X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/6e9e952088e8aa586060aa2464a19186f3d58341..d40a94b97d318ea943d466abf6c123a71bcbf87a:/ssh.c diff --git a/ssh.c b/ssh.c index da2ca51f..1077b335 100644 --- a/ssh.c +++ b/ssh.c @@ -122,6 +122,12 @@ #define SSH2_EXTENDED_DATA_STDERR 1 /* 0x1 */ +/* + * Various remote-bug flags. + */ +#define BUG_CHOKES_ON_SSH1_IGNORE 1 +#define BUG_SSH2_HMAC 2 + #define GET_32BIT(cp) \ (((unsigned long)(unsigned char)(cp)[0] << 24) | \ ((unsigned long)(unsigned char)(cp)[1] << 16) | \ @@ -173,9 +179,7 @@ const static struct ssh2_ciphers *ciphers[] = { }; const static struct ssh_kex *kex_algs[] = { -#ifdef DO_DIFFIE_HELLMAN_GEX &ssh_diffiehellman_gex, -#endif &ssh_diffiehellman }; const static struct ssh_signkey *hostkey_algs[] = { &ssh_rsa, &ssh_dss }; @@ -196,10 +200,12 @@ static int ssh_comp_none_block(unsigned char *block, int len, unsigned char **outblock, int *outlen) { return 0; } +static int ssh_comp_none_disable(void) { return 0; } const static struct ssh_compress ssh_comp_none = { "none", ssh_comp_none_init, ssh_comp_none_block, - ssh_comp_none_init, ssh_comp_none_block + ssh_comp_none_init, ssh_comp_none_block, + ssh_comp_none_disable }; extern const struct ssh_compress ssh_zlib; const static struct ssh_compress *compressions[] = { @@ -252,6 +258,7 @@ static unsigned char session_key[32]; static int ssh1_compressing; static int ssh_agentfwd_enabled; static int ssh_X11_fwd_enabled; +static int ssh_remote_bugs; static const struct ssh_cipher *cipher = NULL; static const struct ssh2_cipher *cscipher = NULL; static const struct ssh2_cipher *sccipher = NULL; @@ -262,7 +269,8 @@ static const struct ssh_compress *sccomp = NULL; static const struct ssh_kex *kex = NULL; static const struct ssh_signkey *hostkey = NULL; static unsigned char ssh2_session_id[20]; -int (*ssh_get_password)(const char *prompt, char *str, int maxlen) = NULL; +int (*ssh_get_line)(const char *prompt, char *str, int maxlen, + int is_pw) = NULL; static char *savedhost; static int savedport; @@ -659,15 +667,16 @@ static int s_wrpkt_prepare(void) { pktout.body[-1] = pktout.type; +#if 0 + debug(("Packet payload pre-compression:\n")); + for (i = -1; i < pktout.length; i++) + debug((" %02x", (unsigned char)pktout.body[i])); + debug(("\r\n")); +#endif + if (ssh1_compressing) { unsigned char *compblk; int complen; -#if 0 - debug(("Packet payload pre-compression:\n")); - for (i = -1; i < pktout.length; i++) - debug((" %02x", (unsigned char)pktout.body[i])); - debug(("\r\n")); -#endif zlib_compress_block(pktout.body-1, pktout.length+1, &compblk, &complen); ssh1_pktout_size(complen-1); @@ -1090,6 +1099,41 @@ static Bignum ssh2_pkt_getmp(void) { return b; } +/* + * Examine the remote side's version string and compare it against + * a list of known buggy implementations. + */ +static void ssh_detect_bugs(char *vstring) { + char *imp; /* pointer to implementation part */ + imp = vstring; + imp += strcspn(imp, "-"); + imp += strcspn(imp, "-"); + + ssh_remote_bugs = 0; + + if (!strcmp(imp, "1.2.18") || !strcmp(imp, "1.2.19") || + !strcmp(imp, "1.2.20") || !strcmp(imp, "1.2.21") || + !strcmp(imp, "1.2.22")) { + /* + * These versions don't support SSH1_MSG_IGNORE, so we have + * to use a different defence against password length + * sniffing. + */ + ssh_remote_bugs |= BUG_CHOKES_ON_SSH1_IGNORE; + logevent("We believe remote version has SSH1 ignore bug"); + } + + if (!strncmp(imp, "2.1.0", 5) || !strncmp(imp, "2.0.", 4) || + !strncmp(imp, "2.2.0", 5) || !strncmp(imp, "2.3.0", 5) || + !strncmp(imp, "2.1 ", 4)) { + /* + * These versions have the HMAC bug. + */ + ssh_remote_bugs |= BUG_SSH2_HMAC; + logevent("We believe remote version has SSH2 HMAC bug"); + } +} + static int do_ssh_init(unsigned char c) { static char *vsp; static char version[10]; @@ -1137,6 +1181,7 @@ static int do_ssh_init(unsigned char c) { *vsp = 0; sprintf(vlog, "Server version: %s", vstring); + ssh_detect_bugs(vstring); vlog[strcspn(vlog, "\r\n")] = '\0'; logevent(vlog); @@ -1148,7 +1193,8 @@ static int do_ssh_init(unsigned char c) { /* * This is a v2 server. Begin v2 protocol. */ - char *verstring = "SSH-2.0-PuTTY"; + char verstring[80]; + sprintf(verstring, "SSH-2.0-%s", sshver); SHA_Init(&exhashbase); /* * Hash our version string and their version string. @@ -1167,8 +1213,9 @@ static int do_ssh_init(unsigned char c) { /* * This is a v1 server. Begin v1 protocol. */ - sprintf(vstring, "SSH-%s-PuTTY\n", - (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5")); + sprintf(vstring, "SSH-%s-%s\n", + (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5"), + sshver); sprintf(vlog, "We claim version: %s", vstring); vlog[strcspn(vlog, "\r\n")] = '\0'; logevent(vlog); @@ -1225,21 +1272,20 @@ static void ssh_gotdata(unsigned char *data, int datalen) crFinishV; } -static int ssh_receive(Socket skt, int urgent, char *data, int len) { - if (urgent==3) { +static int ssh_closing (Plug plug, char *error_msg, int error_code, int calling_back) { + ssh_state = SSH_STATE_CLOSED; + sk_close(s); + s = NULL; + if (error_msg) { /* A socket error has occurred. */ - ssh_state = SSH_STATE_CLOSED; - sk_close(s); - s = NULL; - connection_fatal(data); - return 0; - } else if (!len) { - /* Connection has closed. */ - ssh_state = SSH_STATE_CLOSED; - sk_close(s); - s = NULL; - return 0; + connection_fatal (error_msg); + } else { + /* Otherwise, the remote side closed the connection normally. */ } + return 0; +} + +static int ssh_receive(Plug plug, int urgent, char *data, int len) { ssh_gotdata (data, len); if (ssh_state == SSH_STATE_CLOSED) { if (s) { @@ -1258,6 +1304,11 @@ static int ssh_receive(Socket skt, int urgent, char *data, int len) { */ static char *connect_to_host(char *host, int port, char **realhost) { + static struct plug_function_table fn_table = { + ssh_closing, + ssh_receive + }, *fn_table_ptr = &fn_table; + SockAddr addr; char *err; #ifdef FWHACK @@ -1295,7 +1346,7 @@ static char *connect_to_host(char *host, int port, char **realhost) /* * Open socket. */ - s = sk_new(addr, port, 0, 1, ssh_receive); + s = sk_new(addr, port, 0, 1, &fn_table_ptr); if ( (err = sk_socket_error(s)) ) return err; @@ -1459,43 +1510,56 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt) static int pos = 0; static char c; if ((flags & FLAG_INTERACTIVE) && !*cfg.username) { - c_write_str("login as: "); - ssh_send_ok = 1; - while (pos >= 0) { - crWaitUntil(!ispkt); - while (inlen--) switch (c = *in++) { - case 10: case 13: - username[pos] = 0; - pos = -1; - break; - case 8: case 127: - if (pos > 0) { - c_write_str("\b \b"); - pos--; - } - break; - case 21: case 27: - while (pos > 0) { - c_write_str("\b \b"); - pos--; - } - break; - case 3: case 4: - random_save_seed(); - exit(0); - break; - default: - if (((c >= ' ' && c <= '~') || - ((unsigned char)c >= 160)) && pos < 40) { - username[pos++] = c; - c_write(&c, 1); - } - break; - } - } - c_write_str("\r\n"); - username[strcspn(username, "\n\r")] = '\0'; - } else { + if (ssh_get_line) { + if (!ssh_get_line("login as: ", + username, sizeof(username), FALSE)) { + /* + * get_line failed to get a username. + * Terminate. + */ + logevent("No username provided. Abandoning session."); + ssh_state = SSH_STATE_CLOSED; + crReturn(1); + } + } else { + c_write_str("login as: "); + ssh_send_ok = 1; + while (pos >= 0) { + crWaitUntil(!ispkt); + while (inlen--) switch (c = *in++) { + case 10: case 13: + username[pos] = 0; + pos = -1; + break; + case 8: case 127: + if (pos > 0) { + c_write_str("\b \b"); + pos--; + } + break; + case 21: case 27: + while (pos > 0) { + c_write_str("\b \b"); + pos--; + } + break; + case 3: case 4: + random_save_seed(); + exit(0); + break; + default: + if (((c >= ' ' && c <= '~') || + ((unsigned char)c >= 160)) && pos < 40) { + username[pos++] = c; + c_write(&c, 1); + } + break; + } + } + c_write_str("\r\n"); + username[strcspn(username, "\n\r")] = '\0'; + } + } else { strncpy(username, cfg.username, 99); username[99] = '\0'; } @@ -1546,10 +1610,11 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt) request[4] = SSH1_AGENTC_REQUEST_RSA_IDENTITIES; agent_query(request, 5, &r, &responselen); response = (unsigned char *)r; - if (response) { + if (response && responselen >= 5 && + response[4] == SSH1_AGENT_RSA_IDENTITIES_ANSWER) { p = response + 5; nkeys = GET_32BIT(p); p += 4; - { char buf[64]; sprintf(buf, "Pageant has %d keys", nkeys); + { char buf[64]; sprintf(buf, "Pageant has %d SSH1 keys", nkeys); logevent(buf); } for (i = 0; i < nkeys; i++) { static struct RSAKey key; @@ -1697,13 +1762,12 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt) sfree(comment); } - if (ssh_get_password) { - if (!ssh_get_password(prompt, password, sizeof(password))) { + if (ssh_get_line) { + if (!ssh_get_line(prompt, password, sizeof(password), TRUE)) { /* - * get_password failed to get a password (for - * example because one was supplied on the command - * line which has already failed to work). - * Terminate. + * get_line failed to get a password (for example + * because one was supplied on the command line + * which has already failed to work). Terminate. */ logevent("No more passwords to try"); ssh_state = SSH_STATE_CLOSED; @@ -1835,38 +1899,65 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt) * N+7. This won't obscure the order of * magnitude of the password length, but it will * introduce a bit of extra uncertainty. + * + * A few servers (the old 1.2.18 through 1.2.22) + * can't deal with SSH1_MSG_IGNORE. For these + * servers, we need an alternative defence. We make + * use of the fact that the password is interpreted + * as a C string: so we can append a NUL, then some + * random data. */ - int bottom, top, pwlen, i; - char *randomstr; - - pwlen = strlen(password); - if (pwlen < 16) { - bottom = 1; - top = 15; + if (ssh_remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE) { + char string[64]; + char *s; + int len; + + len = strlen(password); + if (len < sizeof(string)) { + s = string; + strcpy(string, password); + len++; /* cover the zero byte */ + while (len < sizeof(string)) { + string[len++] = (char)random_byte(); + } + } else { + s = password; + } + send_packet(pwpkt_type, PKT_INT, len, + PKT_DATA, s, len, PKT_END); } else { - bottom = pwlen &~ 7; - top = bottom + 7; - } + int bottom, top, pwlen, i; + char *randomstr; - assert(pwlen >= bottom && pwlen <= top); + pwlen = strlen(password); + if (pwlen < 16) { + bottom = 0; /* zero length passwords are OK! :-) */ + top = 15; + } else { + bottom = pwlen &~ 7; + top = bottom + 7; + } - randomstr = smalloc(top+1); + assert(pwlen >= bottom && pwlen <= top); - for (i = bottom; i <= top; i++) { - if (i == pwlen) - defer_packet(pwpkt_type, PKT_STR, password, PKT_END); - else { - for (j = 0; j < i; j++) { - do { - randomstr[j] = random_byte(); - } while (randomstr[j] == '\0'); + randomstr = smalloc(top+1); + + for (i = bottom; i <= top; i++) { + if (i == pwlen) + defer_packet(pwpkt_type, PKT_STR, password, PKT_END); + else { + for (j = 0; j < i; j++) { + do { + randomstr[j] = random_byte(); + } while (randomstr[j] == '\0'); + } + randomstr[i] = '\0'; + defer_packet(SSH1_MSG_IGNORE, + PKT_STR, randomstr, PKT_END); } - randomstr[i] = '\0'; - defer_packet(SSH1_MSG_IGNORE, - PKT_STR, randomstr, PKT_END); } + ssh_pkt_defersend(); } - ssh_pkt_defersend(); } else { send_packet(pwpkt_type, PKT_STR, password, PKT_END); } @@ -1894,7 +1985,7 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt) } void sshfwd_close(struct ssh_channel *c) { - if (c) { + if (c && !c->closes) { if (ssh_version == 1) { send_packet(SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid, PKT_END); } else { @@ -2258,7 +2349,7 @@ static void ssh2_mkkey(Bignum K, char *H, char *sessid, char chr, char *keyspace */ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt) { - static int i, j, len, nbits; + static int i, j, len, nbits, pbits; static char *str; static Bignum p, g, e, f, K; static int kex_init_value, kex_reply_value; @@ -2307,7 +2398,7 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt) /* * Be prepared to work around the buggy MAC problem. */ - if (cfg.buggymac) + if (cfg.buggymac || (ssh_remote_bugs & BUG_SSH2_HMAC)) maclist = buggymacs, nmacs = lenof(buggymacs); else maclist = macs, nmacs = lenof(macs); @@ -2481,30 +2572,34 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt) } /* + * Work out the number of bits of key we will need from the key + * exchange. We start with the maximum key length of either + * cipher... + */ + { + int csbits, scbits; + + csbits = cscipher_tobe->keylen; + scbits = sccipher_tobe->keylen; + nbits = (csbits > scbits ? csbits : scbits); + } + /* The keys only have 160-bit entropy, since they're based on + * a SHA-1 hash. So cap the key size at 160 bits. */ + if (nbits > 160) nbits = 160; + + /* * If we're doing Diffie-Hellman group exchange, start by * requesting a group. */ if (kex == &ssh_diffiehellman_gex) { - int csbits, scbits; - logevent("Doing Diffie-Hellman group exchange"); /* - * Work out number of bits. We start with the maximum key - * length of either cipher... - */ - csbits = cscipher_tobe->keylen; - scbits = sccipher_tobe->keylen; - nbits = (csbits > scbits ? csbits : scbits); - /* The keys only have 160-bit entropy, since they're based on - * a SHA-1 hash. So cap the key size at 160 bits. */ - if (nbits > 160) nbits = 160; - /* - * ... and then work out how big a DH group we will need to - * allow that much data. - */ - nbits = 512 << ((nbits-1) / 64); + * Work out how big a DH group we will need to allow that + * much data. + */ + pbits = 512 << ((nbits-1) / 64); ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST); - ssh2_pkt_adduint32(nbits); + ssh2_pkt_adduint32(pbits); ssh2_pkt_send(); crWaitUntil(ispkt); @@ -2527,7 +2622,7 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt) /* * Now generate and send e for Diffie-Hellman. */ - e = dh_create_e(); + e = dh_create_e(nbits*2); ssh2_pkt_init(kex_init_value); ssh2_pkt_addmp(e); ssh2_pkt_send(); @@ -2545,7 +2640,7 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt) sha_string(&exhash, hostkeydata, hostkeylen); if (kex == &ssh_diffiehellman_gex) { - sha_uint32(&exhash, nbits); + sha_uint32(&exhash, pbits); sha_mpint(&exhash, p); sha_mpint(&exhash, g); } @@ -2768,40 +2863,53 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt) */ pos = 0; if ((flags & FLAG_INTERACTIVE) && !*cfg.username) { - c_write_str("login as: "); - ssh_send_ok = 1; - while (pos >= 0) { - crWaitUntilV(!ispkt); - while (inlen--) switch (c = *in++) { - case 10: case 13: - username[pos] = 0; - pos = -1; - break; - case 8: case 127: - if (pos > 0) { - c_write_str("\b \b"); - pos--; - } - break; - case 21: case 27: - while (pos > 0) { - c_write_str("\b \b"); - pos--; - } - break; - case 3: case 4: - random_save_seed(); - exit(0); - break; - default: - if (((c >= ' ' && c <= '~') || - ((unsigned char)c >= 160)) && pos < 40) { - username[pos++] = c; - c_write(&c, 1); - } - break; - } - } + if (ssh_get_line) { + if (!ssh_get_line("login as: ", + username, sizeof(username), FALSE)) { + /* + * get_line failed to get a username. + * Terminate. + */ + logevent("No username provided. Abandoning session."); + ssh_state = SSH_STATE_CLOSED; + crReturnV; + } + } else { + c_write_str("login as: "); + ssh_send_ok = 1; + while (pos >= 0) { + crWaitUntilV(!ispkt); + while (inlen--) switch (c = *in++) { + case 10: case 13: + username[pos] = 0; + pos = -1; + break; + case 8: case 127: + if (pos > 0) { + c_write_str("\b \b"); + pos--; + } + break; + case 21: case 27: + while (pos > 0) { + c_write_str("\b \b"); + pos--; + } + break; + case 3: case 4: + random_save_seed(); + exit(0); + break; + default: + if (((c >= ' ' && c <= '~') || + ((unsigned char)c >= 160)) && pos < 40) { + username[pos++] = c; + c_write(&c, 1); + } + break; + } + } + } c_write_str("\r\n"); username[strcspn(username, "\n\r")] = '\0'; } else { @@ -2930,10 +3038,11 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt) request[4] = SSH2_AGENTC_REQUEST_IDENTITIES; agent_query(request, 5, &r, &responselen); response = (unsigned char *)r; - if (response) { + if (response && responselen >= 5 && + response[4] == SSH2_AGENT_IDENTITIES_ANSWER) { p = response + 5; nkeys = GET_32BIT(p); p += 4; - { char buf[64]; sprintf(buf, "Pageant has %d keys", nkeys); + { char buf[64]; sprintf(buf, "Pageant has %d SSH2 keys", nkeys); logevent(buf); } for (i = 0; i < nkeys; i++) { static char *pkblob, *alg, *commentp; @@ -3083,13 +3192,14 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt) } if (need_pw) { - if (ssh_get_password) { - if (!ssh_get_password(pwprompt, password, sizeof(password))) { + if (ssh_get_line) { + if (!ssh_get_line(pwprompt, password, + sizeof(password), TRUE)) { /* - * get_password failed to get a password (for - * example because one was supplied on the command - * line which has already failed to work). - * Terminate. + * get_line failed to get a password (for + * example because one was supplied on the + * command line which has already failed to + * work). Terminate. */ logevent("No more passwords to try"); ssh_state = SSH_STATE_CLOSED; @@ -3350,9 +3460,7 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt) * Potentially enable agent forwarding. */ if (cfg.agentfwd && agent_exists()) { - char proto[20], data[64]; logevent("Requesting OpenSSH-style agent forwarding"); - x11_invent_auth(proto, sizeof(proto), data, sizeof(data)); ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST); ssh2_pkt_adduint32(mainchan->remoteid); ssh2_pkt_addstring("auth-agent-req@openssh.com");