726d0d148
Martin Lewis
2020-06-09
Subject
dhcpc: code shrink in good_hostname
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networking/udhcp/dhcpc.c+14 -48
| @@ -159,61 +159,27 @@ static int mton(uint32_t mask) | |
| } | |
| #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT | |
| - | /* Check if a given label represents a valid DNS label |
| - | * Return pointer to the first character after the label |
| - | * (NUL or dot) upon success, NULL otherwise. |
| - | * See RFC1035, 2.3.1 |
| - | */ |
| + | /* Check if a given name represents a valid DNS name */ |
| + | /* See RFC1035, 2.3.1 */ |
| /* We don't need to be particularly anal. For example, allowing _, hyphen | |
| * at the end, or leading and trailing dots would be ok, since it | |
| - | * can't be used for attacks. (Leading hyphen can be, if someone uses |
| - | * cmd "$hostname" |
| + | * can't be used for attacks. (Leading hyphen can be, if someone uses cmd "$hostname" |
| * in the script: then hostname may be treated as an option) | |
| */ | |
| - | static const char *valid_domain_label(const char *label) |
| - | { |
| - | unsigned char ch; |
| - | //unsigned pos = 0; |
| - | |
| - | if (label[0] == '-') |
| - | return NULL; |
| - | for (;;) { |
| - | ch = *label; |
| - | if ((ch|0x20) < 'a' || (ch|0x20) > 'z') { |
| - | if (ch < '0' || ch > '9') { |
| - | if (ch == '\0' || ch == '.') |
| - | return label; |
| - | /* DNS allows only '-', but we are more permissive */ |
| - | if (ch != '-' && ch != '_') |
| - | return NULL; |
| - | } |
| - | } |
| - | label++; |
| - | //pos++; |
| - | //Do we want this? |
| - | //if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */ |
| - | // return NULL; |
| - | } |
| - | } |
| - | |
| - | /* Check if a given name represents a valid DNS name */ |
| - | /* See RFC1035, 2.3.1 */ |
| static int good_hostname(const char *name) | |
| { | |
| - | //const char *start = name; |
| - | |
| - | for (;;) { |
| - | name = valid_domain_label(name); |
| - | if (!name) |
| - | return 0; |
| - | if (!name[0]) |
| - | return 1; |
| - | //Do we want this? |
| - | //return ((name - start) < 1025); /* NS_MAXDNAME */ |
| - | name++; |
| - | if (*name == '\0') |
| - | return 1; // We allow trailing dot too |
| + | if (*name == '-') /* Can't start with '-' */ |
| + | return 0; |
| + | |
| + | while (*name) { |
| + | unsigned char ch = *name++; |
| + | if (!isalnum(ch)) |
| + | /* DNS allows only '-', but we are more permissive */ |
| + | if (ch != '-' && ch != '_' && ch != '.') |
| + | return 0; |
| + | // TODO: do we want to validate lengths against NS_MAXLABEL and NS_MAXDNAME? |
| } | |
| + | return 1; |
| } | |
| #else | |
| # define good_hostname(name) 1 | |