lib-mail: qp-encoder: Ensure trailing white space is followed by printable

In case a qp-encoded line ends with space or tab append a soft line
break to prevent white space being cut off by decoding instance.

diff --git a/src/lib-mail/qp-encoder.c b/src/lib-mail/qp-encoder.c
index b41a1d5ee851812abada98ad90fb0404a6138ca0..37a4412612277f67f42283f44c8e1738eb6ff9be 100644 (file)
--- a/src/lib-mail/qp-encoder.c
+++ b/src/lib-mail/qp-encoder.c
@@ -7,14 +7,20 @@
 #include "qp-encoder.h"
 #include <ctype.h>
 
+enum qp_encoder_last_char {
+       QP_ENCODER_LAST_ANY = 0,
+       QP_ENCODER_LAST_CR,
+       QP_ENCODER_LAST_WHITE_SPACE,
+};
+
 struct qp_encoder {
        const char *linebreak;
        string_t *dest;
        size_t line_len;
        size_t max_len;
        enum qp_encoder_flag flags;
+       enum qp_encoder_last_char last_char;
        bool add_header_preamble:1;
-       bool cr_last:1;
 };
 
 struct qp_encoder *
@@ -106,29 +112,45 @@ void qp_encoder_more(struct qp_encoder *qp, const void *_src, size_t src_size)
                   CRLF */
                if (c == '\n' &&
                    ((qp->flags & (QP_ENCODER_FLAG_BINARY_DATA|QP_ENCODER_FLAG_HEADER_FORMAT)) == 0 ||
-                     qp->cr_last)) {
+                     qp->last_char == QP_ENCODER_LAST_CR)) {
                        str_append_c(qp->dest, '\r');
                        str_append_c(qp->dest, '\n');
                        /* reset line length here */
                        qp->line_len = 0;
-                       qp->cr_last = FALSE;
+                       qp->last_char = QP_ENCODER_LAST_ANY;
                        continue;
-               } else if (qp->cr_last) {
+               } else if (qp->last_char == QP_ENCODER_LAST_CR) {
                        qp_encode_or_break(qp, '\r');
-                       qp->cr_last = FALSE;
+                       qp->last_char = QP_ENCODER_LAST_ANY;
                }
-               if (c == '\r') {
-                       qp->cr_last = TRUE;
-               } else {
+
+               if (c == ' ' || c == '\t')
+                       qp->last_char = QP_ENCODER_LAST_WHITE_SPACE;
+               else if (c == '\r')
+                       qp->last_char = QP_ENCODER_LAST_CR;
+               else
+                       qp->last_char = QP_ENCODER_LAST_ANY;
+
+               if (c != '\r')
                        qp_encode_or_break(qp, c);
-               }
        }
 }
 
 void qp_encoder_finish(struct qp_encoder *qp)
 {
-       if (qp->cr_last)
+       switch (qp->last_char) {
+       case QP_ENCODER_LAST_CR:
+               /* Last char was CR which was not yet encoded */
                qp_encode_or_break(qp, '\r');
+               break;
+       case QP_ENCODER_LAST_WHITE_SPACE:
+               /* Last char was a white space, it must be followed by
+                * a printable char. */
+               str_append_c(qp->dest, '=');
+               break;
+       default:
+               break;
+       }
 
        if ((qp->flags & QP_ENCODER_FLAG_HEADER_FORMAT) != 0 &&
            !qp->add_header_preamble)
@@ -136,5 +158,5 @@ void qp_encoder_finish(struct qp_encoder *qp)
        if ((qp->flags & QP_ENCODER_FLAG_HEADER_FORMAT) != 0)
                qp->add_header_preamble = TRUE;
        qp->line_len = 0;
-       qp->cr_last = FALSE;
+       qp->last_char = QP_ENCODER_LAST_ANY;
 }