellows & SSH_BUG_BANNER)) + return; + + if ((banner = PRIVSEP(auth2_read_banner())) == NULL) + goto done; + + packet_start(SSH2_MSG_USERAUTH_BANNER); + packet_put_cstring(banner); + packet_put_cstring(""); /* language, unused */ + packet_send(); + debug("userauth_banner: sent"); +done: + if (banner) + xfree(banner); + return; +} + +static int +userauth_none(Authctxt *authctxt) +{ + /* disable method "none", only allowed one time */ + Authmethod *m = authmethod_lookup("none"); + if (m != NULL) + m->enabled = NULL; + packet_check_eom(); + userauth_banner(); + return (authctxt->valid ? PRIVSEP(auth_password(authctxt, "")) : 0); +} + +static int +userauth_passwd(Authctxt *authctxt) +{ + char *password; + int authenticated = 0; + int change; + u_int len; + change = packet_get_char(); + if (change) + log("password change not supported"); + password = packet_get_string(&len); + packet_check_eom(); + if (authctxt->valid && + PRIVSEP(auth_password(authctxt, password)) == 1) + authenticated = 1; + memset(password, 0, len); + xfree(password); + return authenticated; +} + +static int +userauth_kbdint(Authctxt *authctxt) +{ + int authenticated = 0; + char *lang, *devs; + + lang = packet_get_string(NULL); + devs = packet_get_string(NULL); + packet_check_eom(); + + debug("keyboard-interactive devs %s", devs); + + if (options.challenge_response_authentication) + authenticated = auth2_challenge(authctxt, devs); + + xfree(devs); + xfree(lang); + return authenticated; +} + +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 */ + log("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_clear(&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 +userauth_hostbased(Authctxt *authctxt) +{ + Buffer b; + Key *key = NULL; + char *pkalg, *cuser, *chost, *service; + u_char *pkblob, *sig; + u_int alen, blen, slen; + int pktype; + int authenticated = 0; + + if (!authctxt->valid) { + debug2("userauth_hostbased: disabled because of invalid user"); + return 0; + } + pkalg = packet_get_string(&alen); + pkblob = packet_get_string(&blen); + chost = packet_get_string(NULL); + cuser = packet_get_string(NULL); + sig = packet_get_string(&slen); + + debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d", + cuser, chost, pkalg, slen); +#ifdef DEBUG_PK + debug("signature:"); + buffer_init(&b); + buffer_append(&b, sig, slen); + buffer_dump(&b); + buffer_free(&b); +#endif + pktype = key_type_from_name(pkalg); + if (pktype == KEY_UNSPEC) { + /* this is perfectly legal */ + log("userauth_hostbased: unsupported " + "public key algorithm: %s", pkalg); + goto done; + } + key = key_from_blob(pkblob, blen); + if (key == NULL) { + error("userauth_hostbased: cannot decode key: %s", pkalg); + goto done; + } + if (key->type != pktype) { + error("userauth_hostbased: type mismatch for decoded key " + "(received %d, expected %d)", key->type, pktype); + goto done; + } + service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" : + authctxt->service; + buffer_init(&b); + 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, service); + buffer_put_cstring(&b, "hostbased"); + buffer_put_string(&b, pkalg, alen); + buffer_put_string(&b, pkblob, blen); + buffer_put_cstring(&b, chost); + buffer_put_cstring(&b, cuser); +#ifdef DEBUG_PK + buffer_dump(&b); +#endif + /* test for allowed key and correct signature */ + authenticated = 0; + if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) && + PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), + buffer_len(&b))) == 1) + authenticated = 1; + + buffer_clear(&b); +done: + debug2("userauth_hostbased: authenticated %d", authenticated); + if (key != NULL) + key_free(key); + xfree(pkalg); + xfree(pkblob); + xfree(cuser); + xfree(chost); + xfree(sig); + return authenticated; +} + /* get current user */ struct passwd* @@ -240,20 +572,18 @@ static char * authmethods_get(void) { + Authmethod *method = NULL; Buffer b; char *list; - int i; buffer_init(&b); - for (i = 0; authmethods[i] != NULL; i++) { - if (strcmp(authmethods[i]->name, "none") == 0) + for (method = authmethods; method->name != NULL; method++) { + if (strcmp(method->name, "none") == 0) continue; - if (authmethods[i]->enabled != NULL && - *(authmethods[i]->enabled) != 0) { + if (method->enabled != NULL && *(method->enabled) != 0) { if (buffer_len(&b) > 0) buffer_append(&b, ",", 1); - buffer_append(&b, authmethods[i]->name, - strlen(authmethods[i]->name)); + buffer_append(&b, method->name, strlen(method->name)); } } buffer_append(&b, "\0", 1); @@ -265,15 +595,174 @@ static Authmethod * authmethod_lookup(const char *name) { - int i; - + Authmethod *method = NULL; if (name != NULL) - for (i = 0; authmethods[i] != NULL; i++) - if (authmethods[i]->enabled != NULL && - *(authmethods[i]->enabled) != 0 && - strcmp(name, authmethods[i]->name) == 0) - return authmethods[i]; - debug2("Unrecognized authentication method name: %s", - name ? name : "NULL"); + for (method = authmethods; method->name != NULL; method++) + if (method->enabled != NULL && + *(method->enabled) != 0 && + strcmp(name, method->name) == 0) + return method; + debug2("Unrecognized authentication method name: %s", name ? name : "NULL"); return NULL; +} + +/* return 1 if user allows given key */ +static int +user_key_allowed2(struct passwd *pw, Key *key, char *file) +{ + char line[8192]; + int found_key = 0; + FILE *f; + u_long linenum = 0; + struct stat st; + Key *found; + char *fp; + + if (pw == NULL) + return 0; + + /* Temporarily use the user's uid. */ + temporarily_use_uid(pw); + + debug("trying public key file %s", file); + + /* Fail quietly if file does not exist */ + if (stat(file, &st) < 0) { + /* Restore the privileged uid. */ + restore_uid(); + return 0; + } + /* Open the file containing the authorized keys. */ + f = fopen(file, "r"); + if (!f) { + /* Restore the privileged uid. */ + restore_uid(); + return 0; + } + if (options.strict_modes && + secure_filename(f, file, pw, line, sizeof(line)) != 0) { + fclose(f); + log("Authentication refused: %s", line); + restore_uid(); + return 0; + } + + found_key = 0; + found = key_new(key->type); + + while (fgets(line, sizeof(line), f)) { + char *cp, *options = NULL; + linenum++; + /* 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); + 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_equal(found, key) && + auth_parse_options(pw, options, file, linenum) == 1) { + 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; +} + +/* check whether given key is in .ssh/authorized_keys* */ +int +user_key_allowed(struct passwd *pw, Key *key) +{ + int success; + char *file; + + file = authorized_keys_file(pw); + success = user_key_allowed2(pw, key, file); + xfree(file); + if (success) + return success; + + /* try suffix "2" for backward compat, too */ + file = authorized_keys_file2(pw); + success = user_key_allowed2(pw, key, file); + xfree(file); + return success; +} + +/* return 1 if given hostkey is allowed */ +int +hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost, + Key *key) +{ + const char *resolvedname, *ipaddr, *lookup; + HostStatus host_status; + int len; + + resolvedname = get_canonical_hostname(options.verify_reverse_mapping); + ipaddr = get_remote_ipaddr(); + + debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s", + chost, resolvedname, ipaddr); + + if (options.hostbased_uses_name_from_packet_only) { + if (auth_rhosts2(pw, cuser, chost, chost) == 0) + return 0; + lookup = chost; + } else { + if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { + debug2("stripping trailing dot from chost %s", chost); + chost[len - 1] = '\0'; + } + if (strcasecmp(resolvedname, chost) != 0) + log("userauth_hostbased mismatch: " + "client sends %s, but we resolve %s to %s", + chost, ipaddr, resolvedname); + if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) + return 0; + lookup = resolvedname; + } + debug2("userauth_hostbased: access allowed by auth_rhosts2"); + + host_status = check_key_in_hostfiles(pw, key, lookup, + _PATH_SSH_SYSTEM_HOSTFILE, + options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); + + /* backward compat if no key has been found. */ + if (host_status == HOST_NEW) + host_status = check_key_in_hostfiles(pw, key, lookup, + _PATH_SSH_SYSTEM_HOSTFILE2, + options.ignore_user_known_hosts ? NULL : + _PATH_SSH_USER_HOSTFILE2); + + return (host_status == HOST_OK); }