diff options
author | Stefan Sperling <ssperling@sysmocom.de> | 2018-07-19 15:25:47 +0200 |
---|---|---|
committer | Stefan Sperling <ssperling@sysmocom.de> | 2018-07-19 19:37:41 +0200 |
commit | d70ab97fa4be4c59f9ebbae19ec8b8f64990a538 (patch) | |
tree | 46b1b65f89c52720eef46d143a859bd63270f82f | |
parent | d1bd6fce9c8447ab9834b57650d1ceb1bdcf1dab (diff) |
fix unaligned access in build_ipcp_pco()
IPCP data can begin at any byte location in the pco_req->v array.
Casting to a 'struct ipcp_hdr' pointer could lead to unaligned access.
Parse IPCP data with u_int8_t pointers instead to avoid this problem.
Add some length checks while here.
pco_contains_proto() and ipcp_contains_option() now receive the minimum
size of the data the caller is looking for, and only return pointers
to items of sufficient size.
Also fix an inifinite loop in ipcp_contains_option() by refusing
IPCP options with length small than 2. Previously, a zero length
option would trigger an infinite loop in the parser.
Change-Id: Ia1410abb216831864042f95679330f4508e1af3d
Related: OS#3194
-rw-r--r-- | ggsn/ggsn.c | 51 |
1 files changed, 31 insertions, 20 deletions
diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c index 6d879c0..30584ef 100644 --- a/ggsn/ggsn.c +++ b/ggsn/ggsn.c @@ -413,16 +413,19 @@ struct ipcp_hdr { } __attribute__ ((packed)); /* determine if IPCP contains given option */ -static struct ipcp_option_hdr *ipcp_contains_option(struct ipcp_hdr *ipcp, enum ipcp_options opt) +static uint8_t *ipcp_contains_option(uint8_t *ipcp, size_t ipcp_len, enum ipcp_options opt, size_t opt_minlen) { - uint8_t *cur = ipcp->options; + uint8_t *cur_opt = ipcp + sizeof(struct ipcp_hdr); /* iterate over Options and check if protocol contained */ - while (cur + 2 <= ((uint8_t *)ipcp) + ntohs(ipcp->len)) { - struct ipcp_option_hdr *cur_opt = (struct ipcp_option_hdr *) cur; - if (cur_opt->type == opt) + while (cur_opt + 2 <= ipcp + ipcp_len) { + uint8_t type = cur_opt[0]; + uint8_t len = cur_opt[1]; /* length value includes 2 bytes type/length */ + if (len < 2) + return NULL; + if (type == opt && len >= 2 + opt_minlen) return cur_opt; - cur += cur_opt->len; + cur_opt += len; } return NULL; } @@ -460,7 +463,7 @@ enum pco_protocols { }; /* determine if PCO contains given protocol */ -static uint8_t *pco_contains_proto(struct ul255_t *pco, uint16_t prot) +static uint8_t *pco_contains_proto(struct ul255_t *pco, uint16_t prot, size_t prot_minlen) { uint8_t *cur = pco->v + 1; @@ -468,7 +471,7 @@ static uint8_t *pco_contains_proto(struct ul255_t *pco, uint16_t prot) while (cur + 3 <= pco->v + pco->l) { uint16_t cur_prot = osmo_load16be(cur); uint8_t cur_len = cur[2]; - if (cur_prot == prot) + if (cur_prot == prot && cur_len >= prot_minlen) return cur; cur += cur_len + 3; } @@ -500,35 +503,45 @@ static struct ippoolm_t *pdp_get_peer_ipv(struct pdp_t *pdp, bool is_ipv6) { } /* construct an IPCP PCO response from request*/ -static int build_ipcp_pco(struct apn_ctx *apn, struct pdp_t *pdp, struct msgb *msg) +static void build_ipcp_pco(struct apn_ctx *apn, struct pdp_t *pdp, struct msgb *msg) { const struct in46_addr *dns1 = &apn->v4.cfg.dns[0]; const struct in46_addr *dns2 = &apn->v4.cfg.dns[1]; - struct ipcp_hdr *ipcp; + uint8_t *ipcp; + uint16_t ipcp_len; uint8_t *len1, *len2, *pco_ipcp; uint8_t *start = msg->tail; unsigned int len_appended; + ptrdiff_t consumed; + size_t remain; - if (!(pco_ipcp = pco_contains_proto(&pdp->pco_req, PCO_P_IPCP))) - return 0; - ipcp = (struct ipcp_hdr*) (pco_ipcp + 3); /* 2=type + 1=len */ + /* pco_contains_proto() returns a potentially unaligned pointer into pco_req->v (see OS#3194) */ + if (!(pco_ipcp = pco_contains_proto(&pdp->pco_req, PCO_P_IPCP, sizeof(struct ipcp_hdr)))) + return; + + ipcp = (pco_ipcp + 3); /* 2=type + 1=len */ + consumed = (ipcp - &pdp->pco_req.v[0]); + remain = sizeof(pdp->pco_req.v) - consumed; + ipcp_len = osmo_load16be(ipcp + 2); /* 1=code + 1=id */ + if (remain < 0 || remain < ipcp_len) + return; /* Three byte T16L header */ msgb_put_u16(msg, 0x8021); /* IPCP */ len1 = msgb_put(msg, 1); /* Length of contents: delay */ msgb_put_u8(msg, 0x02); /* ACK */ - msgb_put_u8(msg, ipcp->id); /* ID: Needs to match request */ + msgb_put_u8(msg, ipcp[1]); /* ID: Needs to match request */ msgb_put_u8(msg, 0x00); /* Length MSB */ len2 = msgb_put(msg, 1); /* Length LSB: delay */ - if (dns1->len == 4 && ipcp_contains_option(ipcp, IPCP_OPT_PRIMARY_DNS)) { + if (dns1->len == 4 && ipcp_contains_option(ipcp, ipcp_len, IPCP_OPT_PRIMARY_DNS, 4)) { msgb_put_u8(msg, 0x81); /* DNS1 Tag */ msgb_put_u8(msg, 2 + dns1->len);/* DNS1 Length, incl. TL */ msgb_put_u32(msg, ntohl(dns1->v4.s_addr)); } - if (dns2->len == 4 && ipcp_contains_option(ipcp, IPCP_OPT_SECONDARY_DNS)) { + if (dns2->len == 4 && ipcp_contains_option(ipcp, ipcp_len, IPCP_OPT_SECONDARY_DNS, 4)) { msgb_put_u8(msg, 0x83); /* DNS2 Tag */ msgb_put_u8(msg, 2 + dns2->len);/* DNS2 Length, incl. TL */ msgb_put_u32(msg, ntohl(dns2->v4.s_addr)); @@ -538,8 +551,6 @@ static int build_ipcp_pco(struct apn_ctx *apn, struct pdp_t *pdp, struct msgb *m len_appended = msg->tail - start; *len1 = len_appended - 3; *len2 = len_appended - 3; - - return 0; } /* process one PCO request from a MS/UE, putting together the proper responses */ @@ -555,7 +566,7 @@ static void process_pco(struct apn_ctx *apn, struct pdp_t *pdp) if (peer_v4) build_ipcp_pco(apn, pdp, msg); - if (pco_contains_proto(&pdp->pco_req, PCO_P_DNS_IPv6_ADDR)) { + if (pco_contains_proto(&pdp->pco_req, PCO_P_DNS_IPv6_ADDR, 0)) { for (i = 0; i < ARRAY_SIZE(apn->v6.cfg.dns); i++) { struct in46_addr *i46a = &apn->v6.cfg.dns[i]; if (i46a->len != 16) @@ -564,7 +575,7 @@ static void process_pco(struct apn_ctx *apn, struct pdp_t *pdp) } } - if (pco_contains_proto(&pdp->pco_req, PCO_P_DNS_IPv4_ADDR)) { + if (pco_contains_proto(&pdp->pco_req, PCO_P_DNS_IPv4_ADDR, 0)) { for (i = 0; i < ARRAY_SIZE(apn->v4.cfg.dns); i++) { struct in46_addr *i46a = &apn->v4.cfg.dns[i]; if (i46a->len != 4) |