Split body of mails not respecting RFC2822

For mails where the body does not respect RFC2822, try to split by words
finding the last space before 1000's character

If no spaces are found then consider the mail to be malformed anyway

This should address corecode#18

mail.c

@@ -38,6 +38,7 @@
 #include <signal.h>
 #include <syslog.h>
 #include <unistd.h>
+#include <ctype.h>
 
 #include "dma.h"
 
@@ -341,18 +342,49 @@ parse_addrs(struct parse_state *ps, char *s, struct queue *queue)
 	goto again;
 }
 
+static int
+writeline(struct queue *queue, const char *line, ssize_t linelen)
+{
+	const char *walk;
+
+	while (linelen > 0) {
+		if (linelen > 1000) {
+			walk = line + 1000;
+			while (!isspace(*walk)) {
+				if (walk == line)
+					errlogx(EX_DATAERR, "bad mail input format:"
+						" from %s (uid %d) (envelope-from %s)",
+						username, useruid, queue->sender);
+				walk--;
+			}
+		} else {
+			walk = line + linelen;
+		}
+		if (fwrite(line, walk - line, 1, queue->mailf) != 1)
+			return (-1);
+		if (linelen <= 1000)
+			break;
+		if (fwrite("\n", 1, 1, queue->mailf) != 1)
+			return (-1);
+		line = walk + 1;
+		linelen = strlen(line);
+	}
+	return (0);
+}
+
 int
 readmail(struct queue *queue, int nodot, int recp_from_header)
 {
 	struct parse_state parse_state;
-	char line[1000];	/* by RFC2822 */
-	size_t linelen;
+	char *line = NULL;
+	ssize_t linelen;
+	size_t linecap = 0;
+	char newline[1000];
 	size_t error;
 	int had_headers = 0;
 	int had_from = 0;
 	int had_messagid = 0;
 	int had_date = 0;
-	int had_last_line = 0;
 	int nocopy = 0;
 
 	parse_state.state = NONE;
@@ -372,24 +404,15 @@ readmail(struct queue *queue, int nodot, int recp_from_header)
 		return (-1);
 
 	while (!feof(stdin)) {
-		if (fgets(line, sizeof(line) - 1, stdin) == NULL)
+		newline[0] = '\0';
+		if ((linelen = getline(&line, &linecap, stdin)) <= 0)
 			break;
-		if (had_last_line)
-			errlogx(EX_DATAERR, "bad mail input format:"
-				" from %s (uid %d) (envelope-from %s)",
-				username, useruid, queue->sender);
-		linelen = strlen(line);
-		if (linelen == 0 || line[linelen - 1] != '\n') {
-			/*
-			 * This line did not end with a newline character.
-			 * If we fix it, it better be the last line of
-			 * the file.
-			 */
-			line[linelen] = '\n';
-			line[linelen + 1] = 0;
-			had_last_line = 1;
-		}
 		if (!had_headers) {
+			if (linelen > 1000)
+				errlogx(EX_DATAERR, "bad mail input format:"
+					" from %s (uid %d) (envelope-from %s)",
+					username, useruid, queue->sender);
+
 			/*
 			 * Unless this is a continuation, switch of
 			 * the Bcc: nocopy flag.
@@ -425,36 +448,44 @@ readmail(struct queue *queue, int nodot, int recp_from_header)
 			}
 		}
 
-		if (strcmp(line, "\n") == 0 && !had_headers) {
+		if (line[0] == '\n' && !had_headers) {
 			had_headers = 1;
 			while (!had_date || !had_messagid || !had_from) {
 				if (!had_date) {
 					had_date = 1;
-					snprintf(line, sizeof(line), "Date: %s\n", rfc822date());
+					snprintf(newline, sizeof(newline), "Date: %s\n", rfc822date());
 				} else if (!had_messagid) {
 					/* XXX msgid, assign earlier and log? */
 					had_messagid = 1;
-					snprintf(line, sizeof(line), "Message-Id: <%"PRIxMAX".%s.%"PRIxMAX"@%s>\n",
+					snprintf(newline, sizeof(newline), "Message-Id: <%"PRIxMAX".%s.%"PRIxMAX"@%s>\n",
 						 (uintmax_t)time(NULL),
 						 queue->id,
 						 (uintmax_t)random(),
 						 hostname());
 				} else if (!had_from) {
 					had_from = 1;
-					snprintf(line, sizeof(line), "From: <%s>\n", queue->sender);
+					snprintf(newline, sizeof(newline), "From: <%s>\n", queue->sender);
 				}
-				if (fwrite(line, strlen(line), 1, queue->mailf) != 1)
-					return (-1);
+				if (fwrite(newline, strlen(newline), 1, queue->mailf) != 1)
+					goto fail;
 			}
-			strcpy(line, "\n");
+			strlcpy(newline, "\n", sizeof(newline));
 		}
 		if (!nodot && linelen == 2 && line[0] == '.')
 			break;
 		if (!nocopy) {
-			if (fwrite(line, strlen(line), 1, queue->mailf) != 1)
-				return (-1);
+			if (newline[0] != '\0') {
+				if (fwrite(newline, strlen(newline), 1, queue->mailf) != 1)
+					goto fail;
+			} else {
+				if (writeline(queue, line, linelen) != 0)
+					goto fail;
+			}
 		}
 	}
 
 	return (0);
+fail:
+	free(line);
+	return (-1);
 }