Stricter limit on POS/MPOS/TLEN in sam_parse1()

Help avoid overflow on arithmetic involving POS, MPOS and TLEN
by limiting values in the SAM parser to fit in 62 bits (or 63
for TLEN as it's signed).  The new limit is still massively bigger
than any known reference so it should not cause any problems
in practice.

Credit to OSS-Fuzz
Fixes oss-fuzz 68750

sam.c

@@ -2947,7 +2947,7 @@ int sam_parse1(kstring_t *s, sam_hdr_t *h, bam1_t *b)
     } else c->tid = -1;
 
     // pos
-    c->pos = hts_str2uint(p, &p, 63, &overflow) - 1;
+    c->pos = hts_str2uint(p, &p, 62, &overflow) - 1;
     if (*p++ != '\t') goto err_ret;
     if (c->pos < 0 && c->tid >= 0) {
         _parse_warn(1, "mapped query cannot have zero coordinate; treated as unmapped");
@@ -2990,15 +2990,16 @@ int sam_parse1(kstring_t *s, sam_hdr_t *h, bam1_t *b)
         _parse_warn(c->mtid < 0, "unrecognized mate reference name %s; treated as unmapped", hts_strprint(logbuf, sizeof logbuf, '"', q, SIZE_MAX));
     }
     // mpos
-    c->mpos = hts_str2uint(p, &p, 63, &overflow) - 1;
+    c->mpos = hts_str2uint(p, &p, 62, &overflow) - 1;
     if (*p++ != '\t') goto err_ret;
     if (c->mpos < 0 && c->mtid >= 0) {
         _parse_warn(1, "mapped mate cannot have zero coordinate; treated as unmapped");
         c->mtid = -1;
     }
     // tlen
-    c->isize = hts_str2int(p, &p, 64, &overflow);
+    c->isize = hts_str2int(p, &p, 63, &overflow);
     if (*p++ != '\t') goto err_ret;
+    _parse_err(overflow, "number outside allowed range");
     // seq
     q = _read_token(p);
     if (strcmp(q, "*")) {

test/sam.c

@@ -1,6 +1,6 @@
 /*  test/sam.c -- SAM/BAM/CRAM API test cases.
 
-    Copyright (C) 2014-2020, 2022-2023 Genome Research Ltd.
+    Copyright (C) 2014-2020, 2022-2024 Genome Research Ltd.
 
     Author: John Marshall <[email protected]>
 
@@ -1408,16 +1408,16 @@ static void check_big_ref(int parse_header)
         "@HD\tVN:1.4\n"
         "@SQ\tSN:large#1\tLN:5000000000\n"
         "@SQ\tSN:small#1\tLN:100\n"
-        "@SQ\tSN:large#2\tLN:9223372034707292158\n"
+        "@SQ\tSN:large#2\tLN:4611686018427387904\n"
         "@SQ\tSN:small#2\tLN:1\n"
         "r1\t0\tlarge#1\t4999999000\t50\t8M\t*\t0\t0\tACGTACGT\tabcdefgh\n"
         "r2\t0\tsmall#1\t1\t50\t8M\t*\t0\t0\tACGTACGT\tabcdefgh\n"
-        "r3\t0\tlarge#2\t9223372034707292000\t50\t8M\t*\t0\t0\tACGTACGT\tabcdefgh\n"
-        "p1\t99\tlarge#2\t1\t50\t8M\t=\t9223372034707292150\t9223372034707292158\tACGTACGT\tabcdefgh\n"
-        "p1\t147\tlarge#2\t9223372034707292150\t50\t8M\t=\t1\t-9223372034707292158\tACGTACGT\tabcdefgh\n"
+        "r3\t0\tlarge#2\t4611686018427387000\t50\t8M\t*\t0\t0\tACGTACGT\tabcdefgh\n"
+        "p1\t99\tlarge#2\t1\t50\t8M\t=\t4611686018427387895\t4611686018427387903\tACGTACGT\tabcdefgh\n"
+        "p1\t147\tlarge#2\t4611686018427387895\t50\t8M\t=\t1\t-4611686018427387903\tACGTACGT\tabcdefgh\n"
         "r4\t0\tsmall#2\t2\t50\t8M\t*\t0\t0\tACGTACGT\tabcdefgh\n";
     const hts_pos_t expected_lengths[] = {
-        5000000000LL, 100LL, 9223372034707292158LL, 1LL
+        5000000000LL, 100LL, 4611686018427387904LL, 1LL
     };
     const int expected_tids[] = {
         0, 1, 2, 2, 2, 3
@@ -1426,11 +1426,11 @@ static void check_big_ref(int parse_header)
         -1, -1, -1, 2, 2, -1
     };
     const hts_pos_t expected_positions[] = {
-        4999999000LL - 1, 1LL - 1, 9223372034707292000LL - 1, 1LL - 1,
-        9223372034707292150LL - 1, 2LL - 1
+        4999999000LL - 1, 1LL - 1, 4611686018427387000LL - 1, 1LL - 1,
+        4611686018427387895LL - 1, 2LL - 1
     };
     const hts_pos_t expected_mpos[] = {
-        -1, -1, -1, 9223372034707292150LL - 1, 1LL - 1, -1
+        -1, -1, -1, 4611686018427387895LL - 1, 1LL - 1, -1
     };
     samFile *in = NULL, *out = NULL;
     sam_hdr_t *header = NULL, *dup_header = NULL;