More robust control sequence parameter handling.

Parameters are now accumulated in unsigned integers and carefully checked
for overflow (which is turned into saturation).  Things that consume them
now have explicit range checks (again, saturating) to ensure that their
inputs are sane.  This should make it much harder to cause overflow by
supplying ludicrously large numbers.

Fixes two bugs found with the help of afl-fuzz.  One of them may be
exploitable and is CVE-2015-5309.

diff --git a/terminal.c b/terminal.c
index 8e5c07bf0fe594d12c45d845e196f446c89a38c0..7aafb58b0e7fb4256f5d8ce366960c5378109436 100644 (file)
--- a/terminal.c
+++ b/terminal.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <ctype.h>
+#include <limits.h>
 
 #include <time.h>
 #include <assert.h>
@@ -3493,8 +3494,15 @@ static void term_out(Terminal *term)
                    if (term->esc_nargs <= ARGS_MAX) {
                        if (term->esc_args[term->esc_nargs - 1] == ARG_DEFAULT)
                            term->esc_args[term->esc_nargs - 1] = 0;
-                       term->esc_args[term->esc_nargs - 1] =
-                           10 * term->esc_args[term->esc_nargs - 1] + c - '0';
+                       if (term->esc_args[term->esc_nargs - 1] <=
+                           UINT_MAX / 10 &&
+                           term->esc_args[term->esc_nargs - 1] * 10 <=
+                           UINT_MAX - c - '0')
+                           term->esc_args[term->esc_nargs - 1] =
+                               10 * term->esc_args[term->esc_nargs - 1] +
+                               c - '0';
+                       else
+                           term->esc_args[term->esc_nargs - 1] = UINT_MAX;
                    }
                    term->termstate = SEEN_CSI;
                } else if (c == ';') {
@@ -3510,8 +3518,10 @@ static void term_out(Terminal *term)
                        term->esc_query = c;
                    term->termstate = SEEN_CSI;
                } else
+#define CLAMP(arg, lim) ((arg) = ((arg) > (lim)) ? (lim) : (arg))
                    switch (ANSI(c, term->esc_query)) {
                      case 'A':       /* CUU: move up N lines */
+                       CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             term->curs.y - def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
@@ -3520,6 +3530,7 @@ static void term_out(Terminal *term)
                        compatibility(ANSI);
                        /* FALLTHROUGH */
                      case 'B':         /* CUD: Cursor down */
+                       CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             term->curs.y + def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
@@ -3535,23 +3546,27 @@ static void term_out(Terminal *term)
                        compatibility(ANSI);
                        /* FALLTHROUGH */
                      case 'C':         /* CUF: Cursor right */ 
+                       CLAMP(term->esc_args[0], term->cols);
                        move(term, term->curs.x + def(term->esc_args[0], 1),
                             term->curs.y, 1);
                        seen_disp_event(term);
                        break;
                      case 'D':       /* CUB: move left N cols */
+                       CLAMP(term->esc_args[0], term->cols);
                        move(term, term->curs.x - def(term->esc_args[0], 1),
                             term->curs.y, 1);
                        seen_disp_event(term);
                        break;
                      case 'E':       /* CNL: move down N lines and CR */
                        compatibility(ANSI);
+                       CLAMP(term->esc_args[0], term->rows);
                        move(term, 0,
                             term->curs.y + def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
                        break;
                      case 'F':       /* CPL: move up N lines and CR */
                        compatibility(ANSI);
+                       CLAMP(term->esc_args[0], term->rows);
                        move(term, 0,
                             term->curs.y - def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
@@ -3559,12 +3574,14 @@ static void term_out(Terminal *term)
                      case 'G':       /* CHA */
                      case '`':       /* HPA: set horizontal posn */
                        compatibility(ANSI);
+                       CLAMP(term->esc_args[0], term->cols);
                        move(term, def(term->esc_args[0], 1) - 1,
                             term->curs.y, 0);
                        seen_disp_event(term);
                        break;
                      case 'd':       /* VPA: set vertical posn */
                        compatibility(ANSI);
+                       CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             ((term->dec_om ? term->marg_t : 0) +
                              def(term->esc_args[0], 1) - 1),
@@ -3575,6 +3592,8 @@ static void term_out(Terminal *term)
                      case 'f':      /* HVP: set horz and vert posns at once */
                        if (term->esc_nargs < 2)
                            term->esc_args[1] = ARG_DEFAULT;
+                       CLAMP(term->esc_args[0], term->rows);
+                       CLAMP(term->esc_args[1], term->cols);
                        move(term, def(term->esc_args[1], 1) - 1,
                             ((term->dec_om ? term->marg_t : 0) +
                              def(term->esc_args[0], 1) - 1),
@@ -3610,6 +3629,7 @@ static void term_out(Terminal *term)
                        break;
                      case 'L':       /* IL: insert lines */
                        compatibility(VT102);
+                       CLAMP(term->esc_args[0], term->rows);
                        if (term->curs.y <= term->marg_b)
                            scroll(term, term->curs.y, term->marg_b,
                                   -def(term->esc_args[0], 1), FALSE);
@@ -3617,6 +3637,7 @@ static void term_out(Terminal *term)
                        break;
                      case 'M':       /* DL: delete lines */
                        compatibility(VT102);
+                       CLAMP(term->esc_args[0], term->rows);
                        if (term->curs.y <= term->marg_b)
                            scroll(term, term->curs.y, term->marg_b,
                                   def(term->esc_args[0], 1),
@@ -3626,11 +3647,13 @@ static void term_out(Terminal *term)
                      case '@':       /* ICH: insert chars */
                        /* XXX VTTEST says this is vt220, vt510 manual says vt102 */
                        compatibility(VT102);
+                       CLAMP(term->esc_args[0], term->cols);
                        insch(term, def(term->esc_args[0], 1));
                        seen_disp_event(term);
                        break;
                      case 'P':       /* DCH: delete chars */
                        compatibility(VT102);
+                       CLAMP(term->esc_args[0], term->cols);
                        insch(term, -def(term->esc_args[0], 1));
                        seen_disp_event(term);
                        break;
@@ -3708,6 +3731,8 @@ static void term_out(Terminal *term)
                        compatibility(VT100);
                        if (term->esc_nargs <= 2) {
                            int top, bot;
+                           CLAMP(term->esc_args[0], term->rows);
+                           CLAMP(term->esc_args[1], term->rows);
                            top = def(term->esc_args[0], 1) - 1;
                            bot = (term->esc_nargs <= 1
                                   || term->esc_args[1] == 0 ?
@@ -4063,6 +4088,7 @@ static void term_out(Terminal *term)
                        }
                        break;
                      case 'S':         /* SU: Scroll up */
+                       CLAMP(term->esc_args[0], term->rows);
                        compatibility(SCOANSI);
                        scroll(term, term->marg_t, term->marg_b,
                               def(term->esc_args[0], 1), TRUE);
@@ -4070,6 +4096,7 @@ static void term_out(Terminal *term)
                        seen_disp_event(term);
                        break;
                      case 'T':         /* SD: Scroll down */
+                       CLAMP(term->esc_args[0], term->rows);
                        compatibility(SCOANSI);
                        scroll(term, term->marg_t, term->marg_b,
                               -def(term->esc_args[0], 1), TRUE);
@@ -4112,6 +4139,7 @@ static void term_out(Terminal *term)
                        /* XXX VTTEST says this is vt220, vt510 manual
                         * says vt100 */
                        compatibility(ANSIMIN);
+                       CLAMP(term->esc_args[0], term->cols);
                        {
                            int n = def(term->esc_args[0], 1);
                            pos cursplus;
@@ -4145,6 +4173,7 @@ static void term_out(Terminal *term)
                        break;
                      case 'Z':         /* CBT */
                        compatibility(OTHER);
+                       CLAMP(term->esc_args[0], term->cols);
                        {
                            int i = def(term->esc_args[0], 1);
                            pos old_curs = term->curs;
@@ -4205,7 +4234,7 @@ static void term_out(Terminal *term)
                        break;
                      case ANSI('F', '='):      /* set normal foreground */
                        compatibility(SCOANSI);
-                       if (term->esc_args[0] >= 0 && term->esc_args[0] < 16) {
+                       if (term->esc_args[0] < 16) {
                            long colour =
                                (sco2ansicolour[term->esc_args[0] & 0x7] |
                                 (term->esc_args[0] & 0x8)) <<
@@ -4219,7 +4248,7 @@ static void term_out(Terminal *term)
                        break;
                      case ANSI('G', '='):      /* set normal background */
                        compatibility(SCOANSI);
-                       if (term->esc_args[0] >= 0 && term->esc_args[0] < 16) {
+                       if (term->esc_args[0] < 16) {
                            long colour =
                                (sco2ansicolour[term->esc_args[0] & 0x7] |
                                 (term->esc_args[0] & 0x8)) <<
@@ -4343,7 +4372,11 @@ static void term_out(Terminal *term)
                  case '7':
                  case '8':
                  case '9':
-                   term->esc_args[0] = 10 * term->esc_args[0] + c - '0';
+                   if (term->esc_args[0] <= UINT_MAX / 10 &&
+                       term->esc_args[0] * 10 <= UINT_MAX - c - '0')
+                       term->esc_args[0] = 10 * term->esc_args[0] + c - '0';
+                   else
+                       term->esc_args[0] = UINT_MAX;
                    break;
                  case 'L':
                    /*
@@ -4425,7 +4458,11 @@ static void term_out(Terminal *term)
                  case '7':
                  case '8':
                  case '9':
-                   term->esc_args[0] = 10 * term->esc_args[0] + c - '0';
+                   if (term->esc_args[0] <= UINT_MAX / 10 &&
+                       term->esc_args[0] * 10 <= UINT_MAX - c - '0')
+                       term->esc_args[0] = 10 * term->esc_args[0] + c - '0';
+                   else
+                       term->esc_args[0] = UINT_MAX;
                    break;
                  default:
                    term->termstate = OSC_STRING;

diff --git a/terminal.h b/terminal.h
index 135ef45a6ce9636f9e3f4d06055905bd952e7dc0..01d5f57a2d7e4f3f189f1ea7276eca6998c58cb6 100644 (file)
--- a/terminal.h
+++ b/terminal.h
@@ -172,7 +172,7 @@ struct terminal_tag {
 #define ARGS_MAX 32                   /* max # of esc sequence arguments */
 #define ARG_DEFAULT 0                 /* if an arg isn't specified */
 #define def(a,d) ( (a) == ARG_DEFAULT ? (d) : (a) )
-    int esc_args[ARGS_MAX];
+    unsigned esc_args[ARGS_MAX];
     int esc_nargs;
     int esc_query;
 #define ANSI(x,y)      ((x)+((y)<<8))