glenda.party
term% ls -F
term% cat index.txt
PUSHTLS(2)                    System Calls Manual                   PUSHTLS(2)



NAME
       pushtls,   tlsClient,   tlsServer,   initThumbprints,  freeThumbprints,
       okThumbprint, 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)

       void freeThumbprints(Thumbprint *table)

       int  okThumbprint(uchar *hash, Thumbprint *table)

DESCRIPTION
       Transport Layer Security (TLS) comprises a record layer protocol, doing
       message digesting and encrypting in the kernel, and a handshake  proto‐
       col, doing initial authentication and secret creation at user level and
       then starting a data channel 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 communications 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 encryption keys.  Pushtls
       returns a file descriptor for the TLS data channel.   Anything  written
       to  this descriptor will get encrypted and authenticated and then writ‐
       ten to the file descriptor, fd.  If dir is non-zero, the path  name  of
       the connection directory is copied into dir.  This path name is guaran‐
       teed 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 */
                   int  certlen, sessionIDlen;
                   void (*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 */
              } TLSconn;

       defined  in  tls.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 connec‐
       tion 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;  ses‐
       sionKey  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.

       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
       previously loaded into factotum.  (See rsa(8) for more about key gener‐
       ation.)

       Readcertchain  will read a PEM-encoded chain of certificates from file‐
       name and return a pointer to a linked list of malloced PEMChain  struc‐
       tures, defined in tls.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 establish 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 certificate:

              uchar hash[SHA1dlen];

              conn = (TLSconn*)mallocz(sizeof *conn, 1);
              fd = tlsClient(fd, conn);
              sha1(conn->cert, conn->certlen, hash, nil);
              if(!okThumbprint(hash,table))
                   exits("suspect server");
              ...application begins...

       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);
              ...application begins...

FILES
       /sys/lib/tls
              thumbprints of trusted services

       /sys/lib/ssl
              PEM certificate files

SOURCE
       /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 implemented.

       Note  that  in the TLS protocol sessionID itself is public;  it is used
       as a pointer to secrets stored in factotum.



                                                                    PUSHTLS(2)