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Diffstat (limited to 'trunk/res/res_crypto.c')
| -rw-r--r-- | trunk/res/res_crypto.c | 624 |
1 files changed, 624 insertions, 0 deletions
diff --git a/trunk/res/res_crypto.c b/trunk/res/res_crypto.c new file mode 100644 index 000000000..f1a2234fd --- /dev/null +++ b/trunk/res/res_crypto.c @@ -0,0 +1,624 @@ +/* + * Asterisk -- An open source telephony toolkit. + * + * Copyright (C) 1999 - 2006, Digium, Inc. + * + * Mark Spencer <markster@digium.com> + * + * See http://www.asterisk.org for more information about + * the Asterisk project. Please do not directly contact + * any of the maintainers of this project for assistance; + * the project provides a web site, mailing lists and IRC + * channels for your use. + * + * This program is free software, distributed under the terms of + * the GNU General Public License Version 2. See the LICENSE file + * at the top of the source tree. + */ + +/*! \file + * + * \brief Provide Cryptographic Signature capability + * + * \author Mark Spencer <markster@digium.com> + * + * \extref Uses the OpenSSL library, available at + * http://www.openssl.org/ + */ + +/*** MODULEINFO + <depend>ssl</depend> + ***/ + +#include "asterisk.h" + +ASTERISK_FILE_VERSION(__FILE__, "$Revision$") + +#include "asterisk/paths.h" /* use ast_config_AST_KEY_DIR */ +#include <openssl/ssl.h> +#include <openssl/err.h> +#include <dirent.h> + +#include "asterisk/module.h" +#include "asterisk/crypto.h" +#include "asterisk/md5.h" +#include "asterisk/cli.h" +#include "asterisk/io.h" +#include "asterisk/lock.h" +#include "asterisk/utils.h" + +/* + * Asterisk uses RSA keys with SHA-1 message digests for its + * digital signatures. The choice of RSA is due to its higher + * throughput on verification, and the choice of SHA-1 based + * on the recently discovered collisions in MD5's compression + * algorithm and recommendations of avoiding MD5 in new schemes + * from various industry experts. + * + * We use OpenSSL to provide our crypto routines, although we never + * actually use full-up SSL + * + */ + +#define KEY_NEEDS_PASSCODE (1 << 16) + +struct ast_key { + /*! Name of entity */ + char name[80]; + /*! File name */ + char fn[256]; + /*! Key type (AST_KEY_PUB or AST_KEY_PRIV, along with flags from above) */ + int ktype; + /*! RSA structure (if successfully loaded) */ + RSA *rsa; + /*! Whether we should be deleted */ + int delme; + /*! FD for input (or -1 if no input allowed, or -2 if we needed input) */ + int infd; + /*! FD for output */ + int outfd; + /*! Last MD5 Digest */ + unsigned char digest[16]; + AST_RWLIST_ENTRY(ast_key) list; +}; + +static AST_RWLIST_HEAD_STATIC(keys, ast_key); + +/*! + * \brief setting of priv key + * \param buf + * \param size + * \param rwflag + * \param userdata + * \return length of string,-1 on failure +*/ +static int pw_cb(char *buf, int size, int rwflag, void *userdata) +{ + struct ast_key *key = (struct ast_key *)userdata; + char prompt[256]; + int res, tmp; + + if (key->infd < 0) { + /* Note that we were at least called */ + key->infd = -2; + return -1; + } + + snprintf(prompt, sizeof(prompt), ">>>> passcode for %s key '%s': ", + key->ktype == AST_KEY_PRIVATE ? "PRIVATE" : "PUBLIC", key->name); + write(key->outfd, prompt, strlen(prompt)); + memset(buf, 0, sizeof(buf)); + tmp = ast_hide_password(key->infd); + memset(buf, 0, size); + res = read(key->infd, buf, size); + ast_restore_tty(key->infd, tmp); + if (buf[strlen(buf) -1] == '\n') + buf[strlen(buf) - 1] = '\0'; + return strlen(buf); +} + +/*! + * \brief return the ast_key structure for name + * \see ast_key_get +*/ +static struct ast_key *__ast_key_get(const char *kname, int ktype) +{ + struct ast_key *key; + + AST_RWLIST_RDLOCK(&keys); + AST_RWLIST_TRAVERSE(&keys, key, list) { + if (!strcmp(kname, key->name) && + (ktype == key->ktype)) + break; + } + AST_RWLIST_UNLOCK(&keys); + + return key; +} + +/*! + * \brief load RSA key from file + * \param dir directory string + * \param fname name of file + * \param ifd incoming file descriptor + * \param ofd outgoing file descriptor + * \param not2 + * \retval key on success. + * \retval NULL on failure. +*/ +static struct ast_key *try_load_key(const char *dir, const char *fname, int ifd, int ofd, int *not2) +{ + int ktype = 0, found = 0; + char *c = NULL, ffname[256]; + unsigned char digest[16]; + FILE *f; + struct MD5Context md5; + struct ast_key *key; + static int notice = 0; + + /* Make sure its name is a public or private key */ + if ((c = strstr(fname, ".pub")) && !strcmp(c, ".pub")) + ktype = AST_KEY_PUBLIC; + else if ((c = strstr(fname, ".key")) && !strcmp(c, ".key")) + ktype = AST_KEY_PRIVATE; + else + return NULL; + + /* Get actual filename */ + snprintf(ffname, sizeof(ffname), "%s/%s", dir, fname); + + /* Open file */ + if (!(f = fopen(ffname, "r"))) { + ast_log(LOG_WARNING, "Unable to open key file %s: %s\n", ffname, strerror(errno)); + return NULL; + } + + MD5Init(&md5); + while(!feof(f)) { + /* Calculate a "whatever" quality md5sum of the key */ + char buf[256] = ""; + fgets(buf, sizeof(buf), f); + if (!feof(f)) + MD5Update(&md5, (unsigned char *) buf, strlen(buf)); + } + MD5Final(digest, &md5); + + /* Look for an existing key */ + AST_RWLIST_TRAVERSE(&keys, key, list) { + if (!strcasecmp(key->fn, ffname)) + break; + } + + if (key) { + /* If the MD5 sum is the same, and it isn't awaiting a passcode + then this is far enough */ + if (!memcmp(digest, key->digest, 16) && + !(key->ktype & KEY_NEEDS_PASSCODE)) { + fclose(f); + key->delme = 0; + return NULL; + } else { + /* Preserve keytype */ + ktype = key->ktype; + /* Recycle the same structure */ + found++; + } + } + + /* Make fname just be the normal name now */ + *c = '\0'; + if (!key) { + if (!(key = ast_calloc(1, sizeof(*key)))) { + fclose(f); + return NULL; + } + } + /* First the filename */ + ast_copy_string(key->fn, ffname, sizeof(key->fn)); + /* Then the name */ + ast_copy_string(key->name, fname, sizeof(key->name)); + key->ktype = ktype; + /* Yes, assume we're going to be deleted */ + key->delme = 1; + /* Keep the key type */ + memcpy(key->digest, digest, 16); + /* Can I/O takes the FD we're given */ + key->infd = ifd; + key->outfd = ofd; + /* Reset the file back to the beginning */ + rewind(f); + /* Now load the key with the right method */ + if (ktype == AST_KEY_PUBLIC) + key->rsa = PEM_read_RSA_PUBKEY(f, NULL, pw_cb, key); + else + key->rsa = PEM_read_RSAPrivateKey(f, NULL, pw_cb, key); + fclose(f); + if (key->rsa) { + if (RSA_size(key->rsa) == 128) { + /* Key loaded okay */ + key->ktype &= ~KEY_NEEDS_PASSCODE; + ast_verb(3, "Loaded %s key '%s'\n", key->ktype == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE", key->name); + ast_debug(1, "Key '%s' loaded OK\n", key->name); + key->delme = 0; + } else + ast_log(LOG_NOTICE, "Key '%s' is not expected size.\n", key->name); + } else if (key->infd != -2) { + ast_log(LOG_WARNING, "Key load %s '%s' failed\n",key->ktype == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE", key->name); + if (ofd > -1) + ERR_print_errors_fp(stderr); + else + ERR_print_errors_fp(stderr); + } else { + ast_log(LOG_NOTICE, "Key '%s' needs passcode.\n", key->name); + key->ktype |= KEY_NEEDS_PASSCODE; + if (!notice) { + if (!ast_opt_init_keys) + ast_log(LOG_NOTICE, "Add the '-i' flag to the asterisk command line if you want to automatically initialize passcodes at launch.\n"); + notice++; + } + /* Keep it anyway */ + key->delme = 0; + /* Print final notice about "init keys" when done */ + *not2 = 1; + } + + /* If this is a new key add it to the list */ + if (!found) + AST_RWLIST_INSERT_TAIL(&keys, key, list); + + return key; +} + +/*! + * \brief signs outgoing message with public key + * \see ast_sign_bin +*/ +static int __ast_sign_bin(struct ast_key *key, const char *msg, int msglen, unsigned char *dsig) +{ + unsigned char digest[20]; + unsigned int siglen = 128; + int res; + + if (key->ktype != AST_KEY_PRIVATE) { + ast_log(LOG_WARNING, "Cannot sign with a public key\n"); + return -1; + } + + /* Calculate digest of message */ + SHA1((unsigned char *)msg, msglen, digest); + + /* Verify signature */ + if (!(res = RSA_sign(NID_sha1, digest, sizeof(digest), dsig, &siglen, key->rsa))) { + ast_log(LOG_WARNING, "RSA Signature (key %s) failed\n", key->name); + return -1; + } + + if (siglen != 128) { + ast_log(LOG_WARNING, "Unexpected signature length %d, expecting %d\n", (int)siglen, (int)128); + return -1; + } + + return 0; + +} + +/*! + * \brief decrypt a message + * \see ast_decrypt_bin +*/ +static int __ast_decrypt_bin(unsigned char *dst, const unsigned char *src, int srclen, struct ast_key *key) +{ + int res, pos = 0; + + if (key->ktype != AST_KEY_PRIVATE) { + ast_log(LOG_WARNING, "Cannot decrypt with a public key\n"); + return -1; + } + + if (srclen % 128) { + ast_log(LOG_NOTICE, "Tried to decrypt something not a multiple of 128 bytes\n"); + return -1; + } + + while(srclen) { + /* Process chunks 128 bytes at a time */ + if ((res = RSA_private_decrypt(128, src, dst, key->rsa, RSA_PKCS1_OAEP_PADDING)) < 0) + return -1; + pos += res; + src += 128; + srclen -= 128; + dst += res; + } + + return pos; +} + +/*! + * \brief encrypt a message + * \see ast_encrypt_bin +*/ +static int __ast_encrypt_bin(unsigned char *dst, const unsigned char *src, int srclen, struct ast_key *key) +{ + int res, bytes, pos = 0; + + if (key->ktype != AST_KEY_PUBLIC) { + ast_log(LOG_WARNING, "Cannot encrypt with a private key\n"); + return -1; + } + + while(srclen) { + bytes = srclen; + if (bytes > 128 - 41) + bytes = 128 - 41; + /* Process chunks 128-41 bytes at a time */ + if ((res = RSA_public_encrypt(bytes, src, dst, key->rsa, RSA_PKCS1_OAEP_PADDING)) != 128) { + ast_log(LOG_NOTICE, "How odd, encrypted size is %d\n", res); + return -1; + } + src += bytes; + srclen -= bytes; + pos += res; + dst += res; + } + return pos; +} + +/*! + * \brief wrapper for __ast_sign_bin then base64 encode it + * \see ast_sign +*/ +static int __ast_sign(struct ast_key *key, char *msg, char *sig) +{ + unsigned char dsig[128]; + int siglen = sizeof(dsig), res; + + if (!(res = ast_sign_bin(key, msg, strlen(msg), dsig))) + /* Success -- encode (256 bytes max as documented) */ + ast_base64encode(sig, dsig, siglen, 256); + + return res; +} + +/*! + * \brief check signature of a message + * \see ast_check_signature_bin +*/ +static int __ast_check_signature_bin(struct ast_key *key, const char *msg, int msglen, const unsigned char *dsig) +{ + unsigned char digest[20]; + int res; + + if (key->ktype != AST_KEY_PUBLIC) { + /* Okay, so of course you really *can* but for our purposes + we're going to say you can't */ + ast_log(LOG_WARNING, "Cannot check message signature with a private key\n"); + return -1; + } + + /* Calculate digest of message */ + SHA1((unsigned char *)msg, msglen, digest); + + /* Verify signature */ + if (!(res = RSA_verify(NID_sha1, digest, sizeof(digest), (unsigned char *)dsig, 128, key->rsa))) { + ast_debug(1, "Key failed verification: %s\n", key->name); + return -1; + } + + /* Pass */ + return 0; +} + +/*! + * \brief base64 decode then sent to __ast_check_signature_bin + * \see ast_check_signature +*/ +static int __ast_check_signature(struct ast_key *key, const char *msg, const char *sig) +{ + unsigned char dsig[128]; + int res; + + /* Decode signature */ + if ((res = ast_base64decode(dsig, sig, sizeof(dsig))) != sizeof(dsig)) { + ast_log(LOG_WARNING, "Signature improper length (expect %d, got %d)\n", (int)sizeof(dsig), (int)res); + return -1; + } + + res = ast_check_signature_bin(key, msg, strlen(msg), dsig); + + return res; +} + +/*! + * \brief refresh RSA keys from file + * \param ifd file descriptor + * \param ofd file descriptor + * \return void +*/ +static void crypto_load(int ifd, int ofd) +{ + struct ast_key *key; + DIR *dir = NULL; + struct dirent *ent; + int note = 0; + + AST_RWLIST_WRLOCK(&keys); + + /* Mark all keys for deletion */ + AST_RWLIST_TRAVERSE(&keys, key, list) { + key->delme = 1; + } + + /* Load new keys */ + if ((dir = opendir(ast_config_AST_KEY_DIR))) { + while((ent = readdir(dir))) { + try_load_key(ast_config_AST_KEY_DIR, ent->d_name, ifd, ofd, ¬e); + } + closedir(dir); + } else + ast_log(LOG_WARNING, "Unable to open key directory '%s'\n", ast_config_AST_KEY_DIR); + + if (note) + ast_log(LOG_NOTICE, "Please run the command 'init keys' to enter the passcodes for the keys\n"); + + /* Delete any keys that are no longer present */ + AST_RWLIST_TRAVERSE_SAFE_BEGIN(&keys, key, list) { + if (key->delme) { + ast_debug(1, "Deleting key %s type %d\n", key->name, key->ktype); + AST_RWLIST_REMOVE_CURRENT(list); + if (key->rsa) + RSA_free(key->rsa); + ast_free(key); + } + } + AST_RWLIST_TRAVERSE_SAFE_END; + + AST_RWLIST_UNLOCK(&keys); +} + +static void md52sum(char *sum, unsigned char *md5) +{ + int x; + for (x = 0; x < 16; x++) + sum += sprintf(sum, "%02x", *(md5++)); +} + +/*! + * \brief show the list of RSA keys + * \param e CLI command + * \param cmd + * \param a list of CLI arguments + * \return CLI_SUCCESS +*/ +static char *handle_cli_keys_show(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a) +{ +#define FORMAT "%-18s %-8s %-16s %-33s\n" + + struct ast_key *key; + char sum[16 * 2 + 1]; + int count_keys = 0; + + switch (cmd) { + case CLI_INIT: + e->command = "keys show"; + e->usage = + "Usage: keys show\n" + " Displays information about RSA keys known by Asterisk\n"; + return NULL; + case CLI_GENERATE: + return NULL; + } + + ast_cli(a->fd, FORMAT, "Key Name", "Type", "Status", "Sum"); + ast_cli(a->fd, FORMAT, "------------------", "--------", "----------------", "--------------------------------"); + + AST_RWLIST_RDLOCK(&keys); + AST_RWLIST_TRAVERSE(&keys, key, list) { + md52sum(sum, key->digest); + ast_cli(a->fd, FORMAT, key->name, + (key->ktype & 0xf) == AST_KEY_PUBLIC ? "PUBLIC" : "PRIVATE", + key->ktype & KEY_NEEDS_PASSCODE ? "[Needs Passcode]" : "[Loaded]", sum); + count_keys++; + } + AST_RWLIST_UNLOCK(&keys); + + ast_cli(a->fd, "\n%d known RSA keys.\n", count_keys); + + return CLI_SUCCESS; + +#undef FORMAT +} + +/*! + * \brief initialize all RSA keys + * \param e CLI command + * \param cmd + * \param a list of CLI arguments + * \return CLI_SUCCESS +*/ +static char *handle_cli_keys_init(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a) +{ + struct ast_key *key; + int ign; + char *kn, tmp[256] = ""; + + switch (cmd) { + case CLI_INIT: + e->command = "keys init"; + e->usage = + "Usage: keys init\n" + " Initializes private keys (by reading in pass code from\n" + " the user)\n"; + return NULL; + case CLI_GENERATE: + return NULL; + } + + if (a->argc != 2) + return CLI_SHOWUSAGE; + + AST_RWLIST_WRLOCK(&keys); + AST_RWLIST_TRAVERSE_SAFE_BEGIN(&keys, key, list) { + /* Reload keys that need pass codes now */ + if (key->ktype & KEY_NEEDS_PASSCODE) { + kn = key->fn + strlen(ast_config_AST_KEY_DIR) + 1; + ast_copy_string(tmp, kn, sizeof(tmp)); + try_load_key(ast_config_AST_KEY_DIR, tmp, a->fd, a->fd, &ign); + } + } + AST_RWLIST_TRAVERSE_SAFE_END + AST_RWLIST_UNLOCK(&keys); + + return CLI_SUCCESS; +} + +static struct ast_cli_entry cli_crypto[] = { + AST_CLI_DEFINE(handle_cli_keys_show, "Displays RSA key information"), + AST_CLI_DEFINE(handle_cli_keys_init, "Initialize RSA key passcodes") +}; + +/*! \brief initialise the res_crypto module */ +static int crypto_init(void) +{ + SSL_library_init(); + ERR_load_crypto_strings(); + ast_cli_register_multiple(cli_crypto, sizeof(cli_crypto) / sizeof(struct ast_cli_entry)); + + /* Install ourselves into stubs */ + ast_key_get = __ast_key_get; + ast_check_signature = __ast_check_signature; + ast_check_signature_bin = __ast_check_signature_bin; + ast_sign = __ast_sign; + ast_sign_bin = __ast_sign_bin; + ast_encrypt_bin = __ast_encrypt_bin; + ast_decrypt_bin = __ast_decrypt_bin; + return 0; +} + +static int reload(void) +{ + crypto_load(-1, -1); + return 0; +} + +static int load_module(void) +{ + crypto_init(); + if (ast_opt_init_keys) + crypto_load(STDIN_FILENO, STDOUT_FILENO); + else + crypto_load(-1, -1); + return AST_MODULE_LOAD_SUCCESS; +} + +static int unload_module(void) +{ + /* Can't unload this once we're loaded */ + return -1; +} + +/* needs usecount semantics defined */ +AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "Cryptographic Digital Signatures", + .load = load_module, + .unload = unload_module, + .reload = reload + ); |