base64dec: don't read out of bounds

[st.git] / st.c

diff --git a/st.c b/st.c
index ede7ae6..a8f8232 100644 (file)
--- a/st.c
+++ b/st.c
@@ -366,7 +366,7 @@ char
 base64dec_getc(const char **src)
 {
        while (**src && !isprint(**src)) (*src)++;
-       return *((*src)++);
+       return **src ? *((*src)++) : '=';  /* emulate padding if string ends */
 }
 
 char *
@@ -384,6 +384,10 @@ base64dec(const char *src)
                int c = base64_digits[(unsigned char) base64dec_getc(&src)];
                int d = base64_digits[(unsigned char) base64dec_getc(&src)];
 
+               /* invalid input. 'a' can be -1, e.g. if src is "\n" (c-str) */
+               if (a == -1 || b == -1)
+                       break;
+
                *dst++ = (a << 2) | ((b & 0x30) >> 4);
                if (c == -1)
                        break;