ftpd: fix command fetching to not do it in 1-byte reads;

 fix command de-escaping. Tested to download files with embeeded \xff and LF.
libbb: tweaks for the above

function                                             old     new   delta
ftpd_main                                           2231    2321     +90
xmalloc_fgets_internal                               190     222     +32
xmalloc_fgets_str_len                                  -      27     +27
xmalloc_fgets_str                                      7      23     +16
xmalloc_fgetline_str                                  10      26     +16
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/0 up/down: 181/0)             Total: 181 bytes

4 files changed, 81 insertions, 22 deletions

diff --git a/include/libbb.h b/include/libbb.h
index bc47ce7ba..8ea493b18 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -594,9 +594,9 @@ extern ssize_t open_read_close(const char *filename, void *buf, size_t maxsz) FA
 // Reads byte-by-byte. Useful when it is important to not read ahead.
 // Bytes are appended to pfx (which must be malloced, or NULL).
 extern char *xmalloc_reads(int fd, char *pfx, size_t *maxsz_p) FAST_FUNC;
-/* Reads block up to *maxsz_p (default: MAX_INT(ssize_t)) */
+/* Reads block up to *maxsz_p (default: INT_MAX - 4095) */
 extern void *xmalloc_read(int fd, size_t *maxsz_p) FAST_FUNC;
-/* Returns NULL if file can't be opened */
+/* Returns NULL if file can't be opened (default max size: INT_MAX - 4095) */
 extern void *xmalloc_open_read_close(const char *filename, size_t *maxsz_p) FAST_FUNC;
 /* Autodetects .gz etc */
 extern int open_zipped(const char *fname) FAST_FUNC;
@@ -619,6 +619,8 @@ extern char *bb_get_chunk_from_file(FILE *file, int *end) FAST_FUNC;
 extern char *bb_get_chunk_with_continuation(FILE *file, int *end, int *lineno) FAST_FUNC;
 /* Reads up to (and including) TERMINATING_STRING: */
 extern char *xmalloc_fgets_str(FILE *file, const char *terminating_string) FAST_FUNC;
+/* Same, with limited max size, and returns the length (excluding NUL): */
+extern char *xmalloc_fgets_str_len(FILE *file, const char *terminating_string, size_t *maxsz_p) FAST_FUNC;
 /* Chops off TERMINATING_STRING from the end: */
 extern char *xmalloc_fgetline_str(FILE *file, const char *terminating_string) FAST_FUNC;
 /* Reads up to (and including) "\n" or NUL byte: */
diff --git a/libbb/fgets_str.c b/libbb/fgets_str.c
index 8026a15da..3fe61cdc3 100644
--- a/libbb/fgets_str.c
+++ b/libbb/fgets_str.c
@@ -10,7 +10,7 @@
 
 #include "libbb.h"
 
-static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string, int chop_off)
+static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string, int chop_off, size_t *maxsz_p)
 {
 	char *linebuf = NULL;
 	const int term_length = strlen(terminating_string);
@@ -18,6 +18,7 @@ static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string,
 	int linebufsz = 0;
 	int idx = 0;
 	int ch;
+	size_t maxsz = *maxsz_p;
 
 	while (1) {
 		ch = fgetc(file);
@@ -30,6 +31,11 @@ static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string,
 		if (idx >= linebufsz) {
 			linebufsz += 200;
 			linebuf = xrealloc(linebuf, linebufsz);
+			if (idx >= maxsz) {
+				linebuf[idx] = ch;
+				idx++;
+				break;
+			}
 		}
 
 		linebuf[idx] = ch;
@@ -48,6 +54,7 @@ static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string,
 	/* Grow/shrink *first*, then store NUL */
 	linebuf = xrealloc(linebuf, idx + 1);
 	linebuf[idx] = '\0';
+	*maxsz_p = idx;
 	return linebuf;
 }
 
@@ -57,10 +64,23 @@ static char *xmalloc_fgets_internal(FILE *file, const char *terminating_string,
  * Return NULL if EOF is reached immediately.  */
 char* FAST_FUNC xmalloc_fgets_str(FILE *file, const char *terminating_string)
 {
-	return xmalloc_fgets_internal(file, terminating_string, 0);
+	size_t maxsz = INT_MAX - 4095;
+	return xmalloc_fgets_internal(file, terminating_string, 0, &maxsz);
+}
+
+char* FAST_FUNC xmalloc_fgets_str_len(FILE *file, const char *terminating_string, size_t *maxsz_p)
+{
+	size_t maxsz;
+
+	if (!maxsz_p) {
+		maxsz = INT_MAX - 4095;
+		maxsz_p = &maxsz;
+	}
+	return xmalloc_fgets_internal(file, terminating_string, 0, maxsz_p);
 }
 
 char* FAST_FUNC xmalloc_fgetline_str(FILE *file, const char *terminating_string)
 {
-	return xmalloc_fgets_internal(file, terminating_string, 1);
+	size_t maxsz = INT_MAX - 4095;
+	return xmalloc_fgets_internal(file, terminating_string, 1, &maxsz);
 }
diff --git a/libbb/read.c b/libbb/read.c
index 815007c1e..37503e84d 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -141,7 +141,7 @@ char* FAST_FUNC xmalloc_reads(int fd, char *buf, size_t *maxsz_p)
 {
 	char *p;
 	size_t sz = buf ? strlen(buf) : 0;
-	size_t maxsz = maxsz_p ? *maxsz_p : MAXINT(size_t);
+	size_t maxsz = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
 
 	goto jump_in;
 	while (sz < maxsz) {
@@ -198,7 +198,7 @@ void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
 	size_t to_read;
 	struct stat st;
 
-	to_read = maxsz_p ? *maxsz_p : MAXINT(ssize_t); /* max to read */
+	to_read = maxsz_p ? *maxsz_p : (INT_MAX - 4095); /* max to read */
 
 	/* Estimate file size */
 	st.st_size = 0; /* in case fstat fails, assume 0 */
@@ -262,7 +262,7 @@ void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
 	len = lseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
 	if (len != (off_t)-1) {
 		xlseek(fd, 0, SEEK_SET);
-		size = maxsz_p ? *maxsz_p : INT_MAX;
+		size = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
 		if (len < size)
 			size = len;
 	}
diff --git a/networking/ftpd.c b/networking/ftpd.c
index 6630db710..39a4d1869 100644
--- a/networking/ftpd.c
+++ b/networking/ftpd.c
@@ -972,23 +972,60 @@ cmdio_get_cmd_and_arg(void)
 
 	free(G.ftp_cmd);
 	len = 8 * 1024; /* Paranoia. Peer may send 1 gigabyte long cmd... */
-	G.ftp_cmd = cmd = xmalloc_reads(STDIN_FILENO, NULL, &len);
+	G.ftp_cmd = cmd = xmalloc_fgets_str_len(stdin, "\r\n", &len);
 	if (!cmd)
 		exit(0);
 
-/* TODO: de-escape telnet here: 0xff,0xff => 0xff */
-/* RFC959 says that ABOR, STAT, QUIT may be sent even during
- * data transfer, and may be preceded by telnet's "Interrupt Process"
- * code (two-byte sequence 255,244) and then by telnet "Synch" code
- * 255,242 (byte 242 is sent with TCP URG bit using send(MSG_OOB)
- * and may generate SIGURG on our side. See RFC854).
- * So far we don't support that (may install SIGURG handler if we'd want to),
- * but we need to at least remove 255,xxx pairs. lftp sends those. */
-
-	/* Trailing '\n' is already stripped, strip '\r' */
-	len = strlen(cmd) - 1;
-	if ((ssize_t)len >= 0 && cmd[len] == '\r')
-		cmd[len--] = '\0';
+	/* De-escape telnet: 0xff,0xff => 0xff */
+	/* RFC959 says that ABOR, STAT, QUIT may be sent even during
+	 * data transfer, and may be preceded by telnet's "Interrupt Process"
+	 * code (two-byte sequence 255,244) and then by telnet "Synch" code
+	 * 255,242 (byte 242 is sent with TCP URG bit using send(MSG_OOB)
+	 * and may generate SIGURG on our side. See RFC854).
+	 * So far we don't support that (may install SIGURG handler if we'd want to),
+	 * but we need to at least remove 255,xxx pairs. lftp sends those. */
+	/* Then de-escape FTP: NUL => '\n' */
+	/* Testing for \xff:
+	 * Create file named '\xff': echo Hello >`echo -ne "\xff"`
+	 * Try to get it:            ftpget -v 127.0.0.1 Eff `echo -ne "\xff\xff"`
+	 * (need "\xff\xff" until ftpget applet is fixed to do escaping :)
+	 * Testing for embedded LF:
+	 * LF_HERE=`echo -ne "LF\nHERE"`
+	 * echo Hello >"$LF_HERE"
+	 * ftpget -v 127.0.0.1 LF_HERE "$LF_HERE"
+	 */
+	{
+		int dst, src;
+
+		/* Strip "\r\n" if it is there */
+		if (len != 0 && cmd[len - 1] == '\n') {
+			len--;
+			if (len != 0 && cmd[len - 1] == '\r')
+				len--;
+			cmd[len] = '\0';
+		}
+		src = strchrnul(cmd, 0xff) - cmd;
+		/* 99,99% there are neither NULs nor 255s and src == len */
+		if (src < len) {
+			dst = src;
+			do {
+				if ((unsigned char)(cmd[src]) == 255) {
+					src++;
+					/* 255,xxx - skip 255 */
+					if ((unsigned char)(cmd[src]) != 255) {
+						/* 255,!255 - skip both */
+						src++;
+						continue;
+					}
+					/* 255,255 - retain one 255 */
+				}
+				/* NUL => '\n' */
+				cmd[dst++] = cmd[src] ? cmd[src] : '\n';
+				src++;
+			} while (src < len);
+			cmd[dst] = '\0';
+		}
+	}
 
 	if (G.verbose > 1)
 		verbose_log(cmd);