Thanks to John Cummings.

src/cmd/upas/common/appendfiletombox.c

@@ -0,0 +1,155 @@
+#include "common.h"
+
+enum {
+	Buffersize = 64*1024,
+};
+
+typedef struct Inbuf Inbuf;
+struct Inbuf
+{
+	char buf[Buffersize];
+	char *wp;
+	char *rp;
+	int eof;
+	int in;
+	int out;
+	int last;
+	ulong bytes;
+};
+
+static Inbuf*
+allocinbuf(int in, int out)
+{
+	Inbuf *b;
+
+	b = mallocz(sizeof(Inbuf), 1);
+	if(b == nil)
+		sysfatal("reading mailbox: %r");
+	b->rp = b->wp = b->buf;
+	b->in = in;
+	b->out = out;
+	return b;
+}
+
+static int
+fill(Inbuf *b, int addspace)
+{
+	int i, n;
+
+	if(b->eof && b->wp - b->rp == 0)
+		return 0;
+
+	n = b->rp - b->buf;
+	if(n > 0){
+		i = write(b->out, b->buf, n);
+		if(i != n)
+			return -1;
+		b->last = b->buf[n-1];
+		b->bytes += n;
+	}
+	if(addspace){
+		if(write(b->out, " ", 1) != 1)
+			return -1;
+		b->last = ' ';
+		b->bytes++;
+	}
+
+	n = b->wp - b->rp;
+	memmove(b->buf, b->rp, n);
+	b->rp = b->buf;
+	b->wp = b->rp + n;
+
+	i = read(b->in, b->buf+n, sizeof(b->buf)-n);
+	if(i < 0)
+		return -1;
+	b->wp += i;
+
+	return b->wp - b->rp;
+}
+
+/* code to escape ' '*From' ' at the beginning of a line */
+int
+appendfiletombox(int in, int out)
+{
+	int addspace;
+	int n;
+	char *p;
+	int sol;
+	Inbuf *b;
+
+	seek(out, 0, 2);
+
+	b = allocinbuf(in, out);
+	addspace = 0;
+	sol = 1;
+
+	for(;;){
+		if(b->wp - b->rp < 5){
+			n = fill(b, addspace);
+			addspace = 0;
+			if(n < 0)
+				goto error;
+			if(n == 0)
+				break;
+			if(n < 5){
+				b->rp = b->wp;
+				continue;
+			}
+		}
+
+		/* state machine looking for ' '*From' ' */
+		if(!sol){
+			p = memchr(b->rp, '\n', b->wp - b->rp);
+			if(p == nil)
+				b->rp = b->wp;
+			else{
+				b->rp = p+1;
+				sol = 1;
+			}
+			continue;
+		} else {
+			if(*b->rp == ' ' || strncmp(b->rp, "From ", 5) != 0){
+				b->rp++;
+				continue;
+			}
+			addspace = 1;
+			sol = 0;
+		}
+	}
+
+	/* mailbox entries always terminate with two newlines */
+	n = b->last == '\n' ? 1 : 2;
+	if(write(out, "\n\n", n) != n)
+		goto error;
+	n += b->bytes;
+	free(b);
+	return n;
+error:
+	free(b);
+	return -1;
+}
+
+int
+appendfiletofile(int in, int out)
+{
+	int n;
+	Inbuf *b;
+
+	seek(out, 0, 2);
+
+	b = allocinbuf(in, out);
+	for(;;){
+		n = fill(b, 0);
+		if(n < 0)
+			goto error;
+		if(n == 0)
+			break;
+		b->rp = b->wp;
+	}
+	n = b->bytes;
+	free(b);
+	return n;
+error:
+	free(b);
+	return -1;
+}

src/cmd/upas/common/aux.c

@@ -0,0 +1,148 @@
+#include "common.h"
+
+/* expand a path relative to some `.' */
+extern String *
+abspath(char *path, char *dot, String *to)
+{
+	if (*path == '/') {
+		to = s_append(to, path);
+	} else {
+		to = s_append(to, dot);
+		to = s_append(to, "/");
+		to = s_append(to, path);
+	}
+	return to;
+}
+
+/* return a pointer to the base component of a pathname */
+extern char *
+basename(char *path)
+{
+	char *cp;
+
+	cp = strrchr(path, '/');
+	return cp==0 ? path : cp+1;
+}
+
+/* append a sub-expression match onto a String */
+extern void
+append_match(Resub *subexp, String *sp, int se)
+{
+	char *cp, *ep;
+
+	cp = subexp[se].s.sp;    /* jpc .sp -> .s.sp */
+	ep = subexp[se].e.ep;    /* jpc .ep -> .e.ep */
+	for (; cp < ep; cp++)
+		s_putc(sp, *cp);
+	s_terminate(sp);
+}
+
+/*
+ *  check for shell characters in a String
+ */
+static char *illegalchars = "\r\n";
+
+extern int
+shellchars(char *cp)
+{
+	char *sp;
+
+	for(sp=illegalchars; *sp; sp++)
+		if(strchr(cp, *sp))
+			return 1;
+	return 0;
+}
+
+static char *specialchars = " ()<>{};=\\'\`^&|";
+static char *escape = "%%";
+
+int
+hexchar(int x)
+{
+	x &= 0xf;
+	if(x < 10)
+		return '0' + x;
+	else
+		return 'A' + x - 10;
+}
+
+/*
+ *  rewrite a string to escape shell characters
+ */
+extern String*
+escapespecial(String *s)
+{
+	String *ns;
+	char *sp;
+
+	for(sp = specialchars; *sp; sp++)
+		if(strchr(s_to_c(s), *sp))
+			break;
+	if(*sp == 0)
+		return s;
+
+	ns = s_new();
+	for(sp = s_to_c(s); *sp; sp++){
+		if(strchr(specialchars, *sp)){
+			s_append(ns, escape);
+			s_putc(ns, hexchar(*sp>>4));
+			s_putc(ns, hexchar(*sp));
+		} else
+			s_putc(ns, *sp);
+	}
+	s_terminate(ns);
+	s_free(s);
+	return ns;
+}
+
+uint
+hex2uint(char x)
+{
+	if(x >= '0' && x <= '9')
+		return x - '0';
+	if(x >= 'A' && x <= 'F')
+		return (x - 'A') + 10;
+	if(x >= 'a' && x <= 'f')
+		return (x - 'a') + 10;
+	return -512;
+}
+
+/*
+ *  rewrite a string to remove shell characters escapes
+ */
+extern String*
+unescapespecial(String *s)
+{
+	String *ns;
+	char *sp;
+	uint c, n;
+
+	if(strstr(s_to_c(s), escape) == 0)
+		return s;
+	n = strlen(escape);
+
+	ns = s_new();
+	for(sp = s_to_c(s); *sp; sp++){
+		if(strncmp(sp, escape, n) == 0){
+			c = (hex2uint(sp[n])<<4) + hex2uint(sp[n+1]);
+			if(c < 0)
+				s_putc(ns, *sp);
+			else {
+				s_putc(ns, c);
+				sp += n+2-1;
+			}
+		} else
+			s_putc(ns, *sp);
+	}
+	s_terminate(ns);
+	s_free(s);
+	return ns;
+
+}
+
+int
+returnable(char *path)
+{
+
+	return strcmp(path, "/dev/null") != 0;
+}

src/cmd/upas/common/become.c

@@ -0,0 +1,28 @@
+#include "common.h"
+#include <auth.h>
+#include <ndb.h>
+
+/*
+ *  become powerless user
+ */
+int
+become(char **cmd, char *who)
+{
+	int fd;
+
+	USED(cmd);
+	if(strcmp(who, "none") == 0) {
+		fd = open("#c/user", OWRITE);
+		if(fd < 0 || write(fd, "none", strlen("none")) < 0) {
+			werrstr("can't become none");
+			return -1;
+		}
+		close(fd);
+		// jpc if(newns("none", 0)) {
+		// jpc 	werrstr("can't set new namespace");
+		// jpc	return -1;
+		// jpc }
+	}
+	return 0;
+}
+

src/cmd/upas/common/common.h

@@ -0,0 +1,79 @@
+#include "sys.h"
+
+/* format of REMOTE FROM lines */
+extern char *REMFROMRE;
+extern int REMSENDERMATCH;
+extern int REMDATEMATCH;
+extern int REMSYSMATCH;
+
+/* format of mailbox FROM lines */
+#define IS_HEADER(p) ((p)[0]=='F'&&(p)[1]=='r'&&(p)[2]=='o'&&(p)[3]=='m'&&(p)[4]==' ')
+#define IS_TRAILER(p) ((p)[0]=='m'&&(p)[1]=='o'&&(p)[2]=='r'&&(p)[3]=='F'&&(p)[4]=='\n')
+extern char *FROMRE;
+extern int SENDERMATCH;
+extern int DATEMATCH;
+
+enum
+{
+	Elemlen= 28,
+	Errlen=	128,
+	Pathlen= 256,
+};
+
+/*
+ *  routines in mail.c
+ */
+extern int	print_header(Biobuf*, char*, char*);
+extern int	print_remote_header(Biobuf*, char*, char*, char*);
+extern int	parse_header(char*, String*, String*);
+
+/*
+ *  routines in aux.c
+ */
+extern String	*abspath(char*, char*, String*);
+extern String	*mboxpath(char*, char*, String*, int);
+extern char	*basename(char*);
+extern int	delivery_status(String*);
+extern void	append_match(Resub*, String*, int);
+extern int	shellchars(char*);
+extern String*	escapespecial(String*);
+extern String*	unescapespecial(String*);
+extern int	returnable(char*);
+
+/* in copymessage */
+extern int	appendfiletombox(int, int);
+extern int	appendfiletofile(int, int);
+
+/* mailbox types */
+#define MF_NORMAL 0
+#define MF_PIPE 1
+#define MF_FORWARD 2
+#define MF_NOMBOX 3
+#define MF_NOTMBOX 4
+
+/* a pipe between parent and child*/
+typedef struct {
+	Biobuf	bb;
+	Biobuf	*fp;	/* parent process end*/
+	int	fd;	/* child process end*/
+} stream;
+
+/* a child process*/
+typedef struct process{
+	stream	*std[3];	/* standard fd's*/
+	int	pid;		/* process identifier*/
+	int	status;		/* exit status*/
+	Waitmsg	*waitmsg;
+} process;
+
+extern stream	*instream(void);
+extern stream	*outstream(void);
+extern void	stream_free(stream*);
+extern process	*noshell_proc_start(char**, stream*, stream*, stream*, int, char*);
+extern process	*proc_start(char*, stream*, stream*, stream*, int, char*);
+extern int	proc_wait(process*);
+extern int	proc_free(process*);
+extern int	proc_kill(process*);
+
+/* tell compiler we're using a value so it won't complain */
+#define USE(x)	if(x)

src/cmd/upas/common/config.c

@@ -0,0 +1,11 @@
+#include "common.h"
+
+char *MAILROOT =	"#9/mail";
+char *UPASLOG =		"#9/sys/log";
+char *UPASLIB = 	"#9/mail/lib";
+char *UPASBIN=		"#9/bin/upas";
+char *UPASTMP = 	"#9/mail/tmp";
+char *SHELL = 		"#9/bin/rc";
+char *POST =		"#9/sys/lib/post/dispatch";
+
+int MBOXMODE = 0662;