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pppd: Be careful not to access beyond end of EAP packets #582

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Merged
paulusmack merged 1 commit into from
Apr 15, 2026
Merged

pppd: Be careful not to access beyond end of EAP packets #582

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55 changes: 36 additions & 19 deletions pppd/eap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1954,14 +1954,14 @@ eap_request(eap_state *esp, u_char *inp, int id, int len)
/* No session key just yet */
esp->es_client.ea_skey = NULL;
if (tc == NULL) {
GETCHAR(vallen, inp);
len--;
if (vallen >= len) {
if (len < 1 || len < inp[0] + 1) {
error("EAP: badly-formed SRP Challenge"
" (name)");
/* Ignore badly-formed messages */
return;
}
GETCHAR(vallen, inp);
len--;
BCOPY(inp, rhostname, vallen);
rhostname[vallen] = '\0';
INCPTR(vallen, inp);
Expand All @@ -1982,27 +1982,27 @@ eap_request(eap_state *esp, u_char *inp, int id, int len)
esp->es_client.ea_peer = strdup(rhostname);
esp->es_client.ea_peerlen = strlen(rhostname);

GETCHAR(vallen, inp);
len--;
if (vallen >= len) {
if (len < 1 || len < inp[0] + 1) {
error("EAP: badly-formed SRP Challenge"
" (s)");
/* Ignore badly-formed messages */
return;
}
GETCHAR(vallen, inp);
len--;
sval.data = inp;
sval.len = vallen;
INCPTR(vallen, inp);
len -= vallen;

GETCHAR(vallen, inp);
len--;
if (vallen > len) {
if (len < 1 || len < inp[0] + 1) {
error("EAP: badly-formed SRP Challenge"
" (g)");
/* Ignore badly-formed messages */
return;
}
GETCHAR(vallen, inp);
len--;
/* If no generator present, then use value 2 */
if (vallen == 0) {
gval.data = (u_char *)"\002";
Expand Down Expand Up @@ -2196,11 +2196,16 @@ eap_request(eap_state *esp, u_char *inp, int id, int len)
u_char *challenge = inp;

unsigned char vsize;

if (len < 1 + MS_CHAP2_PEER_CHAL_LEN) {
error("EAP: received invalid MSCHAPv2 packet, invalid length: %d", len);
return;
}
GETCHAR(vsize, inp);
len -= 1;

/* Validate the VALUE field */
if (vsize != MS_CHAP2_PEER_CHAL_LEN || len < MS_CHAP2_PEER_CHAL_LEN) {
if (vsize != MS_CHAP2_PEER_CHAL_LEN) {
error("EAP: received invalid MSCHAPv2 packet, invalid value-length: %d", vsize);
return;
}
Expand Down Expand Up @@ -2622,17 +2627,17 @@ eap_response(eap_state *esp, u_char *inp, int id, int len)
eap_figure_next_state(esp, 1);
break;
}
/* skip MS ID + len */
INCPTR(3, inp);
GETCHAR(vallen, inp);
len -= 4;

if (vallen != MS_CHAP2_RESPONSE_LEN || vallen > len) {
error("EAP: Invalid MSCHAPv2-Response "
"length %d", vallen);
/* skip MS ID + len */
if (len < 4 + MS_CHAP2_RESPONSE_LEN || inp[3] != MS_CHAP2_RESPONSE_LEN) {
error("EAP: Invalid/short MSCHAPv2-Response, "
"length %d", len);
eap_figure_next_state(esp, 1);
break;
}
INCPTR(3, inp);
GETCHAR(vallen, inp);
len -= 4;

/* Not so likely to happen. */
if (len - vallen >= sizeof (rhostname)) {
Expand Down Expand Up @@ -3010,14 +3015,16 @@ eap_printpkt(u_char *inp, int inlen,
GETCHAR(code, inp);
GETCHAR(id, inp);
GETSHORT(len, inp);
if (len < EAP_HEADERLEN || len > inlen)
return (0);

if (code >= 1 && code <= sizeof(eap_codenames) / sizeof(char *))
printer(arg, " %s", eap_codenames[code-1]);
else
printer(arg, " code=0x%x", code);
printer(arg, " id=0x%x", id);
if (len < EAP_HEADERLEN || len > inlen) {
printer(arg, " <bad length=%d>", len);
return (0);
}
len -= EAP_HEADERLEN;
switch (code) {
case EAP_REQUEST:
Expand Down Expand Up @@ -3075,6 +3082,8 @@ eap_printpkt(u_char *inp, int inlen,
len--;
switch (opcode) {
case CHAP_CHALLENGE:
if (len < 4)
goto truncated;
INCPTR(3, inp);
len -= 3;
GETCHAR(vallen, inp);
Expand All @@ -3100,20 +3109,26 @@ eap_printpkt(u_char *inp, int inlen,
}
break;
case CHAP_SUCCESS:
if (len < 3)
goto truncated;
INCPTR(3, inp);
len -= 3;
printer(arg, " Success <Message ");
print_string((char *)inp, len, printer, arg);
printer(arg, ">");
break;
case CHAP_FAILURE:
if (len < 3)
goto truncated;
INCPTR(3, inp);
len -= 3;
printer(arg, " Failure <Message ");
print_string((char *)inp, len, printer, arg);
printer(arg, ">");
break;
default:
if (len < 3)
goto truncated;
INCPTR(3, inp);
len -= 3;
printer(arg, " opcode=0x%x <%.*B>", opcode, len, inp);
Expand Down Expand Up @@ -3317,6 +3332,8 @@ eap_printpkt(u_char *inp, int inlen,
len--;
switch (opcode) {
case CHAP_RESPONSE:
if (len < 4)
goto truncated;
INCPTR(3, inp);
len -= 3;
GETCHAR(vallen, inp);
Expand Down
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