X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/95500969652dbe32f924217f71b2abed67f85228..HEAD:/auth-rsa.c diff --git a/auth-rsa.c b/auth-rsa.c index 4403c149..bf546207 100644 --- a/auth-rsa.c +++ b/auth-rsa.c @@ -1,3 +1,4 @@ +/* $OpenBSD: auth-rsa.c,v 1.73 2008/07/02 12:03:51 dtucker Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -14,24 +15,38 @@ */ #include "includes.h" -RCSID("$OpenBSD: auth-rsa.c,v 1.49 2001/12/28 12:14:27 markus Exp $"); + +#include +#include #include #include +#include +#include +#include +#include + +#include "xmalloc.h" #include "rsa.h" #include "packet.h" -#include "xmalloc.h" #include "ssh1.h" -#include "mpaux.h" #include "uidswap.h" #include "match.h" +#include "buffer.h" #include "auth-options.h" #include "pathnames.h" #include "log.h" #include "servconf.h" -#include "auth.h" +#include "key.h" #include "hostfile.h" +#include "auth.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "ssh.h" +#include "misc.h" /* import */ extern ServerOptions options; @@ -48,10 +63,64 @@ extern u_char session_id[16]; * options bits e n comment * where bits, e and n are decimal numbers, * and comment is any string of characters up to newline. The maximum - * length of a line is 8000 characters. See the documentation for a + * length of a line is SSH_MAX_PUBKEY_BYTES characters. See sshd(8) for a * description of the options. */ +BIGNUM * +auth_rsa_generate_challenge(Key *key) +{ + BIGNUM *challenge; + BN_CTX *ctx; + + if ((challenge = BN_new()) == NULL) + fatal("auth_rsa_generate_challenge: BN_new() failed"); + /* Generate a random challenge. */ + if (BN_rand(challenge, 256, 0, 0) == 0) + fatal("auth_rsa_generate_challenge: BN_rand failed"); + if ((ctx = BN_CTX_new()) == NULL) + fatal("auth_rsa_generate_challenge: BN_CTX_new failed"); + if (BN_mod(challenge, challenge, key->rsa->n, ctx) == 0) + fatal("auth_rsa_generate_challenge: BN_mod failed"); + BN_CTX_free(ctx); + + return challenge; +} + +int +auth_rsa_verify_response(Key *key, BIGNUM *challenge, u_char response[16]) +{ + u_char buf[32], mdbuf[16]; + MD5_CTX md; + int len; + + /* don't allow short keys */ + if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) { + error("auth_rsa_verify_response: RSA modulus too small: %d < minimum %d bits", + BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE); + return (0); + } + + /* The response is MD5 of decrypted challenge plus session id. */ + len = BN_num_bytes(challenge); + if (len <= 0 || len > 32) + fatal("auth_rsa_verify_response: bad challenge length %d", len); + memset(buf, 0, 32); + BN_bn2bin(challenge, buf + 32 - len); + MD5_Init(&md); + MD5_Update(&md, buf, 32); + MD5_Update(&md, session_id, 16); + MD5_Final(mdbuf, &md); + + /* Verify that the response is the original challenge. */ + if (memcmp(response, mdbuf, 16) != 0) { + /* Wrong answer. */ + return (0); + } + /* Correct answer. */ + return (1); +} + /* * Performs the RSA authentication challenge-response dialog with the client, * and returns true (non-zero) if the client gave the correct answer to @@ -59,29 +128,19 @@ extern u_char session_id[16]; */ int -auth_rsa_challenge_dialog(RSA *pk) +auth_rsa_challenge_dialog(Key *key) { BIGNUM *challenge, *encrypted_challenge; - BN_CTX *ctx; - u_char buf[32], mdbuf[16], response[16]; - MD5_CTX md; - u_int i; - int plen, len; + u_char response[16]; + int i, success; if ((encrypted_challenge = BN_new()) == NULL) fatal("auth_rsa_challenge_dialog: BN_new() failed"); - if ((challenge = BN_new()) == NULL) - fatal("auth_rsa_challenge_dialog: BN_new() failed"); - /* Generate a random challenge. */ - BN_rand(challenge, 256, 0, 0); - if ((ctx = BN_CTX_new()) == NULL) - fatal("auth_rsa_challenge_dialog: BN_CTX_new() failed"); - BN_mod(challenge, challenge, pk->n, ctx); - BN_CTX_free(ctx); + challenge = PRIVSEP(auth_rsa_generate_challenge(key)); /* Encrypt the challenge with the public key. */ - rsa_public_encrypt(encrypted_challenge, challenge, pk); + rsa_public_encrypt(encrypted_challenge, challenge, key->rsa); /* Send the encrypted challenge to the client. */ packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE); @@ -91,53 +150,30 @@ auth_rsa_challenge_dialog(RSA *pk) packet_write_wait(); /* Wait for a response. */ - packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE); + packet_read_expect(SSH_CMSG_AUTH_RSA_RESPONSE); for (i = 0; i < 16; i++) - response[i] = packet_get_char(); + response[i] = (u_char)packet_get_char(); packet_check_eom(); - /* The response is MD5 of decrypted challenge plus session id. */ - len = BN_num_bytes(challenge); - if (len <= 0 || len > 32) - fatal("auth_rsa_challenge_dialog: bad challenge length %d", len); - memset(buf, 0, 32); - BN_bn2bin(challenge, buf + 32 - len); - MD5_Init(&md); - MD5_Update(&md, buf, 32); - MD5_Update(&md, session_id, 16); - MD5_Final(mdbuf, &md); + success = PRIVSEP(auth_rsa_verify_response(key, challenge, response)); BN_clear_free(challenge); - - /* Verify that the response is the original challenge. */ - if (memcmp(response, mdbuf, 16) != 0) { - /* Wrong answer. */ - return 0; - } - /* Correct answer. */ - return 1; + return (success); } /* - * Performs the RSA authentication dialog with the client. This returns - * 0 if the client could not be authenticated, and 1 if authentication was - * successful. This may exit if there is a serious protocol violation. + * check if there's user key matching client_n, + * return key if login is allowed, NULL otherwise */ int -auth_rsa(struct passwd *pw, BIGNUM *client_n) +auth_rsa_key_allowed(struct passwd *pw, BIGNUM *client_n, Key **rkey) { - char line[8192], *file; - int authenticated; + char line[SSH_MAX_PUBKEY_BYTES], *file; + int allowed = 0; u_int bits; FILE *f; u_long linenum = 0; - struct stat st; Key *key; - char *fp; - - /* no user given */ - if (pw == NULL) - return 0; /* Temporarily use the user's uid. */ temporarily_use_uid(pw); @@ -145,35 +181,15 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) /* The authorized keys. */ file = authorized_keys_file(pw); debug("trying public RSA key file %s", file); - - /* Fail quietly if file does not exist */ - if (stat(file, &st) < 0) { - /* Restore the privileged uid. */ - restore_uid(); - xfree(file); - return 0; - } - /* Open the file containing the authorized keys. */ - f = fopen(file, "r"); + f = auth_openkeyfile(file, pw, options.strict_modes); if (!f) { - /* Restore the privileged uid. */ - restore_uid(); - packet_send_debug("Could not open %.900s for reading.", file); - packet_send_debug("If your home is on an NFS volume, it may need to be world-readable."); - xfree(file); - return 0; - } - if (options.strict_modes && - secure_filename(f, file, pw, line, sizeof(line)) != 0) { xfree(file); - fclose(f); - log("Authentication refused: %s", line); - packet_send_debug("Authentication refused: %s", line); restore_uid(); - return 0; + return (0); } - /* Flag indicating whether authentication has succeeded. */ - authenticated = 0; + + /* Flag indicating whether the key is allowed. */ + allowed = 0; key = key_new(KEY_RSA1); @@ -182,11 +198,10 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) * found, perform a challenge-response dialog to verify that the * user really has the corresponding private key. */ - while (fgets(line, sizeof(line), f)) { + while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { char *cp; - char *options; - - linenum++; + char *key_options; + int keybits; /* Skip leading whitespace, empty and comment lines. */ for (cp = line; *cp == ' ' || *cp == '\t'; cp++) @@ -202,7 +217,7 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) */ if (*cp < '0' || *cp > '9') { int quoted = 0; - options = cp; + key_options = cp; for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { if (*cp == '\\' && cp[1] == '"') cp++; /* Skip both */ @@ -210,7 +225,7 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) quoted = !quoted; } } else - options = NULL; + key_options = NULL; /* Parse the key from the line. */ if (hostfile_read_key(&cp, &bits, key) == 0) { @@ -225,8 +240,9 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) continue; /* check the real bits */ - if (bits != BN_num_bits(key->rsa->n)) - log("Warning: %s, line %lu: keysize mismatch: " + keybits = BN_num_bits(key->rsa->n); + if (keybits < 0 || bits != (u_int)keybits) + logit("Warning: %s, line %lu: keysize mismatch: " "actual %d vs. announced %d.", file, linenum, BN_num_bits(key->rsa->n), bits); @@ -235,35 +251,11 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) * If our options do not allow this key to be used, * do not send challenge. */ - if (!auth_parse_options(pw, options, file, linenum)) + if (!auth_parse_options(pw, key_options, file, linenum)) continue; - /* Perform the challenge-response dialog for this key. */ - if (!auth_rsa_challenge_dialog(key->rsa)) { - /* Wrong response. */ - verbose("Wrong response to RSA authentication challenge."); - packet_send_debug("Wrong response to RSA authentication challenge."); - /* - * Break out of the loop. Otherwise we might send - * another challenge and break the protocol. - */ - break; - } - /* - * Correct response. The client has been successfully - * authenticated. Note that we have not yet processed the - * options; this will be reset if the options cause the - * authentication to be rejected. - * Break out of the loop if authentication was successful; - * otherwise continue searching. - */ - authenticated = 1; - - fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX); - verbose("Found matching %s key: %s", - key_type(key), fp); - xfree(fp); - + /* break out, this key is allowed */ + allowed = 1; break; } @@ -274,13 +266,59 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n) xfree(file); fclose(f); - key_free(key); - - if (authenticated) - packet_send_debug("RSA authentication accepted."); + /* return key if allowed */ + if (allowed && rkey != NULL) + *rkey = key; else + key_free(key); + return (allowed); +} + +/* + * Performs the RSA authentication dialog with the client. This returns + * 0 if the client could not be authenticated, and 1 if authentication was + * successful. This may exit if there is a serious protocol violation. + */ +int +auth_rsa(Authctxt *authctxt, BIGNUM *client_n) +{ + Key *key; + char *fp; + struct passwd *pw = authctxt->pw; + + /* no user given */ + if (!authctxt->valid) + return 0; + + if (!PRIVSEP(auth_rsa_key_allowed(pw, client_n, &key))) { auth_clear_options(); + return (0); + } + + /* Perform the challenge-response dialog for this key. */ + if (!auth_rsa_challenge_dialog(key)) { + /* Wrong response. */ + verbose("Wrong response to RSA authentication challenge."); + packet_send_debug("Wrong response to RSA authentication challenge."); + /* + * Break out of the loop. Otherwise we might send + * another challenge and break the protocol. + */ + key_free(key); + return (0); + } + /* + * Correct response. The client has been successfully + * authenticated. Note that we have not yet processed the + * options; this will be reset if the options cause the + * authentication to be rejected. + */ + fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX); + verbose("Found matching %s key: %s", + key_type(key), fp); + xfree(fp); + key_free(key); - /* Return authentication result. */ - return authenticated; + packet_send_debug("RSA authentication accepted."); + return (1); }