dns response handling: don't treat too many addresses as an error

[musl] / src / network / lookup_name.c

diff --git a/src/network/lookup_name.c b/src/network/lookup_name.c
index c4d994a..be0c0bd 100644 (file)
--- a/src/network/lookup_name.c
+++ b/src/network/lookup_name.c
@@ -50,7 +50,7 @@ static int name_from_hosts(struct address buf[static MAXADDRS], char canon[stati
 {
        char line[512];
        size_t l = strlen(name);
-       int cnt = 0, badfam = 0;
+       int cnt = 0, badfam = 0, have_canon = 0;
        unsigned char _buf[1032];
        FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
        if (!f) switch (errno) {
@@ -79,15 +79,20 @@ static int name_from_hosts(struct address buf[static MAXADDRS], char canon[stati
                case 0:
                        continue;
                default:
-                       badfam = EAI_NONAME;
-                       continue;
+                       badfam = EAI_NODATA;
+                       break;
                }
 
+               if (have_canon) continue;
+
                /* Extract first name as canonical name */
                for (; *p && isspace(*p); p++);
                for (z=p; *z && !isspace(*z); z++);
                *z = 0;
-               if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
+               if (is_valid_hostname(p)) {
+                       have_canon = 1;
+                       memcpy(canon, p, z-p+1);
+               }
        }
        __fclose_ca(f);
        return cnt ? cnt : badfam;
@@ -97,32 +102,37 @@ struct dpc_ctx {
        struct address *addrs;
        char *canon;
        int cnt;
+       int rrtype;
 };
 
 #define RR_A 1
 #define RR_CNAME 5
 #define RR_AAAA 28
 
+#define ABUF_SIZE 768
+
 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
 {
        char tmp[256];
        struct dpc_ctx *ctx = c;
-       if (ctx->cnt >= MAXADDRS) return -1;
+       if (ctx->cnt >= MAXADDRS) return 0;
        switch (rr) {
        case RR_A:
+               if (rr != ctx->rrtype) return 0;
                if (len != 4) return -1;
                ctx->addrs[ctx->cnt].family = AF_INET;
                ctx->addrs[ctx->cnt].scopeid = 0;
                memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
                break;
        case RR_AAAA:
+               if (rr != ctx->rrtype) return 0;
                if (len != 16) return -1;
                ctx->addrs[ctx->cnt].family = AF_INET6;
                ctx->addrs[ctx->cnt].scopeid = 0;
                memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
                break;
        case RR_CNAME:
-               if (__dn_expand(packet, (const unsigned char *)packet + 512,
+               if (__dn_expand(packet, (const unsigned char *)packet + ABUF_SIZE,
                    data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
                        strcpy(ctx->canon, tmp);
                break;
@@ -132,10 +142,10 @@ static int dns_parse_callback(void *c, int rr, const void *data, int len, const
 
 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, const struct resolvconf *conf)
 {
-       unsigned char qbuf[2][280], abuf[2][512];
+       unsigned char qbuf[2][280], abuf[2][ABUF_SIZE];
        const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
        unsigned char *ap[2] = { abuf[0], abuf[1] };
-       int qlens[2], alens[2];
+       int qlens[2], alens[2], qtypes[2];
        int i, nq = 0;
        struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
        static const struct { int af; int rr; } afrr[2] = {
@@ -148,8 +158,12 @@ static int name_from_dns(struct address buf[static MAXADDRS], char canon[static
                        qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr,
                                0, 0, 0, qbuf[nq], sizeof *qbuf);
                        if (qlens[nq] == -1)
-                               return EAI_NONAME;
+                               return 0;
+                       qtypes[nq] = afrr[i].rr;
                        qbuf[nq][3] = 0; /* don't need AD flag */
+                       /* Ensure query IDs are distinct. */
+                       if (nq && qbuf[nq][0] == qbuf[0][0])
+                               qbuf[nq][0]++;
                        nq++;
                }
        }
@@ -157,14 +171,19 @@ static int name_from_dns(struct address buf[static MAXADDRS], char canon[static
        if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0)
                return EAI_SYSTEM;
 
-       for (i=0; i<nq; i++)
+       for (i=0; i<nq; i++) {
+               if (alens[i] < 4 || (abuf[i][3] & 15) == 2) return EAI_AGAIN;
+               if ((abuf[i][3] & 15) == 3) return 0;
+               if ((abuf[i][3] & 15) != 0) return EAI_FAIL;
+       }
+
+       for (i=nq-1; i>=0; i--) {
+               ctx.rrtype = qtypes[i];
                __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
+       }
 
        if (ctx.cnt) return ctx.cnt;
-       if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
-       if ((abuf[0][3] & 15) == 0) return EAI_NONAME;
-       if ((abuf[0][3] & 15) == 3) return 0;
-       return EAI_FAIL;
+       return EAI_NODATA;
 }
 
 static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)