PUSHTLS(2) PUSHTLS(2) NAME pushtls, tlsClient, tlsServer, initThumbprints, freeThumbprints, okThumbprint, okCertificate, readcert, readcertchain - attach TLS1 or SSL3 encryption to a communication channel SYNOPSIS #include <u.h> #include <libc.h> int pushtls(int fd, char *hashalg, char *encalg, int isclient, char *secret, char *dir) #include <mp.h> #include <libsec.h> int tlsClient(int fd, TLSconn *conn) int tlsServer(int fd, TLSconn *conn) uchar *readcert(char *filename, int *pcertlen) PEMchain *readcertchain(char *filename) Thumbprint *initThumbprints(char *ok, char *crl, char *tag) void freeThumbprints(Thumbprint *table) int okThumbprint(uchar *hash, int len, Thumbprint *table) int okCertificate(uchar *cert, int len, Thumbprint *table) DESCRIPTION Transport Layer Security (TLS) comprises a record layer pro- tocol, doing message digesting and encrypting in the kernel, and a handshake protocol, doing initial authentication and secret creation at user level and then starting a data chan- nel in the record protocol. TLS is nearly the same as SSL 3.0, and the software should interoperate with implementa- tions of either standard. To use just the record layer, as described in tls(3), call pushtls to open the record layer device, connect to the com- munications channel fd, and start up encryption and message authentication as specified in hashalg, encalg, and secret. These parameters must have been arranged at the two ends of the conversation by other means. For example, hashalg could be sha1, encalg could be rc4_128, and secret could be the base-64 encoding of two (client-to-server and server-to- client) 20-byte digest keys and two corresponding 16-byte Page 1 Plan 9 (printed 10/14/24) PUSHTLS(2) PUSHTLS(2) encryption keys. Pushtls returns a file descriptor for the TLS data channel. Anything written to this descriptor will get encrypted and authenticated and then written to the file descriptor, fd. Pushtls , tlsClient and tlsServer close the original file descriptor on success. If dir is non-zero, the path name of the connection directory is copied into dir. This path name is guaranteed to be less than 40 bytes long. Certificates Alternatively, call tlsClient to speak the full handshake protocol, negotiate the algorithms and secrets, and return a new data file descriptor for the data channel. Conn points to a (caller-allocated) struct: typedef struct TLSconn { char dir[40]; /* OUT connection directory */ uchar *cert; /* IN/OUT certificate */ uchar *sessionID; /* IN/OUT session ID */ uchar *psk; /* opt IN pre-shared key */ int certlen, sessionIDlen, psklen; int (*trace)(char*fmt, ...); PEMChain *chain; char *sessionType; /* opt IN session type */ uchar *sessionKey; /* opt IN/OUT session key */ int sessionKeylen; /* opt IN session key length */ char *sessionConst; /* opt IN session constant */ char *serverName; /* opt IN server name */ char *pskID; /* opt IN pre-shared key ID */ } TLSconn; defined in libsec.h. On input, the caller can provide options such as cert, the local certificate, and sessionID, used by a client to resume a previously negotiated security association. On output, the connection directory is set, as with listen (see dial(2)). The input cert is freed and a freshly allocated copy of the remote's certificate is returned in conn, to be checked by the caller according to its needs. One way to check the remote certificate is to use initThumbprints and freeThumbprints which allocate and free, respectively, a table of hashes from files of known trusted and revoked certificates. okThumbprint confirms that a particular hash is in the table. TlsClient will optionally compute a session key for use by higher-level protocols. To compute a session key, the caller must set sessionType to a known session type; sessionKeylen to the desired key length; sessionKey to a buffer of length sessionKeylen; and sessionConst to the desired salting constant. The only supported session type is ttls, as used by 802.1x. Page 2 Plan 9 (printed 10/14/24) PUSHTLS(2) PUSHTLS(2) TlsServer executes the server side of the handshake. The caller must initialize conn->cert, usually by calling readcert to read and decode the PEM-encoded certificate from filename, return a pointer to malloced storage containing the certificate, and store its length through pcertlen. The private key corresponding to cert.pem should have been pre- viously loaded into factotum. (See rsa(8) for more about key generation.) Readcertchain will read a PEM-encoded chain of certificates from filename and return a pointer to a linked list of malloced PEMChain structures, defined in libsec.h: typedef struct PEMChain PEMChain; struct PEMChain { PEMChain*next; uchar *pem; int pemlen; }; By setting conn->chain = readcertchain("intermediate-certs.pem"); the server can present extra certificate evidence to estab- lish the chain of trust to a root authority known to the client. Conn is not required for the ongoing conversation and may be freed by the application whenever convenient. EXAMPLES Start the client half of TLS and check the remote certifi- cate: conn = (TLSconn*)mallocz(sizeof *conn, 1); fd = tlsClient(fd, conn); if(!okCertificate(conn->cert, conn->certlen, table)) sysfatal("suspect server: %r"); Run the server side: fd = accept(lcfd, ldir); conn = (TLSconn*)mallocz(sizeof *conn, 1); conn->cert = readcert("cert.pem", &conn->certlen); fd = tlsServer(fd, conn); FILES /sys/lib/tls thumbprints of trusted services /sys/lib/ssl PEM certificate files SOURCE Page 3 Plan 9 (printed 10/14/24) PUSHTLS(2) PUSHTLS(2) /sys/src/libc/9sys/pushtls.c /sys/src/libsec/port SEE ALSO dial(2), tls(3), factotum(4), thumbprint(6) DIAGNOSTICS Return -1 on failure. BUGS Client certificates and client sessionIDs are not yet imple- mented. Note that pushtls, tlsClient and tlsServer do not close the original file descriptor on failure, only on success. The sessionID and cert pointers in the TLSconn structure have to be freed by the caller. Note that in the TLS protocol sessionID itself is public; it is used as a pointer to secrets stored in factotum. Page 4 Plan 9 (printed 10/14/24)