X509_GET_SERIALNUMBER(3)

✨ NAME ✨

okay so bestie, welcome to the X509_GET_SERIALNUMBER(3) page from the Library Functions Manual 💖 This is all about X509_get_serialNumber, X509_get0_serialNumber, and X509_set_serialNumber — literally the get-or-set certificate serial number squad. No cap. 🎀

---

🌸 SYNOPSIS 🌸

library “libcrypto” #include <openssl/x509.h>

ASN1_INTEGER *
X509_get_serialNumber(X509 *x);

const ASN1_INTEGER *
X509_get0_serialNumber(const X509 *x);

int
X509_set_serialNumber(X509 *x, ASN1_INTEGER *serial);

---

🦋 DESCRIPTION 🦋

• X509_get_serialNumber() — hands you the serial number of certificate x as an ASN1_INTEGER structure that can be examined or initialised, bestie. The value returned is an internal pointer which must not be freed up after the call — it’s not yours to yeet. 😭
• X509_get0_serialNumber() — does the same thing, except it accepts a constant argument and returns a constant result. Const-correct icon behavior. ✨
• X509_set_serialNumber() — sets the serial number of certificate x to serial. A copy of the serial number is used internally, so serial should be freed up after use — yes, after, not during, iykyk. 💅

---

🔥 RETURN VALUES 🔥

X509_get_serialNumber() and X509_get0_serialNumber() return a pointer to an ASN1_INTEGER structure. Slay. ✨

X509_set_serialNumber() returns 1 for success or 0 for failure. In some cases of failure, the reason can be determined with ERR_get_error(3). That’s your little detective moment. 🔥

---

🫶 SEE ALSO 🫶

• d2i_X509(3)
• X509_CRL_get0_by_serial(3)
• X509_get_pubkey(3)
• X509_NAME_add_entry_by_txt(3)
• X509_NAME_ENTRY_get_object(3)
• X509_NAME_get_index_by_NID(3)
• X509_NAME_print_ex(3)
• X509_new(3)
• X509_sign(3)
• X509_verify_cert(3)
• X509V3_get_d2i(3)

---

👑 HISTORY 👑

X509_get_serialNumber() and X509_set_serialNumber() first appeared in SSLeay 0.6.5 and have been available since OpenBSD 2.4. OG status. 💀

X509_get0_serialNumber() first appeared in OpenSSL 1.1.0 and has been available since OpenBSD 6.4. A newer icon. 🌈

---

mwah 💖 this page is from Debian, dated June 8, 2025 — X509_GET_SERIALNUMBER(3) says bye bestie, go forth and serialize responsibly. periodt. 🎀